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不同功能型植物对梭梭群落碳水通量的贡献
杨洁
学位类型硕士
导师唐立松
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业环境科学
关键词土壤呼吸 生态系统呼吸 二氧化碳通量 涡度相关
摘要在全球气候变化与陆地生态系统响应的研究领域,陆地生态系统的碳循环和水循环是陆地表层系统物质循环和能量传输的核心,是地圈—生物圈—大气圈相互作用关系的纽带,这两个最基本的相互耦合的生态学过程一直是全球变化生态学研究的前沿性科学问题。近年来,涡度相关技术的进步使得陆地生态系统碳、水通量的长期和连续观测成为可能。本文以中国科学院阜康荒漠生态站为实验平台,以古尔班通古特沙漠南缘梭梭群落为研究对象,通过箱式法和涡度相关法相结合,拆分生态系统碳、水交换中植物和土壤的贡献。实验于2013−2014年生长季开展,通过同步观测灌木层片、草本层片和群落水平碳、水交换,探讨不同功能型植物对梭梭群落碳、水通量的贡献;通过连续的观测土壤CO2通量,并结合环境因子的季节性波动,着重分析土壤呼吸对生态系统呼吸的贡献。主要结果包括以下几方面: (1)草本层片对群落碳、水通量的贡献主要集中在4月—6月,这与研究区的水分条件密切相关,积雪在4月初融化,土壤水分充足,早春的短命植物得以快速生长;灌木层片的碳、水通量在整个生长季都比较稳定,说明草本层片对群落碳固定的贡献集中在5月,灌木对群落碳固定的贡献一直较稳定,是群落碳固定的主要贡献者。 (2)本研究的结果表明,箱式法计算出的生态系统呼吸结果,比涡度相关法的结果要高,许多专家学者在研究和对比涡度相关法以及箱式法的时候,得出了相似的结论,被高估的比例大概是20—40%。涡度相关通量系统的这种夜间低估通量的现象越来越受到人们的重视,可以采用WPL校正、摩擦速度阈值去除等方法对通量数据进行预处理。 (3)在整个生长季,生态系统呼吸呈单峰式变化,峰值出现在7月,为0.75 gC m-2 d-1;最小值出现在3月,为0.09 gC m-2 d-1;土壤呼吸在5~7月之间变化不大(0.34~0.51 gC m-2 d-1),7月底以后呈逐渐减小的趋势; (4)土壤呼吸与生态系统呼吸的比值(Rsoil/Reco)在整个生长季介于0.38~0.98之间,平均值为0.67;季节变化上总体呈“U”型,即生长季初期和末期较高,而生长季中期较低;Rsoil/Reco与梭梭同化枝生物量相关性分析表明二者呈显著负相关(R2=0.458,P<0.05),说明随着梭梭同化枝生物量的增加,其对生态系统呼吸的贡献升高,导致了植物生长季中期Rsoil/Reco的下降。
其他摘要As the core of the material circulation and the energy transmission of the terrestrial system, the carbon cycle and the water cycle play critical roles in the research of the global climate change and the response of the terrestrial system. Now, due to the improvement of eddy covariance technique, we can directly obtain net ecosystem carbon flux or total water flux, but it cannot distinguish their components. Using chamber-based method and eddy covariance method, we simultaneously measured the carbon flux and total water flux in a Haloxylon ammodendron community, located in the southern margin of Gurbantunggut Desert in western China, to partition the contributions of the different kinds of functional plants and soil to the carbon flux and water flux of the community. In order to investigate different functional plant's contribution to the carbon and water flux of community level, the synchronous observation of carbon and water exchange in shrub layer, herb layer and community levels were carried out during the growing season of 2013 and 2014. Considering of seasonal variation of environmental factors, special attention was paid on the seasonal variation of the ratio of Rsoil to Reco by the continuous observation of soil CO2 flux. The main results include the following aspects: The contribution of herbaceous layer to carbon-water flux mainly focused in April to June, which was closely related to water conditions in research area.. The soil moisture was sufficient due to snow melting water at the beginning of April, which was beneficial for the fast growth of ephemeral plants. Whereas the carbon and water flux of the shrub layer were relatively stable in the whole growing season, which further illustrated the main contribution of the shrub layer to community carbon fixed. The values of ecosystem respiration deriving from chamber-based method were higher than values of eddy covariance method, which was consistent with the former consequence of ecosystem respiration deriving from the two contrasting methods, the higher proportion ranging between 20%−40%. The phenomenon of flux underestimation during night has attracted more and more attentions, in spite of flux data were optimized previously by eliminating CO2 advection, removing linear trend, WPL correction and getting rid of friction wind speed threshold, the fact that flux underestimation during night was still not changed. The Reco was unimodal distribution during the whole growing season, the maximum Reco was 0.75 gC m-2d-1 and the minimum was 0.09 gC m-2d-1. The change of Rsoil was not obvious during May to July (0.34-0.51 gC m-2d-1), and Rsoil began decreasing since the end of July. The ratio of Rsoil and Reco ranged from 0.38 to 0.98, with an average of 0.67 across the whole growing season. On a seasonal basis, Rsoil/Reco presented an obvious “U” pattern: the value of Rsoil/Reco was high at the beginning and ending of growing season, but was low in the middle of growing season. There was a significant linear correlation between the Rsoil/Reco ratios and biomass of H.ammodendron assimilating twigs (R2 = 0.458, P < 0.05), indicating that as the H.ammodendron growth, the contribution of H.ammodendron aboveground respiration (especially with leaf respiration) to Reco was also increased.
学科领域环境科学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14639
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
杨洁. 不同功能型植物对梭梭群落碳水通量的贡献[D]. 北京. 中国科学院大学,2015.
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