Long-term organic carbon turnover rates in natural and semi-natural topsoils
Long-term organic carbon turnover rates in natural and semi-natural topsoils
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DOI：
10.1007/s10533-013-9928-z
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发表时间：
2014-04
期刊：
影响因子：
4
通讯作者：
Robert T. E. Mills;Robert T. E. Mills;Edward Tipping;Charlotte L. Bryant;Bridget A. Emmett
中科院分区：
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作者：
Robert T. E. Mills;Robert T. E. Mills;Edward Tipping;Charlotte L. Bryant;Bridget A. Emmett
我们将未开垦表层土壤（通常为15厘米深）的已发表的和新的放射性碳和辅助数据结合起来，建立了两个数据库，一个是英国的（133个地点），一个是全球的（114个地点）。森林表层土壤的放射性碳含量明显高于非森林土壤，如果假设稳态条件，这表明“炸弹碳”的富集程度更高，因此碳的周转速度更快。稳态模型考虑了大气中二氧化碳的变化，包括20世纪核武器试验和放射性衰变的影响，用来量化土壤碳周转率。在考虑整个数据集时，采用变慢（20年平均停留时间，MRT）和被动（1000年平均停留时间）碳库模型，在两个碳库之间大致平均地划分了表层土壤C。森林土壤的平均慢被动比为0.65:0.35，与非森林土壤的平均慢被动比为0.40:0.60差异极显著（p< 0.001）。缓慢和被动组分的值呈正态分布，而非森林组分的变化更大，其相对标准差约为森林组分的2倍。假设凋落物输入量为500 g C m−2a−1，森林土壤的全球平均碳通量（g C m−2a−1）估计为298（通过MRT 1年的快速库）、200（慢库）和2.0（被动库），而非森林土壤的平均通量分别为347、150和3.3 g C m−2a−1。研究结果强调了表层土壤碳异质性的全球普遍现象，并指出了森林和非森林土壤之间与理解和管理土壤碳相关的关键差异。
We combined published and new radiocarbon and ancillary data for uncultivated topsoils (typically 15 cm depth), to make two databases, one for the United Kingdom (133 sites), and one global (114 sites). Forest topsoils are significantly higher in radiocarbon than non-forest soils, indicating greater enrichment with “bomb carbon” and therefore faster C turnover, if steady-state conditions are assumed. Steady-state modelling, taking into account variations in atmospheric14CO2, including the effects of 20th century nuclear weapons testing and radioactive decay, was used to quantify soil carbon turnover rates. Application of a model with variable slow (20 year mean residence time, MRT) and passive (1,000 year MRT) carbon pools partitioned the topsoil C approximately equally, on average, between the two pools when the entire data set was considered. However, the mean slow:passive ratio of 0.65:0.35 for forest soil was highly significantly different (p< 0.001) from the 0.40:0.60 ratio for non-forest soils. Values of the slow and passive fractions were normally distributed, but the non-forest fractions showed greater variation, with approximately twice the relative standard deviations of the forest values. Assuming a litter input of 500 g C m−2a−1, average global C fluxes (g C m−2a−1) of forest soils are estimated to be 298 (through a fast pool of MRT 1 year), 200 (slow pool) and 2.0 (passive pool), while for non-forest soils, respective average fluxes of 347, 150 and 3.3 g C m−2a−1are obtained. The results highlight the widespread global phenomenon of topsoil C heterogeneity, and indicate key differences between forest and non-forest soils relevant for understanding and managing soil C.