Does elevated nitrogen deposition or ecosystem recovery from acidification drive increased dissolved organic carbon loss from upland soil? A review of evidence from field nitrogen addition experiments
Does elevated nitrogen deposition or ecosystem recovery from acidification drive increased dissolved organic carbon loss from upland soil? A review of evidence from field nitrogen addition experiments
复制标题
DOI：
10.1007/s10533-008-9256-x
复制
发表时间：
2008-10-01
期刊：
影响因子：
4
通讯作者：
Sheppard, Lucy J.
中科院分区：
文献类型：
--
作者：
Evans, Chris D.;Goodale, Christine L.;Sheppard, Lucy J.
溶解有机碳（DOC）浓度在欧洲和北美大片地区的高地沃茨中有所上升。这些增加的两个拟议驱动因素是（1）大气污染物氮（N）的沉积，从而对植物和分解者碳动态的影响，（2）土壤从酸化中恢复与减少硫沉积有关。12个欧洲和北美的现场N添加实验的检查显示不一致（积极的，中性的，和消极的）DOC的反应N添加。然而，反应与添加的N的形式和由此产生的土壤酸度的变化。硝酸钠的添加始终增加DOC，而铵盐的添加通常会降低DOC。渗滤液化学被用来计算施肥对酸碱平衡的影响的“ANC强迫”的指数，这表明DOC增加响应于所有去酸化N的添加，并响应于所有，但三个酸化N的添加减少。发生在两个站点的N增加导致树木死亡，和一个实验位于一个较老的，未冰川化的土壤具有较高的阴离子吸附能力。我们的结论是，集体这些实验没有提供明确的支持的作用，氮沉积的唯一驱动程序上升DOC，但在很大程度上是一致的酸度变化机制。然而，这是可能的，意想不到的影响，酸度变化对DOC的流动性掩盖真正的影响实验N富集DOC的生产和降解。我们建议，有必要，更一般地说，解释N操纵实验，考虑到实验引起的酸度变化的影响，而不是升高的N本身，可能对生态系统的地球化学。
Dissolved organic carbon (DOC) concentrations have risen in upland waters across large areas of Europe and North America. Two proposed drivers of these increases are (1) deposition of atmospheric pollutant nitrogen (N) with consequent effects on plant and decomposer carbon dynamics, and (2) soil recovery from acidification associated with decreasing sulphur deposition. Examination of 12 European and North American field N addition experiments showed inconsistent (positive, neutral, and negative) responses of DOC to N addition. However, responses were linked to the form of N added and to resulting changes in soil acidity. Sodium nitrate additions consistently increased DOC, whereas ammonium salts additions usually decreased DOC. Leachate chemistry was used to calculate an index of ``ANC forcing'' of the effect of fertilization on the acid-base balance, which showed that DOC increased in response to all de-acidifying N additions, and decreased in response to all but three acidifying N additions. Exceptions occurred at two sites where N additions caused tree mortality, and one experiment located on an older, unglaciated soil with high anion adsorption capacity. We conclude that collectively these experiments do not provide clear support for the role of N deposition as the sole driver of rising DOC, but are largely consistent with an acidity-change mechanism. It is however possible that the unintended effect of acidity change on DOC mobility masks genuine effects of experimental N enrichment on DOC production and degradation. We suggest that there is a need, more generally, for interpretation of N manipulation experiments to take account of the effects that experimentally-induced changes in acidity, rather than elevated N per se, may have on ecosystem biogeochemistry.