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Soil water dynamics, growth of Dendrocalamus strictus and herbage productivity influenced by rainwater harvesting in Aravalli hills of Rajasthan
Forest Ecology and Management 258 (2009) 2519–2528
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Soil water dynamics, growth of Dendrocalamus strictus and herbage productivity influenced by rainwater harvesting in Aravalli hills of Rajasthan G. Singh * Division of Forest Ecology, Arid Forest Research Institute, New Pali Road, Jodhpur 342005, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 November 2008 Received in revised form 31 August 2009 Accepted 4 September 2009
Degraded Aravalli hills in western India require rehabilitation through resource conservation and afforestation for meeting the biomass needs of resource-poor tribes of the region. Rainwater harvesting treatments i.e., control, Contour trench (CT), Gradonie (G), Box trench (BT) and V-ditch (VD) were prepared in <10%, 10–20% and >20% slopes categories and Dendrocalamus strictus L. seedlings were planted in August 2005 with a view to conserve soil and water and increase the productivity of the hills. Soil water content (SWC), survival and height of D. strictus plants were highest (P < 0.05) in <10% slope and all these variables decreased with increase in slope. SWC increased by 27.45% and 25.68% in <10% and >20% slopes, respectively than in 10–20% slope. From lowest in control SWC increased by 11.95%, 20.21%, 17.61% and 11.49% in CT, G, BT and VD treatments, respectively. Growth variables were highest in VD plots but the increase in shoot number was highest (2.9-fold) in CT plots. Increase in effects of rainwater harvesting with time indicated by a change in production pattern from highest (P < 0.05) fresh and dry herbage in <10% slope in 2005 to 10–20% slope (24.66% and 26.09%) in 2006 and >20% slope (42.42% and 48.35%, respectively) in 2007. The increase in herbage was 1.17–2.40-fold in fresh and 1.20– 2.52-fold in dry herbage over control. Highest (P < 0.01) production was in V-ditch plots. The treatments order for herbage production was C < CT < G < BT < VD. But the production was highest in BT in <10% and in V-ditch plots in 10–20 and >20% slopes. Conclusively, soil water status is affected by natural slope, stony soil surface and rainwater harvesting structures influencing seedling growth and herbage production. Box trench and V-ditch enhanced surface soil water facilitating herbage growth, whereas contour trench facilitated deep soil water storage, which was made available to the plants after monsoon. Thus rainwater harvesting practices enhanced vegetation cover and productivity of the degraded hills and can be replicated to conserve soil resource and increase biomass for rural poor of the region. ß 2009 Elsevier B.V. All rights reserved.
Keywords: Afforestation Degraded Aravalli Site productivity Soil and water conservation
1. Introduction Over-exploitation and unsustained vegetation removal induced land degradation in Aravalli hills in India. Very limited numbers of vegetations are growing though many of the hillocks are exposed and devoid of vegetation. Rehabilitation of these degraded hills is an essential requisite for eco-environmental improvement and to meet the basic needs of fuel wood and fodder in the region. However, the establishment of vegetation is quite difficult due to inadequate availability of soil moisture (Li et al., 2008) in these degraded hills. Low and irregular rainfall is the most critical factor to plant growth (Barron et al., 2003). A small fraction of the rainwater reaches and remains in the soil long enough to be useful
* Tel.: +91 291 2729150; fax: +91 291 2722764. E-mail addresses: [email protected], [email protected]. 0378-1127/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2009.09.008
for plants and animals. More than 70% of the rainfall is lost as evaporation, or run-off that causes erosion and flooding downstream (Singh et al., 2007). Thus, both floods and droughts and their detrimental consequences are result of this wastage of valuable rainwater. Because the water and soil resource is finite, the only option for increasing biomass production is to increase the water productivity i.e., the water use efficiency (WUE), by producing more biomass per unit of water (Gregory, 1989). Adoption of improved water conservation and harvesting technologies contributes to increase in groundwater recharge, soil nutrients and biomass production and supports a higher number of plants (Gowing et al., 1999; Vohland and Barry, 2009). The principle requirement is the adequate soil and water management techniques that guarantee a maximum of infiltration and transpiration for increased biomass production in intensively grazed and degraded hills of dry areas (Venketeswarlu, 1987; Hatibu et al., 2006; Wezel, 2006). Many rainwater harvesting
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structures are in use to conserve soil and water in the hilly tracts depending upon the slope gradient but only few structures have been quantified in terms of growth and productivity of forestry species (Gupta, 1995). Bamboo is a group of plants belonging to family Gramineae and subfamily Bambusoideae. Being an important forest type bamboo forest occurs in subtropical and tropical areas with a total area of 22 million ha worldwide (Liu et al., 2001). Importance of this genus is such that total forest areas in many countries have drastically declined, whereas the area under bamboo forest has increased (Ben-Zhi et al., 2005). Because of its enormous potential for alleviating many economic and environmental problems bamboo is an ideal economic investment (Chakraborty, 1988; Singh and Singh, 1999). There are approximately 1500 species under 87 genera of Bamboo worldwide (Li and Kobayashi, 2004). Existence of bamboos is edaphic climax type in dry deciduous forest in the form of ‘Dry Bamboo Brakes’ (3/2S1 and 5/E9) in western India (Champion and Seth, 1968). Out of 22 species of bamboos reported in this region Bambusa arundinacea and Dendrocalamus strictus are dominant species. D. strictus is more suited with multiple uses in this dry region. However, its occurrence along streams and drainage lines indicated relatively greater water requirement of this species. The increase in water yield through micro-catchment rainwater harvesting may enhance growth and productivity of this species along with herbage production and rehabilitation of the degraded hills. Thus the objective of this study was to compare the impacts of different rainwater harvesting structures on soil water storage, growth of D. strictus and productivity of associated vegetation for further replication to meet the fuel and fodder requirements of the local inhabitants. Resource conservations and rehabilitation of these degraded hills are the ultimate objective.
2.2. Experimental design The experiment was laid in complete randomized block design with five replicate plots. Seventy-five plots of 700 m2 area were laid in <10%, 10–20% and >20% slope areas with five rainwater harvesting treatments. Each plot was separated by individual boundary of trench (2025 cm2 cross-section area, 45 cm 45 cm) cum bund to avoid water intrusion from other areas or plots and had a rainwater harvesting structure of 30 running meter length (Singh, 2008) except the control plots. Contour trenches (CT) were excavated at different contour levels to conserve the run-off water and are 2025 square cm in cross-section (45 cm 45 cm). Box trenches (BTs) were intermittent trenches of 2 m length (15 numbers) with cross-section area similar to that in the CT. Vditches (V) are across the contour and 1800 cm2 cross-section area [(120 W 30 H)/2], where W is width and H is height of the cut. The vertical (height of 30 cm) cut was downside of the slope. Gradonie ditches (G) also have 1800 cm2 cross-section area [(30 H 120 W)/2] but the vertical cut was upside of the slope with a view to reduce velocity of surface run-off water. In all the structure, the excavated soil was heaped towards the down slope. The control plots are without rain water harvesting structures (i.e., with boundary bund only). Each plot was planted with 35 numbers of seedlings of different tree species in August 2005 with an average population of 6 clumps for D. strictus L. Vegetatively raised seedlings of D. strictus of about 40 cm height were planted in a pit size of 45 cm 45 cm 45 cm and towards the lower one third of the plot. A small microcatchment of 1600 cm2 area (micro-gradonie with a catchment towards up slope) was also prepared around each planted seedling. Thus, 75 plots with five rainwater harvesting treatments were distributed in three slopes (3 slopes five treatments five replications).
2. Materials and methods 2.3. Observations recording 2.1. Site characteristics The study was carried out along hills with pediment covering an area of about 17 ha, which spread over 238250 27.000 N to 238250 43.400 N latitudes and 748240 00.500 E to 748240 23.100 E longitude. Altitude of the area ranged between 248 m and 320 m msl. The site is located 17 km south-west of district head quarter Banswara (238320 28.200 N and 748260 30.300 E). Banswara is situated in the southern part of Rajasthan, and surrounded in the north by Udaipur, north-east by Chittorgarh and west by Dungarpur districts. It is bounded in east and south-east by Madhya Pradesh and in south-west by Gujarat states. Air temperature varied from 4 8C in January to 42 8C in May. The mean minimum and maximum annual temperature is about 15 8C and 33 8C, respectively. Average annual rainfall from 1993 to 2004 was 960 mm with 54 numbers of rainy days. However, years 2005, 2006 and 2007 received 990 mm, 2266 mm and 1391 mm rainfall in 42, 63 and 44 events, respectively. Hillslopes ranged from 3% to 53% in the study area. These slopes were categorized in to steep (>208), medium (10–20%) and gentle (<10%) slopes. The surface of steep slopes was covered with crystalline gravels and pebbles of varying size with randomly growing Lantana camera. Medium slope had light textured sandy loam soils of shallow depth and was mostly covered by Prosopis juliflora with occasional L. camera. Soils in gentle slope were loamy to clay loam in texture and shallow to deep in soil depth. The gentle slope area was dominantly covered by P. juliflora and L. camera bushes. Soil pH was acidic to slightly alkaline in reaction (6.34– 7.02). Average SOC, available NH4-N, NO3-N and PO4-P of the site were 0.760%, 22.15 mg kg1, 2.50 mg kg1 and 4.51 mg kg1, respectively.
Because of low soil depth in steep slope area (maximum 40 cm) soil samples were collected from 0–40 cm soil layer to maintain similarity in all the slopes. Soil samples for texture and initial nutrient analysis were collected in June 2005, dried and passed to a 2 mm sieve for separation of gravel and soil. Soil pH and soil organic carbon (SOC) was determined using standard procedures (Jackson, 1973). Available nitrogen (NH4-N and NO3-N) was determined after 0.5 M K2SO4 extraction using uv-vis-spectrophotometer Model Shimadzu-1650PC. Extractable phosphorus was determined by the Olson’s extraction method (Jackson, 1973) using above-mentioned spectrophotometer. For soil water content (SWC) determination, collected soil samples from the vicinity of the plants were put immediately into polyethylene bag to avoid water loss during transport to laboratory. Sampling was carried out 11 times from December 2005 to December 2007 to observe changes in soil water content throughout the year. Soil water content was estimated by oven drying of the sample at 110 8C for a constant weight. Soil water depletion during vegetation growth was calculated as per cent decrease in SWC from August to December and again from December to June. Height and number of shoots of D. strictus were recorded in September 2005 and again in December and June of each year to monitor seasonal growth i.e., monsoon and spring. Per cent increment in growth variables were calculated as: % increment = (x in December x in June) 100/x in June. Where x is height and number shoots of D. strictus. Aboveground biomass (herbage production) was harvested from 1 m 1 m area from lower one third of the plots with uniform vegetation in October of 2005, 2006 and 2007. Fresh herbage biomass was recorded after clipping the biomass from the soil surface and converted to kg m2 area. Dry
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Table 1 Soil composition and soil characteristics of the experimental sites recorded in June 2005. Values are mean SE of five replicates. RWH structure
Gravel
Sand
Silt + clay
%
NH4-N
NO3-N
<10%
Control C. trench Gradonie B. trench V-ditch
81.31 3.55 85.72 0.91 82.18 3.26 85.20 3.58 84.28 3.76
14.31 2.74 11.33 0.79 14.32 2.83 11.17 2.71 11.86 2.76
3.53 0.53 2.29 0.04 2.69 0.45 2.54 0.63 3.12 0.85
0.98 0.10 0.78 0.14 0.98 0.16 0.92 0.10 0.87 0.06
27.47 2.18 20.31 1.67 23.99 3.11 24.39 2.75 25.08 3.28
2.85 0.27 2.40 0.36 2.83 0.25 2.97 0.23 2.82 0.37
7.73 0.23 5.07 0.52 6.42 1.57 6.06 1.05 4.93 0.72
10–20%
Control C. trench Gradonie B. trench V-ditch
81.45 3.52 78.80 2.35 81.84 2.48 78.39 1.69 79.09 3.45
15.19 2.80 17.28 2.13 14.47 1.69 17.48 1.63 16.00 1.74
2.21 0.50 2.17 0.34 2.97 0.82 2.97 0.26 2.58 0.56
0.58 0.05 0.49 0.08 0.69 0.11 0.69 0.10 0.83 0.13
23.42 3.48 18.94 1.65 20.05 1.72 20.91 2.38 25.91 2.87
2.44 0.26 2.16 0.20 2.27 0.15 2.13 0.05 2.39 0.12
3.70 0.50 5.27 1.21 5.36 0.76 4.30 0.23 4.01 0.45
>20%
Control C. trench Gradonie B. trench V-ditch
84.15 1.88 83.08 2.07 83.40 2.70 81.31 2.79 87.71 1.37
11.44 1.25 12.47 1.49 11.95 1.82 12.59 1.75 8.51 0.90
3.12 0.25 3.45 0.50 2.77 0.51 4.13 0.74 2.31 0.31
0.69 0.13 0.86 0.12 0.62 0.15 0.85 0.16 0.59 0.17
19.13 2.44 25.66 3.00 22.07 3.21 17.50 1.53 17.33 1.57
2.50 0.26 2.64 0.13 2.45 0.23 2.41 0.29 2.17 0.16
2.41 0.30 2.32 0.25 2.63 0.48 3.29 0.68 3.10 0.64
3.361* 0.216NS 0.663NS
7.035** 0.342NS 0.722NS
1.492NS 0.595NS 1.248NS
5.568** 0.325NS 1.142NS
F values of two-way ANOVA Slope Treatment Slope treat
Soil composition (%)
Soil nutrient (mg kg1)
Slope
SOC
3.001NS 0.413NS 1.878NS
5.712** 0.276NS 0.709NS
PO4-P
21.898** 0.776NS 1.909NS
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
biomass was recorded after drying the above-mentioned biomass at 65 8C and presented in kg m2. Herbage water content was calculated based on the water loss during drying of the sample.
20% slope area. However, the variations in these soil variables among the treatments were not significant (P > 0.05) initially in June 2005.
2.4. Statistical analysis
3.2. Soil water dynamics
The data collected were statistically analyzed using SPSS statistical package version 8.0 for ‘‘Windows 2000’’. Soil variables, soil water depletion and plant survival were analyzed using a twoway ANOVA. Above-mentioned parameters were the dependent variables. Slope and rainwater harvesting treatments were the fixed factors. Since height, number of shoots, soil water content and herbage biomass (both fresh and dry) were determined at different times/years; the data were analyzed using a repeated measure ANOVA considering months/years as tests of withinsubjects effects and slope and treatments as tests of betweensubjects effects. Per cent increment in height and number of shoots were also analyzed using repeated measure ANOVA. Per cent soil water was square root transformed before statistical analysis to reduce heteroscenesdity (Sokal and Rohlf, 1981). To obtain the relations between plant growth, herbage production and soil water content, Pearson correlation coefficient were calculated. The least significant difference test was used to compare treatments at the P < 0.05 levels.
Multivariate analysis of soil water content (SWC) in 0–40 cm soil layer indicated significant (P < 0.01) variation among months (Table 2). SWC (average of 11 observations) was 18.32% in August 2006 and 1.22% in June 2006 (Fig. 1). Month slope interaction indicated lowest (P < 0.01) SWC in 10–20% slope throughout the year except in December 2005, when SWC was lowest in >20% slope. SWC was 26.30% and 22.52% greater in <10% and >20% slopes, respectively as compared to 6.53% in 10–20% slope. Duncan Multiple Range Test (DMRT) indicated greater (P < 0.05) SWC in <10% slope in most of the observations except in August 2006, November 2006, December 2006 and August 2007, when SWC was highest in >20% slope. SWC was lowest in the control plots (P < 0.05 in December 2005) and average increase in SWC was 12.25%, 21.29%, 16.82% and 15.31% in CT, G, BT and VD plots, respectively. SWC was highest in G and V plots during monsoon months of August and September, whereas it was highest in CT and BT plots in rest of the period. Slope treatment interactions were not significant (P > 0.05) but SWC was highest in BT/VD plots in <10%, G plots in 10–20% and BT/G plots in the >20% slopes.
3. Results 3.1. Soil characteristics Gravel (>2 mm size) concentration was highest (P < 0.05) in >20 slope and lowest in 10–20% slope area (Table 1). Silt + clay concentration did not vary within slopes. Sand content was 16.07% in 10–20% slope. Lowest (P < 0.05) sand content was in >20% slope. Soil pH ranged from 5.63 to 8.12 and it was significantly greater (P < 0.05) in <10% slope than in 10–20% slope area. Soil organic carbon (SOC) ranged from 0.49% to 0.98% being the highest (P < 0.01) in <10% slope. Ammonium (18.94–25.91 mg kg1) and PO4-P (2.31–7.73 mg kg1) concentration was lowest in >20% slope and highest in <10% slope area. NO3-N (2.13–2.97 mg kg1) concentration was highest (P < 0.05) in <10% and lowest in 10–
Table 2 Repeated measure ANOVA of soil water content (%, w/w) influenced by natural slopes and rainwater harvesting treatments under D. strictus plants in degraded hills of Aravalli, India. Tests of within-subjects effects
df
TSS
MSE
F value
P value
Month Month slope
10 20
27,527.71 441.36
2752.77 22.07
442.05 3.54
<0.001 <0.001
2 4 8
453.23 182.61 371.72
226.61 45.65 46.47
4.32 0.87 0.89
Tests of between-subjects effects Slope Treatment Slope treat
TSS: type III sum of squares, MS: mean square.
<0.05 NS NS
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Fig. 1. Soil water dynamics influenced by natural slopes and rain water harvesting treatments in degraded hills of Aravalli. C: control; CT: contour trench; G: gradonie; BT: box trench and VD: V-ditch. Error bars are SE of five replicate plots.
Soil water depletion was less in >20 slope area during December 2005 to June 2006 (P < 0.05). In <10% slope soil water depletion was less during August to December in both 2006 and 2007. However, soil water depletion was less in 10–20% slope area in December to June 2007 (Table 3). Among the treatments, greatest soil water depletion was in VD plots during December 2005 and June 2006 and in CT plot during August to December 2006. The depletions during December 2006 to June 2007 and during August 2007 to December 2007 were highest in G plots and control plots, respectively. 3.3. Plant survival Per cent survival of D. strictus seedlings was 84% in June 2008. Survival did not differ (P > 0.05) due to both slope and rainwater harvesting treatments. But the survival was highest (89.6%) in <10% slope and lowest (78.4%) in >20% slope area (Table 4). Among the treatments, survival was lowest (77.4%) in the control
plots and highest in VD plots. Survival of D. strictus was highest in control/CT plots in <10% and G/BT plots in 10–20% slopes. 3.4. Growth of D. strictus Repeated measure ANOVA indicated significant (P < 0.01) difference in height growth (Fig. 2, left panels) and number of shoots (Fig. 2, right panels) of D. strictus seedlings between the season/year. The growth was highest during July to December i.e., monsoon growth. Season slope interaction was significant (P < 0.05). Plants were taller (P < 0.01) in <10% slope than in the other slopes and plant height decreased with increase in slope gradient. Plants height did not differ (P > 0.05) in both December 2005 and June 2008 due to treatments. However, there was a change in growth pattern from shortest and tallest plants in CT and control plots in December 2005 to tallest and shortest plants in VD and control plots respectively, in June 2008. Thus highest growth was in VD ditch plots in June 2008 (Table 5). However, intermittent
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Table 3 Soil water usage (% of December in June and of August in December) by D. strictus plants and vegetation influence by natural slopes and rainwater harvesting treatments in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
RWH structure
Soil water depletion December 05–June 06
August 06–December 06
December 06–June 07
August 07–December 07
<10%
Control C. trench Gradonie B. trench V-ditch
73.60 2.28 80.93 6.61 86.38 3.97 84.13 2.61 84.37 5.15
62.23 5.60 69.75 7.02 65.73 5.39 73.53 2.33 72.78 2.84
64.98 9.17 76.28 2.79 61.84 13.24 60.47 6.85 66.65 7.39
82.47 3.35 79.10 3.70 75.63 3.55 67.25 3.08 67.13 3.38
10–20%
Control C. trench Gradonie B. trench V-ditch
68.71 17.42 76.42 5.39 63.42 8.32 69.16 10.11 83.58 6.96
77.46 3.62 75.42 4.96 80.16 4.82 73.36 4.88 77.18 6.00
50.46 10.23 74.12 5.08 75.78 4.55 56.06 9.07 51.83 17.84
82.48 4.95 74.13 6.52 82.38 2.12 80.59 2.77 78.79 1.73
>20%
Control C. trench Gradonie B. trench V-ditch
59.00 14.75 58.81 11.58 47.18 19.15 47.47 10.03 45.11 4.73
74.84 6.06 77.25 4.33 74.32 4.25 62.23 5.56 79.06 4.67
73.10 6.94 62.99 11.79 77.75 5.02 79.45 3.28 71.28 10.23
78.54 5.77 78.44 3.47 83.79 3.37 87.93 1.23 82.94 2.20
Two-way ANOVA Slope Treatment Slope treat
df 2 4 8
F value 12.109** 0.238NS 0.550NS
F value 3.213* 0.781NS 1.087NS
F value 1.936NS 0.667NS 1.064NS
F value 6.139** 0.979NS 2.309*
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
Table 4 Survival* of D. strictus seedlings affected by slope gradient and rainwater harvesting in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
Treatment
Mean
Control
Contour trench
Gradonie
Box trench
V-ditch
<10% 10–20% >20%
90.06 5.88 63.10 25.49 73.33 6.67
95.50 2.78 71.11 19.75 80.61 11.56
84.16 8.12 92.15 5.10 72.92 10.42
87.82 6.90 91.67 5.89 75.00 10.21
89.54 7.98 88.89 11.11 91.53 4.33
89.61 83.15 78.42
Mean
77.36
83.77
84.79
85.06
89.91
84.43
*
Two-way ANOVA did not indicate significant (P > 0.05) differences both due to treatments and slopes.
growth indicated significantly (P < 0.05) greater height growth in BT/VD plots in December 2006. Number of shoots was highest (P < 0.05) in 10–20% slope area, though it did not differ with that in <10% slope area. Lowest number of shoots was in >20% slope in all the observations (Table 5). In December 2005, the highest number of shoots was in G plots, but it was highest in CT plots in December 2006 and June 2007, and in BT and VD plots in December 2007 and June 2008, respectively. When compared with the data of December 2005, the increase in number of shoots was 3.4-, 2.1- and 1.6-fold in <10%, 10–20% and >20% slope, respectively (Fig. 2, right panels). The increase in number of shoots among treatments was 2.3–2.9-fold and the highest increase was in CT plots. 3.5. Plant growth increments Per cent increment in height and number of shoots varied (P < 0.05) between the years (Table 6). Height increment was highest (P < 0.05) in 2006–07 and the lowest in 2005–06. Year slope interactions were significant (P < 0.01) only for number of shoots. Per cent height increment did not differ due to both slope and rainwater harvesting treatments. However it was highest in <10% and lowest in >20% slope. The increment was lowest in control plots and highest in VD plots among the treatments. Per cent increment in number of shoots was highest in <10% slope and lowest in the >20% slope. The per cent increase in number of shoot was highest in CT plots (P < 0.05) in 2006–07.
3.6. Herbage production Multivariate analysis indicated lowest (P < 0.05) fresh (0.69 kg m2) and dry (0.31 kg m2) herbage production in 2005. Production increased to highest in 2007 (Table 7). Significant year slope interaction showed highest (P < 0.01) herbage in <10% slope in 2005 to >20% slope in 2007 through 10–20% slope in 2006. Year treatment interaction was also significant (P < 0.05) indicating highest herbage in VD plots in 2005 and 2007 and in G plots in 2006. Tests of between-subjects effects indicated nonsignificant variations in fresh herbage production between the slopes, but it differed among the treatments. However, DMRT indicated low (P < 0.05) herbage in 2005 to highest herbage production in 2007 in >20% slope. The reverse trend was observed in <10% slope area. Herbage production was highest (P < 0.05) in VD plots in 2005 and 2007, and in G plots in 2006. Dry herbage followed the trend similar to the fresh herbage except in 2005, when the dry herbage did not differ (P < 0.05) both due to slope and water harvesting treatments. When compared with those in <10% slope, fresh and dry herbage were lesser by 21.11% and 14.39% in 10–20% slope, and 34.56% and 29.19% in >20% slope area, respectively in 2005. In 2006, the reduction in respective herbage was only in >20% slope i.e., by 13.52% and 14.13%, whereas these herbage increased by 24.66% and 26.09% in 10–20% slope. Both fresh and dry herbage increased with slope in 2007, and the respective increases were 31.96% and 28.37% in 10–20% slope, and 42.42% and 48.35% in >20% slope. In rainwater harvesting treatments fresh and dry
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Fig. 2. Growth pattern of height and number of shoots of D. strictus influenced by natural slopes and rain water harvesting treatments in degraded Aravalli hills. C: control; CT: contour trench; G: gradonie; BT: box trench and VD: V-ditch. Error bars are SE of five replicate plots.
herbage production increased (16.18–42.77% in fresh and 26.20– 51.25% dry herbage in G plots and VD plots, respectively) over the control. All the treatments indicated greater fresh (1.40-fold in BT to 2.14-fold in G plots) and dry (1.38–2.15-fold) herbage than in the control plots in 2006. In 2007, G plots (by 30.68% and 36.13%) and CT plots (by 15.62% and 14.63% fresh and dry herbage, respectively) indicated lesser herbage production; whereas 1.64– 4.08-fold increase in fresh and 1.69–4.10-fold increase in dry herbage were observed in BT and VD plots, respectively, than those in the control plots. Slope treatment interactions were also significant and the production was highest in BT plots in <10% slope and in VD plots in 10–20% and >20% slope areas.
3.7. Correlation in different variables Slope gradient was negatively correlated with survival (r = 0.265, P < 0.05, n = 57), plant height (r = 0.369, P < 0.01, n = 63) and number of shoots (r = 0.478, P < 0.01) of D. strictus, SWC in December 2005 (r = 0.615, P < 0.01, n = 75) and June 2007(r = 0.267, P < 0.05), per cent increment in number of shoots (r = 0.463, P < 0.01) and soil water usage during December 2005 to June 2006 (r = 0.393, P < 0.01). However, slope was positively correlated with soil water usage during August to December 2007 (r = 0.258, P < 0.05). Gravel content was positively related with SWC in December 2005 (r = 0.227, P < 0.05), August 2006 (r = 0.251,
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Table 5 Average height and number of shoots of D. strictus seedlings under the influence of natural slopes and rainwater harvesting treatments in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
RWH structure
Height (cm) September 2005
Number of shoots (Nos.) June 2008
September 2005
June 2008
<10%
Control C. trench Gradonie B. trench V-ditch
60.39 2.94 62.92 4.47 53.93 + 8.76 57.58 7.89 62.20 7.08
300.12 + 19.89 393.50 + 21.96 270.25 + 33.39 357.56 + 15.96 372.39 + 23.87
1.12 + 0.07 1.04 + 0.02 1.13 + 0.13 1.18 + 0.08 1.14 + 0.12
3.79 + 0.29 3.99 + 0.10 3.01 + 0.45 3.76 + 0.15 4.30 + 0.56
10–20%
Control C. trench Gradonie B. trench V-ditch
69.39 13.05 52.38 2.24 58.97 + 3.97 63.99 + 9.22 58.70 + 4.04
270.67 + 25.75 286.62 + 32.39 268.26 + 35.92 354.49 + 21.52 297.11 + 58.10
1.43 + 0.23 1.52 + 0.22 1.80 + 0.14 1.90 + 0.32 1.84 + 0.25
3.25 + 0.51 3.82 + 0.44 3.93 + 0.71 4.18 + 0.21 3.72 + 0.15
>20%
Control C. trench Gradonie B. trench V-ditch
61.50 + 3.50 66.60 + 9.15 55.93 + 3.93 51.25 + 2.91 61.95 + 3.54
182.50 + 42.65 302.70 + 02.87 281.22 + 12.05 261.70 + 45.72 309.85 + 49.50
1.10 + 0.11 1.10 + 0.10 1.58 + 0.36 1.22 + 0.17 1.10 + 0.06
2.42 + 0.23 2.59 + 0.54 3.12 + 0.18 2.72 + 0.24 2.82 + 0.30
df MSE Repeated measure ANOVA (tests of within-subjects effects) Season 5 554,176.1 Season slope 10 5,772.2 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
F value
MSE
F value
486.41** 5.07**
35.96 0.84
226.98** 5.28**
8.00** 1.39NS 1.84NS
50,074.14 8,730.25 11,519.06
10.69** 0.24NS 0.65NS
15.53 0.355 0.938
NS: not- significant. ** Significant at P < 0.01.
Table 6 Average annual increments in height and number of shoots of D. strictus plants under the influence of slopes and rainwater harvesting treatments. Values are mean SE of five replicates. Slope
RWH structure
Height increment (%) 2005–06
Shoot increment (%)
2006–07
2007–08
2005–06
2006–07
2007–08
<10%
Control C. trench Gradonie B. trench V-ditch
26.27 9.60 22.36 10.29 25.36 8.92 43.78 18.41 12.80 5.97
163.99 43.22 204.81 41.35 178.42 46.57 183.59 26.04 239.19 46.42
59.22 12.38 76.90 07.97 43.99 8.08 66.92 12.12 67.12 08.01
93.49 2.22 48.00 6.52 39.17 16.69 81.43 11.43 46.34 27.17
11.52 4.75 88.63 15.41 53.29 13.42 18.64 6.01 66.01 8.98
59.47 17.41 41.68 11.69 39.99 06.53 52.20 09.40 65.61 18.53
10–20%
Control C. trench Gradonie B. trench V-ditch
19.27 3.15 44.46 12.35 12.71 2.65 27.05 9.11 17.21 4.61
196.93 79.53 166.09 53.28 152.23 43.07 270.96 98.79 210.24 58.61
20.80 .800 57.31 16.36 65.48 06.17 34.50 13.28 57.44 17.90
3.70 3.70 18.50 8.500 10.73 3.77 5.00 5.00 11.86 5.13
43.33 26.66 70.12 20.37 25.26 6.42 57.80 24.52 39.48 20.28
33.87 23.28 46.93 17.59 52.20 15.23 48.14 19.82 47.17 09.20
>20%
Control C. trench Gradonie B. trench V-ditch
5.57 2.12 23.70 6.64 19.36 12.19 22.82 4.97 11.22 1.41
108.57 51.43 176.56 45.19 161.92 6.54 167.35 16.97 195.44 62.05
70.90 15.45 61.30 23.45 65.00 9.64 47.10 10.86 57.09 20.04
33.33 33.33 2.38 2.38 7.91 5.90 1.00 .00 2.78 2.78
57.50 42.50 35.89 15.39 44.92 23.96 47.98 28.38 26.83 13.78
23.10 14.40 62.48 08.34 45.92 22.94 57.59 14.41 101.55 28.10
df Repeated measure ANOVA (tests of within-subjects effects) Year 2 Year slope 4 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
MSE
F value **
MSE
365,575.02 1,885.75
88.99 0.46NS
8528.85 5614.94
3,011.62 2,325.88 1,001.88
1.17NS 0.91NS 0.39NS
751.73 422.53 309.73
F value 7.85** 5.17** 12.60** 0.79NS 0.84NS
NS: not- significant. ** Significant at P < 0.01.
P < 0.05), November 2006 (r = 0.293, P < 0.05) and April 2007 (r = 0.349, P < 0.01) and December 2007 (r = 0.251, P < 0.05). Sand content was negatively correlated (r = 0.238, P < 0.05) with SWC in most of the observations. Plant survival was positively related with SWC in December 2005 (r = 0.272, P < 0.05) and September 2007 (r = 0.310, P < 0.05), whereas plant height of December 2006 was
negatively related with SWC in August and September 2006 (r = 0.296, P < 0.05) and fresh herbage production (r = 0.256, P < 0.05). SWC of December 2005 was positively related with herbage production (0.282, P < 0.05). Per cent increment in number of shoots of D. strictus in June 2006 was positively (r = 0.330, P < 0.01) related with soil water depletion during December 2005 to June 2006.
G. Singh / Forest Ecology and Management 258 (2009) 2519–2528
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Table 7 Year-wise average aboveground fresh and dry herbage production under the influence of natural slope and rainwater harvesting treatments. Values are mean SE of five replicates. Slope
RWH
Aboveground mass (kg m2) 2006
Dry biomass (kg m2)
Treatment
2005
<10%
Control C. trench Gradonie B. trench V-ditch
0.87 0.13 0.86 0.03 0.83 0.05 0.71 0.08 0.85 0.09
0.51 0.10 0.53 0.09 0.70 0.11 0.96 0.05 0.70 0.09
2007 0.55 0.19 0.34 0.10 0.54 0.12 1.25 0.24 1.03 0.32
0.34 0.06 0.37 0.02 0.38 0.03 0.32 0.05 0.40 0.02
0.24 0.04 0.28 0.05 0.34 0.05 0.34 0.03 0.33 0.04
0.27 0.09 0.17 0.06 0.26 0.06 0.70 0.23 0.49 0.16
10–20%
Control C. trench Gradonie B. trench V-ditch
0.50 0.04 0.71 0.23 0.91 0.35 0.43 0.03 0.78 0.20
0.48 0.16 0.82 0.24 1.23 0.37 0.61 0.08 0.78 0.13
0.47 0.15 0.45 0.11 0.36 0.03 0.83 0.32 2.80 0.23
0.27 0.02 0.33 0.11 0.42 0.21 0.20 0.01 0.36 0.10
0.24 0.07 0.43 0.13 0.62 0.19 0.29 0.03 0.37 0.07
0.24 0.07 0.22 0.05 0.17 0.02 0.40 0.16 1.41 0.13
>20%
Control C. trench Gradonie B. trench V-ditch
0.45 0.05 0.60 0.23 0.38 0.02 0.46 0.03 0.88 0.28
0.26 0.05 0.64 0.15 0.74 0.21 0.45 0.06 0.62 0.16
0.67 0.24 0.63 0.25 0.27 0.03 0.68 0.11 3.03 0.34
0.19 0.02 0.28 0.11 0.18 0.02 0.21 0.02 0.42 0.14
0.14 0.03 0.31 0.07 0.37 0.11 0.22 0.03 0.28 0.07
0.35 0.13 0.35 0.12 0.12 0.02 0.35 0.05 1.64 0.18
df MSE Repeated measure ANOVA (tests of within-subjects effects) Year 2 1,661,134.85 Year slope 4 703,039.81 Year treatment 8 2,941,884.56 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
173,795.93 4,093,924.12 697,497.99
F value 13.54** 5.73** 23.98**
0.617NS 14.530** 2.475*
2005
2006
2007
MSE 645,559.91 169,749.24 824,773.58
41,836.68 1,024,556.85 214,199.72
F value 19.683** 5.176** 25.147**
0.588NS 14.411** 3.013**
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
4. Discussion 4.1. Soil water dynamics Continuous rain during July and August increased SWC in >20% slope by facilitating infiltration and its storage in soil profiles. But soil water use by the growing vegetation, water percolation into deeper soil profile and increased evaporative demand with increase in temperature resulted in a decrease in SWC to lowest value in June. Thus water utilization of different plant species like deep-rooting shrubs/trees and shallow-rooting annual plants influence the spatial distribution of water inside the soil profile resulting in changes in composition, coverage and biomass of vegetation (Li et al., 2004). Despite of greater soil content (P < 0.05) less SWC in 10–20% slope throughout the year than in the other slopes was due to greater (P < 0.05) sand content, which reduced soil water retention. But highest SWC in <10% slope in most of the observations was probably due to less run-off loss (un-published data) and greater infiltration of water into soil. Relatively greater SWC in >20% slope in June and November 2006 and April 2007 was due to greater per cent of gravel/stone present on soil surface that facilitated water infiltration during rain through surface roughness and reduced evaporation loss during water stress. The study of Danalatos et al. (1995) showed that under conditions of moderate water tress, water conservation is generally greater in stony soil and the soil with large cobbles on surface conserved the most water enhancing total dry matter yield of rainfed wheat. The observations of Van Wesemael et al. (1996) and Katra et al. (2008) also showed that rock fragments on dry hill slopes affect rainwater redistribution and overland flow, where the topsoil moisture content under rock fragments was higher over time than that of bare soil areas. However, difference in SWC between the slopes might also be due to variations in soil texture and silt + clay content, which was greater in >20% slope influencing vegetation
cover and soil water status as in the observations of Singh et al. (1998). Relatively greater decrease in SWC in >20% slope from highest in August to lowest in December showed faster depletion of soil water in higher slopes and was shown by a positive relation of slope with soil water depletion (r = 0.258, P < 0.05). However, such depletion in soil water was also due to relatively greater growth and productivity of vegetation (Singh and Rathod, 2004). Absence of rainwater harvesting structures was the reason for low SWC in control plots, but the impact of growing D. strictus plants and the herbage cannot be ruled out. Increase in SWC by 12.25–21.29% in treated area suggested the beneficial effects of rainwater harvesting structures in improving soil water status. Highest SWC in G plots was due to its effects in conserving run-off water by reducing water velocity and distributing the water into the soil profile particularly in 10–20% slope. Despite of larger storage capacity per plot, low SWC in CT and BT plots during monsoon was probably due to their influence on deep water storage that remained available for longer period of time indicated by greater SWC in June. Highest SWC in G and V plots during rainy season that depleted at faster rate after monsoon as compared to that in CT and BT plots was due to surface distribution of soil water facilitating herbage growth and production in former than in latter treatments. Lesser soil water depletion in CT and BT plots provided relatively more water for its usage in spring growth. However, soil water depletion is also related with root distribution of plants/ vegetation in different soil layers and utilization of soil water by the growing vegetation (Givnish, 1986; Singh et al., 1998). 4.2. Survival and growth of seedlings Availability of soil resources and its gradient affected survival and growth of planted seedlings of D. strictus. Highest survival in <10% and lowest survival in >20% slope was related with soil water content, which decreased with increase in slope gradient
G. Singh / Forest Ecology and Management 258 (2009) 2519–2528
particularly during summer affecting the survival. Lowest plant survival in the control plot was due to absence of rainwater harvesting structures and thus low SWC. Thus adoption of rainwater harvesting influenced seedling survival positively. Highest survival in VD plots showed its beneficial effects on water storage in top soil layer available to the plant roots. However, relatively greater survival of D. strictus plants in 10–20% slope in G and BT treatments showed the suitability of these microcatchments in this slope. Highest (P < 0.05) growth during monsoon (June to December) as compared to that during January to June was due to rainfall and soil water availability (Fig. 2) influencing nutrient mobility and utilization (Marion and Everett, 2006). This is indicated by highest (P < 0.09) per cent increment in height and number of shoot in 2006–07 during which the rainfall was highest. Thus decrease in plant height (r = 0.280, P < 0.05, n = 63) and number of shoots (r = 0.396, P < 0.01) with slope was associated with decrease in concentration of SWC, SOC, NH4-N, NO3-N and PO4-P in higher slopes. Highest concentration of these soil variables in <10% slope enhanced plants height by 5.8-fold as compared to 4.8-fold in 10–20% and 4.9-fold in >20% slope than those in December 2005. Smaller plants due to less fertile soils have also been observed in Ghanian tropical rainforest (Baker et al., 2003). Highest growth increments in <10% slope area and its positive relation with shoots increment in June 2006 (r = 0.509, P < 0.01) and soil water depletion (r = 0.333, P < 0.01) during December 2005 to June 2006 suggesting the influence of soil water availability on growth of D. strictus plants. Relatively greater number of shoots in 10–20% slope was probably due to greater amount of water received down slope of the plots (D. strictus planted area) enhancing surface soil water availability and thus shoot multiplication. Tsui et al. (2004) and Yong et al. (2006) also observed that spatial redistribution of surface run-off resulting in higher nutrients and soil water availability on lower slope positions and contributed to the vegetation growth. About 1.6–3.4-fold increase in number of shoot was also related with soil water availability. However, greater increase in number of shoots in CT plots (2.9-fold) suggested utilization of water stored in deep soil layers after monsoon indicated by greater (P < 0.05) shoots increment in CT in 2006–07 and its relation with soil water usage during August 2006 to June 2007. The study of Gupta (1995) indicated higher growth of Azadirachta indica in ring-pit micro-catchment that harvested greater quantity of rain water influencing deep storage and its utilization for plant growth throughout the year. 4.3. Herbage production Altitudinal distribution pattern of the plant communities on the hill and the aspect is closely related to soil resource availability, erosion feature, and to some extent plant attribute (GuerreroCampo et al., 1999). Increased herbage production from 2005 to 2007 showed improvement in soil resource status with time. Despite of lesser rainfall in 2007 as compared to that in 2006, greater fresh and dry herbage production in 2007 was due to soil improvement influencing soil water and nutrient availability. Initial pattern of highest productivity in <10% slope in 2005 was due to appropriate distribution of water as compared to that in steep slope and thus available for vegetation growth initially. It was also due to less competition for soil resources by the newly planted seedlings in 2005 (Ainalis and Tsiouvaras, 1998.) that increased with age and size of the plant affecting vegetation growth in later years. Thus significant (P < 0.05) increase in herbage production in 10–20% and >20% slope areas in 2006 and 2007 suggested the effect of water harvesting, which was greater in higher slopes as compared to that in <10% slope area. Greater water availability in down slope area of the plots through run-off
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and/or subsurface drainage of the soil stored water during monsoon might also have influenced herbage growth and production in higher slopes. Xu et al. (2006) observed significant correlation between biomass of Astragalus adsurgens and Lespedeza davurica and total precipitation and thus soil water availability. Despite of lowest SWC, greater herbage production in 10–20% slope area suggests that profiles with the lowest soil water content also had greater herbage growth and was probably due to utilization of deeper soil water indicated by highest (73.50%) soil water usage during August to December 2006 in this slope (Liu and Stutzel, 2004). Thus herbage production exhibited positive (P < 0.05) response to soil water usage indicating an inverse relationship between aboveground production and soil water content during the growth period. Singh et al. (1998) also observed highest total vegetation cover on the mid slope position and was greatest on the clay loam site, which was the wettest in terms of soil water. About 2.40- and 2.52-fold greater (P < 0.05) fresh and dry herbage production in VD plots as compared to the control was due to greater water conservation and its distribution in top soil layer making the water available for herbage growth (McMaster and Wilhelm, 1997). De Abelleyra et al. (2008) also recorded an increase in growth and biomass of Cynodon dactylon with increase in soil water availability. The order of treatment effects in increasing fresh and dry herbage production is C < CT < G < BT < VD. However, lesser herbage production in BT in 2005 and in G and CT plots in 2007 as compared to that in the control was due to less water availability in surface soil layer when rainfall is average or near optimal. But significantly higher rainfall increased soil water availability in upper soil layer thus increasing herbage production to highest in G plots in 2006. However, significant slope treatment interaction indicated highest herbage production in BT plots in <10% and in VD plots in 10–20% and >20% slopes. The second order treatments were VD in <10%, G in 10–20% and CT in >20% slopes. 5. Conclusions and recommendations There was a large variation in soil water content annually with highest in August to lowest in June. Rainwater micro-catchments and their efficiency in soil water storage in different soil layers influenced growth of D. strictus and herbage production. Relatively greater water and nutrients availability in <10% slope resulted in greater initial growth than in the higher slopes. Low nutrient availability and greater herbage growth adversely affected the growth of D. strictus in higher slopes. Increase in herbage production in higher slopes from 2005 to 2007 is an indicator of improved soil water status and nutrient availability during growth period. Rainwater harvesting enhanced herbage production significantly and its facilitative effects was more under Box trench in <10% and V-ditch in 10–20% and >20% slope area by increasing water availability in surface soil layer. Contour trench/Gradonie reduced surface water flow and probably facilitated water infiltration into deeper soil profile and could be accessed by woody perennials. Thus V-ditch and Box trench facilitated water distribution in upper soil layers for vegetation growth, whereas Contour trench facilitated water storage in deep soil profile that was utilised for the growth of D. strictus in non-monsoon season and thus facilitated spring growth. Gradonie structure was beneficial in influencing both growth of herbage and woody perennials only during high rainfall years particularly in 10–20% slope area. These rainwater harvesting structures behaved differently in facilitating soil water and nutrient availability among the slope and thus can be replicated accordingly in rehabilitation of the degraded hills depending upon the need i.e., herbage and woody perennials.
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Acknowledgements I wish to express my sincere thanks to the Director Arid Forest Research Institute, Jodhpur for providing the facilities to carry out research. Financial support from Forest Department, Government of Rajasthan and Meteorological Department, Banswara for providing climatic data are gratefully acknowledged. The assistance provided by all the research staff of Forest Ecology Division, is gratefully acknowledged. References Ainalis, A., Tsiouvaras, C., 1998. Forage production of woody fodder species and herbaceous vegetation in a silvopastoral system in northern Greece. Agroforestry Systems 42, 1–11. Baker, T.R., Burslem, D.F.R.P., Swaine, M.D., 2003. Associations between tree growth, soil fertility and water availability at local and regional scales in Ghanaian tropical rain forest. Journal of Tropical Ecology 19, 109–125. Barron, J., Rockstro¨m, J., Gichuki, F., Hatibu, N., 2003. Dry spell analysis and maize yields for two semi-arid locations in East Africa. Agricultural and Forest Meteorology 117, 23–37. Ben-Zhi, Z., Yi, F.M., Jhong, X.J., Sheng, Y.X., Cai, L.Z., 2005. Ecological function of bamboo forest research and application. Journal of Forestry Research 16, 143– 147. Chakraborty, D., 1988. Utilization of bamboo as raw material in the handicraft industries in Tripura. Indian Forester 114, 635–636. Champion, H.G., Seth, S.K., 1968. A Revised Survey of the Forest Types of India. The Manager of Publications, New Delhi, India, p. 404. Danalatos, N.G., Kosmas, C.S., Moustakas, N.C., Assoglou, N., 1995. Rock fragments. II. Their impact on soil physical properties and biomass production under Mediterranean conditions. Soil Use and Management 11, 145–154. De Abelleyra, D., Verdu, A.M.C., Kruk, B.C., Satorre, E.H., 2008. Soil water availability affects green area and biomass growth of Cynodon dactylon. Weed Research 48, 248–256. Givnish, T.J., 1986. On the Economy of Plant Form and Function. Cambridge University Press, New York, p. 717. Gowing, J.W., Mahoo, H.F., Mzirai, O.B., Hatibu, N., 1999. Review of rainwater harvesting technique and their evidence for their use in semi-arid Tanzania. Tanzania Journal of Agriculture Science 2, 171–180. Guerrero-Campo, J., Alberto, F., Hodgson, J., Garcı´a-Ruiz, J.M., Montserrat-Martı´, G., 1999. Plant community patterns in a gypsum area of NE Spain. I. Interactions with topographic factors and soil erosion. Journal of Arid Environment 41, 401– 410. Gupta, G.N., 1995. Rain water management for tree planting in Indian desert. Journal of Arid Environment 31, 219–235. Gregory, P.J., 1989. Water-use-efficiency of crops in the semi-arid tropics. In: Soil, Crop and Water Management in the Sudano-Sahelian Zone, ICRISAT, Hyderbad, India, pp. 85–98. Hatibu, N., Mutabazi, K., Senkondo, E.M., Msangi, A.S.K., 2006. Economics of rainwater harvesting for crop enterprises in semi-arid areas of East Africa. Agriculture Water Management 80, 74–86. Jackson, M.L., 1973. Soil Chemical Analysis. Prentice Hall of India Private Ltd., New Delhi, India, p. 497.
Katra, I., Lavee, H., Sarah, P., 2008. The effect of rock fragment size and position on topsoil moisture on arid and semi-arid hillslopes. Catena 72, 49–55. Li, Z., Kobayashi, M., 2004. Plantation future of bamboo in China. Journal of Forestry Research 15, 233–242. Li, W.Q., Xiao-Jing, L., Khan, M.A., Gul, B., 2008. Relationship between soil characteristics and halophytic vegetation in coastal region of north China. Pakistan Journal of Botany 40, 1081–1090. Li, X.R., Ma, F.Y., Xiao, H.L., Wang, X.P., Kim, K.C., 2004. Long-term effects of revegetation on soil water content of sand dunes in arid region of Northern China. Journal of Arid Environment 57, 1–16. Liu, F., Stutzel, H., 2004. Biomass partitioning, specific leaf area, and water use efficiency of vegetable amaranth (Amaranthus spp.) in response to drought stress. Scientia Horticulturae 102, 15–27. Liu, J., Linderman, M., Ouyang, Z., An, L., Yang, J., Zhang, H., 2001. Ecological degradation in protected areas: the case of wolong nature reserve for giant pandas. Science 292, 98–101. McMaster, G.S., Wilhelm, W.W., 1997. Conservation compliance credit for winter wheat fall biomass production and implications for grain yield. Journal of soil and Water Conservation 52, 358–363. Marion, G.M., Everett, K.R., 2006. The effect of nutrient and water additions on elemental mobility through small tundra watersheds. Ecography 12, 317–323. Singh, A.N., Singh, J.S., 1999. Biomass, net primary production and impact of bamboo plantation on soil redevelopment in a dry tropical region. Forest Ecology and Management 119, 195–207. Singh, G., 2008. Gaining momentum: growing Jatropha curcus with rainwater harvesting in degraded hillocks of Aravalli. Wasteland News 23, 17–19. Singh, G., Bala, N., Kumar, P., Baloach, S.R., Rathod, T.R., Limba, N.K., 2007. Flood disaster in western Rajasthan: disadvantages and the benefits. In: State of Art Report—Floods of August 2006 in Rajasthan: Causes: Magnitude and Strategies. INCOH Publication No. INCOH/SAR 29/2007, National Institute of Hydrology, Roorki, India, pp. 52–59. Singh, G., Rathod, T.R., 2004. Lysimetric study of soil water utilization by tree seedlings in arid environment. In: National Workshop on ‘Forest and Water Conservation: Mythes and Realities’ held at FRI, Dehradun on June 8–10. pp. 54–56. Singh, J.S., Milchunas, D.G., Lauenroth, W.K., 1998. Soil water dynamics and vegetation patterns in a semiarid grassland. Plant Ecology 134, 77–89. Sokal, R.R., Rohlf, P.J., 1981. Biometery, 2nd edition. W.H. Freeman, New York, p. 859. Tsui, C.C., Zueng-Sang Chen, Z.S., Hsieh, C.F., 2004. Relationships between soil properties and slope position in a lowland rain forest of southern Taiwan. Geoderma 123, 131–142. Van Wesemael, B., Poesen, J., Kosmas, C.S., Danalatos, N.G., Nachtergaele, J., 1996. Evaporation from cultivated soils containing rock fragments. Journal of Hydrology 182, 62–82. Venketeswarlu, J., 1987. Efficient resource management systems for drylands in India. Advances in Soil Science 7, 209–216. Vohland, K., Barry, B., 2009. A review of in situ rainwater harvesting (RWH) practices modifying landscape functions in African drylands. Agriculture, Ecosystem & Environment 134, 119–127. Wezel, A., 2006. Variation of soil and site parameters on extensively and intensively grazed hillslopes in semiarid Cuba. Geoderma 134, 106–109. Xu, B.P., Gichuki, P., Shan, L., Li, F.M., 2006. Aboveground biomass production and soil water dynamics of four leguminous forages in semiarid region, northwest China. South African Journal of Botany 72, 507–516. Yong, L., Wang, C.W., Hongliang, T., 2006. Research advances in nutrient runoff on sloping land in watersheds. Aquatic Ecosystem Health & Management 9, 27–32.
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Soil water dynamics, growth of Dendrocalamus strictus and herbage productivity influenced by rainwater harvesting in Aravalli hills of Rajasthan G. Singh * Division of Forest Ecology, Arid Forest Research Institute, New Pali Road, Jodhpur 342005, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 November 2008 Received in revised form 31 August 2009 Accepted 4 September 2009
Degraded Aravalli hills in western India require rehabilitation through resource conservation and afforestation for meeting the biomass needs of resource-poor tribes of the region. Rainwater harvesting treatments i.e., control, Contour trench (CT), Gradonie (G), Box trench (BT) and V-ditch (VD) were prepared in <10%, 10–20% and >20% slopes categories and Dendrocalamus strictus L. seedlings were planted in August 2005 with a view to conserve soil and water and increase the productivity of the hills. Soil water content (SWC), survival and height of D. strictus plants were highest (P < 0.05) in <10% slope and all these variables decreased with increase in slope. SWC increased by 27.45% and 25.68% in <10% and >20% slopes, respectively than in 10–20% slope. From lowest in control SWC increased by 11.95%, 20.21%, 17.61% and 11.49% in CT, G, BT and VD treatments, respectively. Growth variables were highest in VD plots but the increase in shoot number was highest (2.9-fold) in CT plots. Increase in effects of rainwater harvesting with time indicated by a change in production pattern from highest (P < 0.05) fresh and dry herbage in <10% slope in 2005 to 10–20% slope (24.66% and 26.09%) in 2006 and >20% slope (42.42% and 48.35%, respectively) in 2007. The increase in herbage was 1.17–2.40-fold in fresh and 1.20– 2.52-fold in dry herbage over control. Highest (P < 0.01) production was in V-ditch plots. The treatments order for herbage production was C < CT < G < BT < VD. But the production was highest in BT in <10% and in V-ditch plots in 10–20 and >20% slopes. Conclusively, soil water status is affected by natural slope, stony soil surface and rainwater harvesting structures influencing seedling growth and herbage production. Box trench and V-ditch enhanced surface soil water facilitating herbage growth, whereas contour trench facilitated deep soil water storage, which was made available to the plants after monsoon. Thus rainwater harvesting practices enhanced vegetation cover and productivity of the degraded hills and can be replicated to conserve soil resource and increase biomass for rural poor of the region. ß 2009 Elsevier B.V. All rights reserved.
Keywords: Afforestation Degraded Aravalli Site productivity Soil and water conservation
1. Introduction Over-exploitation and unsustained vegetation removal induced land degradation in Aravalli hills in India. Very limited numbers of vegetations are growing though many of the hillocks are exposed and devoid of vegetation. Rehabilitation of these degraded hills is an essential requisite for eco-environmental improvement and to meet the basic needs of fuel wood and fodder in the region. However, the establishment of vegetation is quite difficult due to inadequate availability of soil moisture (Li et al., 2008) in these degraded hills. Low and irregular rainfall is the most critical factor to plant growth (Barron et al., 2003). A small fraction of the rainwater reaches and remains in the soil long enough to be useful
* Tel.: +91 291 2729150; fax: +91 291 2722764. E-mail addresses: [email protected], [email protected]. 0378-1127/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2009.09.008
for plants and animals. More than 70% of the rainfall is lost as evaporation, or run-off that causes erosion and flooding downstream (Singh et al., 2007). Thus, both floods and droughts and their detrimental consequences are result of this wastage of valuable rainwater. Because the water and soil resource is finite, the only option for increasing biomass production is to increase the water productivity i.e., the water use efficiency (WUE), by producing more biomass per unit of water (Gregory, 1989). Adoption of improved water conservation and harvesting technologies contributes to increase in groundwater recharge, soil nutrients and biomass production and supports a higher number of plants (Gowing et al., 1999; Vohland and Barry, 2009). The principle requirement is the adequate soil and water management techniques that guarantee a maximum of infiltration and transpiration for increased biomass production in intensively grazed and degraded hills of dry areas (Venketeswarlu, 1987; Hatibu et al., 2006; Wezel, 2006). Many rainwater harvesting
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structures are in use to conserve soil and water in the hilly tracts depending upon the slope gradient but only few structures have been quantified in terms of growth and productivity of forestry species (Gupta, 1995). Bamboo is a group of plants belonging to family Gramineae and subfamily Bambusoideae. Being an important forest type bamboo forest occurs in subtropical and tropical areas with a total area of 22 million ha worldwide (Liu et al., 2001). Importance of this genus is such that total forest areas in many countries have drastically declined, whereas the area under bamboo forest has increased (Ben-Zhi et al., 2005). Because of its enormous potential for alleviating many economic and environmental problems bamboo is an ideal economic investment (Chakraborty, 1988; Singh and Singh, 1999). There are approximately 1500 species under 87 genera of Bamboo worldwide (Li and Kobayashi, 2004). Existence of bamboos is edaphic climax type in dry deciduous forest in the form of ‘Dry Bamboo Brakes’ (3/2S1 and 5/E9) in western India (Champion and Seth, 1968). Out of 22 species of bamboos reported in this region Bambusa arundinacea and Dendrocalamus strictus are dominant species. D. strictus is more suited with multiple uses in this dry region. However, its occurrence along streams and drainage lines indicated relatively greater water requirement of this species. The increase in water yield through micro-catchment rainwater harvesting may enhance growth and productivity of this species along with herbage production and rehabilitation of the degraded hills. Thus the objective of this study was to compare the impacts of different rainwater harvesting structures on soil water storage, growth of D. strictus and productivity of associated vegetation for further replication to meet the fuel and fodder requirements of the local inhabitants. Resource conservations and rehabilitation of these degraded hills are the ultimate objective.
2.2. Experimental design The experiment was laid in complete randomized block design with five replicate plots. Seventy-five plots of 700 m2 area were laid in <10%, 10–20% and >20% slope areas with five rainwater harvesting treatments. Each plot was separated by individual boundary of trench (2025 cm2 cross-section area, 45 cm 45 cm) cum bund to avoid water intrusion from other areas or plots and had a rainwater harvesting structure of 30 running meter length (Singh, 2008) except the control plots. Contour trenches (CT) were excavated at different contour levels to conserve the run-off water and are 2025 square cm in cross-section (45 cm 45 cm). Box trenches (BTs) were intermittent trenches of 2 m length (15 numbers) with cross-section area similar to that in the CT. Vditches (V) are across the contour and 1800 cm2 cross-section area [(120 W 30 H)/2], where W is width and H is height of the cut. The vertical (height of 30 cm) cut was downside of the slope. Gradonie ditches (G) also have 1800 cm2 cross-section area [(30 H 120 W)/2] but the vertical cut was upside of the slope with a view to reduce velocity of surface run-off water. In all the structure, the excavated soil was heaped towards the down slope. The control plots are without rain water harvesting structures (i.e., with boundary bund only). Each plot was planted with 35 numbers of seedlings of different tree species in August 2005 with an average population of 6 clumps for D. strictus L. Vegetatively raised seedlings of D. strictus of about 40 cm height were planted in a pit size of 45 cm 45 cm 45 cm and towards the lower one third of the plot. A small microcatchment of 1600 cm2 area (micro-gradonie with a catchment towards up slope) was also prepared around each planted seedling. Thus, 75 plots with five rainwater harvesting treatments were distributed in three slopes (3 slopes five treatments five replications).
2. Materials and methods 2.3. Observations recording 2.1. Site characteristics The study was carried out along hills with pediment covering an area of about 17 ha, which spread over 238250 27.000 N to 238250 43.400 N latitudes and 748240 00.500 E to 748240 23.100 E longitude. Altitude of the area ranged between 248 m and 320 m msl. The site is located 17 km south-west of district head quarter Banswara (238320 28.200 N and 748260 30.300 E). Banswara is situated in the southern part of Rajasthan, and surrounded in the north by Udaipur, north-east by Chittorgarh and west by Dungarpur districts. It is bounded in east and south-east by Madhya Pradesh and in south-west by Gujarat states. Air temperature varied from 4 8C in January to 42 8C in May. The mean minimum and maximum annual temperature is about 15 8C and 33 8C, respectively. Average annual rainfall from 1993 to 2004 was 960 mm with 54 numbers of rainy days. However, years 2005, 2006 and 2007 received 990 mm, 2266 mm and 1391 mm rainfall in 42, 63 and 44 events, respectively. Hillslopes ranged from 3% to 53% in the study area. These slopes were categorized in to steep (>208), medium (10–20%) and gentle (<10%) slopes. The surface of steep slopes was covered with crystalline gravels and pebbles of varying size with randomly growing Lantana camera. Medium slope had light textured sandy loam soils of shallow depth and was mostly covered by Prosopis juliflora with occasional L. camera. Soils in gentle slope were loamy to clay loam in texture and shallow to deep in soil depth. The gentle slope area was dominantly covered by P. juliflora and L. camera bushes. Soil pH was acidic to slightly alkaline in reaction (6.34– 7.02). Average SOC, available NH4-N, NO3-N and PO4-P of the site were 0.760%, 22.15 mg kg1, 2.50 mg kg1 and 4.51 mg kg1, respectively.
Because of low soil depth in steep slope area (maximum 40 cm) soil samples were collected from 0–40 cm soil layer to maintain similarity in all the slopes. Soil samples for texture and initial nutrient analysis were collected in June 2005, dried and passed to a 2 mm sieve for separation of gravel and soil. Soil pH and soil organic carbon (SOC) was determined using standard procedures (Jackson, 1973). Available nitrogen (NH4-N and NO3-N) was determined after 0.5 M K2SO4 extraction using uv-vis-spectrophotometer Model Shimadzu-1650PC. Extractable phosphorus was determined by the Olson’s extraction method (Jackson, 1973) using above-mentioned spectrophotometer. For soil water content (SWC) determination, collected soil samples from the vicinity of the plants were put immediately into polyethylene bag to avoid water loss during transport to laboratory. Sampling was carried out 11 times from December 2005 to December 2007 to observe changes in soil water content throughout the year. Soil water content was estimated by oven drying of the sample at 110 8C for a constant weight. Soil water depletion during vegetation growth was calculated as per cent decrease in SWC from August to December and again from December to June. Height and number of shoots of D. strictus were recorded in September 2005 and again in December and June of each year to monitor seasonal growth i.e., monsoon and spring. Per cent increment in growth variables were calculated as: % increment = (x in December x in June) 100/x in June. Where x is height and number shoots of D. strictus. Aboveground biomass (herbage production) was harvested from 1 m 1 m area from lower one third of the plots with uniform vegetation in October of 2005, 2006 and 2007. Fresh herbage biomass was recorded after clipping the biomass from the soil surface and converted to kg m2 area. Dry
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Table 1 Soil composition and soil characteristics of the experimental sites recorded in June 2005. Values are mean SE of five replicates. RWH structure
Gravel
Sand
Silt + clay
%
NH4-N
NO3-N
<10%
Control C. trench Gradonie B. trench V-ditch
81.31 3.55 85.72 0.91 82.18 3.26 85.20 3.58 84.28 3.76
14.31 2.74 11.33 0.79 14.32 2.83 11.17 2.71 11.86 2.76
3.53 0.53 2.29 0.04 2.69 0.45 2.54 0.63 3.12 0.85
0.98 0.10 0.78 0.14 0.98 0.16 0.92 0.10 0.87 0.06
27.47 2.18 20.31 1.67 23.99 3.11 24.39 2.75 25.08 3.28
2.85 0.27 2.40 0.36 2.83 0.25 2.97 0.23 2.82 0.37
7.73 0.23 5.07 0.52 6.42 1.57 6.06 1.05 4.93 0.72
10–20%
Control C. trench Gradonie B. trench V-ditch
81.45 3.52 78.80 2.35 81.84 2.48 78.39 1.69 79.09 3.45
15.19 2.80 17.28 2.13 14.47 1.69 17.48 1.63 16.00 1.74
2.21 0.50 2.17 0.34 2.97 0.82 2.97 0.26 2.58 0.56
0.58 0.05 0.49 0.08 0.69 0.11 0.69 0.10 0.83 0.13
23.42 3.48 18.94 1.65 20.05 1.72 20.91 2.38 25.91 2.87
2.44 0.26 2.16 0.20 2.27 0.15 2.13 0.05 2.39 0.12
3.70 0.50 5.27 1.21 5.36 0.76 4.30 0.23 4.01 0.45
>20%
Control C. trench Gradonie B. trench V-ditch
84.15 1.88 83.08 2.07 83.40 2.70 81.31 2.79 87.71 1.37
11.44 1.25 12.47 1.49 11.95 1.82 12.59 1.75 8.51 0.90
3.12 0.25 3.45 0.50 2.77 0.51 4.13 0.74 2.31 0.31
0.69 0.13 0.86 0.12 0.62 0.15 0.85 0.16 0.59 0.17
19.13 2.44 25.66 3.00 22.07 3.21 17.50 1.53 17.33 1.57
2.50 0.26 2.64 0.13 2.45 0.23 2.41 0.29 2.17 0.16
2.41 0.30 2.32 0.25 2.63 0.48 3.29 0.68 3.10 0.64
3.361* 0.216NS 0.663NS
7.035** 0.342NS 0.722NS
1.492NS 0.595NS 1.248NS
5.568** 0.325NS 1.142NS
F values of two-way ANOVA Slope Treatment Slope treat
Soil composition (%)
Soil nutrient (mg kg1)
Slope
SOC
3.001NS 0.413NS 1.878NS
5.712** 0.276NS 0.709NS
PO4-P
21.898** 0.776NS 1.909NS
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
biomass was recorded after drying the above-mentioned biomass at 65 8C and presented in kg m2. Herbage water content was calculated based on the water loss during drying of the sample.
20% slope area. However, the variations in these soil variables among the treatments were not significant (P > 0.05) initially in June 2005.
2.4. Statistical analysis
3.2. Soil water dynamics
The data collected were statistically analyzed using SPSS statistical package version 8.0 for ‘‘Windows 2000’’. Soil variables, soil water depletion and plant survival were analyzed using a twoway ANOVA. Above-mentioned parameters were the dependent variables. Slope and rainwater harvesting treatments were the fixed factors. Since height, number of shoots, soil water content and herbage biomass (both fresh and dry) were determined at different times/years; the data were analyzed using a repeated measure ANOVA considering months/years as tests of withinsubjects effects and slope and treatments as tests of betweensubjects effects. Per cent increment in height and number of shoots were also analyzed using repeated measure ANOVA. Per cent soil water was square root transformed before statistical analysis to reduce heteroscenesdity (Sokal and Rohlf, 1981). To obtain the relations between plant growth, herbage production and soil water content, Pearson correlation coefficient were calculated. The least significant difference test was used to compare treatments at the P < 0.05 levels.
Multivariate analysis of soil water content (SWC) in 0–40 cm soil layer indicated significant (P < 0.01) variation among months (Table 2). SWC (average of 11 observations) was 18.32% in August 2006 and 1.22% in June 2006 (Fig. 1). Month slope interaction indicated lowest (P < 0.01) SWC in 10–20% slope throughout the year except in December 2005, when SWC was lowest in >20% slope. SWC was 26.30% and 22.52% greater in <10% and >20% slopes, respectively as compared to 6.53% in 10–20% slope. Duncan Multiple Range Test (DMRT) indicated greater (P < 0.05) SWC in <10% slope in most of the observations except in August 2006, November 2006, December 2006 and August 2007, when SWC was highest in >20% slope. SWC was lowest in the control plots (P < 0.05 in December 2005) and average increase in SWC was 12.25%, 21.29%, 16.82% and 15.31% in CT, G, BT and VD plots, respectively. SWC was highest in G and V plots during monsoon months of August and September, whereas it was highest in CT and BT plots in rest of the period. Slope treatment interactions were not significant (P > 0.05) but SWC was highest in BT/VD plots in <10%, G plots in 10–20% and BT/G plots in the >20% slopes.
3. Results 3.1. Soil characteristics Gravel (>2 mm size) concentration was highest (P < 0.05) in >20 slope and lowest in 10–20% slope area (Table 1). Silt + clay concentration did not vary within slopes. Sand content was 16.07% in 10–20% slope. Lowest (P < 0.05) sand content was in >20% slope. Soil pH ranged from 5.63 to 8.12 and it was significantly greater (P < 0.05) in <10% slope than in 10–20% slope area. Soil organic carbon (SOC) ranged from 0.49% to 0.98% being the highest (P < 0.01) in <10% slope. Ammonium (18.94–25.91 mg kg1) and PO4-P (2.31–7.73 mg kg1) concentration was lowest in >20% slope and highest in <10% slope area. NO3-N (2.13–2.97 mg kg1) concentration was highest (P < 0.05) in <10% and lowest in 10–
Table 2 Repeated measure ANOVA of soil water content (%, w/w) influenced by natural slopes and rainwater harvesting treatments under D. strictus plants in degraded hills of Aravalli, India. Tests of within-subjects effects
df
TSS
MSE
F value
P value
Month Month slope
10 20
27,527.71 441.36
2752.77 22.07
442.05 3.54
<0.001 <0.001
2 4 8
453.23 182.61 371.72
226.61 45.65 46.47
4.32 0.87 0.89
Tests of between-subjects effects Slope Treatment Slope treat
TSS: type III sum of squares, MS: mean square.
<0.05 NS NS
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Fig. 1. Soil water dynamics influenced by natural slopes and rain water harvesting treatments in degraded hills of Aravalli. C: control; CT: contour trench; G: gradonie; BT: box trench and VD: V-ditch. Error bars are SE of five replicate plots.
Soil water depletion was less in >20 slope area during December 2005 to June 2006 (P < 0.05). In <10% slope soil water depletion was less during August to December in both 2006 and 2007. However, soil water depletion was less in 10–20% slope area in December to June 2007 (Table 3). Among the treatments, greatest soil water depletion was in VD plots during December 2005 and June 2006 and in CT plot during August to December 2006. The depletions during December 2006 to June 2007 and during August 2007 to December 2007 were highest in G plots and control plots, respectively. 3.3. Plant survival Per cent survival of D. strictus seedlings was 84% in June 2008. Survival did not differ (P > 0.05) due to both slope and rainwater harvesting treatments. But the survival was highest (89.6%) in <10% slope and lowest (78.4%) in >20% slope area (Table 4). Among the treatments, survival was lowest (77.4%) in the control
plots and highest in VD plots. Survival of D. strictus was highest in control/CT plots in <10% and G/BT plots in 10–20% slopes. 3.4. Growth of D. strictus Repeated measure ANOVA indicated significant (P < 0.01) difference in height growth (Fig. 2, left panels) and number of shoots (Fig. 2, right panels) of D. strictus seedlings between the season/year. The growth was highest during July to December i.e., monsoon growth. Season slope interaction was significant (P < 0.05). Plants were taller (P < 0.01) in <10% slope than in the other slopes and plant height decreased with increase in slope gradient. Plants height did not differ (P > 0.05) in both December 2005 and June 2008 due to treatments. However, there was a change in growth pattern from shortest and tallest plants in CT and control plots in December 2005 to tallest and shortest plants in VD and control plots respectively, in June 2008. Thus highest growth was in VD ditch plots in June 2008 (Table 5). However, intermittent
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Table 3 Soil water usage (% of December in June and of August in December) by D. strictus plants and vegetation influence by natural slopes and rainwater harvesting treatments in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
RWH structure
Soil water depletion December 05–June 06
August 06–December 06
December 06–June 07
August 07–December 07
<10%
Control C. trench Gradonie B. trench V-ditch
73.60 2.28 80.93 6.61 86.38 3.97 84.13 2.61 84.37 5.15
62.23 5.60 69.75 7.02 65.73 5.39 73.53 2.33 72.78 2.84
64.98 9.17 76.28 2.79 61.84 13.24 60.47 6.85 66.65 7.39
82.47 3.35 79.10 3.70 75.63 3.55 67.25 3.08 67.13 3.38
10–20%
Control C. trench Gradonie B. trench V-ditch
68.71 17.42 76.42 5.39 63.42 8.32 69.16 10.11 83.58 6.96
77.46 3.62 75.42 4.96 80.16 4.82 73.36 4.88 77.18 6.00
50.46 10.23 74.12 5.08 75.78 4.55 56.06 9.07 51.83 17.84
82.48 4.95 74.13 6.52 82.38 2.12 80.59 2.77 78.79 1.73
>20%
Control C. trench Gradonie B. trench V-ditch
59.00 14.75 58.81 11.58 47.18 19.15 47.47 10.03 45.11 4.73
74.84 6.06 77.25 4.33 74.32 4.25 62.23 5.56 79.06 4.67
73.10 6.94 62.99 11.79 77.75 5.02 79.45 3.28 71.28 10.23
78.54 5.77 78.44 3.47 83.79 3.37 87.93 1.23 82.94 2.20
Two-way ANOVA Slope Treatment Slope treat
df 2 4 8
F value 12.109** 0.238NS 0.550NS
F value 3.213* 0.781NS 1.087NS
F value 1.936NS 0.667NS 1.064NS
F value 6.139** 0.979NS 2.309*
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
Table 4 Survival* of D. strictus seedlings affected by slope gradient and rainwater harvesting in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
Treatment
Mean
Control
Contour trench
Gradonie
Box trench
V-ditch
<10% 10–20% >20%
90.06 5.88 63.10 25.49 73.33 6.67
95.50 2.78 71.11 19.75 80.61 11.56
84.16 8.12 92.15 5.10 72.92 10.42
87.82 6.90 91.67 5.89 75.00 10.21
89.54 7.98 88.89 11.11 91.53 4.33
89.61 83.15 78.42
Mean
77.36
83.77
84.79
85.06
89.91
84.43
*
Two-way ANOVA did not indicate significant (P > 0.05) differences both due to treatments and slopes.
growth indicated significantly (P < 0.05) greater height growth in BT/VD plots in December 2006. Number of shoots was highest (P < 0.05) in 10–20% slope area, though it did not differ with that in <10% slope area. Lowest number of shoots was in >20% slope in all the observations (Table 5). In December 2005, the highest number of shoots was in G plots, but it was highest in CT plots in December 2006 and June 2007, and in BT and VD plots in December 2007 and June 2008, respectively. When compared with the data of December 2005, the increase in number of shoots was 3.4-, 2.1- and 1.6-fold in <10%, 10–20% and >20% slope, respectively (Fig. 2, right panels). The increase in number of shoots among treatments was 2.3–2.9-fold and the highest increase was in CT plots. 3.5. Plant growth increments Per cent increment in height and number of shoots varied (P < 0.05) between the years (Table 6). Height increment was highest (P < 0.05) in 2006–07 and the lowest in 2005–06. Year slope interactions were significant (P < 0.01) only for number of shoots. Per cent height increment did not differ due to both slope and rainwater harvesting treatments. However it was highest in <10% and lowest in >20% slope. The increment was lowest in control plots and highest in VD plots among the treatments. Per cent increment in number of shoots was highest in <10% slope and lowest in the >20% slope. The per cent increase in number of shoot was highest in CT plots (P < 0.05) in 2006–07.
3.6. Herbage production Multivariate analysis indicated lowest (P < 0.05) fresh (0.69 kg m2) and dry (0.31 kg m2) herbage production in 2005. Production increased to highest in 2007 (Table 7). Significant year slope interaction showed highest (P < 0.01) herbage in <10% slope in 2005 to >20% slope in 2007 through 10–20% slope in 2006. Year treatment interaction was also significant (P < 0.05) indicating highest herbage in VD plots in 2005 and 2007 and in G plots in 2006. Tests of between-subjects effects indicated nonsignificant variations in fresh herbage production between the slopes, but it differed among the treatments. However, DMRT indicated low (P < 0.05) herbage in 2005 to highest herbage production in 2007 in >20% slope. The reverse trend was observed in <10% slope area. Herbage production was highest (P < 0.05) in VD plots in 2005 and 2007, and in G plots in 2006. Dry herbage followed the trend similar to the fresh herbage except in 2005, when the dry herbage did not differ (P < 0.05) both due to slope and water harvesting treatments. When compared with those in <10% slope, fresh and dry herbage were lesser by 21.11% and 14.39% in 10–20% slope, and 34.56% and 29.19% in >20% slope area, respectively in 2005. In 2006, the reduction in respective herbage was only in >20% slope i.e., by 13.52% and 14.13%, whereas these herbage increased by 24.66% and 26.09% in 10–20% slope. Both fresh and dry herbage increased with slope in 2007, and the respective increases were 31.96% and 28.37% in 10–20% slope, and 42.42% and 48.35% in >20% slope. In rainwater harvesting treatments fresh and dry
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Fig. 2. Growth pattern of height and number of shoots of D. strictus influenced by natural slopes and rain water harvesting treatments in degraded Aravalli hills. C: control; CT: contour trench; G: gradonie; BT: box trench and VD: V-ditch. Error bars are SE of five replicate plots.
herbage production increased (16.18–42.77% in fresh and 26.20– 51.25% dry herbage in G plots and VD plots, respectively) over the control. All the treatments indicated greater fresh (1.40-fold in BT to 2.14-fold in G plots) and dry (1.38–2.15-fold) herbage than in the control plots in 2006. In 2007, G plots (by 30.68% and 36.13%) and CT plots (by 15.62% and 14.63% fresh and dry herbage, respectively) indicated lesser herbage production; whereas 1.64– 4.08-fold increase in fresh and 1.69–4.10-fold increase in dry herbage were observed in BT and VD plots, respectively, than those in the control plots. Slope treatment interactions were also significant and the production was highest in BT plots in <10% slope and in VD plots in 10–20% and >20% slope areas.
3.7. Correlation in different variables Slope gradient was negatively correlated with survival (r = 0.265, P < 0.05, n = 57), plant height (r = 0.369, P < 0.01, n = 63) and number of shoots (r = 0.478, P < 0.01) of D. strictus, SWC in December 2005 (r = 0.615, P < 0.01, n = 75) and June 2007(r = 0.267, P < 0.05), per cent increment in number of shoots (r = 0.463, P < 0.01) and soil water usage during December 2005 to June 2006 (r = 0.393, P < 0.01). However, slope was positively correlated with soil water usage during August to December 2007 (r = 0.258, P < 0.05). Gravel content was positively related with SWC in December 2005 (r = 0.227, P < 0.05), August 2006 (r = 0.251,
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Table 5 Average height and number of shoots of D. strictus seedlings under the influence of natural slopes and rainwater harvesting treatments in degraded hills of Aravalli, India. Values are mean SE of five replicates. Slope
RWH structure
Height (cm) September 2005
Number of shoots (Nos.) June 2008
September 2005
June 2008
<10%
Control C. trench Gradonie B. trench V-ditch
60.39 2.94 62.92 4.47 53.93 + 8.76 57.58 7.89 62.20 7.08
300.12 + 19.89 393.50 + 21.96 270.25 + 33.39 357.56 + 15.96 372.39 + 23.87
1.12 + 0.07 1.04 + 0.02 1.13 + 0.13 1.18 + 0.08 1.14 + 0.12
3.79 + 0.29 3.99 + 0.10 3.01 + 0.45 3.76 + 0.15 4.30 + 0.56
10–20%
Control C. trench Gradonie B. trench V-ditch
69.39 13.05 52.38 2.24 58.97 + 3.97 63.99 + 9.22 58.70 + 4.04
270.67 + 25.75 286.62 + 32.39 268.26 + 35.92 354.49 + 21.52 297.11 + 58.10
1.43 + 0.23 1.52 + 0.22 1.80 + 0.14 1.90 + 0.32 1.84 + 0.25
3.25 + 0.51 3.82 + 0.44 3.93 + 0.71 4.18 + 0.21 3.72 + 0.15
>20%
Control C. trench Gradonie B. trench V-ditch
61.50 + 3.50 66.60 + 9.15 55.93 + 3.93 51.25 + 2.91 61.95 + 3.54
182.50 + 42.65 302.70 + 02.87 281.22 + 12.05 261.70 + 45.72 309.85 + 49.50
1.10 + 0.11 1.10 + 0.10 1.58 + 0.36 1.22 + 0.17 1.10 + 0.06
2.42 + 0.23 2.59 + 0.54 3.12 + 0.18 2.72 + 0.24 2.82 + 0.30
df MSE Repeated measure ANOVA (tests of within-subjects effects) Season 5 554,176.1 Season slope 10 5,772.2 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
F value
MSE
F value
486.41** 5.07**
35.96 0.84
226.98** 5.28**
8.00** 1.39NS 1.84NS
50,074.14 8,730.25 11,519.06
10.69** 0.24NS 0.65NS
15.53 0.355 0.938
NS: not- significant. ** Significant at P < 0.01.
Table 6 Average annual increments in height and number of shoots of D. strictus plants under the influence of slopes and rainwater harvesting treatments. Values are mean SE of five replicates. Slope
RWH structure
Height increment (%) 2005–06
Shoot increment (%)
2006–07
2007–08
2005–06
2006–07
2007–08
<10%
Control C. trench Gradonie B. trench V-ditch
26.27 9.60 22.36 10.29 25.36 8.92 43.78 18.41 12.80 5.97
163.99 43.22 204.81 41.35 178.42 46.57 183.59 26.04 239.19 46.42
59.22 12.38 76.90 07.97 43.99 8.08 66.92 12.12 67.12 08.01
93.49 2.22 48.00 6.52 39.17 16.69 81.43 11.43 46.34 27.17
11.52 4.75 88.63 15.41 53.29 13.42 18.64 6.01 66.01 8.98
59.47 17.41 41.68 11.69 39.99 06.53 52.20 09.40 65.61 18.53
10–20%
Control C. trench Gradonie B. trench V-ditch
19.27 3.15 44.46 12.35 12.71 2.65 27.05 9.11 17.21 4.61
196.93 79.53 166.09 53.28 152.23 43.07 270.96 98.79 210.24 58.61
20.80 .800 57.31 16.36 65.48 06.17 34.50 13.28 57.44 17.90
3.70 3.70 18.50 8.500 10.73 3.77 5.00 5.00 11.86 5.13
43.33 26.66 70.12 20.37 25.26 6.42 57.80 24.52 39.48 20.28
33.87 23.28 46.93 17.59 52.20 15.23 48.14 19.82 47.17 09.20
>20%
Control C. trench Gradonie B. trench V-ditch
5.57 2.12 23.70 6.64 19.36 12.19 22.82 4.97 11.22 1.41
108.57 51.43 176.56 45.19 161.92 6.54 167.35 16.97 195.44 62.05
70.90 15.45 61.30 23.45 65.00 9.64 47.10 10.86 57.09 20.04
33.33 33.33 2.38 2.38 7.91 5.90 1.00 .00 2.78 2.78
57.50 42.50 35.89 15.39 44.92 23.96 47.98 28.38 26.83 13.78
23.10 14.40 62.48 08.34 45.92 22.94 57.59 14.41 101.55 28.10
df Repeated measure ANOVA (tests of within-subjects effects) Year 2 Year slope 4 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
MSE
F value **
MSE
365,575.02 1,885.75
88.99 0.46NS
8528.85 5614.94
3,011.62 2,325.88 1,001.88
1.17NS 0.91NS 0.39NS
751.73 422.53 309.73
F value 7.85** 5.17** 12.60** 0.79NS 0.84NS
NS: not- significant. ** Significant at P < 0.01.
P < 0.05), November 2006 (r = 0.293, P < 0.05) and April 2007 (r = 0.349, P < 0.01) and December 2007 (r = 0.251, P < 0.05). Sand content was negatively correlated (r = 0.238, P < 0.05) with SWC in most of the observations. Plant survival was positively related with SWC in December 2005 (r = 0.272, P < 0.05) and September 2007 (r = 0.310, P < 0.05), whereas plant height of December 2006 was
negatively related with SWC in August and September 2006 (r = 0.296, P < 0.05) and fresh herbage production (r = 0.256, P < 0.05). SWC of December 2005 was positively related with herbage production (0.282, P < 0.05). Per cent increment in number of shoots of D. strictus in June 2006 was positively (r = 0.330, P < 0.01) related with soil water depletion during December 2005 to June 2006.
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Table 7 Year-wise average aboveground fresh and dry herbage production under the influence of natural slope and rainwater harvesting treatments. Values are mean SE of five replicates. Slope
RWH
Aboveground mass (kg m2) 2006
Dry biomass (kg m2)
Treatment
2005
<10%
Control C. trench Gradonie B. trench V-ditch
0.87 0.13 0.86 0.03 0.83 0.05 0.71 0.08 0.85 0.09
0.51 0.10 0.53 0.09 0.70 0.11 0.96 0.05 0.70 0.09
2007 0.55 0.19 0.34 0.10 0.54 0.12 1.25 0.24 1.03 0.32
0.34 0.06 0.37 0.02 0.38 0.03 0.32 0.05 0.40 0.02
0.24 0.04 0.28 0.05 0.34 0.05 0.34 0.03 0.33 0.04
0.27 0.09 0.17 0.06 0.26 0.06 0.70 0.23 0.49 0.16
10–20%
Control C. trench Gradonie B. trench V-ditch
0.50 0.04 0.71 0.23 0.91 0.35 0.43 0.03 0.78 0.20
0.48 0.16 0.82 0.24 1.23 0.37 0.61 0.08 0.78 0.13
0.47 0.15 0.45 0.11 0.36 0.03 0.83 0.32 2.80 0.23
0.27 0.02 0.33 0.11 0.42 0.21 0.20 0.01 0.36 0.10
0.24 0.07 0.43 0.13 0.62 0.19 0.29 0.03 0.37 0.07
0.24 0.07 0.22 0.05 0.17 0.02 0.40 0.16 1.41 0.13
>20%
Control C. trench Gradonie B. trench V-ditch
0.45 0.05 0.60 0.23 0.38 0.02 0.46 0.03 0.88 0.28
0.26 0.05 0.64 0.15 0.74 0.21 0.45 0.06 0.62 0.16
0.67 0.24 0.63 0.25 0.27 0.03 0.68 0.11 3.03 0.34
0.19 0.02 0.28 0.11 0.18 0.02 0.21 0.02 0.42 0.14
0.14 0.03 0.31 0.07 0.37 0.11 0.22 0.03 0.28 0.07
0.35 0.13 0.35 0.12 0.12 0.02 0.35 0.05 1.64 0.18
df MSE Repeated measure ANOVA (tests of within-subjects effects) Year 2 1,661,134.85 Year slope 4 703,039.81 Year treatment 8 2,941,884.56 Tests of between-subjects effects Slope 2 Treatment 4 Slope treat 8
173,795.93 4,093,924.12 697,497.99
F value 13.54** 5.73** 23.98**
0.617NS 14.530** 2.475*
2005
2006
2007
MSE 645,559.91 169,749.24 824,773.58
41,836.68 1,024,556.85 214,199.72
F value 19.683** 5.176** 25.147**
0.588NS 14.411** 3.013**
NS: not- significant. * Significant at P < 0.05. ** Significant at P < 0.01.
4. Discussion 4.1. Soil water dynamics Continuous rain during July and August increased SWC in >20% slope by facilitating infiltration and its storage in soil profiles. But soil water use by the growing vegetation, water percolation into deeper soil profile and increased evaporative demand with increase in temperature resulted in a decrease in SWC to lowest value in June. Thus water utilization of different plant species like deep-rooting shrubs/trees and shallow-rooting annual plants influence the spatial distribution of water inside the soil profile resulting in changes in composition, coverage and biomass of vegetation (Li et al., 2004). Despite of greater soil content (P < 0.05) less SWC in 10–20% slope throughout the year than in the other slopes was due to greater (P < 0.05) sand content, which reduced soil water retention. But highest SWC in <10% slope in most of the observations was probably due to less run-off loss (un-published data) and greater infiltration of water into soil. Relatively greater SWC in >20% slope in June and November 2006 and April 2007 was due to greater per cent of gravel/stone present on soil surface that facilitated water infiltration during rain through surface roughness and reduced evaporation loss during water stress. The study of Danalatos et al. (1995) showed that under conditions of moderate water tress, water conservation is generally greater in stony soil and the soil with large cobbles on surface conserved the most water enhancing total dry matter yield of rainfed wheat. The observations of Van Wesemael et al. (1996) and Katra et al. (2008) also showed that rock fragments on dry hill slopes affect rainwater redistribution and overland flow, where the topsoil moisture content under rock fragments was higher over time than that of bare soil areas. However, difference in SWC between the slopes might also be due to variations in soil texture and silt + clay content, which was greater in >20% slope influencing vegetation
cover and soil water status as in the observations of Singh et al. (1998). Relatively greater decrease in SWC in >20% slope from highest in August to lowest in December showed faster depletion of soil water in higher slopes and was shown by a positive relation of slope with soil water depletion (r = 0.258, P < 0.05). However, such depletion in soil water was also due to relatively greater growth and productivity of vegetation (Singh and Rathod, 2004). Absence of rainwater harvesting structures was the reason for low SWC in control plots, but the impact of growing D. strictus plants and the herbage cannot be ruled out. Increase in SWC by 12.25–21.29% in treated area suggested the beneficial effects of rainwater harvesting structures in improving soil water status. Highest SWC in G plots was due to its effects in conserving run-off water by reducing water velocity and distributing the water into the soil profile particularly in 10–20% slope. Despite of larger storage capacity per plot, low SWC in CT and BT plots during monsoon was probably due to their influence on deep water storage that remained available for longer period of time indicated by greater SWC in June. Highest SWC in G and V plots during rainy season that depleted at faster rate after monsoon as compared to that in CT and BT plots was due to surface distribution of soil water facilitating herbage growth and production in former than in latter treatments. Lesser soil water depletion in CT and BT plots provided relatively more water for its usage in spring growth. However, soil water depletion is also related with root distribution of plants/ vegetation in different soil layers and utilization of soil water by the growing vegetation (Givnish, 1986; Singh et al., 1998). 4.2. Survival and growth of seedlings Availability of soil resources and its gradient affected survival and growth of planted seedlings of D. strictus. Highest survival in <10% and lowest survival in >20% slope was related with soil water content, which decreased with increase in slope gradient
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particularly during summer affecting the survival. Lowest plant survival in the control plot was due to absence of rainwater harvesting structures and thus low SWC. Thus adoption of rainwater harvesting influenced seedling survival positively. Highest survival in VD plots showed its beneficial effects on water storage in top soil layer available to the plant roots. However, relatively greater survival of D. strictus plants in 10–20% slope in G and BT treatments showed the suitability of these microcatchments in this slope. Highest (P < 0.05) growth during monsoon (June to December) as compared to that during January to June was due to rainfall and soil water availability (Fig. 2) influencing nutrient mobility and utilization (Marion and Everett, 2006). This is indicated by highest (P < 0.09) per cent increment in height and number of shoot in 2006–07 during which the rainfall was highest. Thus decrease in plant height (r = 0.280, P < 0.05, n = 63) and number of shoots (r = 0.396, P < 0.01) with slope was associated with decrease in concentration of SWC, SOC, NH4-N, NO3-N and PO4-P in higher slopes. Highest concentration of these soil variables in <10% slope enhanced plants height by 5.8-fold as compared to 4.8-fold in 10–20% and 4.9-fold in >20% slope than those in December 2005. Smaller plants due to less fertile soils have also been observed in Ghanian tropical rainforest (Baker et al., 2003). Highest growth increments in <10% slope area and its positive relation with shoots increment in June 2006 (r = 0.509, P < 0.01) and soil water depletion (r = 0.333, P < 0.01) during December 2005 to June 2006 suggesting the influence of soil water availability on growth of D. strictus plants. Relatively greater number of shoots in 10–20% slope was probably due to greater amount of water received down slope of the plots (D. strictus planted area) enhancing surface soil water availability and thus shoot multiplication. Tsui et al. (2004) and Yong et al. (2006) also observed that spatial redistribution of surface run-off resulting in higher nutrients and soil water availability on lower slope positions and contributed to the vegetation growth. About 1.6–3.4-fold increase in number of shoot was also related with soil water availability. However, greater increase in number of shoots in CT plots (2.9-fold) suggested utilization of water stored in deep soil layers after monsoon indicated by greater (P < 0.05) shoots increment in CT in 2006–07 and its relation with soil water usage during August 2006 to June 2007. The study of Gupta (1995) indicated higher growth of Azadirachta indica in ring-pit micro-catchment that harvested greater quantity of rain water influencing deep storage and its utilization for plant growth throughout the year. 4.3. Herbage production Altitudinal distribution pattern of the plant communities on the hill and the aspect is closely related to soil resource availability, erosion feature, and to some extent plant attribute (GuerreroCampo et al., 1999). Increased herbage production from 2005 to 2007 showed improvement in soil resource status with time. Despite of lesser rainfall in 2007 as compared to that in 2006, greater fresh and dry herbage production in 2007 was due to soil improvement influencing soil water and nutrient availability. Initial pattern of highest productivity in <10% slope in 2005 was due to appropriate distribution of water as compared to that in steep slope and thus available for vegetation growth initially. It was also due to less competition for soil resources by the newly planted seedlings in 2005 (Ainalis and Tsiouvaras, 1998.) that increased with age and size of the plant affecting vegetation growth in later years. Thus significant (P < 0.05) increase in herbage production in 10–20% and >20% slope areas in 2006 and 2007 suggested the effect of water harvesting, which was greater in higher slopes as compared to that in <10% slope area. Greater water availability in down slope area of the plots through run-off
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and/or subsurface drainage of the soil stored water during monsoon might also have influenced herbage growth and production in higher slopes. Xu et al. (2006) observed significant correlation between biomass of Astragalus adsurgens and Lespedeza davurica and total precipitation and thus soil water availability. Despite of lowest SWC, greater herbage production in 10–20% slope area suggests that profiles with the lowest soil water content also had greater herbage growth and was probably due to utilization of deeper soil water indicated by highest (73.50%) soil water usage during August to December 2006 in this slope (Liu and Stutzel, 2004). Thus herbage production exhibited positive (P < 0.05) response to soil water usage indicating an inverse relationship between aboveground production and soil water content during the growth period. Singh et al. (1998) also observed highest total vegetation cover on the mid slope position and was greatest on the clay loam site, which was the wettest in terms of soil water. About 2.40- and 2.52-fold greater (P < 0.05) fresh and dry herbage production in VD plots as compared to the control was due to greater water conservation and its distribution in top soil layer making the water available for herbage growth (McMaster and Wilhelm, 1997). De Abelleyra et al. (2008) also recorded an increase in growth and biomass of Cynodon dactylon with increase in soil water availability. The order of treatment effects in increasing fresh and dry herbage production is C < CT < G < BT < VD. However, lesser herbage production in BT in 2005 and in G and CT plots in 2007 as compared to that in the control was due to less water availability in surface soil layer when rainfall is average or near optimal. But significantly higher rainfall increased soil water availability in upper soil layer thus increasing herbage production to highest in G plots in 2006. However, significant slope treatment interaction indicated highest herbage production in BT plots in <10% and in VD plots in 10–20% and >20% slopes. The second order treatments were VD in <10%, G in 10–20% and CT in >20% slopes. 5. Conclusions and recommendations There was a large variation in soil water content annually with highest in August to lowest in June. Rainwater micro-catchments and their efficiency in soil water storage in different soil layers influenced growth of D. strictus and herbage production. Relatively greater water and nutrients availability in <10% slope resulted in greater initial growth than in the higher slopes. Low nutrient availability and greater herbage growth adversely affected the growth of D. strictus in higher slopes. Increase in herbage production in higher slopes from 2005 to 2007 is an indicator of improved soil water status and nutrient availability during growth period. Rainwater harvesting enhanced herbage production significantly and its facilitative effects was more under Box trench in <10% and V-ditch in 10–20% and >20% slope area by increasing water availability in surface soil layer. Contour trench/Gradonie reduced surface water flow and probably facilitated water infiltration into deeper soil profile and could be accessed by woody perennials. Thus V-ditch and Box trench facilitated water distribution in upper soil layers for vegetation growth, whereas Contour trench facilitated water storage in deep soil profile that was utilised for the growth of D. strictus in non-monsoon season and thus facilitated spring growth. Gradonie structure was beneficial in influencing both growth of herbage and woody perennials only during high rainfall years particularly in 10–20% slope area. These rainwater harvesting structures behaved differently in facilitating soil water and nutrient availability among the slope and thus can be replicated accordingly in rehabilitation of the degraded hills depending upon the need i.e., herbage and woody perennials.
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Acknowledgements I wish to express my sincere thanks to the Director Arid Forest Research Institute, Jodhpur for providing the facilities to carry out research. Financial support from Forest Department, Government of Rajasthan and Meteorological Department, Banswara for providing climatic data are gratefully acknowledged. The assistance provided by all the research staff of Forest Ecology Division, is gratefully acknowledged. References Ainalis, A., Tsiouvaras, C., 1998. Forage production of woody fodder species and herbaceous vegetation in a silvopastoral system in northern Greece. Agroforestry Systems 42, 1–11. Baker, T.R., Burslem, D.F.R.P., Swaine, M.D., 2003. Associations between tree growth, soil fertility and water availability at local and regional scales in Ghanaian tropical rain forest. Journal of Tropical Ecology 19, 109–125. Barron, J., Rockstro¨m, J., Gichuki, F., Hatibu, N., 2003. Dry spell analysis and maize yields for two semi-arid locations in East Africa. Agricultural and Forest Meteorology 117, 23–37. Ben-Zhi, Z., Yi, F.M., Jhong, X.J., Sheng, Y.X., Cai, L.Z., 2005. Ecological function of bamboo forest research and application. Journal of Forestry Research 16, 143– 147. Chakraborty, D., 1988. Utilization of bamboo as raw material in the handicraft industries in Tripura. Indian Forester 114, 635–636. Champion, H.G., Seth, S.K., 1968. A Revised Survey of the Forest Types of India. The Manager of Publications, New Delhi, India, p. 404. Danalatos, N.G., Kosmas, C.S., Moustakas, N.C., Assoglou, N., 1995. Rock fragments. II. Their impact on soil physical properties and biomass production under Mediterranean conditions. Soil Use and Management 11, 145–154. De Abelleyra, D., Verdu, A.M.C., Kruk, B.C., Satorre, E.H., 2008. Soil water availability affects green area and biomass growth of Cynodon dactylon. Weed Research 48, 248–256. Givnish, T.J., 1986. On the Economy of Plant Form and Function. Cambridge University Press, New York, p. 717. Gowing, J.W., Mahoo, H.F., Mzirai, O.B., Hatibu, N., 1999. Review of rainwater harvesting technique and their evidence for their use in semi-arid Tanzania. Tanzania Journal of Agriculture Science 2, 171–180. Guerrero-Campo, J., Alberto, F., Hodgson, J., Garcı´a-Ruiz, J.M., Montserrat-Martı´, G., 1999. Plant community patterns in a gypsum area of NE Spain. I. Interactions with topographic factors and soil erosion. Journal of Arid Environment 41, 401– 410. Gupta, G.N., 1995. Rain water management for tree planting in Indian desert. Journal of Arid Environment 31, 219–235. Gregory, P.J., 1989. Water-use-efficiency of crops in the semi-arid tropics. In: Soil, Crop and Water Management in the Sudano-Sahelian Zone, ICRISAT, Hyderbad, India, pp. 85–98. Hatibu, N., Mutabazi, K., Senkondo, E.M., Msangi, A.S.K., 2006. Economics of rainwater harvesting for crop enterprises in semi-arid areas of East Africa. Agriculture Water Management 80, 74–86. Jackson, M.L., 1973. Soil Chemical Analysis. Prentice Hall of India Private Ltd., New Delhi, India, p. 497.
Katra, I., Lavee, H., Sarah, P., 2008. The effect of rock fragment size and position on topsoil moisture on arid and semi-arid hillslopes. Catena 72, 49–55. Li, Z., Kobayashi, M., 2004. Plantation future of bamboo in China. Journal of Forestry Research 15, 233–242. Li, W.Q., Xiao-Jing, L., Khan, M.A., Gul, B., 2008. Relationship between soil characteristics and halophytic vegetation in coastal region of north China. Pakistan Journal of Botany 40, 1081–1090. Li, X.R., Ma, F.Y., Xiao, H.L., Wang, X.P., Kim, K.C., 2004. Long-term effects of revegetation on soil water content of sand dunes in arid region of Northern China. Journal of Arid Environment 57, 1–16. Liu, F., Stutzel, H., 2004. Biomass partitioning, specific leaf area, and water use efficiency of vegetable amaranth (Amaranthus spp.) in response to drought stress. Scientia Horticulturae 102, 15–27. Liu, J., Linderman, M., Ouyang, Z., An, L., Yang, J., Zhang, H., 2001. Ecological degradation in protected areas: the case of wolong nature reserve for giant pandas. Science 292, 98–101. McMaster, G.S., Wilhelm, W.W., 1997. Conservation compliance credit for winter wheat fall biomass production and implications for grain yield. Journal of soil and Water Conservation 52, 358–363. Marion, G.M., Everett, K.R., 2006. The effect of nutrient and water additions on elemental mobility through small tundra watersheds. Ecography 12, 317–323. Singh, A.N., Singh, J.S., 1999. Biomass, net primary production and impact of bamboo plantation on soil redevelopment in a dry tropical region. Forest Ecology and Management 119, 195–207. Singh, G., 2008. Gaining momentum: growing Jatropha curcus with rainwater harvesting in degraded hillocks of Aravalli. Wasteland News 23, 17–19. Singh, G., Bala, N., Kumar, P., Baloach, S.R., Rathod, T.R., Limba, N.K., 2007. Flood disaster in western Rajasthan: disadvantages and the benefits. In: State of Art Report—Floods of August 2006 in Rajasthan: Causes: Magnitude and Strategies. INCOH Publication No. INCOH/SAR 29/2007, National Institute of Hydrology, Roorki, India, pp. 52–59. Singh, G., Rathod, T.R., 2004. Lysimetric study of soil water utilization by tree seedlings in arid environment. In: National Workshop on ‘Forest and Water Conservation: Mythes and Realities’ held at FRI, Dehradun on June 8–10. pp. 54–56. Singh, J.S., Milchunas, D.G., Lauenroth, W.K., 1998. Soil water dynamics and vegetation patterns in a semiarid grassland. Plant Ecology 134, 77–89. Sokal, R.R., Rohlf, P.J., 1981. Biometery, 2nd edition. W.H. Freeman, New York, p. 859. Tsui, C.C., Zueng-Sang Chen, Z.S., Hsieh, C.F., 2004. Relationships between soil properties and slope position in a lowland rain forest of southern Taiwan. Geoderma 123, 131–142. Van Wesemael, B., Poesen, J., Kosmas, C.S., Danalatos, N.G., Nachtergaele, J., 1996. Evaporation from cultivated soils containing rock fragments. Journal of Hydrology 182, 62–82. Venketeswarlu, J., 1987. Efficient resource management systems for drylands in India. Advances in Soil Science 7, 209–216. Vohland, K., Barry, B., 2009. A review of in situ rainwater harvesting (RWH) practices modifying landscape functions in African drylands. Agriculture, Ecosystem & Environment 134, 119–127. Wezel, A., 2006. Variation of soil and site parameters on extensively and intensively grazed hillslopes in semiarid Cuba. Geoderma 134, 106–109. Xu, B.P., Gichuki, P., Shan, L., Li, F.M., 2006. Aboveground biomass production and soil water dynamics of four leguminous forages in semiarid region, northwest China. South African Journal of Botany 72, 507–516. Yong, L., Wang, C.W., Hongliang, T., 2006. Research advances in nutrient runoff on sloping land in watersheds. Aquatic Ecosystem Health & Management 9, 27–32.