Cross-site evaluation of eddy covariance GPP and RE decomposition techniques
Cross-site evaluation of eddy covariance GPP and RE decomposition techniques
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DOI：
10.1016/j.agrformet.2007.11.012
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发表时间：
2008-06-30
影响因子：
6.2
通讯作者：
Stauch, Vanessa J.
中科院分区：
文献类型：
--
作者：
Desai, Ankur R.;Richardson, Andrew D.;Stauch, Vanessa J.
涡旋协方差通量塔测量陆地-大气通量的净交换。对于二氧化碳的通量，这种净生态系统交换(NEE)由两个过程控制，总初级生产力(GPP)和自养和异养呼吸成分的总和，称为生态系统呼吸(RE)。许多统计通量划分方法也可用于从NEE时间序列估计GPP和RE，这些方法通常是用来填补缺失的NEE数据的。在这里，我们展示了这些分区方法的第一次全面的、多站点比较的结果。在从生态系统模型产生的NEE中提取GPP和RE的方法子集中进行了初步测试，该NEE也被现实噪声退化。所有方法产生的GPP和RE估计与每日和年度时间尺度的合成数据高度相关，但大多数都偏低，包括原始模型的参数反演。然后，我们将23种不同的方法应用于10个立地年的温带森林通量数据，包括10个不同的人工林隙情景(去除10%的观测值)，以调查分区方法选择、数据缺口和站间变异性对估计的GPP和RE的影响。大多数方法对GPP和RE的估计相差不到10%。GAP增加了额外的6-7%的变异性，但不会导致额外的偏倚。方差分析显示，大多数方法在确定不同地点的GPP和RE差异方面是一致的，从而增加了对先前发表的多地点比较和综合的信心。有几种方法在一些地点产生了异常值，有些方法系统性地与集合平均值背道而驰。与温带或北方站点相比，地中海站点发现了更大的模型扩散。无论是真实数据还是合成数据，都发现日RE循环的模型具有很高的变异性，这表明对日RE机制的额外研究可能有助于改进划分算法。(C)2007 Elsevier B.V.保留所有权利。
Eddy covariance flux towers measure net exchange of land-atmosphere flux. For the flux of carbon dioxide, this net ecosystem exchange (NEE) is governed by two processes, gross primary production (GPP) and a sum of autotrophic and heterotrophic respiration components known as ecosystem respiration (RE). A number of statistical flux-partitioning methods, often developed to fill missing NEE data, can also be used to estimate GPP and RE from NEE time series. Here we present results of the first comprehensive, multi-site comparison of these partitioning methods. An initial test was performed with a subset of methods in retrieving GPP and RE from NEE generated by an ecosystem model, which was also degraded with realistic noise. All methods produced GPP and RE estimates that were highly correlated with the synthetic data at the daily and annual timescales, but most were biased low, including a parameter inversion of the original model. We then applied 23 different methods to 10 site years of temperate forest flux data, including 10 different artificial gap scenarios (10% removal of observations), in order to investigate the effects of partitioning method choice, data gaps, and intersite variability on estimated GPP and RE. Most methods differed by less than 10% in estimates of both GPP and RE. Gaps added an additional 6-7% variability, but did not result in additional bias. ANOVA showed that most methods were consistent in identifying differences in GPP and RE across sites, leading to increased confidence in previously published multi-site comparisons and syntheses. Several methods produced outliers at some sites, and some methods were systematically biased against the ensemble mean. Larger model spread was found for Mediterranean sites compared to temperate or boreal sites. For both real and synthetic data, high variability was found in modeling of the diurnal RE cycle, suggesting that additional study of diurnal RE mechanisms could help to improve partitioning algorithms. (C) 2007 Elsevier B.V. All rights reserved.