ABSTRACT There are many nitrogen (N) pools in soil, so their availability and different status can give information about bulk soil response to N deposition. However, the different size of N pools in forest soils and the relationship between them have not been well studied under N deposition when considering the role of litter. Here soil in an N-deposition experiment carried out for 5 years in a broad-leaved forest was used as an object to study the response of N pools to N deposition by stepwise extraction using water or solutions containing 0.5 M K2SO4, 2.5 M H2SO4 (LPI), or 13 M H2SO4 (LPII), and calculation of recalcitrant (RC) N pool. Under N control (CT), soil with the presence of litter had a higher N of 23.8–106.8% in the first four pools, but lower of 80.6% in recalcitrant N pool compared with soil with the absence of litter. In the absence of litter, N addition increased soil N in labile pool but decreased N in the RC pool compared to CT and these impacts were greater at high added N (HN) than low-added N (LN) rates. However, in the presence of litter, LN increased the amount of N in the K2SO4- extracted pool and HN reduced that in the water extracted pool. Additionally, LN and HN increased TN in the RC pool and HN increased the total soluble N (TSN) in the LPI and LPII pool. N changes in the water extraction pool were attributed to inorganic N, whereas they were NH4 + and soluble organic N (SON) in the K2SO4-extracted, LPI, and LPII pools. In the presence of litter, HN increased the SON concentration in the K2SO4, LPI, and LPII extractions; thus, SON may be a potentially important N form for N availability. These results suggested that N additions improve the accumulation of N in RC pool with the presence of litter. The different effects of N additions on soil N pool or N form in each pool depend on litter present or not.

中文翻译：

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加氮改变亚热带森林凋落物与不凋落物的土壤氮库

摘要 土壤中有许多氮 (N) 库，因此它们的可用性和不同状态可以提供大量土壤对 N 沉积响应的信息。然而，在考虑凋落物的作用时，还没有很好地研究森林土壤中氮库的不同大小及其之间的关系。在这里，以在阔叶林中进行了 5 年的氮沉积实验中的土壤为对象，通过使用水或含有 0.5 M K2SO4、2.5 M H2SO4 的溶液逐步提取来研究 N 库对 N 沉积的响应（ LPI) 或 13 M H2SO4 (LPII)，以及顽固 (RC) N 池的计算。在 N 控制 (CT) 下，与没有凋落物的土壤相比，前四个池中存在凋落物的土壤的 N 较高，为 23.8-106.8%，但顽固的 N 池中的氮含量较低，为 80.6%。在没有凋落物的情况下，与 CT 相比，添加 N 增加了不稳定池中的土壤 N，但减少了 RC 池中的 N，并且这些影响在高添加 N (HN) 时比低添加 N (LN) 率更大。然而，在垃圾存在的情况下，LN 增加了 K2SO4 提取池中的 N 量，而 HN 减少了水提取池中的 N 量。此外，LN 和 HN 增加了 RC 池中的 TN，HN 增加了 LPI 和 LPII 池中的总可溶性 N (TSN)。水提取池中的 N 变化归因于无机 N，而在 K2SO4 提取池、LPI 和 LPII 池中，它们是 NH4 + 和可溶性有机 N (SON)。在垃圾存在的情况下，HN 增加了 K2SO4、LPI 和 LPII 提取物中的 SON 浓度；因此，SON 可能是 N 可用性的潜在重要 N 形式。这些结果表明，在存在凋落物的情况下，N 添加改善了 RC 池中 N 的积累。氮添加对土壤氮库或每个池中氮形式的不同影响取决于凋落物的存在与否。