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贡嘎山峨眉冷杉生态系统水碳关系及时空分异机制
Alternative TitleThe mechanism of water and carbon relationship in temporal and altitude scale for Abies fabri in Mt. Gongga
Language中文
孙向阳
Thesis Advisor王根绪
2013
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Abstract陆地生态系统碳循环和水循环是陆地表层系统物质能量循环的核心,是地圈-生物圈-大气圈相互作用的纽带,也是陆地生态系统相互耦合的2个重要生态学过程,更是全球变化科学研究的核心问题。然而,对水碳平衡关系及其对气候变化的响应的认识还十分有限。陆地生态系统水循环和碳循环的过程机制是分析气候变化机制、预测气候变化、制定气候变化适应性政策的科学基础。峨眉冷杉是广泛分布于我国西南亚高山区的一种典型的暗针叶林,也是生长于亚高山林线处的典型林型。本论文基于海拔2800~3700m垂直带谱上的峨眉冷杉生态系统为研究对象,采用野外试验、室内试验和模型模拟相结合的方法,分别分析了蒸散发、碳循环和WUE的时空变异及控制因子,系统阐述了影响水、碳循环及耦合关系的主要机制。论文的主要结论如下:(1)贡嘎山亚高山暗针叶林生态系统年均蒸散发总量为640(±49) mm, 林冠截留在总蒸散发中所占的比例最大(52.1%),森林生态系统蒸腾量次之(32.5%);蒸腾量占总蒸散发的比例在干季较高,湿季较低。净辐射是总蒸散发量的主要影响因素,也是控制蒸散发季节变化的主要因子;气孔导度是树木蒸腾的主要影响因素。蒸散发量随着海拔梯度的升高而逐渐减小,其中蒸腾量减小的最快,林冠截留蒸发表现为增加趋势,地表蒸发量表现为下降趋势;通过分析得出,温度是控制海拔梯度上蒸散发变化的主要因素。(2)大气降水的18O、2H同位素值随着海拔升高而降低,而不同月份的大气降水量线也不同。冷杉枝干18O、2H对同样随海拔梯度增加而降低。表层土壤和深层土壤水分的18O、2H在海拔梯度上的变化不明显。海拔梯度上,冷杉枝水分的变化受到降水的影响较明显。海拔梯度升高,冷杉叶片的δ13C和WUE均表现为增加的趋势,叶片δ13C随着温度和比叶面积增加而降低,随着叶片氮含量的增加而增加,但降水对叶片δ13C影响不显著。随海拔升高,气孔导度降低,气孔导度和枝条水分的δ18O表现正相关关系,枝条水分的δ18O与叶片δ13C之间表现为负相关关系。(3)年均GPP和NPP的累计量分别为18.3 (± 3.7) t ha-1 a-1和11.0 (± 2.3) t ha-1 a-1。GPP和NPP的年际变化主要受到总辐射的影响。小时尺度上,非生长季GPP随净辐射和饱和水汽压的增加而增加,并逐渐趋于稳定,生长季GPP随净辐射和饱和水汽压的增加表现为先增加后减小的趋势。GPP和NPP均随海拔高度的增加而降低,其变化与温度的相关性较好。水分利用效率具有年际变化特征,GPP/Et、GPP/ET、GPP/(Eint+Et)、NPP/Et、NPP/ET、和NPP/(Eint+Et)分别为10.45(±0.79)、3.30(±0.06)、3.99(±0.17)、6.40(±0.19)、2.03(±0.02)和2.47(±0.06)、mg CO2/g H2O,水分利用效率变化对年均温度和年降水量较敏感。生长季水分利用效率较高,但在不同的生长季内其又有明显的波动。GPP、NPP和蒸散发与温度关系变化不同步性导致WUE的年内变化。(4)幼龄林、中龄林和成熟林全年土壤CO2通量分别为13.73 t ha-1 a-1、15.55 t ha-1 a-1和9.49 t ha-1 a-1,非生长季土壤呼吸占年土壤呼吸通量比分别为0.33、0.36和0.30。生长季土壤呼吸速率分别与5cm土壤温度和0~10cm土壤含水量具有显著的指数函数关系和二次线性函数关系。峨眉冷杉中龄林的土壤呼吸速率与土壤温度的指数关系并不显著。雪盖厚度影响冬季土壤呼吸的速率,但雪盖厚度可能并不足以隔绝土壤和大气之间的交换,因此并不能通过雪盖厚度来完全反应冬季的土壤呼吸变化。海拔3000m冷杉林自养呼吸量为8.58 t ha-1 a-1,异养呼吸量为7.82 t ha-1 a-1。生态系统呼吸及其组分随着海拔升高而减小。生态系统呼吸和光合速率有显著的关系。在年内尺度上,生态系统呼吸和总蒸散量之间的一致性不显著;但在海拔梯度上,生态系统呼吸速率变化和总蒸散发量之间具有一致性,其表现为二次线性函数关系。(5)贡嘎山亚高山区近20年来,气温明显增加,但是降水量年际间波动较大。气候变化情景下,温度升高4.5℃,蒸腾量增加约14.1%。生长季,GPP和NPP的变化趋势相似,均在温度升高1.8℃时增加,之后随着温度升高而降低,非生长季,GPP和NPP均随着温度的升高而增加,温度升高会降低峨眉冷杉的碳利用效率(NPP/GPP)。降水量增加均会促进GPP和NPP的增加。生长季,各种表达方式的WUE均随着温度的升高而减小;非生长季,GPP/Et和GPP/ET随温度升高而显著增加,但是NPP/Et则表现为相反的趋势,NPP/ET随温度升高而变化较小;降水量增加在一定程度上促进了蒸腾指标下WUE的增加,对总蒸散发指标下的WUE影响较小。
Other AbstractThe carbon cycle and water cycle of terrestrial ecosystem are the kernal cycles of matter and energy in land surface, the link of geosphere-biosphere-atmosphere interactions, the two important coupled ecosystem processes, and even the key issue of the global change. However, the trade-off relationship between water and carbon and their feedback to climate change is ambiguity. The process mechanism of terrestrial water cycle and carbon cycle is the scientific basis to analyze the climate change mechanism, predict the climate change, and draft the policy of climate change adaptation. Abies fabri is one of the typical dark coniferous forests, which has a wide distribution in Southwest China. It is also a typical treeline forest. This study mainly focused on the Abies fabri ecosystem between the altitudes of 2800 to 3700 m. In-situ experiments, in-door experiments and process models are used to study the spatial and temporal pattern of evapotranspiration, carbon cycle and water use efficiency (WUE), and understand the controlling factors of these processes. We also demonstrate the main mechanism that influencing the water cycle, carbon cycle and the coupled relationship. The main conclusions are as following:
(1) The annual evapotranspiration of dark coniferous ecosystem was 640(±49) mm in Mt. Gongga. Canopy interception had the largest ratio of 52.1%, and the transpiration accounted for 32.5% of total evapotranspiration, the rest was ground evaporation. The ratio of transpiration to evapotranspiraiton had the higher value in non-growing season compared to growing season. Net radiation was the main factor for evapotranspiration. Stomatal conductance was the main factor of transpiration. The evapotranspiration amount decreased with increasing altitude, so were transpiration and ground evaporation, while canopy interception had the reverse The carbon cycle and water cycle of terrestrial ecosystem are the kernal cycles of matter and energy in land surface, the link of geosphere-biosphere-atmosphere interactions, the two important coupled ecosystem processes, and even the key issue of the global change. However, the trade-off relationship between water and carbon and their feedback to climate change is ambiguity. The process mechanism of terrestrial water cycle and carbon cycle is the scientific basis to analyze the climate change mechanism, predict the climate change, and draft the policy of climate change adaptation. Abies fabri is one of the typical dark coniferous forests, which has a wide distribution in Southwest China. It is also a typical treeline forest. This study mainly focused on the Abies fabri ecosystem between the altitudes of 2800 to 3700 m. In-situ experiments, in-door experiments and process models are used to study the spatial and temporal pattern of evapotranspiration, carbon cycle and water use efficiency (WUE), and understand the controlling factors of these processes. We also demonstrate the main mechanism that influencing the water cycle, carbon cycle and the coupled relationship. The main conclusions are as following:
(1) The annual evapotranspiration of dark coniferous ecosystem was 640(±49) mm in Mt. Gongga. Canopy interception had the largest ratio of 52.1%, and the transpiration accounted for 32.5% of total evapotranspiration, the rest was ground evaporation. The ratio of transpiration to evapotranspiraiton had the higher value in non-growing season compared to growing season. Net radiation was the main factor for evapotranspiration. Stomatal conductance was the main factor of transpiration. The evapotranspiration amount decreased with increasing altitude, so were transpiration and ground evaporation, while canopy interception had the reverse respiration can not be reflected by snow depth absolutely. The annual autotrophic respiration and heterotrophic respiration of Abies fabri ecosystem grew at 3000 m altitude was 8.58 and 7.82 t ha-1 a-1, respectively. The ecosystem respiration and its components decreased with altitude increasing. A significant positive relationship was found between ecosystem respiration and photosynthesis, especially in non-growing season. In inter-annual temporal scale, the ecosystem respiration and evapotranspiration had no significant consistency. However, there was a significant consistency between ecosystem respiration and evapotranspiration along altitude.
(5) The annual air temperature had increasing trend for the passing two decades in Mt. Gongga, while the precipitation had no significant trend only with annual variation. Under the climate changing scenario of temperature increasing 4.5 ℃, the evapotranspiration increased 14.1%. In the growing season, both GPP and NPP increased with the temperature increasing 1.8 ℃, and decreased with the temperature continue increasing. While in the non-growing season, there was a consistent increasing trend with temperature increasing for GPP and NPP. The carbon use efficiency (NPP/GPP) decreased with temperature increasing. Precipitation had positive effect on GPP and NPP. In growing season, the WUE decreased with temperature increasing. In non-growing season, GPP/Et and GPP/ET increased with temperature, while NPP/Et had opposite trend, and NPP/ET had slightly variation with temperature. Precipitation increasing stimulate WUE expressed with transpiration, but had no effect on WUE expressed with evapotranspiration.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7042
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
孙向阳. 贡嘎山峨眉冷杉生态系统水碳关系及时空分异机制[D]. 北京. 中国科学院研究生院,2013.
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