Abstract Traditionally, experiments testing the impacts of nitrogen (N) deposition on ecosystem processes have been conducted by adding N directly to forest floors, yet, in reality, atmospheric N passes through the canopy layer before it reaches the forest floor. Furthermore, we know little about how N-deposition mediated changes in soil fauna communities affect litter decomposition. Here, we use a novel experiment to contrast canopy addition of N (CAN) to understory addition of N (UAN) in a subtropical forest and a temperate forest to investigate the impact of N-deposition approaches and N-concentrations on soil fauna and leaf litter decomposition rate. We found that CAN increased the soil fauna diversity and accelerated litter decomposition whereas UAN did not significantly affect soil fauna or litter decomposition. In addition, N-deposition concentration significantly influenced soil fauna density, H′ diversity, and species richness at the subtropical forest, but only affected H′ diversity of soil fauna at the temperate forest. The high N-deposition concentration treatment in the subtropical forest and low N-deposition concentration treatment in our temperate forest had significantly higher decomposition rates compared with the control (no N) treatment. We assert that addition of N through the canopy is a more realistic approach for simulating the actual processes of atmospheric N-deposition in forests. Future experiments using CAN methods will provide an improved understanding of the effect of N-deposition on soil fauna-decomposition interactions and inform reliable predictions of the consequences of global change on soil ecosystems.

中文翻译：

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冠层氮添加对温带和亚热带森林土壤动物群和凋落物分解率的影响

摘要 传统上，测试氮 (N) 沉积对生态系统过程影响的实验是通过将 N 直接添加到森林地面来进行的，但实际上，大气 N 在到达森林地面之前会穿过冠层。此外，我们对氮沉积介导的土壤动物群落变化如何影响凋落物分解知之甚少。在这里，我们使用一个新的实验来对比亚热带森林和温带森林中树冠添加 N (CAN) 与林下添加 N (UAN) 的情况，以研究 N 沉积方法和 N 浓度对土壤动物群和叶的影响凋落物分解率。我们发现 CAN 增加了土壤动物群多样性并加速了凋落物分解，而 UAN 没有显着影响土壤动物群或凋落物分解。此外，N-沉积浓度显着影响亚热带森林土壤动物群密度、H'多样性和物种丰富度，但仅影响温带森林土壤动物群H'多样性。与对照（无N）处理相比，亚热带森林中的高氮沉积浓度处理和温带森林中的低氮沉积浓度处理具有显着更高的分解率。我们断言通过树冠添加 N 是一种更现实的方法，用于模拟森林中大气 N 沉积的实际过程。未来使用 CAN 方法的实验将提供对氮沉积对土壤动物-分解相互作用影响的更好理解，并为全球变化对土壤生态系统的后果的可靠预测提供信息。