Spatial analysis of growing season length control over net ecosystem exchange
Spatial analysis of growing season length control over net ecosystem exchange
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DOI：
10.1111/j.1365-2486.2005.001012.x
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发表时间：
2005-10-01
影响因子：
11.6
通讯作者：
Xiao, XM
中科院分区：
文献类型：
--
作者：
Churkina, G;Schimel, D;Xiao, XM
利用28个通量测点的数据，分析了年净生态系统交换（NEE）与碳吸收期（CUP）（生态系统为净碳汇的天数）之间的关系。观测结果表明这两个量之间存在线性相关关系。年平均日碳交换量在落叶和常绿植被类型间存在显著差异。短叶植被（少于1年）的立地碳吸收和呼吸速率高于常绿植被。在不同植被类型中，碳吸收期和碳释放期的日平均碳交换率之比相对稳定（2.73 +/- 1.08）。这意味着尽管光合作用途径、生命形式和叶片习性不同，但碳释放期和吸收期之间存在平衡。这些生态系统的平均每日碳固存率从未超过碳排放量的3倍以上。研究点的生长季节长度由先进高分辨率辐射计的归一化植被指数（NDVI）和植被SPOT-4的增强植被指数（EVI）得到。NDVI和EVI与CUP密切相关，因此它们也可以用来近似生态系统的年碳交换。这种方法有可能在给定一定数量的辅助信息的情况下，从遥感数据推断出大面积的NEE。这种方法可以补充目前现有的外推技术，后者依赖于对单个总通量的建模。
Using data from 28 flux measurement sites, we performed an analysis of the relationship between annual net ecosystem exchange (NEE) and the length of the carbon uptake period (CUP) (the number of days when the ecosystem is a net carbon sink). The observations suggest a linear correlation between the two quantities. The change in annual carbon exchange per day of the CUP differs significantly between deciduous and evergreen vegetation types. The sites containing vegetation with short-lived foliage (less than 1 year) have higher carbon uptake and respiration rates than evergreen vegetation. The ratio between mean daily carbon exchange rates during carbon uptake and release periods is relatively invariant (2.73 +/- 1.08) across different vegetation types. This implies that a balance between carbon release and uptake periods exists despite different photosynthetic pathways, life forms, and leaf habits. The mean daily carbon sequestration rate for these ecosystems never exceeds the carbon emission rate by more than a factor of 3. Growing season lengths for the study sites were derived from the normalized difference vegetation index (NDVI) of advanced very-high-resolution radiometer and from the enhanced vegetation index (EVI) of VEGETATION SPOT-4. NDVI and EVI were found to be closely related to the CUP, and consequently they also can be used to approximate annual carbon exchange of the ecosystems. This approach has potential for allowing extrapolation of NEE over large areas from remotely sensed data, given a certain amount of ancillary information. This method could complement the currently existing techniques for extrapolation, which rely upon modeling of the individual gross fluxes.