青藏高原高寒灌丛生态系统二氧化碳通量研究

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	青藏高原高寒灌丛生态系统二氧化碳通量研究
	徐世晓
学位类型	博士
导师	赵新全
	2006
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位专业	其它专业
关键词	：青藏高原高寒灌丛净生态系统co2交换时动态日变化生长季节非生长季节年际差异温度光合有效辐射叶面积指数
摘要	本论文以青藏高原东北部海北地区高寒灌丛（Alpine Shrub）生态系统为研究对象，利用微气象观测系统及涡度相关（Eddy Covariance）技术，自2003年1月1日至2005年12月31日对该类广布于青藏高原的典型高寒草地类型进行长期连续观测。在对生态系统CO2净交换（NEE）以及群落叶面积指数（LAI）、生物量等生物学指标和光合有效辐射（PAR）、温度、土壤水分、脉冲性降水事件等主要环境因子进行连续监测的基础上，重点分析和探讨了海北地区高寒灌丛生态系统净生态系统CO2交换(NEE)在时、日、月及年际尺度上的变化模式，生长季与非生长季高寒灌丛生态系统CO2净交换特征，高寒灌丛生态系统大气CO2源/汇年际差异，土壤温度、昼夜温差、光合有效辐射、脉冲性降水事件等主要环境因子影响。从而，揭示了不同时间尺度下的高寒灌丛生态系统NEE变化规律，阐明主要环境因子对生态系统NEE的影响，明确了该生态系统大气CO2源/汇状况及其季节分布模式；同时，也为青藏高原区域尺度的高寒草地生态系统CO2通量研究和碳收支的估算提供科学依据和基础数据，对进一步揭示我国乃至亚洲陆地生态系统的碳收支状况有着重要意义。主要研究结果概括为以下几个方面： 1、海北地区高寒灌丛生态系统净生态系统CO2交换时动态特征存在很大的季节性差异，暖季小时NEE变化振幅大，CO2净吸收的极值一般出现在午间，最大吸收量为1.7 g CO2 m-2 h-1左右。夜间为CO2净释放，净生态系统交换值较为稳定（0.5~ 0.9 g CO2 m-2 h-1）；冷季日变化振幅极小，除14:00~18:00时一定量CO2释放外，其余时段通量均很小。 2、从日平均净生态系统CO2交换来看，6~9月日平均NEE一般为负值（CO2净吸收），2003~2005年6~9 月间日平均NEE分别为-5.65 g CO2 m-2 d-1、-6.08 g CO2 m-2 d-1和-4.81 g CO2 m-2 d-1；而10~12月及翌年1~5月期间日平均NEE通常为正值（CO2净释放），该时段3年高寒灌丛日平均净生态系统CO2交换分别为1.91 g CO2 m-2 d-1、1.90 g CO2 m-2 d-1和2.19 g CO2 m-2 d-1。2003~2004年高寒灌丛生态系统CO2净释放维持天数分别为249 d、 254 d和264 d，2003年净释放维持天数最少，而净吸收维持天数2005年最少（101d）。2003、2004和2005年全年日平均CO2净吸收分别为0.611 g CO2 m-2 d-1、0.759 g CO2 m-2 d-1和0.167 g CO2 m-2 d-1。 3、就季节差异而言，2003、2004和2005年整个生长季节高寒灌丛平均CO2日净生态系统交换分别为-3.99 g CO2 m-2 d-1、-4.59 g CO2 m-2 d-1、-3.27 g CO2 m-2 d-1。7、8月生长季节CO2净吸收的最高，2003、2004、2005年7月和8月份高寒灌丛生态系统CO2净吸收分别为222 g CO2 m-2 和224 g CO2 m-2、355 g CO2 m-2和216 g CO2 m-2、263 g CO2 m-2和186 g CO2 m-2。在相对短暂的生长季节海北地区高寒灌丛生态系统表现出显著的大气CO2净吸收能力，2003、2004和2005年生长季节高寒灌丛生态系统CO2净吸收量分别为610 g CO2 m-2、701 g CO2 m-2和500 g CO2 m-2。相对于温度等环境因子，高寒灌丛生态系统生长季白昼NEE小时变化规律更受光合有效辐射变化的影响。 4、2003～2005年非生长季节日平均NEE分别为1.83 g CO2 m-2、2.01 g CO2 m-2和2.07 g CO2 m-2。4月和10月是非生长季节CO2净释放的最高月份，2003、2004和2005年全月净释放量为105 g CO2 m-2和77 g CO2 m-2、105 g CO2 m-2和117 g CO2 m-2及105 g CO2 m-2和138 g CO2 m-2，2003～2005年整个非生长季CO2净释放分别为CO2为388 g CO2 m-2、425 g CO2 m-2和439 g CO2 m-2。非生长季节海北地区高寒灌丛生态系统NEE小时变化与5 cm土壤温度存在极显著的正相关关联，表明在非生长季节土壤温度是影响青藏高原高寒灌丛生态系统NEE的重要环境因子。 5、从生态系统CO2源/汇特征来看，海北地区高寒灌丛生态系统2003、2004和2005年全年净CO2固定总量分别为223 g CO2 m-2 a-1、277 g CO2 m-2 a-1和61 g CO2 m-2 a-1，3年平均CO2值为187 g CO2 m-2 a-1。在为期3年的研究时段海北地区高寒灌丛生态系统表现为弱的大气二氧化碳的汇。 6、高寒灌丛群落表观光合量子产额（a）和表观最大光合速率（Pmax）受叶面积指数的影响。在6～9月份期间，由于LAI的不同，a和Pmax值差异明显，7、8月份较高而6月和9月明显较低。海北地区高寒灌丛生态系统a和Pmax值高于西藏当雄地区高寒草甸生态系统，但低于平原地区相关生态系统。维持天数2005年最少（101d）。2003、2004和2005年全年日平均CO2净吸收分别为0.611 g CO2 m-2 d-1、0.759 g CO2 m-2 d-1和0.167 g CO2 m-2 d-1。 3、就季节差异而言，2003、2004和2005年整个生长季节高寒灌丛平均CO2日净生态系统交换分别为-3.99 g CO2 m-2 d-1、-4.59 g CO2 m-2 d-1、-3.27 g CO2 m-2 d-1。7、8月生长季节CO2净吸收的最高，2003、2004、2005年7月和8月份高寒灌丛生态系统CO2净吸收分别为222 g CO2 m-2 和224 g CO2 m-2、355 g CO2 m-2和216 g CO2 m-2、263 g CO2 m-2和186 g CO2 m-2。在相对短暂的生长季节海北地区高寒灌丛生态系统表现出显著的大气CO2净吸收能力，2003、2004和2005年生长季节高寒灌丛生态系统CO2净吸收量分别为610 g CO2 m-2、701 g CO2 m-2和500 g CO2 m-2。相对于温度等环境因子，高寒灌丛生态系统生长季白昼NEE小时变化规律更受光合有效辐射变化的影响。 4、2003～2005年非生长季节日平均NEE分别为1.83 g CO2 m-2、2.01 g CO2 m-2和2.07 g CO2 m-2。4月和10月是非生长季节CO2净释放的最高月份，2003、2004和2005年全月净释放量为105 g CO2 m-2和77 g CO2 m-2、105 g CO2 m-2和117 g CO2 m-2及105 g CO2 m-2和138 g CO2 m-2，2003～2005年整个非生长季CO2净释放分别为CO2为388 g CO2 m-2、425 g CO2 m-2和439 g CO2 m-2。非生长季节海北地区高寒灌丛生态系统NEE小时变化与5 cm土壤温度存在极显著的正相关关联，表明在非生长季节土壤温度是影响青藏高原高寒灌丛生态系统NEE的重要环境因子。 5、从生态系统CO2源/汇特征来看，海北地区高寒灌丛生态系统2003、2004和2005年全年净CO2固定总量分别为223 g CO2 m-2 a-1、277 g CO2 m-2 a-1和61 g CO2 m-2 a-1，3年平均CO2值为187 g CO2 m-2 a-1。在为期3年的研究时段海北地区高寒灌丛生态系统表现为弱的大气二氧化碳的汇。 6、高寒灌丛群落表观光合量子产额（a）和表观最大光合速率（Pmax）受叶面积指数的影响。在6～9月份期间，由于LAI的不同，a和Pmax值差异明显，7、8月份较高而6月和9月明显较低。海北地区高寒灌丛生态系统a和Pmax值高于西藏当雄地区高寒草甸生态系统，但低于平原地区相关生态系统。
其他摘要	To clarify the hourly, diurnal, seasonal and interannual variations in CO2 flux and main factors affecting CO2 flux between an alpine shrub ecosystem and atmosphere, the eddy covariance technique was used to measure CO2 flux continuously for three years (2003~ 2005) in typical alpine shrub ecosystem (37°40'N, 101°20'E, 3293 m a.s.l.) on the northeast of Qinghai-Tibet Plateau. Continuous measurements include net ecosystem CO2 exchange (NEE) and environment factors such as photosynthesis active radiation (PAR), temperature, precipitation, soil water content, and vegetation characteristics with biomass and leave area index (LAI). Based on those continuous monitoring and investigation, we analyzed temporal variations in CO2 flux of the alpine shrub ecosystem and its relationship to environmental factors. We also provided some significant data on the atmospheric CO2 sour or sink status and its seasonal patterns of the alpine shrub ecosystem in the unique plateau; at the same time, continuously monitoring and research work concerning CO2 flux for the alpine shrub ecosystem on the Qinghai-Tibet Plateau will supply scientific basis and fundamental for regional carbon budget, and then facilitate determination of source or sink status of typical alpine grassland ecosystems on the plateau. This study is very important as well as for assessing the carbon budget and carbon process study for temperate grassland. The primary results can be summarized as follow: 1. The distinct seasonal differences in hourly net ecosystem CO2 exchange (NEE) were observed in the alpine shrub on the Qinghai-Tibet Plateau. With larger hourly NEE fluctuation in growing seasons, the net CO2 influx process occurred in daytime with its peak value of 1.7 g CO2 m-2 h-1at 12:00, approximately, a stable net CO2 efflux (0.5~ 0.9 g CO2 m-2 h-1) appeared in nighttime. On the contrary, the CO2 efflux changed with small fluctuation in the non-growing seasons, a small amount of CO2 efflux mainly occurred between 14:00 and 18:00. 2. As for diurnal variations, mean diurnal NEE were -5.6 g CO2 m-2 d-1、-6.1 g CO2 m-2 d-1 and -4.8 g CO2 m-2 d-1 (net CO2 influx) from June to September in 2003, 2004 and 2005; while, the mean diurnal CO2 efflux were 1.91 g CO2 m-2 d-1、1.90 g CO2m-2 d-1 and 2.19 g CO2 m-2 d-1 from October to next April in 2003, 2004 and 2005. Mean annual diurnal net ecosystem CO2 exchange were -0.611 g CO2 m-2 d-1、-0.759 g CO2 m-2 d-1 and -0.167 g CO2 m-2 d-1 (net CO2 influx ) in 2003, 2004 and 2005, respectively. 3. Over the course of the growing season, mean diurnal net ecosystem CO2 exchange between the alpine shrub ecosystem and atmosphere were -3.99 g CO2 m-2 d-1, -4.59 g CO2 m-2 d-1 and -3.27 g CO2 m-2 d-1 from 2003 to 2005. The largest CO2 influx occurred in July and August for one year, with values of 222 g CO2 m-2, 224 g CO2 m-2, and 355 g CO2 m-2 in July, and 216 g CO2 m-2, 263 g CO2 m-2 and 186 g CO2 m-2 in August , respectively, for three years. There was a remarkable capacity of CO2 assimilating during the short growing season in the alpine shrub ecosystem with total net CO2 influx of 610 g CO2 m-2、701 g CO2 m-2 and 500 g CO2 m-2 in 2003, 2004 and 2005, respectively. The results showed that the significant correlation between the hourly NEE and soil temperature has not been found during the growing season, the NEE was mainly dominated by photosynthestically active radiation (PAR). 4. The mean diurnal CO2 efflux during the non-growing seasons in the alpine shrub ecosystem were 1.83 g CO2 m-2, 2.01 g CO2 m-2, 2.07 g CO2 m-2 in 2003, 2004 and 2005, respectively. With a net CO2 efflux of 105 g CO2 m-2 and 77 g CO2 m-2, 105 g CO2 m-2 and 117 g CO2 m-2, 105 g CO2 m-2 and 138 g CO2 m-2 in 2003, 2004 and 2005, respectively, April and October were the month with the largest CO2 net efflux. The total NEE during the non-growing seasons were 388 g CO2 m-2, 425 g CO2 m-2 and 439 g CO2 m-2 (net CO2 efflux) for three years, respectively. There is a significant positive correlation between the diurnal net ecosystem CO2 exchange variations and the variance of the soil temperature in the non-growing seasons, indicating that temperature is a dominant environmental factor affecting hourly NEE in the non-growing season in the alpine shrub ecosystem on the Qinghai-Tibet Plateau. 5. The alpine shrub ecosystem was a weak sink for atmospheric CO2 with a net ecosystem CO2 exchange of 223 g CO2 m-2 a-1, 277 g CO2 m-2 a-1 and 61 g CO2 m-2 a-1 in 2003, 2004 and 2005, respectively. Mean annual NEE was 187 g CO2 m-2 a-1 for 3 years. 6. Over the course of growing season, monthly apparent quantum yield (a) and maximum ecosystem assimilation (Pmax) were dominated by variations in leaf area index (LAI). From May to September, difference in LAI result in different a and Pmax, both a and Pmax in July and August with higher LAI were higher than that in June and September. In this alpine shrub ecosystem, a and Pmax were much lower than that in lowland ecosystems, and higher than alpine meadow in Dangxiong of the Qinghai-Tibet Plateau. 7. NEE increased along with the increase of photosynthestically active radiation(PAR) during growing season in the alpine shrub ecosystem, and reached its peak value at about 1100 μmol m-2 s-1, on the contrary, NEE declined along with ulteriorly increasing of PAR. Over the course of the growing seasons, day-to-day variations in NEE, were highly correlated with variations in temperature difference between daytime and night, diurnal NEE increased with the increase in day/night temperature difference. Soil temperature (5 cm) was a key environmental factor, which effect NEE during the non-growing seasons of the alpine shrub ecosystem, diurnal variations in NEE followed closely to changes in soil temperature. 8. The results showed that there was a significant positive correlation between diurnal ecosystem respiration (Reco) and soil temperature at 5 cm depth（P<0.01）from June to September for 2003 and 2004. As for influence of rain events on Reco, large pulses of Reco after individual rain events were observed in the alpine shrub ecosystem, the results also indicated that the Reco was strongly affected by precipitation events, the daily Reco markedly increased after the occurrence of precipitation.
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/1483
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	徐世晓. 青藏高原高寒灌丛生态系统二氧化碳通量研究[D]. 北京. 中国科学院研究生院,2006.

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