- Email: [email protected]
Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China
Agricultural and Forest Meteorology 279 (2019) 107713
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China
T
⁎
Jian Shengqia, , Hu Caihonga, Zhang Guodongb, Zhang Jinpinga a b
College of Water Conservancy & Environment, Zhengzhou University, Science Road 100, Zhengzhou, China Henan Yellow River Hydrological Survey and Design Institute, Chengdong Road 100, Zhengzhou, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Throughfall Stemflow Canopy interception Water storage capacity Loess Plateau
The Loess Plateau, China, has been subject to 40 years of re-vegetation predominantly with the xerophytic shrubs Caragana korshinskii and Hippophae rhamnoides. Throughfall, stemflow, canopy interception, and water storage capacity experiments for the two shrubs were conducted from May to September during the period 2009–2013. The results showed that the throughfall percentages averaged 62.4% and 70.1% of gross rainfall for H. rhamnoides and C. korshinskii, respectively, while stemflow accounted for 2.4% and 6.7% of the gross rainfall for the two shrubs. The rainfall threshold for stemflow generation was 2.46 and 1.06 mm for H. rhamnoides and C. korshinskii, respectively. The wetting front depths for the two shrubs in the area around the stems were deeper than away from the shrubs. The averaged percentages of interception loss in H. rhamnoides and C. korshinskii were 35.2% and 23.2%. Additionally, H. rhamnoides had greater water storage capacity per leaf area for each simulated rainfall intensity (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities. For all the tested rainfall intensities, H. rhamnoides could store more water per dry biomass (mean, 0.72 g−1; range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1). The present study can inform revegetation projects, water budget analyses, and modeling efforts aimed at understanding rainfall water movement within shrub communities in the semiarid Chinese Loess Plateau, China.
1. Introduction Intensive soil erosion, soil desertification, and vegetation degradation are features of the soil and water transition zone in the Loess Plateau region in China (Fu et al., 2011). Numerous vegetation restoration measures have been implemented by the Chinese government, including the planting of perennial shrubs and grasses, in an attempt to restore the environment and reduce soil and water loss in the region. Improving the hydrological aspects of the environment via ecological restoration is two-tiered and involves (1) the prevention of water and soil loss by altering water cycle paths. Indigenous perennial plants can achieve this by increasing the effective vegetation coverage and thus minimizing surface runoff. The second aspect is related to (2) increasing the soil moisture content in order to effectively enhance productivity (Zhao et al., 2004). The precipitation that falls on vegetation is intercepted by the plant canopy for a certain time period. A portion of the water evaporates (interception loss) and some of it infiltrates into the soil as it trickles down from the plant canopy (throughfall) or runs down the stems to the
⁎
bottom of the plants (stemflow). Thus, the spatial distribution of precipitation is altered via throughfall and stemflow, and together with interception losses, these can significantly influence the ecology and hydrology in water-stressed areas. From an ecological perspective, stemflow results in the concentration of rainfall and nutrients in the vicinity of the stems of the plants, where water can easily infiltrate into the soil, which enhances water availability during periods of drought and promotes plant growth and survival (Moran et al., 2009). Stemflow is actually believed to be an adaptive mechanism for survival during periods of drought (Mauchamp and Janeau, 1993; Carlyle-Moses and Price, 2004). In terms of hydrology, alterations in plant cover have major impacts. For instance, the replacement of pasture or agricultural crops with woody plants results in reduced surface runoff (Trimble, 1987; Owens et al., 2006) and, vice versa, when trees are replaced with forage species, stream and river discharge increases (Bosch and Hewlett, 1982; Dingman, 2002; Williamson et al., 2005). One explanation for this is that woody plants store rainwater on a greater surface area, thus resulting in greater interception losses. These losses can exceed 25% of the gross annual
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Jian).
https://doi.org/10.1016/j.agrformet.2019.107713 Received 25 December 2018; Received in revised form 14 August 2019; Accepted 16 August 2019 0168-1923/ © 2019 Elsevier B.V. All rights reserved.
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
shaped with a narrow main stem with thick leaves (30–60 mm in length; 5–l0 mm in width) and a rough surface (Fig. 1). Caragana korshinskii has a more developed root system than H. rhamnoides, with more than half of the fine roots occurring in the 0- and 40-cm soil layer (Jian et al., 2014). Almost no ground cover exists in the H. rhamnoides and C. korshinskii plantations.
rainfall with mean estimates of 26% for conifer woods, 28% for broadleaf and 20% for shrubs (Sahin and Hall, 1996; Carlyle-Moses, 2004; Sun et al., 2015; Jian et al., 2018). Throughfall, stemflow, and interception measurements were initially conducted in the mid-19th century in Europe (Molchanov, 1963) and in the early 20th century in the USA (Janik and Pichler, 2008; Pérez-Suárez et al., 2008) and involved assessing rainfall partitioning in the hydrological cycle. The modeling of interception loss was first attempted by Horton (1919) and later reproduced by Gash and Shuttleworth (2007). However, estimates of interception loss were empirically derived from gross precipitation until the 1970s. Following Horton's work, Rutter et al. (1975) established the first conceptual model that considered interception as an evaporative loss (Muzylo et al., 2009). Numerous studies on throughfall, stemflow, and interception in different plant species exist (Xiao et al., 1998; Ahmadi et al., 2009; Asadian and Weiler, 2009; Yurtseven and Zengin, 2013; Sun et al., 2015). These studies on interception are pivotal for ascertaining the water-cycle elements related to various types of stands and for evaluating the water budget, allowing for significant alterations in forest ecosystems and climate to be assessed. A recent review of rain interception by vegetation in the Loess Plateau of China demonstrated that the data available in the literature were predominantly focused on tree species, while only 9% of published reports included shrub species (Jian et al., 2018) despite the fact that significant areas of the Loess Plateau constitute shrublands as a result of the ecological restoration efforts. The rainfall interception present in forest canopies typically results in a net water loss, while this is not always the result when the plant cover is reduced in height (David et al., 2005). Additionally, the measurement of interception fluxes is technically challenging (Dunkerley, 2000). The characteristics of throughfall, stemflow, and interception have been studied in re-vegetated shrub ecosystems (Wang et al., 2011). However, most research used experimental data spanning 1–2 years, which are not appropriate for assessing long term impacts on rainfall partitioning. Additionally, the patterns of stemflow infiltration associated with soil water content enhancement have not been extensively studied. The aims of the present study were to (1) estimate the long-term (five years) throughfall, stemflow, interception, and water storage capacity in Caragana korshinskii and Hippophae rhamnoides in a small catchment in the western Chinese Loess Plateau; and (2) assess the features of stemflow water infiltration in the re-vegetated shrublands in the Loess Plateau.
2.2. Experimental design In the experimental plots, we selected 12 H. rhamnoides individuals and 12 C. korshinskii individuals to measure throughfall and stemflow, respectively. The plants were growing on flat terrain (assuming that all the stemflow water had reached the soil) and were isolated from one another (Table 2). A recording gage (Onset Computer Corporation, Pocasset, MA, USA) was used to measure the total gross rainfall and rainfall intensity. Throughfall and stemflow were calculated under natural rainfall conditions based on Hamilton and Rowe's (1949) standard for storm and rainfall events, defined as follows: (1) an individual storm is a rainfall period separated by dry intervals of at least 24 h; (2) an individual rainfall event is considered to be a rainfall event separated by dry intervals of at least 4 h. 2.2.1. Throughfall We measured the throughfall of each C. korshinskii and H. rhamnoides plant by means of nine throughfall collecting cups situated 15 cm above the ground below the canopies of individual plants (Fig. 1). The throughfall collecting cups had an inner diameter of 200 mm (in accordance with that of a standard rain gage). Beneath the canopy, the cups were placed 120° apart in three directions. The cups were not placed entirely beneath a gap in the shrub canopy or beneath foliage in an attempt to prevent the under- or over-estimation of interception. The cups were positioned 20, 50 and 100 cm from the stems. To reduce evaporative loss from the open cups, throughfall was measured immediately following each rainfall treatment. 2.2.2. Stemflow Stemflow was measured using funnels constituted of flexible aluminum foil plates that were fixed over the branches. The stemflow collectors extended less than 5 mm from the stem to stop the throughfall water from running into the collectors. A plastic hose connected the funnels and the collection container (Fig. 1). Stemflow depth is the stemflow volume divided by the canopy projected area. Herwitz (1986) found that stemflow at the point scale can be expressed as a funneling ratio, F:
2. Materials and methods
F = V /(B × P )
2.1. Study area
(1)
where V is the stemflow volume (L), B is the basal area of the shrub (m2), and P is the quantity of rainfall at the top of the canopy (mm). The product B × P indicates the volume of water that would have been measured by a rain gage with an opening equivalent to that of the tree B. Thus, F indicates the ratio of the rainfall reaching the base of the tree to the rainfall that would have reached the ground in the absence of a tree. Funneling ratios >1 indicate that canopy characteristics other than tree bole are accounting for stemflow (Herwitz, 1986; Carlyle–Moses and Price, 2006). Three individuals each of C. korshinskii and H. rhamnoides situated on a flat surface were selected for determining the patterns of stemflow infiltration related to the soil water content enhancement. Volumetric soil moisture was determined using EC-5 sensors (Decagon Devices Inc., Pullman, WA, USA) (Em 50, Decagon Devices, Pullman, WA, USA), which were installed at depths of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, and 200 cm below the ground surface about 5 cm from the shrub stem and in an open area approximately 30 cm from the periphery of the plant. Data were collected by a logger every10 min. For probe installation, a pit of sufficient width was dug in the soil and the probes were inserted into the soil through the
Fieldwork was performed in H. rhamnoides and C. korshinskii plantations from 2009 to 2013 in the Anjiapo catchment of the western Chinese Loess Plateau. The area has an average annual precipitation of 420 mm (1965–2008), 60% of which occurs between July and September. The monthly average air temperature varies from −7.4 to 27.5°C, and the annual mean temperature is 6.3°C (1958–2008). The average annual evaporation is 1510 mm (1958–2008). The soil is silt loam of loess origin (Wang et al., 2010) and is classified as Chernozem according to the IUSS Working Group WRB (2006). Land use in the research area includes croplands, artificial shrublands, grasslands, and woodlands. All the experiments were conducted in representative C. korshinskii and H. rhamnoides experimental plots of 100 × 100 m size in the study area. Table 1 provides basic information on the C. korshinskii and H. rhamnoides plots. Both C. korshinskii and H. rhamnoides have been extensively planted in the study region and were sown in 1988 as 2-year-old seedlings with a spacing of 3 × 3 m. The leguminous shrub C. korshinskii has a semispherical shape, many slender branches, a smooth plant surface, and even, pinnate composite leaves. In contrast, H. rhamnoides is cone2
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Table 1 A brief overview of the sampling areas for the C. korshinskii and H. rhamnoides plantations in the Anjiagou catchment. Parameter
Geographical parameters Biological parameters
Soil parameters
Sample numbers
Slope aspect Slope position Plant height (mm) Basic diameter-branch (mm) Basic diameter-twig (mm) Projected area (m2) Leaf area index (LAI)
– – 80 150 150 50 320
Clay (<0.002 mm; %) Silt (0.05–0.002 mm; %) Sand (0.05–2 mm; %) Organic matter (%) pH
3 3 3 3 3
Mean ± SD C. korshinskii
H. rhamnoides
SE Middle 1700 ± 110 15.91 ± 2.1 19.11 ± 0.19 3.02 ± 0.44 1.04 ± 0.09, 1.58 ± 0.22, 2.15 ± 0.16, 2.16 ± 0.15 9.17 ± 1.20 75.59 ± 9.21 15.24 ± 1.16 0.68 ± 0.08 8.1 ± 0.94
SE Upper 191 ± 17 13.51 ± 0.48 19.54 ± 0.32 3.54 ± 0.21 0.93 ± 0.12, 1.15 ± 0.17 1.87 ± 0.21, 2.15 ± 0.20 11.04 ± 2.3 76.69 ± 11.34 12.27 ± 2.81 0.71 ± 0.04 7.9 ± 0.75
*Slope aspect and slope position were determined by a compass; LAI was determined by a canopy analyzer (LAI2000, LI–COR, USA) on 14th June, 15th July, 15th August, and 14th September. The four values for LAI are from June to September. Soil organic matter was determined using the potassium dichromate volumetric method; pH was determined by potentiometry; particle size distribution was determined by sedimentation. Soil properties are for the top 1 m. Data = mean ± SD.
Fig. 1. Schematic diagram. (A) C. korshinskii; (B) H. rhamnoides; and (C) stemflow collection. (D) and (E) are the leaf characteristics of the two shrubs.
Table 2 Descriptive statistics (mean ± standard deviation) of branches and canopy projection of the 12 sampled C. korshinskii individuals and 12 H. rhamnoides individuals used in the experiments. Shrub branch Species
Number
Diameter (cm)
Length (cm)
Height (cm)
Angle (°)a
Projected area (m2)
Canopy bulk (m3)
C. korshinskii H. rhamnoides
20 ± 5 12 ± 4
1.66 ± 0.19 1.76 ± 0.25
196 ± 21 208 ± 25
178 ± 12 199 ± 21
50 ± 8 55 ± 12
4.93 ± 1.21 4.12 ± 1.55
2.54 ± 0.42 2.81 ± 0.53
a
Angle in degrees of the upward branch to the ground surface. Data = mean ± SD.
current study, there was almost no ground cover in the plantations, and thus the water intercepted beneath the shrub canopies was ignored. The soil moisture sensor is capable of measuring volumetric saturation values between 0% and 100%, with an accuracy of ± 1.0% and
side of the pit and placed horizontally in the direction of maximum slope of the terrain. The pit was then carefully refilled, avoiding perturbations and minimizing damage to the root system as far as possible, and the surface was contoured similarly to the surrounding slope. In the 3
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 2. Rainfall distribution, intensity, and events from 2009 to 2013. The black bars represent the frequency of mean annual rainfall depths in each rainfall class, the gray bars represent the frequency of mean annual numbers of rainfall events in each rainfall class. Data = mean ± standard deviation (SD).
be stored in the shrub canopy with increasing rainfall intensity. Thus, under wet conditions, the canopy would not influence the total amount of water stored across the various experimental stages. Each simulated rainfall treatment started with the lowest intensity (1.03 mm h−1) until the weight reached a steady-state value (Keim et al., 2006). The simulator was then turned off for 5 min to facilitate the escape of excess water from the plants, following which the rainfall intensity was increased from 1.67 mm h−1 to 10.24 mm h−1.
a resolution of 0.1%. Wetting front location can be detected by measuring the changes of water content in a soil profile. In the present study, the infiltration process was determined by measuring the changes of water content in a soil profile at the different soil depths, based on the assumption that the water reaches a certain depth when the soil moisture content begins to increase. 2.2.3. Canopy interception and canopy storage capacity Canopy interception was calculated by precipitation minus throughfall minus stemflow. In the present study, simulated rainfall experiments for the two shrubs were performed in a controlled environment. A rainfall simulator (model DIK-6000, Daiki Rika Kogyo Co., Japan) was used to simulate rainfall events with varied intensities. The DIK-6000 rainfall simulator has a height of 2 m, a spray grid (1.02m × 1.02 m) and 324 needles (18 × 18), an effective rainfall area of 1.1648 m2, and a rainfall intensity between 0 and 200 mm h−1. By combined use of the coarse and fine adjustment floater on the control panel, eight rainfall intensities established (20, 30, 40, 60, 80, 120, 160, and 200 ml min−1) equivalent to intensities of 1.03, 1.67, 2.24, 3.59, 4.37, 6.74, 9.36, and 10.24 mm h−1 as calibrated by a standard rain gage. The representative shrub individuals in the experimental plots were selected based on the mean values of biology parameters as shown in Table 1. Six samples were obtained for each shrub. The stems of the samples were cut, and the cut end was sealed with liquid paraffin to inhibit immediate wilting (Keim et al., 2006). Following the experiments, the samples were dissected into leaves, stems, and branches. The one-sided leaf area (LA) was calculated based on the photograph method of Li et al. (2004). The longest and shortest diameters through the center of the majority of the canopy were used to calculate the shrub canopy projection area. The leaf area index (LAI) was calculated based on the ratio of leaf area to the canopy projection area. The dry biomass of the leaves, stems, and branches was obtained using the oven drying method (75 °C for about 48 h) and were summed for the dry biomass of the entire shrub. The shrub specimens, which were selected from the experimental plots, were hung from a 1 mm-diameter cable. According to Keim et al. (2006), these specimens were draped from the base of an electronic balance (model LA16001S, Sartorius Co., German, precision: ± 0.1 g) placed on the ceiling immediately above the rainfall simulator. The electronic balance was linked to a laptop computer that automatically saved the weights of the specimens at 3-s intervals during the rainfall treatments (Dunkerley, 2008). We hypothesized that more water would
2.3. Data analysis Rainfall characteristics, throughfall, stemflow, canopy interception, soil moisture, and funneling ratios were statistically analyzed. Data were evaluated using SPSS for Windows 18.0 (SPSS Inc., Chicago, ILL, USA). A one-way analysis of variance (ANOVA) was used to assess the influence of soil moisture in different locations for the two shrubs. Stepwise multiple linear regressions were used to understand the relationship between the canopy structures and stemflow. Multicollinearity was addressed. Based on the soil water balance principle, the cumulative infiltration of stemflow could thus be described as:
CI = (Se − Sb) × Zf
(2)
where CI is the cumulative infiltration (mm); Sb is the soil moisture (%) in the beginning; Se is the soil moisture (%) at the end; and Zf, is the infiltration depth (cm).
3. Results 3.1. Rainfall A total of 241 rainfall events were observed during the study period. There were 160 rainfall events at night and 81 rainfall events during the daytime. The plant surfaces were not completely dry before 40 rainfall events. Low rainfall intensity (<0.5 mm h–1) characterized 41.8% of the rainfall events during the experimental period (Fig. 2A). The mean annual rainfall was 362.9 mm, and the rainfall class distributions are indicated in Fig. 2B. During the experimental period, throughfall and stemflow were measurable for 197 and 135 rainfall events, respectively.
4
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 3. Relationship between rainfall and throughfall, stemflow from 2009 to 2013 for C. korshinskii and H. rhamnoides.
deviations of 24.6 and 73.3 for H. rhamnoides and C. korshinskii, respectively. The water from stemflow moistened the front depth area around the stems more deeply than the area away from the stems (Fig. 5), and the wetting front depths were 1.4–2.8 and 1.5–6.6 times greater, respectively, in the vicinity of the stems than away from the shrubs for H. rhamnoides and C. korshinskii. Volumetric soil water content of the soil layer from 0 to 20 cm was the highest and changed obviously with rainfall with standard deviation of 5.3%. Soil water contents and variation coefficient in deeper soil layers were relatively low (Fig. 6). Soil water content at 0–20 cm depth responded to rain events if the cumulative rainfall over a 3–5 days period exceeded 10–12 mm. Single rain events of less than 10 mm had little effect on soil water content at 20 cm, 30 cm and 40 cm depths (Fig. 6). Soil moisture at soil depth 0–200 cm was 16.4%, 13.2% and 15.3%, 12.8% in area around stem than that away from the shrubs for C. korshinskii and H. rhamnoides from May to September of 2012. The data from the other four years (2009, 2010, 2011 and 2013) are not shown (Fig. 6). The cumulative infiltration I (mm) in the areas both near the stems and away from the shrubs increased with increasing rainfall depth (Fig. 7).
3.2. Throughfall, stemflow, and canopy interception 3.2.1. Throughfall Based on the 197 individual rainfall events that generated throughfall, the throughfall varied from 23.2% to 98.1% with a mean of 62.4% of the total precipitation and a standard deviation of 15.4% for H. rhamnoides. The comparable throughfall values for C. korshinskii were 70.1% with a range 21%–98.3% and a standard deviation of 21.4%. The throughfall for C. korshinskii was higher than that for H. rhamnoides by 7.7% under the same rainfall conditions. Throughfall did not occur when the values of rainfall were less than 0.95 and 0.86 mm for H. rhamnoides and C. korshinskii, respectively. Thus, 0.95 mm and 0.86 mm constitute the storage capacity of the two shrubs (Fig. 3). 3.2.2. Stemflow According to the 135 individual rainfall events that generated stemflow, the stemflow values accounted for 6.7% and 2.4% of gross rainfall and ranged from 0.06 to 4.6% and 1.6%–17.8% with standard deviations of 25.4% and 17.6% for H. rhamnoides and C. korshinskii, respectively. The linear regression equations between stemflow and gross rainfall were presented in Fig. 3.When rainfall was greater than 1.06 and 2.46 mm, stemflow occurred in C. korshinskii and H. rhamnoides, respectively. The funneling ratios were steady when the rainfall depth exceeded 17.0 mm for the two shrubs (Fig. 4). The averaged funneling ratios were 59.1 and 167.4 and ranged 1.5–114.7 and 38.9–444.4 with standard
3.2.3. Canopy interception and water storage capacity During the study period, the averaged percentages of interception loss of C. korshinskii and H. rhamnoides were 23.2% and 35.2%, respectively (Fig. 8). The logarithmic regression equations between canopy interception loss and gross rainfall were presented in Fig. 8. The exponential regression relationships between water storage per 5
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 4. Relationship between funneling ratio and daily rainfall from 2009 to 2013 for C. korshinskii and H. rhamnoides.
Fig. 5. Relationship between rainfall depths and wetting front depths in different positions from 2009 to 2013 for C. korshinskii and H. rhamnoides.
the simulated rainfall intensity was higher than the canopy storage capacity (Fig. 10). Increasing rainfall intensity was associated with an exponential increase in water storage per dry biomass (expressed in g−1) (Fig. 10). Furthermore, H. rhamnoides stored more water per dry biomass (mean, 0.72 g−1, range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1) for all tested rainfall treatments.
leaf area (expressed in an equivalent depth of water) and simulated rainfall intensity were presented in Fig. 9. We discovered that H. rhamnoides could store more water per leaf area for each simulated rainfall treatment (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities and increased with increasing rainfall intensity in both C. korshinskii and H. rhamnoides. The accumulated canopy water storage increased until reaching equilibrium prior to the increased rainfall intensity in succession. The accumulated water storage did not increase further until
6
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 6. Soil moisture distribution in the soil profile around the shrub stem and outside the shrub canopy of 2012 for the two shrubs. A, around the stem for C. korshinskii; B, outside shrub for C. korshinskii; C, around the stem for H. rhamnoides; D, outside shrub for H. rhamnoides.
4. Discussion
growing season. Evapotranspiration losses were reduced and soil moisture accumulated throughout the rainy season, providing the basis for plant growth during the spring of the next year. Heavy rainfall usually has a large amount and a short duration, resulting in high rainfall intensity and large floods, which lead to soil erosion. Because of the vegetative restoration, the runoff has begun to decrease in the Loess Plateau. Land use changes are beginning to create a new water balance in this area. Also, Wang et al. (2011) reported that during medium and large rainfall events, stemflow can effectively supply water to the soil profile. The corresponding rainfall threshold was approximately 4 mm and supplied moisture to the soil at depths lower than 5 cm for the area around the stem of C. korshinskii, while rainfall of 3.5 mm limited soil moisture infiltration within the upper 5 cm soil layer. As there was predominantly no ground cover in the present study, we thus overlooked water interception by ground cover (Jian et al., 2014).
4.1. Effective rainfall for the replenishment of soil moisture The soil moisture profiles show different vertical characteristics among the area close to stem and away from the canopy for C. korshinskii and H. rhamnoides. The infiltration is determined by biophysical factors, rainfall characteristics, meteorological conditions, seasonality and shrub canopy structure and soil surface features (Zhang et al., 2013). The consecutive years of meteorological data indicate that from July to September is the main period of precipitation for the year, accounting for approximately half of the annual precipitation. The soil moisture was replenished by 2–3 rainfall events of >10 mm (Fig. 6). The relationship between increased soil moisture and precipitation, and the thresholds for different land cover types were presented in Fig. 7. The soil moisture increased from July to September, after the end of the 7
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 7. The relationship between rainfall and cumulative infiltration for the two shrubs from 2009 to 2013.
greater water potential gradient was formed in the soil. Thus, the area around the stems had a deeper wetting front (Fig. 5). Also, our previous study found H. rhamnoides consumed more soil water than C. korshinskii, and H. rhamnoides cannot prevent further cavitation or facilitate repair of embolism during the progression of drought (Jian et al., 2015). With a prolonged period of withholding water, water stress inevitably induces xylem cavitation, consequently reducing the hydraulic efficiency of the conductive system. These results suggest that C. korshinskii is more suitable for afforestation than H. rhamnoides in our study area. The rainwater that reached the ground close to the stems of the plants was increased by the presence of the shrubs such that the soil received on average 59.1 and 167.4-times more water than had the shrubs not been there for C. korshinskii and H. rhamnoides, respectively. The funneling ratio varied greatly for different rainfall events, depending on the rainfall depth. Funneling ratios could be greater than 10, and in some studies, far greater than 10 (e.g., Carlyle-Moses, 2004; Li et al., 2008). Our study found that there can be ten or even a hundred times the rainwater that may reach the root area by stemflow water as compared to an open area. Consequently, the probability of water infiltrating to the deeper soil becomes higher near shrub stems. Also, stemflow water in semi-arid shrubs may be assumed to be distributed to a deep soil layer by preferential flow along root channels. Thus,
4.2. Throughfall and stemflow We determined the mean throughfall percentages to be 62.4% and 70.01% of gross rainfall for C. korshinskii and H. rhamnoides, respectively, which are within the ranges detected by Huber and Iroume (2001) for a variety of shrub species (ranging from 55% to 90%). Throughfall values of as high as 96% (African moist brush) and as low as 27% (matorral) of incident rainfall are common (Levia and Frost, 2006). In comparison to the available data, the throughfall percentages for C. korshinskii and H. rhamnoides were mid-range (Crockford and Richardson, 2000). The rainfall thresholds were 1.06 and 2.46 mm to initiate stemflow according to the five-year data (Fig. 3). Our thresholds agreed with those of previous studies in similar regions (Carlyle–Moses, 2004; Li et al., 2008; Wang et al., 2013; Zhang et al., 2013). We found that C. korshinskii could generate more stemflow water and that the rainfall threshold was lower than H. rhamnoides, which we believe is related to the smooth bark of C. korshinskii. The leaves, twigs, and branches of the C. korshinskii individuals have a layer of wax, which contributed to stemflow generation. In contrast, H. rhamnoides has thick leaves and rough bark with many diagonal cracks, thus resulting in less efficient stemflow production (Jian et al., 2013). The excess water significantly enhanced the moisture of the upper soil layer, and a
Fig. 8. Relationship between gross rainfall and interception of C. korshinskii and H. rhamnoides. 8
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 9. Canopy storage capacity per leaf area and dry biomass of sample varying with eight rainfall intensities for C. korshinskii and H. rhamnoides. Values are equilibrium storage averaged across all test for each species (n = 6). Vertical bars represent the standard error.
for C. korshinskii and H. rhamnoides, respectively. This discrepancy was attributed to the collected aggregate throughfall data being unable to estimate the disaggregation of interception losses as a result of static canopy storage and intra-storm evaporation during rainfall events (Dunkerley, 2008). The indirect method thus overestimates water storage capacity. On the contrary, our previous study found the specific storage capacity of samples soaked in water to be 20% higher than the indirect method. However, immersion will inexorably cause more water to be absorbed by the samples than natural rainfall events. Garcia-Estringana et al. (2010) reported that the magnitude of the canopy stored water per dry biomass within the range. Based on a simulated rainfall intensity of 11.53 mm h−1, water storage per dry biomass (expressed in mL g−1) of A. ordosica was similar to that of Dorycnium pentaphyllum, and water storage per dry biomass of C. korshinskii and H. scoparium was akin to that of Cistus albidus in GarciaEstringana et al. (2010) using a simulated rainfall of 13 mm h−1. A comparison of thin/thicker leaves and thin/larger stems revealed that broad-leafed plants store more water per biomass than fine-leafed plants (Keim et al., 2006). The aforementioned study noted that sample biomass was an unreliable predictor of storage across species and suggested that leaf biomass was of intermediate use as a storage predictor.
Fig. 10. Example data from tests of rainfall simulation on shrubs. In each case, the black line is the depth-equivalent mass of water stored on the shrub; vertical dashed lines indicate step increases in rainfall intensity. Dips in stored water are the result of 3-min rainfall pauses.
5. Conclusions In the present study, the interception losses by the xerophytic shrubs used for re-vegetation in the Loess Plateau in China were estimated. Elucidating the impact of re-vegetation efforts in the semiarid Loess Plateau is of practical significance for effectively managing the vegetation to maximize the hydrological cycle of natural rainfall. Thus, one may establish an artificial ecology system with xerophytic shrubs such as C. korshinskii and H. rhamnoides. The hydrological outcomes of interception by xerophytic shrubs vary depending on the vegetation cover, canopy structure, and rainfall characteristics (e.g. rainfall intensity, depth, and annual rainfall distribution characteristics). Typically, interception results in a net loss of water for the hydrological cycle. The findings of shrub canopy rainfall interception studies thus contribute to the implementation of re-vegetation and assessments of water budget in the Loess Plateau. We hope that the findings of this study can be applied to other shrub-dominated ecosystems.
stemflow water could infiltrate to deeper soil layers that can be utilized by the shrub plants effectively. Because of the structural properties of shrubs and the surface characteristics of leaves provide the possibility for deposition and accumulation of dust and dry fall on the surface of leaves, so stemflow could transport these substances to the soil, which could improve the soil quality and develop the ‘fertile islands’ under shrub canopies (Martinez-Meza and Whitford, 1996). Higher funneling ratios for C. korshinskii and H. rhamnoides indicate that stemflow can be an available nutrient source for plant growth in semi-arid Loess Plateau.
4.3. Canopy interception and water storage capacity Based on the regression analysis of indirect open-field and direct simulated rainfall-throughfall methods, the water storage capacity for C. korshinskii and H. rhamnoides was determined to be 0.86, 0.95 mm and 0.44, 0.59 mm, respectively, for each method. The indirect method obtained values that were 49% and 38% higher than the direct method
Acknowledgments This project was supported by the National Key Research Priorities 9
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Program of China (2016YFC0402402); National Natural Science Foundation of China (31700370); National Natural Science Foundation of China (51409116); Startup Research Fund of Zhengzhou University (1512323001); Institution of higher learning key scientific research project, Henan Province (16A570010); Foundation of drought climate science (IAM201705); China postdoctoral science foundation (2016M602255); Henan province postdoctoral science foundation; National Natural Science Foundation of China (91025015). We would like to thank LetPub (www.letpub.com) for providing linguistic assistance during the preparation of this manuscript.
Jian, S.Q., Zhang, X.L., Li, D., Wang, D., Wu, Z.N., Hu, C.H., 2018. The effects of stemflow on redistributing precipitation and infiltration around shrubs. J. Hydrol. Hydromech. 66 (1), 79–86. Levia, D.F., Frost, E.E., 2006. A Review and Evaluation of Stemflow Literature in the Hydrologic and Biogeochemical Cycles of Forested and Agricultural Ecosystems. Department of Geography, Southern Illinois University, Carbondale, IL, pp. 62901–64514 J. Hydrol. 274, 1–29. Li, X.Y., Liu, L.Y., Gao, S.Y., Ma, Y.J., Yang, Z.P., 2008. Stemflow in three shrubs and its effect on soil water enhancement in semiarid loess region of China. Agric. Forest Meteorol. 148 (10) 1501–150. 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 Chin. J. Arid Environ. 57, 1–16. Keim, R.F., Skaugset, A.E., Weiler, M., 2006. Storage of water on vegetation under simulated rainfall of varying intensity. Adv. Water Resour. 26, 974–986. Martinez-Meza, E., Whitford, W.G., 1996. Stemflow, throughfall and channelization of stemflow by roots in three Chihuahuan desert shrubs. J. Arid Environ. 32 (3), 271–287. Mauchamp, A., Janeau, J.L., 1993. Water funneling by the crown of Flourensia cernua, a Chihuahuan Desert shrub. J. Arid Environ 25, 299–306. Molchanov, A.A., 1963. The Hydrological Role of Forests. Israel Program for Scientific Translations, Israel, pp. 407. Moran, M.S., Scott, R.L., Keefer, T.O., Emmerich, W.E., Hernandez, M., Nearing, G.S., Paige, G.B., Cosh, M.H., O'Neill, P.E., 2009. Partitioning evapotranspiration in semiarid grassland and shrubland ecosystems using time series of soil surface temperature. Agric. For. Meteorol. 149 (1), 59–72. Muzylo, A., Llorens, P., Valente, F., Keizer, J.J., Domingo, F., Gash, J.H.C., 2009. A review of rainfall interception modelling. J. Hydrol. 370, 191–206. Owens, M.K., Lyons, R.K., Alejandro, C.L., 2006. Rainfall partitioning within semiarid juniper communities: effects of event size and canopy cover. Hydrol. Processes 20, 3179–3189. Pérez-Suárez, M., Fenn, M.E., Cetina-Alcala, V.M., Aldrete, A., 2008. The effects of canopy cover on throughfall and soil chemistry in two forest sites in the México City air basin. Atmósfera 21 (1), 83–100. Rutter, A., Morton, A., Robins, P., 1975. A predictive model of rainfall interception in forests. II. Generalization of the model and comparison with observations in some coniferous and hardwood stands. J. Appl. Eco. 12, 367–380. Sahin, V., Hall, M.J., 1996. The effects of afforestation and deforestation on water yields. J. Hydro. 178, 293–309. Sun, X., Onda, Y., Kato, H., Gomi, T., Komatsu, H., 2015. Effect of strip thinning on rainfall interception in a Japanese cypress plantation. J. Hydrol. 525, 607–618. Tromble, J.M., 1987. Water interception by two arid land shrubs. J. Arid Environ. 15, 65–70. Wang, Y.Q., Shao, M.A., Shao, H.B., 2010. A preliminary investigation of the dynamic characteristics of dried soil layers on the Loess Plateau of China. J. Hydrol. 381, 9–17. Wang, Y.Q., Shao, M.A., Zhu, Y.J., Liu, Z.P., 2011. Impacts of land use and plant characteristics on dried soil layers in different climatic regions on the Loess Plateau of China. Agric. For. Meteorol. 151, 437–448. Wang, X.P., Zhang, Y.F., Wang, Z.N., Pan, Y.X., Hu, R., Li, X.J., Zhang, H., 2013. Influence of shrub canopy morphology and rainfall characteristics on stemflow within a revegetated sand dune in the Tengger Desert. NW China. Hydrol. Process 27, 1501–1509. Williamson, T.N., Newman, B.D., Graham, R.C., Shouse, P.J., 2005. Regolith water in zero-order chaparral and perennial grass watersheds four decades after vegetation conversion. Vadose Zone J 3, 1007–1016. Xiao, Q., McPherso, E.G., Simpson, J.R., Ustin, S.L., 1998. Raınfall ınterceptıon by Sacramento's urban forest. Journal of Arboricul 24 (4), 235–244. Yurtseven, I., Zengin, M., 2013. Neural network modeling of rainfall interception in four different forest stands. Ann. For. Res. 56 (2), 351–362. Zhao, C.Y., Feng, Z.D., Chen, G.D., 2004. Soil water balance simulation of alfalfa (Medicago sativa L.) in the semiarid Chinese Loess Plateau. Agr. Water Manage 69 (2), 101–114. Zhang, Y.F., Wang, X.P., Hu, R., Pan, Y.X., Zhang, H., 2013. Stemflow in two xerophytic shrubs and its significance to soil water and nutrient enrichment. Ecol. Res. 28, 567–579.
References Ahmadi, M.T., Attarod, P., Mohadjer, M.M.R., Rahmani, R., Fathi, J., 2009. Partitioning rainfall into throughfall, stemflow, and interception loss in an oriental beech (Fagus orientalis Lipsky) forest during the growing season. Turk. J. Agric. For. 33, 557–568. Asadian, Y., Weiler, M., 2009. A new approach in measuring rainfall interception by urban trees in coastal British Columbia. Water Qual. Res. J. Can. 44 (1), 16–25. Bosch, J.H., Hewlett, J.D., 1982. A review of catchment experiments to determine the effect of vegetation changes and water yield and evapotranspiration. J. Hydrol. 55, 3–23. Carlyle-Moses, D.E., 2004. Throughfall, stemflow, and canopy interception loss fluxes in a semi-arid Sierra Madre Oriental matorral community. J. Arid Environ. 58, 181–202. Carlyle-Moses, D.E., Price, A.G., 2006. Growing-season stemflow production within a deciduous forest of southern Ontario. Hydrol. Process. 20, 3651–3663. Crockford, R.H., Richardson, D.P., 2000. Partitioning of rainfall into throughfall, stemflow and interception: effect of forest type, ground cover and climate. Hydro. Process. 14, 2903–2920. David, J.S., Valente, F., Gash, J.H.C., 2005. Evaporation of intercepted rainfall. In: Anderson, M.G. (Ed.), Encyclopaedia of Hydrological Sciences. John Wiley, Chichester, pp. 627–634. Dingman, S., 2002. Physical Hydrology. Prentice Hall, Upper Saddle River, pp. 646. Dunkerley, D., 2000. Measuring interception loss and canopy storage in dryland vegetation: a brief review and evaluation of available research strategies. Hydrol. Process. 14, 669–678. Dunkerley, D.L., 2008. Intra-storm evaporation as a component of canopy interception loss in dryland shrubs: observations from Fowlers Gap, Australia. Hydrol. Proc. 22, 1985–1995. Fu, B.J., Liu, Y., Lu, Y.H., He, C.S., Zeng, Y., Wu, B.F., 2011. Assessing the soil erosion control service of ecosystems change in the Loess Plateau of China. Ecol. Complex. 8 (4), 284–293. Gash, J., Shuttleworth, W., 2007. Evaporation. Benchmark Papers in Hydrology 2. IAHS Press, Wallingford, pp. 521. Hamilton, E.L., Rowe, P.B., 1949. Rainfall Interception by Chaparral in California. State of California, Dept of Natural Resources, Division of Forestry, Sacramento, California, USA. Herwitz, S.R., 1986. Infiltration-excess caused by stemflow in a cyclone-prone tropical rainforest. Earth Surf. Proc. Land 11, 401–412. Horton, R., 1919. Rainfall interception. Mon. Weather Rev 47, 603–623. Huber, A., Iroume, A., 2001. Variability of annual rainfall partitioning for different sites and forest covers in Chile. J. Hydro. 248, 78–92. IUSS Working Group WRB. 2006. World Reference Base for Soil Resources 2006. 2nd editioned.. World Soil Resources Reports No. 203.FAO, Rome. Janík, R., Pichler, J., 2008. Amounts of throughfall and lysimetric water in a submountain beech forest in the Kremnické vrchy MTS (West Carpathian Mts., Slovakia). J. For. Sci. 54 (5), 207–211. Jian, S.Q., Zhao, C.Y., Fang, S.M., Yu, K., 2014. Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau. J. Hydrol. Hydromech 62 (2), 89–96. Jian, S.Q., Zhao, C.Y., Fang, S.M., Yu, K., 2015. Evaluation of water use of Caragana korshinskii and Hippophae rhamnoides in the Chinese Loess Plateau. Can. J. For. Res 45, 15–25.
10
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China
T
⁎
Jian Shengqia, , Hu Caihonga, Zhang Guodongb, Zhang Jinpinga a b
College of Water Conservancy & Environment, Zhengzhou University, Science Road 100, Zhengzhou, China Henan Yellow River Hydrological Survey and Design Institute, Chengdong Road 100, Zhengzhou, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Throughfall Stemflow Canopy interception Water storage capacity Loess Plateau
The Loess Plateau, China, has been subject to 40 years of re-vegetation predominantly with the xerophytic shrubs Caragana korshinskii and Hippophae rhamnoides. Throughfall, stemflow, canopy interception, and water storage capacity experiments for the two shrubs were conducted from May to September during the period 2009–2013. The results showed that the throughfall percentages averaged 62.4% and 70.1% of gross rainfall for H. rhamnoides and C. korshinskii, respectively, while stemflow accounted for 2.4% and 6.7% of the gross rainfall for the two shrubs. The rainfall threshold for stemflow generation was 2.46 and 1.06 mm for H. rhamnoides and C. korshinskii, respectively. The wetting front depths for the two shrubs in the area around the stems were deeper than away from the shrubs. The averaged percentages of interception loss in H. rhamnoides and C. korshinskii were 35.2% and 23.2%. Additionally, H. rhamnoides had greater water storage capacity per leaf area for each simulated rainfall intensity (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities. For all the tested rainfall intensities, H. rhamnoides could store more water per dry biomass (mean, 0.72 g−1; range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1). The present study can inform revegetation projects, water budget analyses, and modeling efforts aimed at understanding rainfall water movement within shrub communities in the semiarid Chinese Loess Plateau, China.
1. Introduction Intensive soil erosion, soil desertification, and vegetation degradation are features of the soil and water transition zone in the Loess Plateau region in China (Fu et al., 2011). Numerous vegetation restoration measures have been implemented by the Chinese government, including the planting of perennial shrubs and grasses, in an attempt to restore the environment and reduce soil and water loss in the region. Improving the hydrological aspects of the environment via ecological restoration is two-tiered and involves (1) the prevention of water and soil loss by altering water cycle paths. Indigenous perennial plants can achieve this by increasing the effective vegetation coverage and thus minimizing surface runoff. The second aspect is related to (2) increasing the soil moisture content in order to effectively enhance productivity (Zhao et al., 2004). The precipitation that falls on vegetation is intercepted by the plant canopy for a certain time period. A portion of the water evaporates (interception loss) and some of it infiltrates into the soil as it trickles down from the plant canopy (throughfall) or runs down the stems to the
⁎
bottom of the plants (stemflow). Thus, the spatial distribution of precipitation is altered via throughfall and stemflow, and together with interception losses, these can significantly influence the ecology and hydrology in water-stressed areas. From an ecological perspective, stemflow results in the concentration of rainfall and nutrients in the vicinity of the stems of the plants, where water can easily infiltrate into the soil, which enhances water availability during periods of drought and promotes plant growth and survival (Moran et al., 2009). Stemflow is actually believed to be an adaptive mechanism for survival during periods of drought (Mauchamp and Janeau, 1993; Carlyle-Moses and Price, 2004). In terms of hydrology, alterations in plant cover have major impacts. For instance, the replacement of pasture or agricultural crops with woody plants results in reduced surface runoff (Trimble, 1987; Owens et al., 2006) and, vice versa, when trees are replaced with forage species, stream and river discharge increases (Bosch and Hewlett, 1982; Dingman, 2002; Williamson et al., 2005). One explanation for this is that woody plants store rainwater on a greater surface area, thus resulting in greater interception losses. These losses can exceed 25% of the gross annual
Corresponding author. E-mail addresses: [email protected], [email protected] (S. Jian).
https://doi.org/10.1016/j.agrformet.2019.107713 Received 25 December 2018; Received in revised form 14 August 2019; Accepted 16 August 2019 0168-1923/ © 2019 Elsevier B.V. All rights reserved.
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
shaped with a narrow main stem with thick leaves (30–60 mm in length; 5–l0 mm in width) and a rough surface (Fig. 1). Caragana korshinskii has a more developed root system than H. rhamnoides, with more than half of the fine roots occurring in the 0- and 40-cm soil layer (Jian et al., 2014). Almost no ground cover exists in the H. rhamnoides and C. korshinskii plantations.
rainfall with mean estimates of 26% for conifer woods, 28% for broadleaf and 20% for shrubs (Sahin and Hall, 1996; Carlyle-Moses, 2004; Sun et al., 2015; Jian et al., 2018). Throughfall, stemflow, and interception measurements were initially conducted in the mid-19th century in Europe (Molchanov, 1963) and in the early 20th century in the USA (Janik and Pichler, 2008; Pérez-Suárez et al., 2008) and involved assessing rainfall partitioning in the hydrological cycle. The modeling of interception loss was first attempted by Horton (1919) and later reproduced by Gash and Shuttleworth (2007). However, estimates of interception loss were empirically derived from gross precipitation until the 1970s. Following Horton's work, Rutter et al. (1975) established the first conceptual model that considered interception as an evaporative loss (Muzylo et al., 2009). Numerous studies on throughfall, stemflow, and interception in different plant species exist (Xiao et al., 1998; Ahmadi et al., 2009; Asadian and Weiler, 2009; Yurtseven and Zengin, 2013; Sun et al., 2015). These studies on interception are pivotal for ascertaining the water-cycle elements related to various types of stands and for evaluating the water budget, allowing for significant alterations in forest ecosystems and climate to be assessed. A recent review of rain interception by vegetation in the Loess Plateau of China demonstrated that the data available in the literature were predominantly focused on tree species, while only 9% of published reports included shrub species (Jian et al., 2018) despite the fact that significant areas of the Loess Plateau constitute shrublands as a result of the ecological restoration efforts. The rainfall interception present in forest canopies typically results in a net water loss, while this is not always the result when the plant cover is reduced in height (David et al., 2005). Additionally, the measurement of interception fluxes is technically challenging (Dunkerley, 2000). The characteristics of throughfall, stemflow, and interception have been studied in re-vegetated shrub ecosystems (Wang et al., 2011). However, most research used experimental data spanning 1–2 years, which are not appropriate for assessing long term impacts on rainfall partitioning. Additionally, the patterns of stemflow infiltration associated with soil water content enhancement have not been extensively studied. The aims of the present study were to (1) estimate the long-term (five years) throughfall, stemflow, interception, and water storage capacity in Caragana korshinskii and Hippophae rhamnoides in a small catchment in the western Chinese Loess Plateau; and (2) assess the features of stemflow water infiltration in the re-vegetated shrublands in the Loess Plateau.
2.2. Experimental design In the experimental plots, we selected 12 H. rhamnoides individuals and 12 C. korshinskii individuals to measure throughfall and stemflow, respectively. The plants were growing on flat terrain (assuming that all the stemflow water had reached the soil) and were isolated from one another (Table 2). A recording gage (Onset Computer Corporation, Pocasset, MA, USA) was used to measure the total gross rainfall and rainfall intensity. Throughfall and stemflow were calculated under natural rainfall conditions based on Hamilton and Rowe's (1949) standard for storm and rainfall events, defined as follows: (1) an individual storm is a rainfall period separated by dry intervals of at least 24 h; (2) an individual rainfall event is considered to be a rainfall event separated by dry intervals of at least 4 h. 2.2.1. Throughfall We measured the throughfall of each C. korshinskii and H. rhamnoides plant by means of nine throughfall collecting cups situated 15 cm above the ground below the canopies of individual plants (Fig. 1). The throughfall collecting cups had an inner diameter of 200 mm (in accordance with that of a standard rain gage). Beneath the canopy, the cups were placed 120° apart in three directions. The cups were not placed entirely beneath a gap in the shrub canopy or beneath foliage in an attempt to prevent the under- or over-estimation of interception. The cups were positioned 20, 50 and 100 cm from the stems. To reduce evaporative loss from the open cups, throughfall was measured immediately following each rainfall treatment. 2.2.2. Stemflow Stemflow was measured using funnels constituted of flexible aluminum foil plates that were fixed over the branches. The stemflow collectors extended less than 5 mm from the stem to stop the throughfall water from running into the collectors. A plastic hose connected the funnels and the collection container (Fig. 1). Stemflow depth is the stemflow volume divided by the canopy projected area. Herwitz (1986) found that stemflow at the point scale can be expressed as a funneling ratio, F:
2. Materials and methods
F = V /(B × P )
2.1. Study area
(1)
where V is the stemflow volume (L), B is the basal area of the shrub (m2), and P is the quantity of rainfall at the top of the canopy (mm). The product B × P indicates the volume of water that would have been measured by a rain gage with an opening equivalent to that of the tree B. Thus, F indicates the ratio of the rainfall reaching the base of the tree to the rainfall that would have reached the ground in the absence of a tree. Funneling ratios >1 indicate that canopy characteristics other than tree bole are accounting for stemflow (Herwitz, 1986; Carlyle–Moses and Price, 2006). Three individuals each of C. korshinskii and H. rhamnoides situated on a flat surface were selected for determining the patterns of stemflow infiltration related to the soil water content enhancement. Volumetric soil moisture was determined using EC-5 sensors (Decagon Devices Inc., Pullman, WA, USA) (Em 50, Decagon Devices, Pullman, WA, USA), which were installed at depths of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, and 200 cm below the ground surface about 5 cm from the shrub stem and in an open area approximately 30 cm from the periphery of the plant. Data were collected by a logger every10 min. For probe installation, a pit of sufficient width was dug in the soil and the probes were inserted into the soil through the
Fieldwork was performed in H. rhamnoides and C. korshinskii plantations from 2009 to 2013 in the Anjiapo catchment of the western Chinese Loess Plateau. The area has an average annual precipitation of 420 mm (1965–2008), 60% of which occurs between July and September. The monthly average air temperature varies from −7.4 to 27.5°C, and the annual mean temperature is 6.3°C (1958–2008). The average annual evaporation is 1510 mm (1958–2008). The soil is silt loam of loess origin (Wang et al., 2010) and is classified as Chernozem according to the IUSS Working Group WRB (2006). Land use in the research area includes croplands, artificial shrublands, grasslands, and woodlands. All the experiments were conducted in representative C. korshinskii and H. rhamnoides experimental plots of 100 × 100 m size in the study area. Table 1 provides basic information on the C. korshinskii and H. rhamnoides plots. Both C. korshinskii and H. rhamnoides have been extensively planted in the study region and were sown in 1988 as 2-year-old seedlings with a spacing of 3 × 3 m. The leguminous shrub C. korshinskii has a semispherical shape, many slender branches, a smooth plant surface, and even, pinnate composite leaves. In contrast, H. rhamnoides is cone2
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Table 1 A brief overview of the sampling areas for the C. korshinskii and H. rhamnoides plantations in the Anjiagou catchment. Parameter
Geographical parameters Biological parameters
Soil parameters
Sample numbers
Slope aspect Slope position Plant height (mm) Basic diameter-branch (mm) Basic diameter-twig (mm) Projected area (m2) Leaf area index (LAI)
– – 80 150 150 50 320
Clay (<0.002 mm; %) Silt (0.05–0.002 mm; %) Sand (0.05–2 mm; %) Organic matter (%) pH
3 3 3 3 3
Mean ± SD C. korshinskii
H. rhamnoides
SE Middle 1700 ± 110 15.91 ± 2.1 19.11 ± 0.19 3.02 ± 0.44 1.04 ± 0.09, 1.58 ± 0.22, 2.15 ± 0.16, 2.16 ± 0.15 9.17 ± 1.20 75.59 ± 9.21 15.24 ± 1.16 0.68 ± 0.08 8.1 ± 0.94
SE Upper 191 ± 17 13.51 ± 0.48 19.54 ± 0.32 3.54 ± 0.21 0.93 ± 0.12, 1.15 ± 0.17 1.87 ± 0.21, 2.15 ± 0.20 11.04 ± 2.3 76.69 ± 11.34 12.27 ± 2.81 0.71 ± 0.04 7.9 ± 0.75
*Slope aspect and slope position were determined by a compass; LAI was determined by a canopy analyzer (LAI2000, LI–COR, USA) on 14th June, 15th July, 15th August, and 14th September. The four values for LAI are from June to September. Soil organic matter was determined using the potassium dichromate volumetric method; pH was determined by potentiometry; particle size distribution was determined by sedimentation. Soil properties are for the top 1 m. Data = mean ± SD.
Fig. 1. Schematic diagram. (A) C. korshinskii; (B) H. rhamnoides; and (C) stemflow collection. (D) and (E) are the leaf characteristics of the two shrubs.
Table 2 Descriptive statistics (mean ± standard deviation) of branches and canopy projection of the 12 sampled C. korshinskii individuals and 12 H. rhamnoides individuals used in the experiments. Shrub branch Species
Number
Diameter (cm)
Length (cm)
Height (cm)
Angle (°)a
Projected area (m2)
Canopy bulk (m3)
C. korshinskii H. rhamnoides
20 ± 5 12 ± 4
1.66 ± 0.19 1.76 ± 0.25
196 ± 21 208 ± 25
178 ± 12 199 ± 21
50 ± 8 55 ± 12
4.93 ± 1.21 4.12 ± 1.55
2.54 ± 0.42 2.81 ± 0.53
a
Angle in degrees of the upward branch to the ground surface. Data = mean ± SD.
current study, there was almost no ground cover in the plantations, and thus the water intercepted beneath the shrub canopies was ignored. The soil moisture sensor is capable of measuring volumetric saturation values between 0% and 100%, with an accuracy of ± 1.0% and
side of the pit and placed horizontally in the direction of maximum slope of the terrain. The pit was then carefully refilled, avoiding perturbations and minimizing damage to the root system as far as possible, and the surface was contoured similarly to the surrounding slope. In the 3
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 2. Rainfall distribution, intensity, and events from 2009 to 2013. The black bars represent the frequency of mean annual rainfall depths in each rainfall class, the gray bars represent the frequency of mean annual numbers of rainfall events in each rainfall class. Data = mean ± standard deviation (SD).
be stored in the shrub canopy with increasing rainfall intensity. Thus, under wet conditions, the canopy would not influence the total amount of water stored across the various experimental stages. Each simulated rainfall treatment started with the lowest intensity (1.03 mm h−1) until the weight reached a steady-state value (Keim et al., 2006). The simulator was then turned off for 5 min to facilitate the escape of excess water from the plants, following which the rainfall intensity was increased from 1.67 mm h−1 to 10.24 mm h−1.
a resolution of 0.1%. Wetting front location can be detected by measuring the changes of water content in a soil profile. In the present study, the infiltration process was determined by measuring the changes of water content in a soil profile at the different soil depths, based on the assumption that the water reaches a certain depth when the soil moisture content begins to increase. 2.2.3. Canopy interception and canopy storage capacity Canopy interception was calculated by precipitation minus throughfall minus stemflow. In the present study, simulated rainfall experiments for the two shrubs were performed in a controlled environment. A rainfall simulator (model DIK-6000, Daiki Rika Kogyo Co., Japan) was used to simulate rainfall events with varied intensities. The DIK-6000 rainfall simulator has a height of 2 m, a spray grid (1.02m × 1.02 m) and 324 needles (18 × 18), an effective rainfall area of 1.1648 m2, and a rainfall intensity between 0 and 200 mm h−1. By combined use of the coarse and fine adjustment floater on the control panel, eight rainfall intensities established (20, 30, 40, 60, 80, 120, 160, and 200 ml min−1) equivalent to intensities of 1.03, 1.67, 2.24, 3.59, 4.37, 6.74, 9.36, and 10.24 mm h−1 as calibrated by a standard rain gage. The representative shrub individuals in the experimental plots were selected based on the mean values of biology parameters as shown in Table 1. Six samples were obtained for each shrub. The stems of the samples were cut, and the cut end was sealed with liquid paraffin to inhibit immediate wilting (Keim et al., 2006). Following the experiments, the samples were dissected into leaves, stems, and branches. The one-sided leaf area (LA) was calculated based on the photograph method of Li et al. (2004). The longest and shortest diameters through the center of the majority of the canopy were used to calculate the shrub canopy projection area. The leaf area index (LAI) was calculated based on the ratio of leaf area to the canopy projection area. The dry biomass of the leaves, stems, and branches was obtained using the oven drying method (75 °C for about 48 h) and were summed for the dry biomass of the entire shrub. The shrub specimens, which were selected from the experimental plots, were hung from a 1 mm-diameter cable. According to Keim et al. (2006), these specimens were draped from the base of an electronic balance (model LA16001S, Sartorius Co., German, precision: ± 0.1 g) placed on the ceiling immediately above the rainfall simulator. The electronic balance was linked to a laptop computer that automatically saved the weights of the specimens at 3-s intervals during the rainfall treatments (Dunkerley, 2008). We hypothesized that more water would
2.3. Data analysis Rainfall characteristics, throughfall, stemflow, canopy interception, soil moisture, and funneling ratios were statistically analyzed. Data were evaluated using SPSS for Windows 18.0 (SPSS Inc., Chicago, ILL, USA). A one-way analysis of variance (ANOVA) was used to assess the influence of soil moisture in different locations for the two shrubs. Stepwise multiple linear regressions were used to understand the relationship between the canopy structures and stemflow. Multicollinearity was addressed. Based on the soil water balance principle, the cumulative infiltration of stemflow could thus be described as:
CI = (Se − Sb) × Zf
(2)
where CI is the cumulative infiltration (mm); Sb is the soil moisture (%) in the beginning; Se is the soil moisture (%) at the end; and Zf, is the infiltration depth (cm).
3. Results 3.1. Rainfall A total of 241 rainfall events were observed during the study period. There were 160 rainfall events at night and 81 rainfall events during the daytime. The plant surfaces were not completely dry before 40 rainfall events. Low rainfall intensity (<0.5 mm h–1) characterized 41.8% of the rainfall events during the experimental period (Fig. 2A). The mean annual rainfall was 362.9 mm, and the rainfall class distributions are indicated in Fig. 2B. During the experimental period, throughfall and stemflow were measurable for 197 and 135 rainfall events, respectively.
4
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 3. Relationship between rainfall and throughfall, stemflow from 2009 to 2013 for C. korshinskii and H. rhamnoides.
deviations of 24.6 and 73.3 for H. rhamnoides and C. korshinskii, respectively. The water from stemflow moistened the front depth area around the stems more deeply than the area away from the stems (Fig. 5), and the wetting front depths were 1.4–2.8 and 1.5–6.6 times greater, respectively, in the vicinity of the stems than away from the shrubs for H. rhamnoides and C. korshinskii. Volumetric soil water content of the soil layer from 0 to 20 cm was the highest and changed obviously with rainfall with standard deviation of 5.3%. Soil water contents and variation coefficient in deeper soil layers were relatively low (Fig. 6). Soil water content at 0–20 cm depth responded to rain events if the cumulative rainfall over a 3–5 days period exceeded 10–12 mm. Single rain events of less than 10 mm had little effect on soil water content at 20 cm, 30 cm and 40 cm depths (Fig. 6). Soil moisture at soil depth 0–200 cm was 16.4%, 13.2% and 15.3%, 12.8% in area around stem than that away from the shrubs for C. korshinskii and H. rhamnoides from May to September of 2012. The data from the other four years (2009, 2010, 2011 and 2013) are not shown (Fig. 6). The cumulative infiltration I (mm) in the areas both near the stems and away from the shrubs increased with increasing rainfall depth (Fig. 7).
3.2. Throughfall, stemflow, and canopy interception 3.2.1. Throughfall Based on the 197 individual rainfall events that generated throughfall, the throughfall varied from 23.2% to 98.1% with a mean of 62.4% of the total precipitation and a standard deviation of 15.4% for H. rhamnoides. The comparable throughfall values for C. korshinskii were 70.1% with a range 21%–98.3% and a standard deviation of 21.4%. The throughfall for C. korshinskii was higher than that for H. rhamnoides by 7.7% under the same rainfall conditions. Throughfall did not occur when the values of rainfall were less than 0.95 and 0.86 mm for H. rhamnoides and C. korshinskii, respectively. Thus, 0.95 mm and 0.86 mm constitute the storage capacity of the two shrubs (Fig. 3). 3.2.2. Stemflow According to the 135 individual rainfall events that generated stemflow, the stemflow values accounted for 6.7% and 2.4% of gross rainfall and ranged from 0.06 to 4.6% and 1.6%–17.8% with standard deviations of 25.4% and 17.6% for H. rhamnoides and C. korshinskii, respectively. The linear regression equations between stemflow and gross rainfall were presented in Fig. 3.When rainfall was greater than 1.06 and 2.46 mm, stemflow occurred in C. korshinskii and H. rhamnoides, respectively. The funneling ratios were steady when the rainfall depth exceeded 17.0 mm for the two shrubs (Fig. 4). The averaged funneling ratios were 59.1 and 167.4 and ranged 1.5–114.7 and 38.9–444.4 with standard
3.2.3. Canopy interception and water storage capacity During the study period, the averaged percentages of interception loss of C. korshinskii and H. rhamnoides were 23.2% and 35.2%, respectively (Fig. 8). The logarithmic regression equations between canopy interception loss and gross rainfall were presented in Fig. 8. The exponential regression relationships between water storage per 5
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 4. Relationship between funneling ratio and daily rainfall from 2009 to 2013 for C. korshinskii and H. rhamnoides.
Fig. 5. Relationship between rainfall depths and wetting front depths in different positions from 2009 to 2013 for C. korshinskii and H. rhamnoides.
the simulated rainfall intensity was higher than the canopy storage capacity (Fig. 10). Increasing rainfall intensity was associated with an exponential increase in water storage per dry biomass (expressed in g−1) (Fig. 10). Furthermore, H. rhamnoides stored more water per dry biomass (mean, 0.72 g−1, range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1) for all tested rainfall treatments.
leaf area (expressed in an equivalent depth of water) and simulated rainfall intensity were presented in Fig. 9. We discovered that H. rhamnoides could store more water per leaf area for each simulated rainfall treatment (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities and increased with increasing rainfall intensity in both C. korshinskii and H. rhamnoides. The accumulated canopy water storage increased until reaching equilibrium prior to the increased rainfall intensity in succession. The accumulated water storage did not increase further until
6
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 6. Soil moisture distribution in the soil profile around the shrub stem and outside the shrub canopy of 2012 for the two shrubs. A, around the stem for C. korshinskii; B, outside shrub for C. korshinskii; C, around the stem for H. rhamnoides; D, outside shrub for H. rhamnoides.
4. Discussion
growing season. Evapotranspiration losses were reduced and soil moisture accumulated throughout the rainy season, providing the basis for plant growth during the spring of the next year. Heavy rainfall usually has a large amount and a short duration, resulting in high rainfall intensity and large floods, which lead to soil erosion. Because of the vegetative restoration, the runoff has begun to decrease in the Loess Plateau. Land use changes are beginning to create a new water balance in this area. Also, Wang et al. (2011) reported that during medium and large rainfall events, stemflow can effectively supply water to the soil profile. The corresponding rainfall threshold was approximately 4 mm and supplied moisture to the soil at depths lower than 5 cm for the area around the stem of C. korshinskii, while rainfall of 3.5 mm limited soil moisture infiltration within the upper 5 cm soil layer. As there was predominantly no ground cover in the present study, we thus overlooked water interception by ground cover (Jian et al., 2014).
4.1. Effective rainfall for the replenishment of soil moisture The soil moisture profiles show different vertical characteristics among the area close to stem and away from the canopy for C. korshinskii and H. rhamnoides. The infiltration is determined by biophysical factors, rainfall characteristics, meteorological conditions, seasonality and shrub canopy structure and soil surface features (Zhang et al., 2013). The consecutive years of meteorological data indicate that from July to September is the main period of precipitation for the year, accounting for approximately half of the annual precipitation. The soil moisture was replenished by 2–3 rainfall events of >10 mm (Fig. 6). The relationship between increased soil moisture and precipitation, and the thresholds for different land cover types were presented in Fig. 7. The soil moisture increased from July to September, after the end of the 7
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 7. The relationship between rainfall and cumulative infiltration for the two shrubs from 2009 to 2013.
greater water potential gradient was formed in the soil. Thus, the area around the stems had a deeper wetting front (Fig. 5). Also, our previous study found H. rhamnoides consumed more soil water than C. korshinskii, and H. rhamnoides cannot prevent further cavitation or facilitate repair of embolism during the progression of drought (Jian et al., 2015). With a prolonged period of withholding water, water stress inevitably induces xylem cavitation, consequently reducing the hydraulic efficiency of the conductive system. These results suggest that C. korshinskii is more suitable for afforestation than H. rhamnoides in our study area. The rainwater that reached the ground close to the stems of the plants was increased by the presence of the shrubs such that the soil received on average 59.1 and 167.4-times more water than had the shrubs not been there for C. korshinskii and H. rhamnoides, respectively. The funneling ratio varied greatly for different rainfall events, depending on the rainfall depth. Funneling ratios could be greater than 10, and in some studies, far greater than 10 (e.g., Carlyle-Moses, 2004; Li et al., 2008). Our study found that there can be ten or even a hundred times the rainwater that may reach the root area by stemflow water as compared to an open area. Consequently, the probability of water infiltrating to the deeper soil becomes higher near shrub stems. Also, stemflow water in semi-arid shrubs may be assumed to be distributed to a deep soil layer by preferential flow along root channels. Thus,
4.2. Throughfall and stemflow We determined the mean throughfall percentages to be 62.4% and 70.01% of gross rainfall for C. korshinskii and H. rhamnoides, respectively, which are within the ranges detected by Huber and Iroume (2001) for a variety of shrub species (ranging from 55% to 90%). Throughfall values of as high as 96% (African moist brush) and as low as 27% (matorral) of incident rainfall are common (Levia and Frost, 2006). In comparison to the available data, the throughfall percentages for C. korshinskii and H. rhamnoides were mid-range (Crockford and Richardson, 2000). The rainfall thresholds were 1.06 and 2.46 mm to initiate stemflow according to the five-year data (Fig. 3). Our thresholds agreed with those of previous studies in similar regions (Carlyle–Moses, 2004; Li et al., 2008; Wang et al., 2013; Zhang et al., 2013). We found that C. korshinskii could generate more stemflow water and that the rainfall threshold was lower than H. rhamnoides, which we believe is related to the smooth bark of C. korshinskii. The leaves, twigs, and branches of the C. korshinskii individuals have a layer of wax, which contributed to stemflow generation. In contrast, H. rhamnoides has thick leaves and rough bark with many diagonal cracks, thus resulting in less efficient stemflow production (Jian et al., 2013). The excess water significantly enhanced the moisture of the upper soil layer, and a
Fig. 8. Relationship between gross rainfall and interception of C. korshinskii and H. rhamnoides. 8
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Fig. 9. Canopy storage capacity per leaf area and dry biomass of sample varying with eight rainfall intensities for C. korshinskii and H. rhamnoides. Values are equilibrium storage averaged across all test for each species (n = 6). Vertical bars represent the standard error.
for C. korshinskii and H. rhamnoides, respectively. This discrepancy was attributed to the collected aggregate throughfall data being unable to estimate the disaggregation of interception losses as a result of static canopy storage and intra-storm evaporation during rainfall events (Dunkerley, 2008). The indirect method thus overestimates water storage capacity. On the contrary, our previous study found the specific storage capacity of samples soaked in water to be 20% higher than the indirect method. However, immersion will inexorably cause more water to be absorbed by the samples than natural rainfall events. Garcia-Estringana et al. (2010) reported that the magnitude of the canopy stored water per dry biomass within the range. Based on a simulated rainfall intensity of 11.53 mm h−1, water storage per dry biomass (expressed in mL g−1) of A. ordosica was similar to that of Dorycnium pentaphyllum, and water storage per dry biomass of C. korshinskii and H. scoparium was akin to that of Cistus albidus in GarciaEstringana et al. (2010) using a simulated rainfall of 13 mm h−1. A comparison of thin/thicker leaves and thin/larger stems revealed that broad-leafed plants store more water per biomass than fine-leafed plants (Keim et al., 2006). The aforementioned study noted that sample biomass was an unreliable predictor of storage across species and suggested that leaf biomass was of intermediate use as a storage predictor.
Fig. 10. Example data from tests of rainfall simulation on shrubs. In each case, the black line is the depth-equivalent mass of water stored on the shrub; vertical dashed lines indicate step increases in rainfall intensity. Dips in stored water are the result of 3-min rainfall pauses.
5. Conclusions In the present study, the interception losses by the xerophytic shrubs used for re-vegetation in the Loess Plateau in China were estimated. Elucidating the impact of re-vegetation efforts in the semiarid Loess Plateau is of practical significance for effectively managing the vegetation to maximize the hydrological cycle of natural rainfall. Thus, one may establish an artificial ecology system with xerophytic shrubs such as C. korshinskii and H. rhamnoides. The hydrological outcomes of interception by xerophytic shrubs vary depending on the vegetation cover, canopy structure, and rainfall characteristics (e.g. rainfall intensity, depth, and annual rainfall distribution characteristics). Typically, interception results in a net loss of water for the hydrological cycle. The findings of shrub canopy rainfall interception studies thus contribute to the implementation of re-vegetation and assessments of water budget in the Loess Plateau. We hope that the findings of this study can be applied to other shrub-dominated ecosystems.
stemflow water could infiltrate to deeper soil layers that can be utilized by the shrub plants effectively. Because of the structural properties of shrubs and the surface characteristics of leaves provide the possibility for deposition and accumulation of dust and dry fall on the surface of leaves, so stemflow could transport these substances to the soil, which could improve the soil quality and develop the ‘fertile islands’ under shrub canopies (Martinez-Meza and Whitford, 1996). Higher funneling ratios for C. korshinskii and H. rhamnoides indicate that stemflow can be an available nutrient source for plant growth in semi-arid Loess Plateau.
4.3. Canopy interception and water storage capacity Based on the regression analysis of indirect open-field and direct simulated rainfall-throughfall methods, the water storage capacity for C. korshinskii and H. rhamnoides was determined to be 0.86, 0.95 mm and 0.44, 0.59 mm, respectively, for each method. The indirect method obtained values that were 49% and 38% higher than the direct method
Acknowledgments This project was supported by the National Key Research Priorities 9
Agricultural and Forest Meteorology 279 (2019) 107713
S. Jian, et al.
Program of China (2016YFC0402402); National Natural Science Foundation of China (31700370); National Natural Science Foundation of China (51409116); Startup Research Fund of Zhengzhou University (1512323001); Institution of higher learning key scientific research project, Henan Province (16A570010); Foundation of drought climate science (IAM201705); China postdoctoral science foundation (2016M602255); Henan province postdoctoral science foundation; National Natural Science Foundation of China (91025015). We would like to thank LetPub (www.letpub.com) for providing linguistic assistance during the preparation of this manuscript.
Jian, S.Q., Zhang, X.L., Li, D., Wang, D., Wu, Z.N., Hu, C.H., 2018. The effects of stemflow on redistributing precipitation and infiltration around shrubs. J. Hydrol. Hydromech. 66 (1), 79–86. Levia, D.F., Frost, E.E., 2006. A Review and Evaluation of Stemflow Literature in the Hydrologic and Biogeochemical Cycles of Forested and Agricultural Ecosystems. Department of Geography, Southern Illinois University, Carbondale, IL, pp. 62901–64514 J. Hydrol. 274, 1–29. Li, X.Y., Liu, L.Y., Gao, S.Y., Ma, Y.J., Yang, Z.P., 2008. Stemflow in three shrubs and its effect on soil water enhancement in semiarid loess region of China. Agric. Forest Meteorol. 148 (10) 1501–150. 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 Chin. J. Arid Environ. 57, 1–16. Keim, R.F., Skaugset, A.E., Weiler, M., 2006. Storage of water on vegetation under simulated rainfall of varying intensity. Adv. Water Resour. 26, 974–986. Martinez-Meza, E., Whitford, W.G., 1996. Stemflow, throughfall and channelization of stemflow by roots in three Chihuahuan desert shrubs. J. Arid Environ. 32 (3), 271–287. Mauchamp, A., Janeau, J.L., 1993. Water funneling by the crown of Flourensia cernua, a Chihuahuan Desert shrub. J. Arid Environ 25, 299–306. Molchanov, A.A., 1963. The Hydrological Role of Forests. Israel Program for Scientific Translations, Israel, pp. 407. Moran, M.S., Scott, R.L., Keefer, T.O., Emmerich, W.E., Hernandez, M., Nearing, G.S., Paige, G.B., Cosh, M.H., O'Neill, P.E., 2009. Partitioning evapotranspiration in semiarid grassland and shrubland ecosystems using time series of soil surface temperature. Agric. For. Meteorol. 149 (1), 59–72. Muzylo, A., Llorens, P., Valente, F., Keizer, J.J., Domingo, F., Gash, J.H.C., 2009. A review of rainfall interception modelling. J. Hydrol. 370, 191–206. Owens, M.K., Lyons, R.K., Alejandro, C.L., 2006. Rainfall partitioning within semiarid juniper communities: effects of event size and canopy cover. Hydrol. Processes 20, 3179–3189. Pérez-Suárez, M., Fenn, M.E., Cetina-Alcala, V.M., Aldrete, A., 2008. The effects of canopy cover on throughfall and soil chemistry in two forest sites in the México City air basin. Atmósfera 21 (1), 83–100. Rutter, A., Morton, A., Robins, P., 1975. A predictive model of rainfall interception in forests. II. Generalization of the model and comparison with observations in some coniferous and hardwood stands. J. Appl. Eco. 12, 367–380. Sahin, V., Hall, M.J., 1996. The effects of afforestation and deforestation on water yields. J. Hydro. 178, 293–309. Sun, X., Onda, Y., Kato, H., Gomi, T., Komatsu, H., 2015. Effect of strip thinning on rainfall interception in a Japanese cypress plantation. J. Hydrol. 525, 607–618. Tromble, J.M., 1987. Water interception by two arid land shrubs. J. Arid Environ. 15, 65–70. Wang, Y.Q., Shao, M.A., Shao, H.B., 2010. A preliminary investigation of the dynamic characteristics of dried soil layers on the Loess Plateau of China. J. Hydrol. 381, 9–17. Wang, Y.Q., Shao, M.A., Zhu, Y.J., Liu, Z.P., 2011. Impacts of land use and plant characteristics on dried soil layers in different climatic regions on the Loess Plateau of China. Agric. For. Meteorol. 151, 437–448. Wang, X.P., Zhang, Y.F., Wang, Z.N., Pan, Y.X., Hu, R., Li, X.J., Zhang, H., 2013. Influence of shrub canopy morphology and rainfall characteristics on stemflow within a revegetated sand dune in the Tengger Desert. NW China. Hydrol. Process 27, 1501–1509. Williamson, T.N., Newman, B.D., Graham, R.C., Shouse, P.J., 2005. Regolith water in zero-order chaparral and perennial grass watersheds four decades after vegetation conversion. Vadose Zone J 3, 1007–1016. Xiao, Q., McPherso, E.G., Simpson, J.R., Ustin, S.L., 1998. Raınfall ınterceptıon by Sacramento's urban forest. Journal of Arboricul 24 (4), 235–244. Yurtseven, I., Zengin, M., 2013. Neural network modeling of rainfall interception in four different forest stands. Ann. For. Res. 56 (2), 351–362. Zhao, C.Y., Feng, Z.D., Chen, G.D., 2004. Soil water balance simulation of alfalfa (Medicago sativa L.) in the semiarid Chinese Loess Plateau. Agr. Water Manage 69 (2), 101–114. Zhang, Y.F., Wang, X.P., Hu, R., Pan, Y.X., Zhang, H., 2013. Stemflow in two xerophytic shrubs and its significance to soil water and nutrient enrichment. Ecol. Res. 28, 567–579.
References Ahmadi, M.T., Attarod, P., Mohadjer, M.M.R., Rahmani, R., Fathi, J., 2009. Partitioning rainfall into throughfall, stemflow, and interception loss in an oriental beech (Fagus orientalis Lipsky) forest during the growing season. Turk. J. Agric. For. 33, 557–568. Asadian, Y., Weiler, M., 2009. A new approach in measuring rainfall interception by urban trees in coastal British Columbia. Water Qual. Res. J. Can. 44 (1), 16–25. Bosch, J.H., Hewlett, J.D., 1982. A review of catchment experiments to determine the effect of vegetation changes and water yield and evapotranspiration. J. Hydrol. 55, 3–23. Carlyle-Moses, D.E., 2004. Throughfall, stemflow, and canopy interception loss fluxes in a semi-arid Sierra Madre Oriental matorral community. J. Arid Environ. 58, 181–202. Carlyle-Moses, D.E., Price, A.G., 2006. Growing-season stemflow production within a deciduous forest of southern Ontario. Hydrol. Process. 20, 3651–3663. Crockford, R.H., Richardson, D.P., 2000. Partitioning of rainfall into throughfall, stemflow and interception: effect of forest type, ground cover and climate. Hydro. Process. 14, 2903–2920. David, J.S., Valente, F., Gash, J.H.C., 2005. Evaporation of intercepted rainfall. In: Anderson, M.G. (Ed.), Encyclopaedia of Hydrological Sciences. John Wiley, Chichester, pp. 627–634. Dingman, S., 2002. Physical Hydrology. Prentice Hall, Upper Saddle River, pp. 646. Dunkerley, D., 2000. Measuring interception loss and canopy storage in dryland vegetation: a brief review and evaluation of available research strategies. Hydrol. Process. 14, 669–678. Dunkerley, D.L., 2008. Intra-storm evaporation as a component of canopy interception loss in dryland shrubs: observations from Fowlers Gap, Australia. Hydrol. Proc. 22, 1985–1995. Fu, B.J., Liu, Y., Lu, Y.H., He, C.S., Zeng, Y., Wu, B.F., 2011. Assessing the soil erosion control service of ecosystems change in the Loess Plateau of China. Ecol. Complex. 8 (4), 284–293. Gash, J., Shuttleworth, W., 2007. Evaporation. Benchmark Papers in Hydrology 2. IAHS Press, Wallingford, pp. 521. Hamilton, E.L., Rowe, P.B., 1949. Rainfall Interception by Chaparral in California. State of California, Dept of Natural Resources, Division of Forestry, Sacramento, California, USA. Herwitz, S.R., 1986. Infiltration-excess caused by stemflow in a cyclone-prone tropical rainforest. Earth Surf. Proc. Land 11, 401–412. Horton, R., 1919. Rainfall interception. Mon. Weather Rev 47, 603–623. Huber, A., Iroume, A., 2001. Variability of annual rainfall partitioning for different sites and forest covers in Chile. J. Hydro. 248, 78–92. IUSS Working Group WRB. 2006. World Reference Base for Soil Resources 2006. 2nd editioned.. World Soil Resources Reports No. 203.FAO, Rome. Janík, R., Pichler, J., 2008. Amounts of throughfall and lysimetric water in a submountain beech forest in the Kremnické vrchy MTS (West Carpathian Mts., Slovakia). J. For. Sci. 54 (5), 207–211. Jian, S.Q., Zhao, C.Y., Fang, S.M., Yu, K., 2014. Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau. J. Hydrol. Hydromech 62 (2), 89–96. Jian, S.Q., Zhao, C.Y., Fang, S.M., Yu, K., 2015. Evaluation of water use of Caragana korshinskii and Hippophae rhamnoides in the Chinese Loess Plateau. Can. J. For. Res 45, 15–25.
10