Direct and indirect effects of nitrogen deposition on litter decomposition
Direct and indirect effects of nitrogen deposition on litter decomposition
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DOI：
10.1016/j.soilbio.2007.08.023
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发表时间：
2008-03-01
影响因子：
9.7
通讯作者：
Tscherko, Dagmar
中科院分区：
文献类型：
--
作者：
Manning, Peter;Saunders, Mark;Tscherko, Dagmar
氮（N）沉降升高可以通过提高土壤氮利用率以及凋落物投入的数量和质量来直接影响凋落物分解，也可以通过改变植物群落组成来间接影响凋落物分解。我们使用放置在一年生草本微生态系统中的垃圾袋研究了这些控制对凋落物分解的重要性，该生态系统受到两种氮沉降率（提高土壤无机氮可用性并刺激凋落物输入）和两种种植制度（即低和高氮沉降环境的植物物种组成）的影响。在每个微观世界中，我们在 8 周的时间内收集了 10 种一年生植物的垃圾袋，以确定分解造成的质量损失。我们的数据表明，物种的可分解性差异很大，但这些差异不太可能影响生态系统水平的分解，因为物种的可分解性与其对氮沉积的响应之间不存在相关性（以高氮下的种群种子产量相对于低氮沉积来衡量）。在高氮沉积微观世界中，凋落物质量损失大约增加了 2%。通过对微观土壤环境的全面测量，我们发现这种效应最可能的统计解释是土壤酶活性（纤维二糖苷酶、β-葡萄糖苷酶和β-木糖苷酶）的增加，这似乎是由于土壤无机氮有效性的提高和凋落物输入的刺激而发生的。我们的数据表明，氮沉降对凋落物输入和土壤氮有效性的直接影响显着影响分解，但间接影响则不然。我们认为，植物物种组成变化的间接影响在自然生态系统中可能更强，因为自然生态系统通常包含比此处考虑的更多样化的植物功能类型。 (c) 2007 Elsevier Ltd. 保留所有权利。
Elevated nitrogen (N) deposition can affect litter decomposition directly, by raising soil N availability and the quantity and quality of litter inputs, and indirectly by altering plant community composition. We investigated the importance of these controls on litter decomposition using litter bags placed in annual herb based microcosm ecosystems that had been subject to two rates of N deposition (which raised soil inorganic N availability and stimulated litter inputs) and two planting regimes, namely the plant species compositions of low and high N deposition environments. In each microcosm, we harvested litter bags of 10 annual plant species, over an 8-week period, to determine mass loss from decomposition. Our data showed that species differed greatly in their decomposability, but that these differences were unlikely to affect decomposition at the ecosystem level because there was no correlation between a species' decomposability and its response to N deposition (measured as population seed production under high N, relative to low N, deposition). Litter mass loss was similar to 2% greater in high N deposition microcosms. Using a comprehensive set of measurements of the microcosm soil environments, we found that the most statistically likely explanation for this effect was increased soil enzyme activity (cellobiosidase, beta-glucosidase and beta-xylosidase), which appears to have occurred in response to a combination of raised soil inorganic N availability and stimulated litter inputs. Our data indicate that direct effects of N deposition on litter input and soil N availability significantly affected decomposition but indirect effects did not. We argue that indirect effects of changes to plant species composition could be stronger in natural ecosystems, which often contain a greater diversity of plant functional types than those considered here. (c) 2007 Elsevier Ltd. All rights reserved.