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题名	多枝柽柳与梭梭对降水变化的响应与适应—— 生理、个体与群落水平的碳水平衡整合研究
作者	许皓
学位类别	博士
答辩日期	2008
授予单位	中国科学院．新疆生态与地理研究所
导师	李彦，中国科学院新疆生态与地理研究所
关键词	生理生态响应
其他题名	WATER AND CARBON BALANCES OF TAMARIX RAMOSISSIMA AND HALOXYLON AMMODENDRON UNDER VARIATION IN PRECIPITATION: FROM LEAF TO COMMUNITY
中文摘要	水是荒漠生态系统的首要限制因素，影响着生态系统生态过程的各环节。荒漠区植物在应对水分缺乏的环境压力时，表现出不同的适应策略。近20年来全球气候变化以及人类活动的加剧，导致古尔班通古特沙漠南缘原始盐生荒漠地区的降水与地下水位正在发生显著的改变；这些改变正导致荒漠植物用水策略的适应性变化，其种间差异性影响着荒漠植物群落组成与生态系统碳水平衡。本研究以中亚荒漠关键种多枝柽柳Tamarix ramosissima和梭梭Haloxylon ammodendron为对象，在生理生态、个体形态与群落水平上整合研究两个优势种对自然生境水分条件改变的响应与适应。实验于2004-2006年生长期开展，在地下水位于2.9m至4.5m之间波动的典型原始生境，追踪自然降水过程的同时，设置双倍和无降水2个人工降水梯度。观测生境水分条件变化时光合作用、蒸腾作用、叶水势和瞬时水分利用效率等生理活动的响应；研究根系分布和地上生物量累积等个体形态特征的适应性改变；利用涡度相关系统测定群落碳水通量，并辅以土壤CO2通量测定，估算群落初级生产力与叶面积指数的季节变化；从而揭示不同水平上多枝柽柳与梭梭的用水策略和碳同化维持机制。实验数据表明，多枝柽柳和梭梭用水策略迥异，不同的根系功能型决定了前者的生存依赖地下水，后者生存依靠直接大气降水。深根系与气孔调节是多枝柽柳碳水平衡适应环境水分状况的两个关键机制：柽柳成熟植株生理与个体水平的水分平衡和碳获取均依赖于相对稳定的地下水源，特殊的气孔行为体现其以高水分消耗为代价，将碳获取最大化的适应对策；群落蒸腾耗水依赖于地下潜水层的供给，并且在生态系统H2O通量中占重要比例；群落碳同化能力的季节变化是光合有效辐射和地下水位共同影响下光合作用物候学特征的体现；降水造成的浅土层水分状况变化对多枝柽柳碳水平衡没有显著影响，而地下水位下降将危及其生存。梭梭主要利用降水形成的浅层土壤水维持生存；极为有效的形态调节和较强的气孔控制是其维持光合能力以及适应降水变化的主要机制；适量增多且在生长期内均匀分布的降水可以对梭梭光合作用、生物量累积和生态系统碳蓄积产生明显正效应，这预示梭梭可能在未来种间竞争和群落演替中占有优势。本研究表明，荒漠区灌木应对水分胁迫和环境水分有效性的改变时，具有高效的自我协调与适应能力：在个体水平上的自我调节，主要通过改变形态特征来实现，体现为吸收根表面积和同化器官面积之间动态平衡的主动维持；群落水平上的动态主要是个体变化所致，生理调节作用对此的直接贡献微弱；生理生态、个体形态与群落水平的适应机制相互协调，共同构成用水与碳获取的最优策略。全球气候变化条件下不同根系功能型荒漠植物的响应特征和适应策略的多水平研究，为预测荒漠生态系统的动态变化提供了关键的理论依据；生理、个体、群落水平整合研究是了解全球变化背景下生态系统过程与植物适应性的有效和必要途径。Within the current background of global climate change, significant increase in precipitation has been recorded in the arid region of central Asia over the past 50 years. In addition, in some transition regions between sandy deserts and oases, the groundwater table has fallen significantly as a result of the overexploitation of groundwater. Variation in precipitation in arid ecosystems is leading to plant adaptation in water use strategies; significant interspecific differences in responses will change the plant composition of desert communities. To understand the effects of these widely acknowledged changes in water conditions, this study integrated the response, acclimation, and adaptation of two native dominant desert shrubs in Central Asia, Tamarix ramosissima and Haloxylon ammodendron, towards variation in precipitation, from the perspective of ecophysiological activities, morphological adjustment and carbon/water balances of plant community. During the growing season of 2004 to 2006, the experiments were carried out under natural precipitation and two manipulated precipitation treatments (double and no precipitation respectively), in their original habitats where the groundwater table fluctuated from 2.9m to 4.5m, on the southern periphery of Gurbantonggut Desert. Changes in photosynthesis, transpiration, leaf water potential, water-use efficiency, above-ground biomass accumulation, and root distribution were examined under the contrasting precipitation treatments, in order to reveal their water-use strategies and mechanisms of photosynthesis maintenance under drought stress and precipitation variation. Meanwhile, CO2 and H2O fluxes above the undisturbed T. ramosissima and H. ammodendron communities were measured by eddy covariance method to evaluate their NEE. The experiment revealed that: (1) Ecophysiological activities, biomass accumulation and community carbon assimilation of T. ramosissima did not respond to sustained drought in the upper soil or the pulse of heavy rain, and the photosynthetic consistency is achieved by its strategic adaptation in water-use pattern. On the individual plant scale, T. ramosissima can efficiently avoid the effects of water deficiency in upper soil with its phreatophytic root system. The LAI indicates that the seasonal pattern in community carbon assimilation represents the combined effects of groundwater table and photosynthetic absorbable radiation on the phenology of specific photosynthesis. On the physiological scale, the special stomatal behavior is one of the main mechanisms in the water-use strategy of desert plants. As a result of tradeoff, T. ramosissima tends to maximize its carbon gain at the cost of higher water consumption, attributed to sufficient groundwater supply. Even under increased precipitation, it will probably maintain its water balance pattern in the long term. The stable groundwater shields its carbon and water balances from significant fluctuation in upper soil water caused by precipitation, and the decline in groundwater will threaten its survival and shift the community succession in this arid region. (2) Ecophysiological activities, morphological adjustment and community carbon assimilation of H. ammodendron responded to rainfall events and precipitation variation significantly. Its efficient morphological adjustment, combined with strong stomatal control, contributes to its maintenance of photosynthesis and acclimation to variation in water condition. On account of its positive responses to increased precipitation, H. ammodendron is predicted to succeed in interspecific competition in a future, moister habitat. In conclusion, this integrated study is an effective approach to further the understanding of the shrub adaptation strategies and the desert ecosystem processes under variation in precipitation and groundwater.
语种	中文
学科主题	植物生理学
公开日期	2010-11-12
页码	共113页
内容类型	学位论文
源URL	[http://ir.xjlas.org/handle/365004/8132]
专题	新疆生态与地理研究所_中国科学院新疆生态与地理研究所(2010年以前数据)
推荐引用方式 GB/T 7714	许皓. 多枝柽柳与梭梭对降水变化的响应与适应—— 生理、个体与群落水平的碳水平衡整合研究[D]. 中国科学院．新疆生态与地理研究所. 2008.

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