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题名: 黄土高原典型生态系统CO2交换的年际变化
作者: 周小平
学位类别: 博士
答辩日期: 2012
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 王效科
关键词: 生态系统CO2交换 ; net ecosystem CO2 exchange ; 土壤呼吸 ; soil respiration ; 年际变化 ; interannual variability ; 功能性变化 ; functional change ; 黄土高原 ; Loess Plateau
其他题名: Interannual variability in ecosystem CO2 exchange of the typical ecosystems in the Loess Plateau
中文摘要:     全球气候变化引起了人们对最重要的温室气体—CO2的源汇问题的极大关注。陆地生态系统与大气间CO2交换是影响大气中CO2的一个最重要的过程,因此也成为了全球C循环研究的热点。随着全球CO2通量网的建立,以及通量数据的累积,越来越多的分析发现生态系统NEE年际间变化显著,并且这种变化的原因很复杂。这种年际间的变化为我们准确估算全球碳平衡带来了挑战,我们必须多NEE的年际变化有更为充分的了解,进而可以改进模型,提高对NEE的估算能力。 我国是一个农业大国,农业生态系统是我国最为重要的生态系统之一。小麦生态系统是黄土高原最重要的生态系统。黄土高原正在经历着干暖化的气候变化,通过研究NEE的年际变化,来揭示气候变化对NEE的影响,对准确估测地区C平衡的关键。本研究用多通道通量箱法,对黄土高原地区小麦田生态系统CO2交换和土壤呼吸进行了为期四年的测定,同时测定了气象因子降雨、光和有效辐射(PPFD)、土壤水分含量(SWC)、土壤温度(soil temperature)和空气温度(air temperature,Tair)—分析了(net ecosystem CO2 exchange)及其组成成分总初级生产力(gross primary productivity, GPP)和生态系统呼吸(TER)以及土壤呼吸的季节变化和年际变化,并分析了土壤呼吸和NEE、GPP和TER时间变异的控制因素。本研究的主要结论如下: (1) 空气温度、土壤温度、降雨量和土壤水分含量都表现出显著的季节变化。空气温度年际间差异最大的月份是2月份,2008年2月气温在四年2月气温中是最低值 ,而2007年2月气温在四年2月气温中为最高。土壤温度的季节变化趋势与空气温度的季节变化趋势一致。年总降雨量年际间差异较大,2009年降雨量显著低于前四年,2005年降雨量最大。在小麦的主要生育期,降雨量差异也较大,2007年3月上旬至5月下旬,几乎没有降雨,导致土壤含水量下降,农田水分亏缺。2006年和2009年3月-5月份降雨充沛,并且时间分布均匀。 (2) 小麦田生态系统和苹果园生态系统土壤呼吸均表现出显著的季节变化,冬季最低,小麦田生态系统和苹果园生态系统土壤呼吸的最低值分别为0.25umol m-2 s-1 和 0.285 umol m-2 s-1 ,冬季之后,随着温度的升高,土壤呼吸也逐渐升高,于7月中下旬达到最大值,小麦田生态系统和苹果园生态系统土壤呼吸最大值分别为7.97 u mol m-2 s-1 和 6.21 u mol m-2 s-1。土壤呼吸的季节变化主要受温度和土壤含水量的影响,在小麦田生态系统中,土壤呼吸与土壤温度和土壤含水量均显著相关,可以用方程Rsoil=1.761+0.119Tsoil - 1.30SWC, R2 = 0.48来描述他们之间的关系。通径分析结果表明土壤温度对土壤呼吸的影响大于土壤含水量。土壤温度的通径系数为0.73, 土壤含水量的通径系数为0.06. 苹果园生态系统中,土壤温度、空气温度和土壤含水量均与土壤呼吸显著相关,空气温度与土壤呼吸的回归系数大于土壤温度与土壤呼吸的回归系数。土壤含水量与土壤呼吸的相关关系在每年有所不同,从2005年到2007年,土壤含水量与土壤呼吸显著相关,但2008-2009年,土壤含水量与土壤呼吸之间的关系并不显著。月降雨量与月土壤呼吸显著相关。 (3) 无论是小麦田生态系统还是苹果园生态系统,土壤呼吸均表现出显著的年际变化,小麦田生态系统中,土壤呼吸年际间变化较大,年总土壤呼吸变化幅度为1625.21 g C m-2 yr-1 -821.38 g C m-2 yr-1. 2007-2008年土壤呼吸最低,2006-2007年土壤呼吸最高。苹果园生态系统年总土壤呼吸的变化幅度为351.92 g C m-2 yr-1 - 521.08 g C m-2 yr-1, 2008-2009年土壤呼吸最低,2005-2006年土壤呼吸最高。 用HOS模型对土壤呼吸的年际变化进行了成因分析,将土壤呼吸年际变化成因分为四种:functional change, 环境因子的年际变化、环境因子的年际变化以及随机误差。在小麦田生态系统中,functional change、环境因子的年际变化、环境因子的年际变化和随机误差分别能解释土壤呼吸年际变化的10.6%, 4.5%, 58.4%, 和26.5%,在苹果园生态系统,functional change、环境因子的年际变化、环境因子的年际变化和随机误差分别能解释土壤呼吸年际变化的12.7%、 5.2%、56.3%、和 25.8 % (4) 小麦田生态系统CO2 交换(NEE)、总初级生产力(GPP)、生态系统总呼吸(TER)均表现出显著的季节变化,NEE、GPP以及TER的季节变化受环境因子和小麦物侯期的调控。TER主要受土壤温度和小麦物侯期的影响,GPP的季节变化主要受空气温度和植物生长的影响。 (5) 小麦生长季年平均NEE为-30.6 mol m-2 yr-1,考虑到撂荒期后,年NEE为-10.11 mol m-2 yr-1, 撂荒期的高温高降雨量以及撂荒期过长,撂荒期TER占全年TER的40%,是本研究区NEE高于其他研究区的重要原因。考虑收获后,小麦生态系统每年损失133.7 g C m-2 yr-1。小麦收获是导致生态系统C损失的最重要因素。 小麦田生态系统NEE和产量表现出显著的年际变化。年降雨总量与NEE和产量没有显著关系,小麦重要的生育期的降雨量分布,是影响小麦NEE和产量的最重要因素。2006 -2007年,因为小麦最重要的生长期(拔节期和孕穗期)没有降雨,降雨量减少降低了小麦GPP和TER,但对GPP的影响大于TER,因而CO2吸收的下降,小麦产量下降。冬季和早春温度是影响年NEE的重要因素。2007-2008年1月和2月的低温导致2008年1-3月GPP下降,产量也低于2005-2006年和2008-2009年。春季低温导致小麦返青期推迟,春季GPP下降,并且产量也下降。 本研究表明,考虑到撂荒期和小麦收获对籽粒和地上部生物量的移除,小麦田生态系统是C源。土壤呼吸、生态系统净CO2交换、总初级生产力、生态系统呼吸以及产量均表现出显著的年纪变化。环境因子土壤呼吸的影响年际间存在差异,Functional change对土壤呼吸年际变化的影响大于环境因子年际变化对土壤呼吸的直接影响,在未来对C平衡的预测中,需要充分考虑到Functional change的作用。
英文摘要:       As the most important greenhouse gas, the air CO2 content and its sinks and sources, were paid more and more interesting. The CO2 exchange between the terrestrial ecosystem and the atmosphere is one of the most important processes that influence the CO2 content. The Flux-Net supplied more long-tem flux measurement data, and the interannual variability was found in most ecosystems. The existence of IAV has brought challenge to the C budget prediction. Understanding the causes of IAV are urgently needed to improve our prediction of global carbon cycling. The agro-ecosystem is one of the most important ecosystems in China. The Loess Plateau is the most important ecosystem in North of China, winter wheat ecosystem is the most ecosystems in this area, but most of the winter wheat was changed to the apple orchard in the past 20 years. To understand the carbon dioxide exchange between the winter wheat ecosystem and the apple orchard and atmosphere, and to learn how the ecosystem CO2 exchange effect on the climate change, we monitored the CO2 flux continuously in a winter wheat ecosystem and an adjacent apple orchard ecosystem using an automated multiplexing chamber system, and the environmental factors such as precipitation, photosynthetically active radiation (PAR), soil water content, soil temperature, air temperature, were monitored continuously, the experiment continued four years (from July, 2005 to June, 2009). We analyzed the seasonal and interannual variability of CO2 exchange and its component, the controlling factor of those variability was analyzed. The main results of this study were following: (1). Air temperature, soil temperature, precipitation water content and the PAR showed significant seasonal and interannual variability. The variation was biggest in February, the air temperature in February was lowest in 2008, and it was highest in 2007. The annual precipitation varied among four years, the precipitation in 2006-2007 and 2008-2009 were about 50mm lower than that in 2005-2006 and 2007-2008. The precipitation in the spring in 2007 was vary low, there almost not rained from the mid-March to late of May. (2) The soil respiration of winter wheat ecosystem and apple ecosystem showed significant seasonal variability. It was lowest in winter, the lowest respiration in winter wheat ecosystem and apple orchard were 0.25umol m-2 s-1 and 0.285 umol m-2 s-1 positively,and it increased from winter to summer with the increasing of temperature, and reached its peak value in July, the highest soil respiration in winter wheat ecosystem and apple orchard were 7.97 u mol m-2 s-1 and 6.21 u mol m-2 s-1 positively. The seasonal variability of soil respiration was controlled by the temperature and soil water content. In winter wheat ecosystem, the soil respiration was significant corrected with the soil temperature and soil water content, the relationship between soil respiration and soil temperature and soil water content was well regressed with the function: Rsoil=1.761+0.119Tsoil - 1.30SWC, R2=0.48. Path analysis revealed that soil temperature was more important, path coefficient pTa = 0.73, and the pTa = 0.06. In apple orchard ecosystem, the soil respiration were corrected with air temperature, soil temperature and soil water content. The regression of air temperature and soil respiration was bigger than soil temperature. The soil water content showed significant influence on soil respiration in 2005-2007, but not significant in 2008-2009. The precipitation showed significant effect on soil respiration in fours year. (3) The soil respiration showed significant interannual variability both in winter wheat ecosystem and apple orchard ecosystem. The annual soil respiration in winter wheat ranged from 1625.21 g C m-2 yr-1 to 821.38 g C m-2 yr-1, it was lowest in 2007-2008, and was biggest in 2006-2007。The soil respiration in apple orchard ranged from 351.92 g C m-2 yr-1 to 521.08 g C m-2 yr-1, it was lowest in 2008-2009, and was highest in 2005-2006. We used regression analysis to distinguish direct effects of interannual variability in climate on soil respiration from functional change, and the interannual variability in soil respiration were partitioning four source: the functional change, the interannual climatic variability, seasonal climatic variation and random error. The functional change, the interannual climatic variability, seasonal climatic variation and random error explained 10.6%, 4.5%, 58.4%, and 26.5% of the observed variation in soil respiration positively in winter wheat ecosystem, and were 12.7%、 5.2%、56.3%、and 25.8 % positively in apple orchard ecosystem. (4) Ecosystem CO2 exchange, ecosystem gross primary gross primary productivity and the ecosystem respiration in winter wheat varied seasonally. The variability was controlled by the environmental factor and the phenological growth stage. The soil temperature and the phenological growth stage influenced on the seasonal variability of ecosystem respiration, and the GPP was influenced by the air temperature and phenological growth stage. (5) The mean annual net ecosystem CO2 exchange in winter wheat was -30.6 mol m-2 yr-1 in growing season, added the CO2 exchange in fallow period, the annual mean net ecosystem exchange was -10.11 mol m-2 yr-1. The ecosystem respiration in fallow period accounted for 40% of the annual ecosystem respiration. Most of the photosynthetic product was removed from the winter wheat ecosystem by the harvest. This resulted to the winter wheat lost about 133.7 g C m-2 yr-1. The variability of ecosystem CO2 exchange was significant in winter wheat ecosystem. The most important factor that controlled the net ecosystem CO2 exchange was the precipitation and the air temperature. The little precipitation in the main growing season in 2006-2007 decreased the gross primary productivity, winter wheat yield and the ecosystem respiration, but the decline of ecosystem respiration was small than gross primary productivity. The low air temperature in January and February declined the gross primary productivity and yield. This study revealed that the winter wheat ecosystem was a carbon source considered the harvest. The soil respiration and ecosystem CO2 exchange, gross productivity, ecosystem respiration and yield varied interannual, and the influence of environment on ecosystem CO2 exchange was varied among years. The functional change explained more of the observed variation in soil respiration than interannual variability of environmental factors, it is necessary to consider the influence of functional change on the ecosystem CO2 exchange to prediction the C balance in future.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/35112
Appears in Collections:城市与区域生态国家重点实验室_学位论文

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Recommended Citation:
周小平. 黄土高原典型生态系统CO2交换的年际变化[D]. 北京. 中国科学院研究生院. 2012.
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