Variable effects of nitrogen additions on the stability and turnover of soil carbon
Variable effects of nitrogen additions on the stability and turnover of soil carbon
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DOI：
10.1038/nature01136
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发表时间：
2002-10-31
期刊：
影响因子：
64.8
通讯作者：
Bowman, WD
中科院分区：
文献类型：
--
作者：
Neff, JC;Townsend, AR;Bowman, WD
土壤含有陆地碳的最大近地表储存库(1)，因此了解控制土壤碳储存和周转的因素对于理解不断变化的全球碳循环至关重要。气候对土壤碳分解的影响已经有了很好的文献记载（2,3），但土壤碳动态对全球快速增加的活性氮（主要来自农业肥料和化石燃料燃烧）的潜在响应仍然存在相当大的不确定性。通过对长期施氮样地的C-14、C-13和土壤碳化合物的具体分析，我们发现氮肥的添加显著加速了土壤轻碳组分的分解（以年代际周转时间计算），同时进一步稳定了土壤重碳组分的土壤碳化合物（以年代际到世纪的寿命计算）。尽管不同土壤库的动态发生了这些变化，但我们观察到总体土壤碳没有显著变化，这突出了仍然广泛使用的单一土壤库方法固有的局限性，即研究土壤碳对变化环境条件的响应。这里观察到的影响——由相对较高的短期肥料添加引起的——是否与由大气沉积向自然生态系统中较低的长期氮添加引起的影响相似，还有待观察，但我们的结果表明，尽管如此，目前的陆地碳循环模型并不包含捕捉氮有效性和土壤碳储量之间复杂关系所需的机制。
Soils contain the largest near-surface reservoir of terrestrial carbon(1) and so knowledge of the factors controlling soil carbon storage and turnover is essential for understanding the changing global carbon cycle. The influence of climate on decomposition of soil carbon has been well documented(2,3), but there remains considerable uncertainty in the potential response of soil carbon dynamics to the rapid global increase in reactive nitrogen (coming largely from agricultural fertilizers and fossil fuel combustion). Here, using C-14, C-13 and compound-specific analyses of soil carbon from long-term nitrogen fertilization plots, we show that nitrogen additions significantly accelerate decomposition of light soil carbon fractions (with decadal turnover times) while further stabilizing soil carbon compounds in heavier, mineral-associated fractions (with multidecadal to century lifetimes). Despite these changes in the dynamics of different soil pools, we observed no significant changes in bulk soil carbon, highlighting a limitation inherent to the still widely used single-pool approach to investigating soil carbon responses to changing environmental conditions. It remains to be seen if the effects observed here-caused by relatively high, short-term fertilizer additions-are similar to those arising from lower, long-term additions of nitrogen to natural ecosystems from atmospheric deposition, but our results suggest nonetheless that current models of terrestrial carbon cycling do not contain the mechanisms needed to capture the complex relationship between nitrogen availability and soil carbon storage.