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The influences of surface water-overflowing disturbance on the fluctuations of Tamarix ramosissima community in Western China
Acta Ecologica Sinica 30 (2010) 245–250
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The influences of surface water-overflowing disturbance on the fluctuations of Tamarix ramosissima community in Western China Yanrui Chen a,b,1, Linke Yin a,c,⇑, Xu Bai b a
Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China The Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011, China c Turpan Eremophytes Botanic Garden, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China b
a r t i c l e
i n f o
Keywords: Surface water-overflowing disturbance Tamarix ramosissim community Fluctuation
a b s t r a c t The main purpose of this study is to examine the fluctuation characteristics of Tamarix ramosissima community from the year of 2007–2008 in desert riparian forest under human surface water-overflowing disturbance in the lower reaches of Tarim River, China. In this paper, community structure, species diversity and dominant species were chosen as the indicators which could reflect the characteristics of community fluctuation. The representative sampling method was used to investigate and measure the fluctuation process of Comm. T. ramosissima. The main results showed that species numbers of the community increased 66.7% under the surface water-overflowing disturbance within two years comparing with it under non-disturbance. The Sorensen similarity coefficient of plant species is 0.75 in community under the disturbance and non-disturbance, indicating that species composition is very similar and main structure of the community has not changed on these two different treatments. Species diversity index of Comm. T. ramosissima changed a lot under the disturbance. Compared with it under non-disturbance, species richness and species diversity have been increasing while species evenness declined slightly under the disturbance. The numbers and kinds of dominant species also changed in community under the disturbance, of which the dominance of T. ramosissima is significantly increased. Compared with the river channel water disturbance, surface water-overflowing disturbance could enhance seed germination and plant growth through the effect of shallow soil moisture and its physic-chemical properties. And it improved the germination of plant seed in the soil and promoted the clone growth of plant reproductive body. As a result, species diversity was increased and species composition happened significantly changed in Comm. T. ramosissima influenced by the water-overflowing disturbance. In addition, community hierarchical structure was getting more complex. And then, it was concluded that water-overflowing disturbance is an effective way to positively affect the fluctuation of Comm. T. ramosissima in the lower reaches of Tarim River. Thus, it can make up for the insufficient effectiveness of river channel water disturbance to restore damaged vegetation. Ó 2010 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
1. Introduction Plant community fluctuation is defined as the varying form of plant community affected by the short-term or cyclical changes of climate or water in a year to year or quarter by quarter. With plant community’s fluctuations, it will have a significant change in plant productivity, the number ratio of each component, its appearance and structure [1]. And community fluctuations could ⇑ Corresponding author at: Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China. E-mail addresses: [email protected], [email protected] (Y.R. Chen), Yinlk@ ms.xjb.ac.cn (L. Yin). 1 Address: Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 Southern Beijing Road, Urumqi 830011, Xinjiang, China.
be reflected by three indicators, including the characteristics of community structure, species diversity and dominant species [2–6]. Fluctuation is one of the biggest sign of dynamics changes in plant community under a short period of disturbance. And it could reflect the role of plant communities on resisting natural ecological factors and human activities. The definition of disturbance has mostly articulated the negative ecological effects from natural or human activities as study object. However moderate disturbance and beneficial human disturbance would have positive ecological effects on ecological object [7]. About the effects of disturbing and restoring natural communities under the river channel water disturbance, more research work has been ongoing and made some progress [8–11]. What kind of fluctuation respond will happen on natural plant communities under surface water-overflowing disturbance as a human restoration
1872-2032/$ - see front matter Ó 2010 Ecological Society of China. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.chnaes.2010.08.003
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2. Research methods
the surface water-overflowing disturbance and non-disturbance in the lower reaches of Tarim River in the northern Tarim Basin, Xinjiang, including three sampling plots under the disturbance and one sampling plots under non-disturbance (Fig. 1). It is located in the 40°310 5000 –40°310 5200 N, 87°420 0800 –87°420 0100 E. The macro-plots of 50 m 50 m were placed for shrub. Then four herbage microplots of 5 m 5 m were uniformly placed respectively in each macro-plots of 2500 m2. There are 30 sampling plots totally. The water-overflowing disturbance began in September, 2005. And then, the replenishment water disturbance is done year to year and one time per year. According to the investigation and research, the quantity of replenishment water reaches 9000 m3/hm2 per year in 2007 and 2008, respectively.
2.1. Study area
2.3. Data collection
The study area is located in the lower reaches of Tarim, Xinjiang, PR China. Belong to the warm temperate continental desert climate. The average annual temperature is 10.5–10.8 °C. Maximum temperature is 43.6 °C in July while minimum temperature is 30.9 °C in January. The annual accumulated temperature (P10 °C) ranges from 4 161 °C to 4 241 °C. The average annual precipitation and evaporation is 30–34 mm and 2429–2910 mm, respectively. The groundwater level is about at depth of 2 m and its salinity is 2–3 g/l generally. On floodplain and the lowland on both sides of the Tarim River and Kongqi River, there are large areas of natural riparian vegetation include the deciduous broad-leaved forest (Populus euphratica as the main constructive species), temperate deciduous shrub, semi-shrub desert and halophytes meadow [12]. Main wild plant species are belongs to Salicaceae, Tamaricaceae, Leguminosae, Apocynaceaea and Graminae in study area. The flora of the region consists of 29 families, 91 genera, and 122 species of vascular plants. There are several representative plants, such as P. euphratica, Tamarix spp., Lycium ruthenicum, Halimodendron halodendron, Phragmites austraris, Karelinia caspica, Poacynum hendersonii, Glycyrrhiza inflata, Alhagi sparsifolia, and Halostashys caspica. The past 50 years, under the effect of natural environment changes and irrational human activities, part of the middle and lower reaches of Tarim River are in a long-term drying up. And large area of the natural vegetation is degenerated and declined. Since May, 2000, our country has been carried out several times emergency channel water along the river for ecological needing in the middle and lower reaches of Tarim River. Through lifting groundwater level by replenishment water measure of artificial river channel, improve the growth of deep-rooted plants back to life and play an important role on hastening and restoring the plant communities in desert riparian forest [8]. However, the phenomenon of seed regeneration does not occur in the community under the water replenishment by river channel disturbance. And it is no large-scale floods spillover process of the disturbance so that there do not happen the update phenomenon of falling species. The role of it is very limited for activating the surface soil seed bank, improving the germination of plant nutrition body and propagation rehabilitation in shallow soil, as well as the role on restoration and propagation of some herb with shallow root. In order to make up for the effect lack of the river channel water disturbance on restoring the damaged vegetation, the ecology water gate has been established in some land sectors of the Tarim River. And through controlling it, the surface water overflowing disturbance has been carried out to restore natural vegetation on both sides of the Tarim River.
In October, 2007 and September, 2008, sampling sites was conducted and investigated. The following data were recorded, including plant height, canopy breadth, coverage, species number and species composition of plant communities in the sampling plots, as well as the altitude, latitude and longitude were measured by GPS.
measure? Compared with it under the river channel water disturbance, what are the changes in the characteristics of natural plant communities under water-overflowing disturbance? On this issue, the related study has not yet reported. In this study, Tamarix ramosissima community as a typical vegetation type of desert riparian forest in middle and lower reaches of Tarim River, we study the indicator values of fluctuations in order to examine the fluctuations characteristics of natural T. ramosissima community under wateroverflowing disturbance. And this study plays an important role on selecting the effective measures to restore natural vegetation in arid desert area.
2.2. Sampling design According to the representative sampling plot method [13], four sampling plots were conducted in T. ramosissima community under
2.4. Data analysis 2.4.1. Species structure amplitude It is expressed as the Sorensen similarity coefficient of community (ISv) [14]. Its formula is as follows:
ISv ¼
2C 100% AþB
ð1Þ
where assuming A is the total number of species in plots under the water-overflowing disturbance, B is the total number of species in plot under non-overflowing disturbance, C is the number of common species in plots under water-overflowing disturbance and non-disturbance. Abundance is expressed as the relative species number and relative cover of a species appeared in the plots.
Relative % density ¼ ðthe individual number of a species= the sum of all the species numbersÞ 100
ð2Þ
Relative % cover ¼ ðthe basal area of a species= the basal area of all speciesÞ 100
ð3Þ
2.4.2. Community species diversity Based on the wide application of species diversity index, this paper choose species richness (R) index, Simpson (J) index, Shannon– Wiener (H0 ) index and the species evenness (J sw ) index to measure species diversity of community [15]. Formula is as follows:
Patrick species richness index : R ¼ S Shannon—Wiener index : H0 ¼
s X
ð4Þ
Pi lnPi ¼
s X
i¼1
ðni =NÞ lnðni =NÞ
i¼1
ð5Þ Simpson index ðJÞ is calculated as : J ¼ 1
s X
ni ðni 1Þ=NðN 1Þ
i¼1
ð6Þ Pielou evenness index ðJ sw Þ is calculated as : J sw ¼ H0 =H0max ¼ H0 =lnS ð7Þ
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Fig. 1. The sampling location diagram of T. ramosissima community under the surface water-overflowing disturbance and non-disturbance in the lower reaches of Tarim River, China.
where S and N are described as species number and the total importance value of all species in the community respectively. The ni is described as the important value of species i. Pi is expressed as a proportion of N made up by the importance value of ith species in the community. And Pi is derived from the equivalent formula (P i ¼ ni =N, i = 1, 2, 3, 4, . . ., n). H0 is Shannon–Wiener information index. H0max is the maximum value of H0 , and it is equal to ln S. 2.4.3. Selection of dominant species from communities Dominant species refers to plant species with the obviously effect on making community structure and the formation of community environment under control. At different levels of community may have its own dominant species [16]. In this study, the importance value of species is used as an index to judge species dominance [12], and then dominant species are determined and selected from communities based on the dominance analysis [17,18].
Relative importance value ½18 ¼ ðrelative percentage density þ relative percentage frequency þ relative percentage cover þ relative percentage heightÞ=4 where relative % frequency = (the number of quadrats with a species existence/the sum of plot numbers with all the species existence) 100, relative % height = (the average plant height of a species/the sum of all the species average plant height) 100. The data is analyzed by the software of Excel2003, DPS6.55 and SAS. And the figures are done and treated by Origin7.5. 3. Results and analysis 3.1. The changes of community structure characteristics 3.1.1. Species composition and abundance change In the T. ramosissima community under non-overflowing disturbance, there are six plant species, such as T. ramosissima, P. austraris, P. hendersonii, G. inflata, L. ruthenicum and Hexinia polydichotoma. Under the disturbance of surface water-overflowing disturbance, there are 10 plant species including four spontaneous immigration and establishment of native species, such as, Halogeton glomeratus, A. sparsifolia, K. caspica and Sonchus oleraceus in the T. ramosissima community. These increased species are mostly seedling sprouts, accounted for 14.29–40.00% of the total number of species, of which A. sparsifolia and K. caspica has stronger ability for colonel reproduction. From Table 1, we can see that species were increased in T. ramosissima community under the wateroverflowing disturbance. Comparing with it under non-distur-
bance, plant species were increased from 6 to 10 species, of which the increased species include one semi-shrub and three herb species.
3.1.2. Community structure amplitude ISv formula (1) combined with Table 1, we can see that Sorensen similarity coefficient of plant species is 0.75 and the percentage of common species was 60% in T. ramosissima community under overflowing disturbance and non-disturbance. It indicates that they have higher similar species composition and closer species relationship. At the same time, the main structure did not change in the community under these two treatments. Under the wateroverflowing disturbance, the increased plant species in T. ramosissima community that are local species in the original indigenous habitat. It indicates that the characteristics of community structure under water-overflowing disturbance are closer to those of the native community.
3.1.3. Species abundance changes in community Using formula (2), (3), species abundance was compared in T. ramosissima community under water-overflowing disturbance and non-disturbance. The results showed that the relative species number of H. glomeratus, T. ramosissima and S. oleraceus are increased in the T. ramosissima communities under the disturbance comparing with them under non-overflowing disturbance. Among them, the relative species number of H. glomeratus has more great increase than other species. Compared to the non-disturbance, the relative species number of P. austraris and Glycyrrhiza inflate showed a clear decline (Fig. 2). It indicated that the disturbance has little influence on the abundance of P. austraris and G. inflate with strong cloned capacity of reproduction. Under the water-overflowing disturbance, the relative coverage of P. austraris, H. glomeratus, P. hendersonii and L. ruthenicum in communities showed a relative increase, in which the relative coverage of P. austraris and H. glomeratus populations are significant increased since the tiller of P. austraris is greatly increased and plenty of H. glomeratus seedlings have germinated under the water-overflowing disturbances. On the contrary, the relative coverage of G. inflata shows a significant decline and the relative cover of T. ramosissima change is not pronounced (Fig. 3). It shows that surface water-overflowing disturbance has significant effect on the abundance of herb species with shallow roots and seedlings occurred by virtue of surface runoff. Moreover it has very small impact on T. ramosissima and G. inflate with deep roots. As a result, the abundance of these species is decreased relatively.
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Table 1 Plant species and its percentage of T. ramosissima community under water-overflowing disturbance or non-disturbance. Non-overflowing disturbance
Overflowing disturbance
Plant species
1. Tamarix ramosissima, 2. Phragmites austraris, 5. Poacynum hendersonii, 6. Glycyrrhiza inflate, 7. Lycium ruthenicum, 8. Hexinia polydichotoma
Species number of shrub or semi-shrub Species % of shrub or semi-shrub Species number of herbage Species % of herbage Hierarchical structure of community
2 33.33 4 66.67 Mainly consisted of shrubs and herbs, and dominated by herbs (of which the P. austraris ?tul?> is relatively abundant than other species, followed by G. inflate)
1. Tamarix ramosissima, 2. Phragmites austraris, 3. Halogeton glomeratus, 4. Alhagi sparsifolia, 5. Poacynum hendersonii, 6. Glycyrrhiza inflate, 7. Lycium ruthenicum, 8. Hexinia polydichotoma, 9. Sonchus oleraceus, 10. Karelinia caspica 3 28.57–50.00 7 50.00–71.43 Mainly consisted of shrub/semi-shrub and herb, which dominated by shrub or semi-shrub
there are three layers in communities, including tall shrub layer dominated by T. ramosissima; sub-shrub layer mainly consisted of L. ruthenicum and A. sparsifolia, and herbaceous layer mainly consisted of P. communis, H. glomeratus, P. hendersonii, and S. oleraceus. Compared with the non-disturbance, species composition and community hierarchical structure changed from simple to complex in the community under water-overflowing disturbance.
1.0
water-overflowing disturbance non-overflowing disturbance
Relative species number
0.9 0.8 0.7 0.6 0.5 0.4
3.2. Changes in species diversity
0.3 0.2 0.1 0.0
1
2
3
4
5
6
7
8
9
10
Plant species Fig. 2. Change of relative species number in Tamarix ramosissima community under water-overflowing disturbance or non-disturbance. (Note: the species is same as the Table 1.)
0.7
water-overflowing disturbance non-overflowing disturbance
Relative coverage of species
0.6 0.5 0.4 0.3
Species diversity indices of community are analyzed basing on the equation from (4)–(7), and the results showed that (Fig. 2) the R index, J index and H0 index of T. ramosissima community are increased from 6, 0.691 and 1.8775 under non-disturbance to 10, 0.7102 and 2.1611 under surface water-overflowing disturbance while the Jsw index of community has slightly decreased from 0.7263 under non-disturbance to 0.6506 under the disturbance. Based on the second analysis on species diversity index, the results showed (Fig. 4) that R index, J index and H0 index of T. ramosissima community under the water-overflowing disturbance are various and increased comparing with them under non-disturbance. Among them, species number is obviously increased while Jsw index is slightly decreased. The J index and the H0 index have a great increase with the increase of species number in the community. It can be seen that T. ramosissima communities has higher species diversity and ecological dominance while evenness of species distribution is relatively decreased under the disturbance.
0.2
3.3. Changes in the number and type of dominant species 0.1 0.0
1
2
3
4
5
6
7
8
9
10
Plant species
3.3.1. Change in the importance value of species According to formula (8), the relative importance value of plant species was analyses basing on the statistical analysis of survey
Fig. 3. The change on relative coverage of species in T. ramosissima community under water-overflowing disturbance or non-disturbance. (Note: the species is same as the Table 1)
11
water-overflowing disturbance non-overtopping disturbance
10
3.1.4. Changes of community hierarchical structure Species composition is relatively simple in T. ramosissima community under non-disturbance. It mainly consisted of shrubs and herbages, and dominated by herbages. And there are three layers in community, including tall shrub layer dominated by T. ramosissima; sub-shrub layer mainly consisted of L. ruthenicum, and herb layer mainly consisted of P. communis and G. inflate. Under the influence of water-overflowing disturbance, there are a number of local herbs and shrub species increased in the community. Species composition and species density are significantly increased in community. It mainly consisted of shrubs or semishrubs and herbages, dominated by shrubs or semi-shrubs. And
Species diversity
9 8 7 6 5 4 3 2 1 0
R
J
H'
Jsw
Species diversity index Fig. 4. The change on species diversity of Tamarix ramosissima community.
Y. Chen et al. / Acta Ecologica Sinica 30 (2010) 245–250
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data in T. ramosissima community under the water-overflowing disturbance or non-overflowing disturbance (Table 2). Under non-disturbance, the relative species importance value is in the range of 31.61–38.19. The main plant species of T. ramosissima and P. austraris are selected from the community by their relative important value. Under the disturbance, the species relative importance value are in the range of 0.37–39.73. And the relative importance value of T. ramosissima, L. ruthenicum and H. polydichotoma are increased while that of P. austraris, G. inflate and P. hendersonii are decreased. Importance value of the increased species accounted for 17.77% of the total importance value, indicating the original species diversity of T. ramosissima has been changed significantly. Comparing with non-disturbance, the relative importance value of T. ramosissima is increased from 39.73 to 36.97. It indicated that T. ramosissima still pay very important role in the maintenance of community structure and its function.
its reconstruction process. On the other hand, disturbance can increase the habitat heterogeneity that is the most important factor in affecting species composition. Major changes have taken place in species composition during the fluctuations process of T. ramosissima community under the water-overflowing disturbance. Species composition of P. austraris T. ramosissima G. inflata + P. hendersonii changed into T. ramosissima P. austraris + H. glomeratus L. ruthenicum H. polydichotoma + P. hendersonii. The hierarchical structure of T. ramosissima community changed from simple into complex under the disturbance. Species richness and abundance shows increasing generally, of which H. glomeratus population is significant increased since plenty of H. glomeratus seedlings have germinated under the water-overflowing disturbances. Community structure characteristics of T. ramosissima under the disturbance are closer to that of its native community in the desert riparian forest.
3.3.2. The dominant species of T. ramosissima community Dominant species are selected from T. ramosissima community under the disturbance and non-disturbance by the important value method (Table 3). There are three dominant species dominated by P. austraris and T. ramosissima (occupy the major advantage of community) in the community under non-disturbance. However, the dominant species has been changed and there are three dominant species dominated by T. ramosissima and P. austraris in the community under the disturbance. As an increased species, H. glomeratus become one dominant species and while G. inflate is declined in the community under the disturbance.
4.2. Great changes in species diversity
4. Conclusions and discussion 4.1. Community structure from simple to complex The effect of disturbance on species composition of plant community is to adjust the plant species, number of plants, and the ratio of plants number. Therefore, disturbance will inevitably play an important role on species composition changes of plant community under the disturbance during plant community updates or
Table 2 The important value of each species in T. ramosissima community under wateroverflowing disturbance or non-disturbance. Plant species
Non-overflowing disturbance
Water-overflowing disturbance
1. Tamarix ramosissima 2. Phragmites austraris 3. Halogeton glomeratus 4. Alhagi sparsifolia 5. Poacynum hendersonii 6. Glycyrrhiza inflata 7. Lycium ruthenicum 8. Hexinia polydichotoma 9. Sonchus oleraceus 10. Karelinia caspica
36.97 38.19 – – 3.81 17.77 1.67 1.61 – –
39.73 34.67 12.70 1.93 2.28 0.37 2.80 2.39 1.96 1.18
Table 3 Changes in dominant species of T. ramosissima community under water-overflowing disturbance or non-disturbance. Dominant species
Surface water-overflowing disturbance
Non-disturbance
1. 2. 3. 6.
+ + +
+ +
Tamarix ramosissima Phragmites austraris Halogeton glomeratus Glycyrrhiza inflata
+
Species diversity of T. ramosissima community under the wateroverflowing disturbance is greater than that under non-disturbance. It can be considered that water-overflowing disturbance could relieve the restrictions of water factors on plant for settlement. And get species richness and species diversity increased obviously. However, the smooth settlement of the species just means the beginning of vegetation restoration. The increased species of the community under the disturbance are all the species in the potential plant community. It indicates that the disturbance improve the germination of species in the soil seed bank and the growth of some seedlings and herb species with shallow roots. The community structure is getting towards more complicated, diversified, and more stable. 4.3. Community positive fluctuations Through the effect of water-overflowing disturbance on shallow soil moisture and its physical and chemical properties, it could improve the germination of plant seed in shallow soil and the cloned growth of plant nutrition and breeding (i.e., buds on the ground and underground stem). There are many seedling plants and ratoon seedling appeared in the sublayer of the community. As a result, species richness and abundance are increasing, species composition changes a lot, and the hierarchy structure is getting more complicated significantly in T. ramosissima community under the influence of water-overflowing disturbance. In addition, the number and kind of dominant species are changed in community too. And then, it is concluded that water-overflowing disturbance is an effective way to affect T. ramosissima community positive fluctuation generally. And the change of the fluctuation is small in the community under the disturbance. The fluctuation type of the community is not reveal fluctuations. Through lifting groundwater level near both sides of the river, the river channel water disturbance can improve the plant with deep root back to life, to save and restore natural vegetation on both sides of the river [10]. In the absence of large-scale flood and water-overflowing process, there is no plant based on water disturbance to happen the update phenomenon of falling species. And the process of the river channel water disturbance mainly is to rescue and rejuvenate the natural desert vegetation [19]. The river channel water disturbance mainly affects the germination of plant with deep root, increases community coverage, plant growth and leaf yield. It fully reflects that water-overflowing disturbance is importance and necessity for the species breeding and update and make up for the insufficient role of river channel water disturbance on restoring natural vegetation.
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Acknowledgements This work described in this paper was financially supported by the National Natural Science Foundation of China (Grant Nos. 30700103 and 40701012) and Xinjiang Institute of Ecology and Geography (No. 40771114). References [1] H. Ren, S.Z. Liu, S.L. Peng, et al., The type and mechanism of fluctuation in plant community, Journal of Tropical and Subtropical Plants 9 (2) (2001) 167–173. [2] Yu Qian, Z.Q. Xie, G.M. Xiong, et al., Community characteristics and population structure of dominant species of Abies fargesii forests in Shennongjia National Nature Reserve, Acta Ecologica Sinica 28 (5) (2008) 1931–1941. [3] Z.H. Mao, J.J. Zhu, Effects of disturbances on species composition and diversity of plant communities, Acta Ecoiogica Sinica 26 (8) (2006) 2695–2701. [4] T. Lu, K.M. Ma, H.W. Ni, et al., Variation in species composition and diversity of wetland communities under different disturbance intensity in the Sanjiang Plain, Acta Ecologlca Sinica 28 (5) (2008) 1893–1900. [5] M. Yue, Y. Ren, G.D. Dang, et al., Species diversity of higher plant communities in Foping national reserve, Chinese Biodiversity 7 (4) (1999) 263–269. [6] X.Z. Liu, J.T. Zhang, Study on niche of dominant species of plant communities in Tianlong Mountain, Shanxi, Journal of Shanxi University 27 (4) (2004) 418–423 (Natural Science Edition). [7] S.T.A. Pickett, P.S. White, The Ecology of Natural Disturbance and Patch Dynamics, Academic Press, Orlando Florida, 1985, p. 585.
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The influences of surface water-overflowing disturbance on the fluctuations of Tamarix ramosissima community in Western China Yanrui Chen a,b,1, Linke Yin a,c,⇑, Xu Bai b a
Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China The Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi 830011, China c Turpan Eremophytes Botanic Garden, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China b
a r t i c l e
i n f o
Keywords: Surface water-overflowing disturbance Tamarix ramosissim community Fluctuation
a b s t r a c t The main purpose of this study is to examine the fluctuation characteristics of Tamarix ramosissima community from the year of 2007–2008 in desert riparian forest under human surface water-overflowing disturbance in the lower reaches of Tarim River, China. In this paper, community structure, species diversity and dominant species were chosen as the indicators which could reflect the characteristics of community fluctuation. The representative sampling method was used to investigate and measure the fluctuation process of Comm. T. ramosissima. The main results showed that species numbers of the community increased 66.7% under the surface water-overflowing disturbance within two years comparing with it under non-disturbance. The Sorensen similarity coefficient of plant species is 0.75 in community under the disturbance and non-disturbance, indicating that species composition is very similar and main structure of the community has not changed on these two different treatments. Species diversity index of Comm. T. ramosissima changed a lot under the disturbance. Compared with it under non-disturbance, species richness and species diversity have been increasing while species evenness declined slightly under the disturbance. The numbers and kinds of dominant species also changed in community under the disturbance, of which the dominance of T. ramosissima is significantly increased. Compared with the river channel water disturbance, surface water-overflowing disturbance could enhance seed germination and plant growth through the effect of shallow soil moisture and its physic-chemical properties. And it improved the germination of plant seed in the soil and promoted the clone growth of plant reproductive body. As a result, species diversity was increased and species composition happened significantly changed in Comm. T. ramosissima influenced by the water-overflowing disturbance. In addition, community hierarchical structure was getting more complex. And then, it was concluded that water-overflowing disturbance is an effective way to positively affect the fluctuation of Comm. T. ramosissima in the lower reaches of Tarim River. Thus, it can make up for the insufficient effectiveness of river channel water disturbance to restore damaged vegetation. Ó 2010 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
1. Introduction Plant community fluctuation is defined as the varying form of plant community affected by the short-term or cyclical changes of climate or water in a year to year or quarter by quarter. With plant community’s fluctuations, it will have a significant change in plant productivity, the number ratio of each component, its appearance and structure [1]. And community fluctuations could ⇑ Corresponding author at: Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China. E-mail addresses: [email protected], [email protected] (Y.R. Chen), Yinlk@ ms.xjb.ac.cn (L. Yin). 1 Address: Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 Southern Beijing Road, Urumqi 830011, Xinjiang, China.
be reflected by three indicators, including the characteristics of community structure, species diversity and dominant species [2–6]. Fluctuation is one of the biggest sign of dynamics changes in plant community under a short period of disturbance. And it could reflect the role of plant communities on resisting natural ecological factors and human activities. The definition of disturbance has mostly articulated the negative ecological effects from natural or human activities as study object. However moderate disturbance and beneficial human disturbance would have positive ecological effects on ecological object [7]. About the effects of disturbing and restoring natural communities under the river channel water disturbance, more research work has been ongoing and made some progress [8–11]. What kind of fluctuation respond will happen on natural plant communities under surface water-overflowing disturbance as a human restoration
1872-2032/$ - see front matter Ó 2010 Ecological Society of China. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.chnaes.2010.08.003
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2. Research methods
the surface water-overflowing disturbance and non-disturbance in the lower reaches of Tarim River in the northern Tarim Basin, Xinjiang, including three sampling plots under the disturbance and one sampling plots under non-disturbance (Fig. 1). It is located in the 40°310 5000 –40°310 5200 N, 87°420 0800 –87°420 0100 E. The macro-plots of 50 m 50 m were placed for shrub. Then four herbage microplots of 5 m 5 m were uniformly placed respectively in each macro-plots of 2500 m2. There are 30 sampling plots totally. The water-overflowing disturbance began in September, 2005. And then, the replenishment water disturbance is done year to year and one time per year. According to the investigation and research, the quantity of replenishment water reaches 9000 m3/hm2 per year in 2007 and 2008, respectively.
2.1. Study area
2.3. Data collection
The study area is located in the lower reaches of Tarim, Xinjiang, PR China. Belong to the warm temperate continental desert climate. The average annual temperature is 10.5–10.8 °C. Maximum temperature is 43.6 °C in July while minimum temperature is 30.9 °C in January. The annual accumulated temperature (P10 °C) ranges from 4 161 °C to 4 241 °C. The average annual precipitation and evaporation is 30–34 mm and 2429–2910 mm, respectively. The groundwater level is about at depth of 2 m and its salinity is 2–3 g/l generally. On floodplain and the lowland on both sides of the Tarim River and Kongqi River, there are large areas of natural riparian vegetation include the deciduous broad-leaved forest (Populus euphratica as the main constructive species), temperate deciduous shrub, semi-shrub desert and halophytes meadow [12]. Main wild plant species are belongs to Salicaceae, Tamaricaceae, Leguminosae, Apocynaceaea and Graminae in study area. The flora of the region consists of 29 families, 91 genera, and 122 species of vascular plants. There are several representative plants, such as P. euphratica, Tamarix spp., Lycium ruthenicum, Halimodendron halodendron, Phragmites austraris, Karelinia caspica, Poacynum hendersonii, Glycyrrhiza inflata, Alhagi sparsifolia, and Halostashys caspica. The past 50 years, under the effect of natural environment changes and irrational human activities, part of the middle and lower reaches of Tarim River are in a long-term drying up. And large area of the natural vegetation is degenerated and declined. Since May, 2000, our country has been carried out several times emergency channel water along the river for ecological needing in the middle and lower reaches of Tarim River. Through lifting groundwater level by replenishment water measure of artificial river channel, improve the growth of deep-rooted plants back to life and play an important role on hastening and restoring the plant communities in desert riparian forest [8]. However, the phenomenon of seed regeneration does not occur in the community under the water replenishment by river channel disturbance. And it is no large-scale floods spillover process of the disturbance so that there do not happen the update phenomenon of falling species. The role of it is very limited for activating the surface soil seed bank, improving the germination of plant nutrition body and propagation rehabilitation in shallow soil, as well as the role on restoration and propagation of some herb with shallow root. In order to make up for the effect lack of the river channel water disturbance on restoring the damaged vegetation, the ecology water gate has been established in some land sectors of the Tarim River. And through controlling it, the surface water overflowing disturbance has been carried out to restore natural vegetation on both sides of the Tarim River.
In October, 2007 and September, 2008, sampling sites was conducted and investigated. The following data were recorded, including plant height, canopy breadth, coverage, species number and species composition of plant communities in the sampling plots, as well as the altitude, latitude and longitude were measured by GPS.
measure? Compared with it under the river channel water disturbance, what are the changes in the characteristics of natural plant communities under water-overflowing disturbance? On this issue, the related study has not yet reported. In this study, Tamarix ramosissima community as a typical vegetation type of desert riparian forest in middle and lower reaches of Tarim River, we study the indicator values of fluctuations in order to examine the fluctuations characteristics of natural T. ramosissima community under wateroverflowing disturbance. And this study plays an important role on selecting the effective measures to restore natural vegetation in arid desert area.
2.2. Sampling design According to the representative sampling plot method [13], four sampling plots were conducted in T. ramosissima community under
2.4. Data analysis 2.4.1. Species structure amplitude It is expressed as the Sorensen similarity coefficient of community (ISv) [14]. Its formula is as follows:
ISv ¼
2C 100% AþB
ð1Þ
where assuming A is the total number of species in plots under the water-overflowing disturbance, B is the total number of species in plot under non-overflowing disturbance, C is the number of common species in plots under water-overflowing disturbance and non-disturbance. Abundance is expressed as the relative species number and relative cover of a species appeared in the plots.
Relative % density ¼ ðthe individual number of a species= the sum of all the species numbersÞ 100
ð2Þ
Relative % cover ¼ ðthe basal area of a species= the basal area of all speciesÞ 100
ð3Þ
2.4.2. Community species diversity Based on the wide application of species diversity index, this paper choose species richness (R) index, Simpson (J) index, Shannon– Wiener (H0 ) index and the species evenness (J sw ) index to measure species diversity of community [15]. Formula is as follows:
Patrick species richness index : R ¼ S Shannon—Wiener index : H0 ¼
s X
ð4Þ
Pi lnPi ¼
s X
i¼1
ðni =NÞ lnðni =NÞ
i¼1
ð5Þ Simpson index ðJÞ is calculated as : J ¼ 1
s X
ni ðni 1Þ=NðN 1Þ
i¼1
ð6Þ Pielou evenness index ðJ sw Þ is calculated as : J sw ¼ H0 =H0max ¼ H0 =lnS ð7Þ
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Fig. 1. The sampling location diagram of T. ramosissima community under the surface water-overflowing disturbance and non-disturbance in the lower reaches of Tarim River, China.
where S and N are described as species number and the total importance value of all species in the community respectively. The ni is described as the important value of species i. Pi is expressed as a proportion of N made up by the importance value of ith species in the community. And Pi is derived from the equivalent formula (P i ¼ ni =N, i = 1, 2, 3, 4, . . ., n). H0 is Shannon–Wiener information index. H0max is the maximum value of H0 , and it is equal to ln S. 2.4.3. Selection of dominant species from communities Dominant species refers to plant species with the obviously effect on making community structure and the formation of community environment under control. At different levels of community may have its own dominant species [16]. In this study, the importance value of species is used as an index to judge species dominance [12], and then dominant species are determined and selected from communities based on the dominance analysis [17,18].
Relative importance value ½18 ¼ ðrelative percentage density þ relative percentage frequency þ relative percentage cover þ relative percentage heightÞ=4 where relative % frequency = (the number of quadrats with a species existence/the sum of plot numbers with all the species existence) 100, relative % height = (the average plant height of a species/the sum of all the species average plant height) 100. The data is analyzed by the software of Excel2003, DPS6.55 and SAS. And the figures are done and treated by Origin7.5. 3. Results and analysis 3.1. The changes of community structure characteristics 3.1.1. Species composition and abundance change In the T. ramosissima community under non-overflowing disturbance, there are six plant species, such as T. ramosissima, P. austraris, P. hendersonii, G. inflata, L. ruthenicum and Hexinia polydichotoma. Under the disturbance of surface water-overflowing disturbance, there are 10 plant species including four spontaneous immigration and establishment of native species, such as, Halogeton glomeratus, A. sparsifolia, K. caspica and Sonchus oleraceus in the T. ramosissima community. These increased species are mostly seedling sprouts, accounted for 14.29–40.00% of the total number of species, of which A. sparsifolia and K. caspica has stronger ability for colonel reproduction. From Table 1, we can see that species were increased in T. ramosissima community under the wateroverflowing disturbance. Comparing with it under non-distur-
bance, plant species were increased from 6 to 10 species, of which the increased species include one semi-shrub and three herb species.
3.1.2. Community structure amplitude ISv formula (1) combined with Table 1, we can see that Sorensen similarity coefficient of plant species is 0.75 and the percentage of common species was 60% in T. ramosissima community under overflowing disturbance and non-disturbance. It indicates that they have higher similar species composition and closer species relationship. At the same time, the main structure did not change in the community under these two treatments. Under the wateroverflowing disturbance, the increased plant species in T. ramosissima community that are local species in the original indigenous habitat. It indicates that the characteristics of community structure under water-overflowing disturbance are closer to those of the native community.
3.1.3. Species abundance changes in community Using formula (2), (3), species abundance was compared in T. ramosissima community under water-overflowing disturbance and non-disturbance. The results showed that the relative species number of H. glomeratus, T. ramosissima and S. oleraceus are increased in the T. ramosissima communities under the disturbance comparing with them under non-overflowing disturbance. Among them, the relative species number of H. glomeratus has more great increase than other species. Compared to the non-disturbance, the relative species number of P. austraris and Glycyrrhiza inflate showed a clear decline (Fig. 2). It indicated that the disturbance has little influence on the abundance of P. austraris and G. inflate with strong cloned capacity of reproduction. Under the water-overflowing disturbance, the relative coverage of P. austraris, H. glomeratus, P. hendersonii and L. ruthenicum in communities showed a relative increase, in which the relative coverage of P. austraris and H. glomeratus populations are significant increased since the tiller of P. austraris is greatly increased and plenty of H. glomeratus seedlings have germinated under the water-overflowing disturbances. On the contrary, the relative coverage of G. inflata shows a significant decline and the relative cover of T. ramosissima change is not pronounced (Fig. 3). It shows that surface water-overflowing disturbance has significant effect on the abundance of herb species with shallow roots and seedlings occurred by virtue of surface runoff. Moreover it has very small impact on T. ramosissima and G. inflate with deep roots. As a result, the abundance of these species is decreased relatively.
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Table 1 Plant species and its percentage of T. ramosissima community under water-overflowing disturbance or non-disturbance. Non-overflowing disturbance
Overflowing disturbance
Plant species
1. Tamarix ramosissima, 2. Phragmites austraris, 5. Poacynum hendersonii, 6. Glycyrrhiza inflate, 7. Lycium ruthenicum, 8. Hexinia polydichotoma
Species number of shrub or semi-shrub Species % of shrub or semi-shrub Species number of herbage Species % of herbage Hierarchical structure of community
2 33.33 4 66.67 Mainly consisted of shrubs and herbs, and dominated by herbs (of which the P. austraris ?tul?> is relatively abundant than other species, followed by G. inflate)
1. Tamarix ramosissima, 2. Phragmites austraris, 3. Halogeton glomeratus, 4. Alhagi sparsifolia, 5. Poacynum hendersonii, 6. Glycyrrhiza inflate, 7. Lycium ruthenicum, 8. Hexinia polydichotoma, 9. Sonchus oleraceus, 10. Karelinia caspica 3 28.57–50.00 7 50.00–71.43 Mainly consisted of shrub/semi-shrub and herb, which dominated by shrub or semi-shrub
there are three layers in communities, including tall shrub layer dominated by T. ramosissima; sub-shrub layer mainly consisted of L. ruthenicum and A. sparsifolia, and herbaceous layer mainly consisted of P. communis, H. glomeratus, P. hendersonii, and S. oleraceus. Compared with the non-disturbance, species composition and community hierarchical structure changed from simple to complex in the community under water-overflowing disturbance.
1.0
water-overflowing disturbance non-overflowing disturbance
Relative species number
0.9 0.8 0.7 0.6 0.5 0.4
3.2. Changes in species diversity
0.3 0.2 0.1 0.0
1
2
3
4
5
6
7
8
9
10
Plant species Fig. 2. Change of relative species number in Tamarix ramosissima community under water-overflowing disturbance or non-disturbance. (Note: the species is same as the Table 1.)
0.7
water-overflowing disturbance non-overflowing disturbance
Relative coverage of species
0.6 0.5 0.4 0.3
Species diversity indices of community are analyzed basing on the equation from (4)–(7), and the results showed that (Fig. 2) the R index, J index and H0 index of T. ramosissima community are increased from 6, 0.691 and 1.8775 under non-disturbance to 10, 0.7102 and 2.1611 under surface water-overflowing disturbance while the Jsw index of community has slightly decreased from 0.7263 under non-disturbance to 0.6506 under the disturbance. Based on the second analysis on species diversity index, the results showed (Fig. 4) that R index, J index and H0 index of T. ramosissima community under the water-overflowing disturbance are various and increased comparing with them under non-disturbance. Among them, species number is obviously increased while Jsw index is slightly decreased. The J index and the H0 index have a great increase with the increase of species number in the community. It can be seen that T. ramosissima communities has higher species diversity and ecological dominance while evenness of species distribution is relatively decreased under the disturbance.
0.2
3.3. Changes in the number and type of dominant species 0.1 0.0
1
2
3
4
5
6
7
8
9
10
Plant species
3.3.1. Change in the importance value of species According to formula (8), the relative importance value of plant species was analyses basing on the statistical analysis of survey
Fig. 3. The change on relative coverage of species in T. ramosissima community under water-overflowing disturbance or non-disturbance. (Note: the species is same as the Table 1)
11
water-overflowing disturbance non-overtopping disturbance
10
3.1.4. Changes of community hierarchical structure Species composition is relatively simple in T. ramosissima community under non-disturbance. It mainly consisted of shrubs and herbages, and dominated by herbages. And there are three layers in community, including tall shrub layer dominated by T. ramosissima; sub-shrub layer mainly consisted of L. ruthenicum, and herb layer mainly consisted of P. communis and G. inflate. Under the influence of water-overflowing disturbance, there are a number of local herbs and shrub species increased in the community. Species composition and species density are significantly increased in community. It mainly consisted of shrubs or semishrubs and herbages, dominated by shrubs or semi-shrubs. And
Species diversity
9 8 7 6 5 4 3 2 1 0
R
J
H'
Jsw
Species diversity index Fig. 4. The change on species diversity of Tamarix ramosissima community.
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data in T. ramosissima community under the water-overflowing disturbance or non-overflowing disturbance (Table 2). Under non-disturbance, the relative species importance value is in the range of 31.61–38.19. The main plant species of T. ramosissima and P. austraris are selected from the community by their relative important value. Under the disturbance, the species relative importance value are in the range of 0.37–39.73. And the relative importance value of T. ramosissima, L. ruthenicum and H. polydichotoma are increased while that of P. austraris, G. inflate and P. hendersonii are decreased. Importance value of the increased species accounted for 17.77% of the total importance value, indicating the original species diversity of T. ramosissima has been changed significantly. Comparing with non-disturbance, the relative importance value of T. ramosissima is increased from 39.73 to 36.97. It indicated that T. ramosissima still pay very important role in the maintenance of community structure and its function.
its reconstruction process. On the other hand, disturbance can increase the habitat heterogeneity that is the most important factor in affecting species composition. Major changes have taken place in species composition during the fluctuations process of T. ramosissima community under the water-overflowing disturbance. Species composition of P. austraris T. ramosissima G. inflata + P. hendersonii changed into T. ramosissima P. austraris + H. glomeratus L. ruthenicum H. polydichotoma + P. hendersonii. The hierarchical structure of T. ramosissima community changed from simple into complex under the disturbance. Species richness and abundance shows increasing generally, of which H. glomeratus population is significant increased since plenty of H. glomeratus seedlings have germinated under the water-overflowing disturbances. Community structure characteristics of T. ramosissima under the disturbance are closer to that of its native community in the desert riparian forest.
3.3.2. The dominant species of T. ramosissima community Dominant species are selected from T. ramosissima community under the disturbance and non-disturbance by the important value method (Table 3). There are three dominant species dominated by P. austraris and T. ramosissima (occupy the major advantage of community) in the community under non-disturbance. However, the dominant species has been changed and there are three dominant species dominated by T. ramosissima and P. austraris in the community under the disturbance. As an increased species, H. glomeratus become one dominant species and while G. inflate is declined in the community under the disturbance.
4.2. Great changes in species diversity
4. Conclusions and discussion 4.1. Community structure from simple to complex The effect of disturbance on species composition of plant community is to adjust the plant species, number of plants, and the ratio of plants number. Therefore, disturbance will inevitably play an important role on species composition changes of plant community under the disturbance during plant community updates or
Table 2 The important value of each species in T. ramosissima community under wateroverflowing disturbance or non-disturbance. Plant species
Non-overflowing disturbance
Water-overflowing disturbance
1. Tamarix ramosissima 2. Phragmites austraris 3. Halogeton glomeratus 4. Alhagi sparsifolia 5. Poacynum hendersonii 6. Glycyrrhiza inflata 7. Lycium ruthenicum 8. Hexinia polydichotoma 9. Sonchus oleraceus 10. Karelinia caspica
36.97 38.19 – – 3.81 17.77 1.67 1.61 – –
39.73 34.67 12.70 1.93 2.28 0.37 2.80 2.39 1.96 1.18
Table 3 Changes in dominant species of T. ramosissima community under water-overflowing disturbance or non-disturbance. Dominant species
Surface water-overflowing disturbance
Non-disturbance
1. 2. 3. 6.
+ + +
+ +
Tamarix ramosissima Phragmites austraris Halogeton glomeratus Glycyrrhiza inflata
+
Species diversity of T. ramosissima community under the wateroverflowing disturbance is greater than that under non-disturbance. It can be considered that water-overflowing disturbance could relieve the restrictions of water factors on plant for settlement. And get species richness and species diversity increased obviously. However, the smooth settlement of the species just means the beginning of vegetation restoration. The increased species of the community under the disturbance are all the species in the potential plant community. It indicates that the disturbance improve the germination of species in the soil seed bank and the growth of some seedlings and herb species with shallow roots. The community structure is getting towards more complicated, diversified, and more stable. 4.3. Community positive fluctuations Through the effect of water-overflowing disturbance on shallow soil moisture and its physical and chemical properties, it could improve the germination of plant seed in shallow soil and the cloned growth of plant nutrition and breeding (i.e., buds on the ground and underground stem). There are many seedling plants and ratoon seedling appeared in the sublayer of the community. As a result, species richness and abundance are increasing, species composition changes a lot, and the hierarchy structure is getting more complicated significantly in T. ramosissima community under the influence of water-overflowing disturbance. In addition, the number and kind of dominant species are changed in community too. And then, it is concluded that water-overflowing disturbance is an effective way to affect T. ramosissima community positive fluctuation generally. And the change of the fluctuation is small in the community under the disturbance. The fluctuation type of the community is not reveal fluctuations. Through lifting groundwater level near both sides of the river, the river channel water disturbance can improve the plant with deep root back to life, to save and restore natural vegetation on both sides of the river [10]. In the absence of large-scale flood and water-overflowing process, there is no plant based on water disturbance to happen the update phenomenon of falling species. And the process of the river channel water disturbance mainly is to rescue and rejuvenate the natural desert vegetation [19]. The river channel water disturbance mainly affects the germination of plant with deep root, increases community coverage, plant growth and leaf yield. It fully reflects that water-overflowing disturbance is importance and necessity for the species breeding and update and make up for the insufficient role of river channel water disturbance on restoring natural vegetation.
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