IMHE OpenIR  > 山地表生过程与生态调控重点实验室
基于水碳关系对贡嘎山东坡不同森林类型蒸散发的估算
Alternative TitleEstimation of Evapotranspiration in Different Forest Types Based on the Relationship between Water and Carbon on the Eastern Slope of Mount Gongga
胡兆永
Subtype博士
Thesis Advisor王根绪
2018
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline自然地理学
Keyword蒸散发 碳通量 水分利用效率 森林 海拔梯度
Abstract山地是全球变化的敏感地带,山地水循环与水资源变化一直是山地生态学研究的热点问题之一。作为水循环的重要组成部分,山地森林生态系统蒸散发的观测和估算一直是难点。本研究以贡嘎山海螺沟流域内的阔叶林、针阔混交林和针叶林为研究对象,依托研究区内的水碳通量观测系统,(1)对以上3种森林类型在不同季节的蒸散发及其组分(树木蒸腾、林冠截留和土壤蒸发)进行观测,分析其时空动态规律及影响因子,意图揭示山地生态系统中植被和气候因子共同影响下蒸散发的时空变异特征;(2)分析3种森林类型的碳通量(净生态系统碳交换量NEE,总生态系统碳交换量GPP,生态系统呼吸Reco和土壤呼吸RS)及水分利用效率WUE的时空变异规律,意图阐明山地生态系统不同森林类型水碳间的相互关系;(3)结合气象观测,构建3种森林类型基于互补关系和水碳关系的蒸散发估算方程。得到的主要结果如下: (1)用组分分析法观测的阔叶林、针阔混交林和针叶林湿季的蒸散发分别为632.2 mm,655.35 mm和607.15 mm;3种森林类型树木蒸腾对蒸散发的贡献率最高(47.5%~54.45),其次为林冠截留;林冠截留对总蒸散发的贡献随海拔的升高而升高;而树木蒸腾对总蒸散发的贡献随海拔的升高而降低。3种森林类型中,用涡度协方差法观测发现2015年阔叶林蒸散发最大,而2016年针阔混交林的蒸散发最大;其中,湿季的蒸散发占年蒸散发的63.70%~69.13%。从蒸散发与气象因子相关分析的结果来看,能量相关的因子(如温度、净辐射等)与蒸散发的相关性要高于水分相关的因子(如相对湿度、土壤湿度等)。(2)组分分析法和涡度协方差法的结果均显示蒸散发对水循环的贡献随海拔的增加而减小,而入渗对对水循环的贡献则相反。2015年的干旱显著增加了湿季的蒸散发,但未显著地改变蒸散发占降水的比值;干旱虽未造成干季蒸散发明显的变化,但却极大地提高了蒸散发对水循环的贡献。由于湿季的降水量占到了全年的70%以上,因此在全尺度上,降水的减小并未显著地改变森林水分布模式。(3)阔叶林,针阔混交林和针叶林的年净生态系统碳交换量(NEE)分别为-7.90 t C hm-2 yr-1,-10.35 t C hm-2 yr-1和-4.55 t C hm-2 yr-1。3种森林类型的NEE均为负值,表现为碳汇。针叶林的年总生态系统碳交换量(GPP)和生态系统呼吸(Reco)均高于其它2种森林类型。受温度,辐射和土壤水分的共同影响,湿季的碳通量(NEE、GPP和Reco)显著高于干季,约占全年的70%~80%。研究区土壤呼吸湿季平均值为511.27 g C m-2,其中异养呼吸约占土壤呼吸的66%~86%。土壤呼吸温度敏感系数(Q10)的变化范围为1.96~2.92。(4)阔叶林、针阔混交林和针叶林的年水分利用效率分别为6.29 mg CO2 g-1 H2O、7.48 mg CO2 g-1 H2O和8.01 mg CO2 g-1 H2O;水分利用效率随着海拔升高而升高,意味着高海拔区域的植被相对于低海拔区域更节水。3种森林类型的水分利用效率均表现出季节的差异;其中阔叶林在湿季大于干季,针阔混交林和针叶林则相反。这说明了不同植物的光合作用和蒸散发对环境变化的响应程度不一致。(5)基于水碳关系,构建了3种不同森林类型月尺度蒸散发的估算方程。通过估算方程模拟的蒸散发与实际蒸散发拟合的线性回归方程斜率范围为0.932~1.125,R2值范围为0.620~0.727。阔叶林的模拟结果要好于其它2种森林类型。(6)利用非线性互补方程,结合涡度通量数据和相关的气象数据,拟合得到的3种森林类型Priestley-Taylor系数(αe)范围为0.98~1.13。利用拟合得到的αe值估算的蒸散发与实测的蒸散发拟合的线性回归方程斜率都接近1(0.89~1.26),R2值为0.71~0.92。3种森林类型的蒸散发和表观潜在蒸散发都表现出非对称性互补关系。在有阔叶树种的区域,将αe的季节变化考虑到非线性互补方程中会提高其模拟的精确度。总的来说,非线性互补方程能够很好地模拟山地森林的蒸散发。
Other AbstractMountainous areas are sensitive to global changes. Water cycle and changes in water resources in mountainous areas have always been one of the hot topics in mountain ecological research. Evapotranspiration is an important part of the water cycle, and it is difficult to observe and estimate evapotranspiration in mountainous forest ecosystems. In this study, the broad-leaved forests, coniferous and broad-leaved mixed forests, and coniferous forests in the Hailuogou Valley of Gongga Mountain were used as research objects, relying on the water-carbon flux observation system in the study area, (1) we observed the seasonal patterns of evapotranspiration and its components (tree transpiration, canopy interception and soil evaporation), and analysed their spatial-temporal dynamics and influencing factors in different forest types. Consequently, we tried to reveal the temporal and spatial variability of evapotranspiration under the combined effects of vegetation and climatic factors in mountain ecosystems; (2) we analyzed the carbon flux (net ecosystem carbon exchange NEE, gross ecosystem carbon exchange GPP, ecosystem respiration Reco, and soil respiration RS) and water use efficiency WUE in the three forest types. Thus, we tried to clarify the trade-off between the carbon and water in different forest types in mountain ecosystem; (3) along with meteorological observations, the estimation equations for evapotranspiration based on complementary relationships and water-carbon relationships were constructed for the three forest types. The main results obtained are as follows:(1) The evapotranspiration of broad-leaved forests, coniferous-broad-leaved mixed forests and coniferous forests was 632.2 mm, 655.35 mm and 607.15 mm, respectively, during the wet sesason using the analysed method. The transpiration rates of the three forest types contributed the most to the evapotranspiration (47.5%~54.45), followed by canopy interception; the contribution of canopy interception to total evapotranspiration increased with elevation, while the contribution of tree transpiration to total evapotranspiration decreased with elevation. Among the three forest types, the evapotranspiration was found to be the largest in the broad-leaved forest in 2015, while the evapotranspiration in coniferous and broad-leaved mixed forests was the largest in 2016; among them, the evapotranspiration in the wet season accounted for 63.70%~69.13% of the annual evapotranspiration. From the results of correlation analysis of evapotranspiration and meteorological factors, the correlation between energy-related factors (such as temperature, net radiation, etc.) and evapotranspiration is higher than the moisture-related factors (such as relative humidity, soil moisture, etc.).(2) Both the component analysis method and the eddy covariance method show that the contribution of evapotranspiration to the water cycle decreases with increasing altitude, while the contribution of infiltration to the water cycle is the opposite. Drought in 2015 significantly increased evapotranspiration in the wet season, but it did not significantly change the ratio of evapotranspiration to precipitation. Drought did not cause significant changes in dry season evapotranspiration, but it greatly increased the contribution of evapotranspiration to the water cycle. Since the precipitation in the wet season accounts for more than 70% of the entire year, the reduction in precipitation does not significantly change the pattern of forest water distribution at the year scale.(3) The annual net ecosystem carbon exchange (NEE) of broad-leaved forests, coniferous and broad-leaved mixed forests, and coniferous forests was -7.90 t C hm-2 yr-1, -10.35 t C hm-2 yr-1, and -4.55 t C hm-2 yr-1. The NEE for all three forest types is negative, indicating a carbon sink. The annual total ecosystem carbon exchange (GPP) and ecosystem respiration (Reco) of coniferous forests were higher than the other two forest types. Affected by temperature, radiation, and soil moisture, the carbon flux (NEE, GPP, and Reco) in the wet season was significantly higher than that in the dry season, accounting for about 70% to 80% of the entire year. The average soil respiration during the wet season in the study area was 511.27 g C m-2, of which heterotrophic respiration accounted for 66% to 86%. The temperature sensitivity of soil respiration (Q10) ranged from 1.96 to 2.92.(4) The annual water use efficiency of broad-leaved forests, coniferous and broad-leaved mixed forests, and coniferous forests were 6.29 mg CO2 g-1 H2O, 7.48 mg CO2 g-1 H2O, and 8.01 mg CO2 g-1 H2O, respectively; water use efficiency increased with elevation, indicating that vegetation in high altitude areas is more water-efficient than low altitude areas. The water use efficiencies of the three forest types showed seasonal variations; among them, broad-leaved forests were greater in the wet season than in the dry season, and coniferous and broad-leaved mixed forests and coniferous forests were opposite. This shows that the photosynthesis and evapotranspiration of different plants are inconsistent with the environmental changes.(5) Based on the relationship between water and carbon, the estimation equations were established in the three forest types. The slopes of the linear regression equation fitted to the measured evapotranspiration and the measured evapotranspiration were 0.932~1.125, and the R2 value was 0.620~0.727. The simulating performance in broadleaf forest was better than the other two forest types.(6) The Priestley-Taylor coefficient (αe) ranged from 0.98 to 1.13 for the three forest types based on the nonlinear complementarity equation and the eddy covariance data and related meteorological data. The slopes of the linear regression equation fitted to the measured evapotranspiration and the measured evapotranspiration were all close to 1 (0.89~1.26), and the R2 value was 0.71~0.92. The actual evapotranspiration and apparent potential evapotranspiration of the three forest types shows asymmetrical complementary relationships. In areas with broad-leaved species, taking the seasonal variation of αe into account in the nonlinear complementarity equation will increase the accuracy of its simulation. In general, the nonlinear complementarity equation can simulate the evapotranspiration of mountain forests well. 
Pages126
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24792
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
胡兆永. 基于水碳关系对贡嘎山东坡不同森林类型蒸散发的估算[D]. 北京. 中国科学院大学,2018.
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