干旱对陆地生态系统生产力的影响

doi:10.17521/cjpe.2007.0027

摘要/Abstract

摘要：

该文综述了干旱对陆地生态系统生产力的影响,分析了其影响机制,并总结了植被对干旱的响应与适应及其机理机制。干旱通过抑制光合作用来降低陆地生态系统总初级生产力,干旱还可以降低生态系统的自养呼吸和异养呼吸。同时干旱还可以通过影响其它干扰形式来间接影响陆地生态系统生产力,如增加火干扰的发生频率和强度,增加植物的死亡率,增加病虫害的发生等。在生态系统水平上干旱可以降低碳固定,减弱碳汇功能,甚至把生态系统从碳汇改变成碳源。目前生态系统水平上的干旱影响研究主要通过两种方法实现,一种是模型模拟,另一种就是大型模拟实验。作为陆地生态系统生产力的实现者,在干旱胁迫条件下,植物也会采取积极的适应策略以减弱干旱对生态系统生产力的影响,其适应策略主要分以下3种:在一些周期性发生干旱的地区,植物会调整生长期以避开干旱或通过休眠来减弱干旱所造成的伤害;还有一些植物会通过调节体内的代谢过程,改变一些生理特性来抵御干旱;而长期生活在干旱条件下的植物则通过进化来改变了自身的生理生化代谢过程,形成耐旱机制。目前,植物对干旱响应的分子学机制,以及生态系统水平上对干旱的响应和适应仍然是薄弱的领域,也必然成为未来研究的重点。

关键词: 干旱, 全球变化, 陆地生态系统生产力, 适应

Abstract:

In recent years, there has been increasing concern about the impacts of drought stress on terrestrial ecosystem productivity and the carbon cycle in the context of global change. In this paper, we have reviewed recent progresses in understanding how drought stress affects terrestrial ecosystem processes and how ecosystems adapt to increasing drought stress. Drought stress could cause terrestrial ecosystems to act as a carbon source to the atmosphere by decreasing terrestrial gross primary productivity. Drought stress also results in a reduction of both autotrophic and heterotrophic respiration. Drought often associates with high rates of fire intensity, plant mortality and disease, which could lead to a large reduction of terrestrial ecosystem productivity. However, plant and ecosystem respond to drought dress in a complex way. There are three adaptation strategies that plants can live with a drought condition: 1) some plants adjust their growing season to avoid drought stress; 2) some other plants modify their internal mechanism to counter drought stress; 3) the other plants hold some physiological properties to tolerate drought stress. Experimental and modeling investigations of how ecosystems respond to drought and associated stresses are clearly needed in the future research.

Key words: drought stress, global change, terrestrial ecosystem productivity, adaptation

田汉勤, 徐小锋, 宋霞. 干旱对陆地生态系统生产力的影响. 植物生态学报, 2007, 31(2): 231-241. DOI: 10.17521/cjpe.2007.0027

TIAN Han-Qin, XU Xiao-Feng, SONG Xia. DROUGHT IMPACTS ON TERRESTRIAL ECOSYSTEM PRODUCTIVITY. Chinese Journal of Plant Ecology, 2007, 31(2): 231-241. DOI: 10.17521/cjpe.2007.0027

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https://www.plant-ecology.com/CN/Y2007/V31/I2/231

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参考文献 109

[1]	Allen CD, Breshears DD (1998). Drought-induced shift of a forest-woodland ecotone: rapid landscape response to climate variation. Proceedings of the Natural Academy of Sciences of the United States of America, 95,14839-14842. DOI URL
[2]	Amede T, Kittlitz EV, Schubert S (1999). Differential drought responses of faba bean ( Vica faba L.) inbred lines. Journal of Agronomy and Crop Science, 183,35-45. DOI URL
[3]	Amthor JS (1989). Respiration and Crop Productivity. Springer-Verleg, Berlin.
[4]	Amthor JS, McCree KJ (1990). Carbon balance of stressed plants:a conceptual model for integrating research results. In: Alscher RG, Cummings JR eds. Stress Responses Implants: Adaptation and Acclimation Mechanisms. Wiley-Liss, New York, 1-15.
[5]	Anyia AO, Herzog H (2004). Water-use efficiency, leaf area and leaf gas exchange of cowpeas under mid-season drought. Europe Journal of Agronomy, 20,327-339.
[6]	Arneth A, Kelliher FM, Mcseveny TM, Byers JN (1999). Assessment of annual carbon exchange in a water-stressed Pinus radiate plantation: an analysis based on eddy covariance measurements and an integrated biophysical model. Global Change Biology, 5,531-545. DOI URL
[7]	Auclair AND, Lill JT, Revenga C (1996). The role of climate variability and global warming in the dieback of Northern Hardwoods. Water, Air and Soil Pollution, 91,163-186.
[8]	Bänziger M, Edmeades GL, Beck D, Bellon M (2000). Breeding for Drought and Nitrogen Stress Tolerance in Maize, From Theory to Practice, CIMMYT, Mexico D.F.
[9]	Barber VA, Juday GP, Finney BP (2000). Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress. Nature, 405,668-673. DOI URL PMID
[10]	Bell DT, Koeppe DE, Miller RJ (1971). The effect of drought stress on respiration of isolated corn Mitochondria. Plant Physiology, 48,413-415. URL PMID
[11]	Borken W, Savage K, Davidson EA, Turmbore SE (2006). Effects of experimental drought on soil respiration and radiocarbon efflux from a temperate forest soil. Global Change Biology, 12,177-193. DOI URL
[12]	Borken W, Xu YJ, Davidson EA, Beese F (2002). Site and temporal variation of soil respiration in European beech, Norway spruce, and Scots pine forests. Global Change Biology, 8,1205-1216. DOI URL
[13]	Boyer JS (1976). Photosynthesis at low water potentials. Philosophical Transactions of the Royal Society B, 273,501-512.
[14]	Boyer JS (1982). Plant productivity and environment. Science, 218,443-448. DOI URL PMID
[15]	Breshears DD, Allen CD (2002). The importance of rapid, disturbance-induced losses in carbon management and sequestration. Global Ecology and Biogeography, 11,1-5. DOI URL
[16]	Brown TJ, Hall BL, Westerling AL (2004). The impact of twenty-first century climate change on wildland fire danger in the western United States: an applications perspective. Climatic Change, 62,365-388. DOI URL
[17]	Bryla DR, Bouma TJ, Hartmond U, Eissenstat DM (2001). Influence of temperature and soil drying on respiration of individual roots in citrus: integrating greenhouse observations into a predictive model for the field. Plant, Cell and Environment, 24,781-790.
[18]	Buckley TN (2005). The control of stomata by water balance. New Phytologist, 168,275-292. DOI URL
[19]	Burton AJ, Pregitzer KS, Zogg GP, Zak DR (1998). Drought reduces root respiration in sugar maple forests. Ecological Applications, 8,771-778. DOI URL
[20]	Cao MK, Prince SD, Shugart HH (2002). Increasing terrestrial carbon uptake from the 1980s to the 1990s with changes in climate and atmosphere CO₂. Global Biogeochemical Cycles, 16, 1069, doi: 10.1029/2001GB001553.
[21]	Cavender-Bares J, Bazzaz FA (2000). Changes in drought response strategies with ontogeny in Quercus rubra: implications for scaling from seedlings to mature trees. Oecologia, 124,8-18. DOI URL
[22]	Chapin FS, Matson PA, Mooney HA (2002). Principles of Terrestrial Ecosystem Ecology. Springer, New York.
[23]	Chaves MM (1991). Effects of water deficits on carbon assimilation. Journal of Experimental Botany, 42,1-16. DOI URL
[24]	Chen THH, Murata N (2002). Enhancement of tolerance of abiotic stress by metabolic engineering of betaines and other compatible solutes. Current Opinion in Plant Biology, 5,250-257. DOI URL
[25]	Chiatante D, Iorio AD, Sciandra S, Scippa GS, Mazzoleni S (2006). Effect of drought and fire on root development in Quercus pubescens Willd. and Fraxinus ornus L. seedlings. Environmental and Experimental Botany, 56,190-197. DOI URL
[26]	Ciais Ph, Reichstein M, Viovy N, Granier A, Ogee J, Allard V, Aubinet M, Buchmann N, Bernhofer C, Carrara A, Chevallier F, Noblet ND, Friend AD, Friedllingstein P, Grunwald T, Heinesch B, Keronen P, Knohl A, Krinner G, Loustau D, Manca G, Matteucci G, Miglietta F, Ourcival JM, Papale D, Pilegaard K, Rambal S, Seufert G, Soussana JF, Sanz MJ, Schulze ED, Vesala T, Valentini R (2005). Europe-wide reduction in primary productivity caused by the heat and drought in 2003. Nature, 437,529-533. DOI URL PMID
[27]	Clark JM, Chapman PJ, Adamson JK, Lane S (2005). Influence of drought-induced acidification on the mobility of dissolved organic carbon in peat soils. Global Change Biology, 11,791-809.
[28]	Clavel D, Drame NK, Roy-Macauley H, Braconnier S, Laffray D (2005). Analysis of early responses to drought associated with field drought adaptation in four Sahelian groundnut ( Arachis hypogaea L.) cultivars. Environmental and Experimental Botany, 54,219-230.
[29]	Cornic G (1994). Drought stress and high light effects on leaf photosynthesis. In: Baker NR, Bowyer JR eds. Photoinhibition of Photosynthesis: From Molecular Mechanisms to the Field. Oxford BIOS Scientific Publishers, Oxford, 297-313.
[30]	Davidson EA, Belk E, Boone RD (1996). Soil water content, soil respiration, and a summer drought in well-drained and poorly-drained soils of a temperate forest. Ecological Society of America Annual Meetings, Providence, RI, August 15.
[31]	Davidson EA, Belk E, Boone RD (1998). Soil water content and temperature as independent or confounded factors controlling soil respiration in a temperate mixed hardwood forest. Global Change Biology, 4,217-227.
[32]	Davies WJ, Tardieu F, Trejo CL (1994). How do chemical signals work in plants that grow in drying soils? Plant Physiology, 104,309-314. DOI URL PMID
[33]	Fang JY(方精云), Tang YH(唐艳鸿), Lin JD(林俊达), Jiang GM(蒋高明) (2000). Global Ecology: Climate Change and Ecological Responses (全球生态学:气候变化与生态响应), Higher Education Press, Beijing. (in Chinese)
[34]	Fay PA, Carlisle JD, Knapp AK, Blair JM, Collins SL (2000). Altering rainfall timing and quantity in a mesic grassland ecocystem: design and performance of rainfall manipulation shelters. Ecosystem, 3,308-319.
[35]	Fensham RJ, Holman JE (1999). Temporal and spatial patterns in drought-related tree dieback in Australian savanna. Journal of Applied Ecology, 36,1035-1050.
[36]	Fosberg MA, Stocks BJ, Lynham TJ (996). Risk analysis in strategic planning: fire and climate change in the boreal forest. In: Goldammer JG, Furyaev VV eds. Fire in Ecosystems of Boreal Eurasia. Kluwer Academic Publishers, Dordecht, The Netherlands,495-505.
[37]	Griffin JJ, Ranney TG, Pharr DM (2004). Heat and drought influence photosynthesis, water relations, and soluble carbohydrates of two ecotypes of redbud (Cercis canadensis). Journal of the American Society for Hortcultural Science, 129,497-502.
[38]	Grulke NE, Retzlaff WA (2001). Changes in physiological attributes of ponderosa pine from seedling to mature tree. Tree Physiology, 21,273-284. DOI URL PMID
[39]	Guo JP(郭建平), Gao SH(高素华) (2004). Tendency and countermeasure of response of plant to CO₂ enrichment and soil drought. Journal of Soil and Water Conservation(水土保持学报), 18(2),170-173. (in Chinese with English abstract)
[40]	Hanson PJ, Weltzin JF (2000). Drought disturbance from climate change: response of United States forests. The Science of Total Environment, 262,205-220.
[41]	Hanson AD, Hitz WD (1982). Metabolic responses of mesophytes to plant water deficits. Annual Review of Plant Physiology, 33,163-203.
[42]	IPCC (2001). Radiative forcing of climate change. In: Ramaswamy V ed. Climate Change 2001. Cambridge University Press, Cambridge, UK,New York,USA.
[43]	Keetch JJ, Byram GM (1968). A Drought Index for Forest Fire Control. Southeast. Forest Exp. Sta. USDA. Forest Service Research. Paper, SE-38,32.
[44]	King AW, Gunderson CA, Post WM, Weston DJ, Wullschleger SD (2006). Plant respiration in a warmer world. Science, 312,356-357.
[45]	Knapp AK, Smith MD (2001). Variation among biomes in temporal dynamics of aboveground primary production. Science, 291,481-484.
[46]	Knapp AK, Fay PA, Blair JM, Collins SL, Smith MD, Carlisle JD, Harper DW, Danner BT, Lett MS, McCarron JK (2002). Rainfall variability, carbon cycling, and plant species diversity in a mesic grassland. Science, 298,2202-2205. DOI URL PMID
[47]	Kozlowski TT, Pallardy SG (2002). Acclimation and adaptive responses of woody plants to environmental stresses. Botanical Review, 68,270-334.
[48]	Laporte MF, Duchesne LC, Wetzel S (2002). Effect of rainfall patterns on soil surface CO₂ efflux, soil moisture, soil temperature and plant growth in a grassland ecosystem of northern Ontario, Canada: implications for climate change. BMC Ecology, 2,10. URL PMID
[49]	Larcher W (1995). Physiological Plant Ecology 3rd edn. Springer, Berlin.
[50]	Law BE, Goldstein AH, Anthoni PM, Unsworth MH, Panek JA, Bauer MR, Fracheboud JM, Hultman N (2001). Carbon dioxide and water vapor exchange by young and old ponderosa pine ecosystems during a dry summer. Tree Physiology, 21,297-306.
[51]	Lawlor DW (1995). The effects of water deficit on photosynthesis. In: Smirnoff N ed. Environment and Plant Metabolism, Flexibility and Acclimation. BIOS Scientific Publisher. Oxford, 129-160.
[52]	Liu YF(刘允芬), Song X(宋霞), Sun XM(孙晓敏), Wen XF(温学发), Chen YR(陈永瑞) (2004). Seasonal variation of CO₂ flux and its environmental factors in evergreen coniferous plantation. Science in China(中国科学), 34(Suppl.),109-117. (in Chinese)
[53]	Lloret F, Siscart D, Dalmases C (2004). Canopy recovery after drought dieback in holm-oak Mediterranean forests of Catalonia (NE Spain). Global Change Biology, 10,2092-2099.
[54]	Mackenzie A, Ball AS, Virdee SR (2001). Instant Notes in Ecology. BIOS Publishers.
[55]	McCully ME, Boyer JS (1997). The expansion of root cap mucilage during hydration. III. Changes in water potential and water content. Physiologia Plantarum, 99,169-177.
[56]	McKee KL, Mendelssohn I, Materne MD (2004). Acute salt marsh dieback in the Mississippi River deltaic plain: a drought-induced phenomenon? Global Ecology and Biogeography, 13,65-73.
[57]	Miyashita K, Tanakamaru S, Maitani T, Kimura K (2005). Recovery responses of photosynthesis, transpiration, and stomatal conductance in kidney bean following drought stress. Environmental and Experimental Botany, 53,205-214.
[58]	Mosena M, Dillenburg LR (2004). Early growth of Brazilian pine ( Araucaria angustifolia (Bertol.) Kuntze) in response to soil compaction and drought. Plant and Soil, 258,293-306.
[59]	Munns R, King RW (1988). Abscisic acid is not the only stomatal inhibitor in the transpiration stream of wheat plants. Plant Physiology, 88,703-708. URL PMID
[60]	Munns R, Passioura JB, Milborrow BV, James RA, Close TJ (1993). Stored xylem sap from wheat and barley in drying soil contains an inhibitor with a large molecular size. Plant, Cell and Environment, 16,867-872.
[61]	National Drought Mitigation Center (2006). What is drought? http://drought.unl.edu/whatis/concept.htm. Cited 10 December 2006.
[62]	Nayyar H, Walia DP (2004). Genotypic variation in wheat in response to water stress in abscisic acid-induced accumulation of osmolytes in developing grains. Journal of Agronomy and Crop Science, 190,39-45.
[63]	Nepstad D, Lefebvre P, Silva ULD, Tomasella J, Schlesinger P, Solorzano L, Moutinho P, Ray D, Benito JG (2004). Amazon drought and its implications for forest flammability and tree growth: a basin-wide analysis. Global Change Biology, 10,704-717.
[64]	Nilsen ET, Muller WH (1982). The influence of photoperiod on drought induction of dormancy in Lotus scoparius. Oecologia, 53,79-83. DOI URL PMID
[65]	Noone K, Steffen W (2006). IGBP Science and Implementation Strategy. Stockholm.
[66]	Ort DR, Oxborough K, Wise RR (1994). Depressions of photosynthesis in crops with water deficits. In: Baker NR, Bowyer JR eds. Photoinhibition of Photosynthesis: From Molecular Mechanisms to the Field. BIOS Scientific Publisher. Oxford.
[67]	Overpeck JT, Rind D, Goldberg R (1990). Climate-induced changes in forest disturbance and vegetation. Nature, 343,51-53.
[68]	Palta JA, Nobel PS (1989a). Root respiration for Agave deserti: influence of temperature, water status, and root age on daily patterns. Journal of Experimental Botany, 40,181-186.
[69]	Palta JA, Nobel PS (1989b). Influences of water status, temperature, and root age on daily patterns of root respiration for two cactus species. Annals of Botany, 63,651-662.
[70]	Palta JA, Gregory PJ (1997). Drought affects the fluxes of carbon to roots and soil in ¹³C pulse-labeled plants of wheat. Soil Biology and Biochemistry, 29,1395-1403.
[71]	Pastenacz A, Erdei L (1996). Calcium-dependent protein kinase in maize and sorghum induced by polyethylene glycol. Physiologia Plantarum, 97,360-364.
[72]	Perez-Molphe-Balch E, Gidekel M, Seguza-Nieto M, Herrera-Estrella L, Ochoa-Alejo N (1996). Effects of water stress on plant growth and root proteins in three cultivars of rice ( Oryza sativa) with different levels of drought tolerance. Physiologia Plantarum, 96,284-290.
[73]	Raich JW, Potter CS, Bhagawati D (2002). Interannual variability in global soil respiration, 1980—94. Global Change Biology, 8,800-912.
[74]	Reddy AR, Chaitanya KV, Vivekanandan M (2004). Drought-induced response of photosynthesis and antioxidant metabolism in higher plants. Journal of Plant Physiology, 161,1189-1202. DOI URL PMID
[75]	Reich PB, Borchert R (1984). Water stress and tree phenology in a tropical dry forest in the lowlands of Costa Rica. Journal of Ecology, 72,61-74.
[76]	Reichstein M, Tenhunen JD, Roupsard O, Ourcival JM, Rambal S, Miglietta F, Peressotti A, Pecchiari M, Tirone G, Valentini R (2002). Severe drought effects on ecosystem CO₂ and H₂O fluxes at three Mediterranean evergreen sites: revision of current hypotheses? Global Change Biology, 8,999-1017.
[77]	Rice KJ, Matzner SL, Byer W, Brown JR (2004). Patterns of tree dieback in Queensland, Australia: the importance of drought stress and the role of resistance to cavitation. Oecologia, 139,190-198. DOI URL PMID
[78]	Robertson M, Cuming AC, Chandler PM (1995). Sequence analysis and hormonal regulation of a dehydrin promoter from barley, Hordeum vulgare. Physiologia Plantarum, 94,470-478.
[79]	Ruan X(阮晓), Wang Q(王强), Xu NY(许宁一), Li JG(李建贵), Huang JH(黄俊化) (2005). Physio-ecological response of Haloxylon persicum photosynthetic shoots to drought stress. Scientia Silvae Sinicae(林业科学), 41(5),28-32. (in Chinese with English abstract)
[80]	Sardans J, Penuelas J (2005). Drought decreases soil enzyme activity in a Mediterranean Quercus ilex L. forest. Soil Biology and Biochemistry, 37,455-461.
[81]	Sauter A, Dietz KJ, Hartung W (2002). A possible stress physiological role of abscisic acid conjugates in root-to-shoot signalling. Plant, Cell & Environment, 25,223-228.
[82]	Savage KE, Davidson EA (2001). Interannual variation of soil respiration in two New England forests. Global Biogeochemical Cycles, 15,337-350.
[83]	Scott-Denton LE, Sparks KL, Monson RK (2003). Spatial and temporal control of soil respiration rate in a high-elevation, subalpine forest. Soil Biology and Biochemistry, 35,525-534.
[84]	Shao HB(邵宏波), Liang ZS(梁宗锁), Shao MA(邵明安) (2005). Adaptation of higher plants to environmental stress and stress signal transduction. Acta Ecologica Sinica(生态学报), 25,1772-1781. (in English with Chinese abstract).
[85]	Sharkey TD (1990). Water stress effects on photosynthesis. Photosynthetica, 24,651.
[86]	Sobrado MA (1999). Drought effects on photosynthesis of the mangrove, Avicennia germinans, under contrasting salinities. Trees, 13,125-130.
[87]	Song X, Yu GR, Liu YF, Sun XM, Lin YM, Wen XF (2006). Seasonal variation of WUE and the environmental factors in subtropical plantation coniferous. Science in China Series D, 49 (Suppl.), II119-126.
[88]	Tang ZC(汤章成) (1998). Mechanism of adaptation to osmosis stress and flooding stress. In: Yu SW (余叔文), Tang ZC (汤章成) eds. Plant Physiology and Molecular Biology (植物生理与分子生物学). Science Press, Beijing. (in Chinese)
[89]	Tezara W, Mitchell WJ, Driscoll SD (1999). Water stress inhibits plant photosynthesis by decreasing coupling factor and ATP. Nature, 401,914-917.
[90]	Tian HQ, Melillo JM, Kicklighter DW, McGuire AD, Helfrich IVK, Moore B, Vorosmarty CJ (1998). Effect of interannual climate variability on carbon storage in Amazonian ecosystems. Nature, 396,664-667.
[91]	Tian HQ, Melillo JM, Kicklighter DW, McGuire AD, Helfrich J (1999). The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO₂ in the United States. Tellus, 51B,414-452.
[92]	Tian HQ, Melillo JM, Kicklighter DW, McGuire AD, Helfrich J, Moore B, Vørøsmarty CJ (2000). Climatic and biotic controls on annual carbon storage in Amazonian ecosystems. Global Ecology and Biogeography, 9,315-336.
[93]	Torrecillas A, Guillaume C, Alarcon JJ, Ruiz-Sanchez MC (1995). Water relations of two tomato species under water stress and recovery. Plant Science, 105,169-176.
[94]	Trenberth K (1998). Atmospheric moisture residence times and cycling: implications for rainfall rates and climate change. Climatic Change, 39,667-694.
[95]	Volaire F (2002). Drought survival, summer dormancy and dehydrin accumulation in contrasting cultivars of Dactylis glomerata. Physiologia Plantarum, 116,42-51. DOI URL PMID
[96]	Walker TS, Bais HP, Grotwold E, Vivanco JM (2003). Root exudation and rhizosphere biology. Plant Physiology, 132,44-51. DOI URL PMID
[97]	Wang Z(王忠) (2000). Plant Physiology (植物生理学). China Agriculture Press, Beijing. (in Chinese)
[98]	Waring RH, Law BE (2001). The ponderosa pine ecosystem and environmental stress: past, present and future. Tree Physiology, 21,273-274. DOI URL PMID
[99]	Wilkinson S, Davies WJ (2002). ABA-based chemical signaling: the co-ordination of responses to stress in plants. Plant, Cell and Environment, 25,195-210.
[100]	Wilson DR, van Bavel CHM, McCree KJ (1980). Carbon balance of water-deficient grain sorghum plants. Crop Science, 20,153-159.
[101]	Wittenmayer L, Merbach W (2005). Plant responses to drought and phosphorus deficiency: contribution of phytohormones in root-related processes. Journal of Plant Nutrient and Soil Science, 168,531-540.
[102]	Woods Hole Research Center (2006). http://www.whrc.org/southamerica/drought-sim/results.htm. Cited 10 December 2006.
[103]	Xu X, Cifre J, Medrano H (2002). Abscisic acid to the nutrient solution induces a water deficit-like response in Trifolium subterraneum. Annals of Applied Biology, 140,297-304.
[104]	Xu ZZ, Zhou GS, Li H (2004). Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis seedling to change of soil moisture and temperature. Journal of Environmental Sciences, 16,666-669.
[105]	Xu ZZ, Zhou GS (2005a). Effects of water stress on photosynthesis and nitrogen metabolism in vegetative and reproductive shoots of Leymus chinensis. Photosyntherica, 43,29-35.
[106]	Xu ZZ, Zhou GS (2005b). Effects of water stress and nocturnal temperature on carbon allocation in the perennial grass, Leymus chinensis. Physiologia Plantarum, 123,272-280.
[107]	Yin CY, Peng YH, Zang RG, Zhu YP, Li CY (2005). Adaptive responses of Populus kangdingensis to drought stress. Physiologia Plantarum, 123,445-451.
[108]	Young IM (1995). Variation in moisture contents between bulk soil and the rhizosheath of Triticum aestivum L. cv. New Phytologist, 130,135-139.
[109]	Zhang J, Davies WJ (1987). Increased synthesis of ABA in partially dehydrated root tips and ABA transport from roots to leaves. Journal of Experimental Botany, 38,2015-2023.