CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
Hainan Jianfengling Forest Ecosystem National Field Science and Observation Station, Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou, China.
Glob Chang Biol. 2021 May;27(10):2076-2087. doi: 10.1111/gcb.15526. Epub 2021 Feb 19.
The effects of nitrogen (N) deposition on forests largely depend on its fate after entering the ecosystem. While several studies have addressed the forest fate of N deposition using N tracers, the long-term fate and redistribution of deposited N in tropical forests remains unknown. Here, we applied N tracers to examine the fates of deposited ammonium ( ) and nitrate ( ) separately over 3 years in a primary and a secondary tropical montane forest in southern China. Three months after N tracer addition, over 60% of N was retained in the forests studied. Total ecosystem retention did not change over the study period, but between 3 months and 3 years following deposition N recovery in plants increased from 10% to 19% and 13% to 22% in the primary and secondary forests, respectively, while N recovery in the organic soil declined from 16% to 2% and 9% to 2%. Mineral soil retained 50% and 35% of N in the primary and secondary forests, with retention being stable over time. The total ecosystem retention of the two N forms did not differ significantly, but plants retained more than and the organic soil more than . Mineral soil did not differ in and retention. Compared to temperate forests, proportionally more N was distributed to mineral soil and plants in these tropical forests. Overall, our results suggest that atmospherically deposited and is rapidly lost in the short term (months) but thereafter securely retained within the ecosystem, with retained N becoming redistributed to plants and mineral soil from the organic soil. This long-term N retention may benefit tropical montane forest growth and enhance ecosystem carbon sequestration.
氮（N）沉降对森林的影响在很大程度上取决于其进入生态系统后的命运。虽然有几项研究使用 N 示踪剂来研究 N 沉降对森林的影响，但热带森林中沉积 N 的长期命运和再分配仍不清楚。在这里，我们应用 N 示踪剂来分别研究中国南方一个原生和次生热带山地森林中沉积的铵（ ）和硝酸盐（ ）在 3 年内的命运。N 示踪剂添加 3 个月后，超过 60%的 N 被保留在研究的森林中。在整个研究期间，总生态系统保留量没有变化，但在沉积后 3 个月至 3 年内，植物中 N 的回收量从 10%增加到 19%和 13%增加到 22%，而有机土壤中 N 的回收量从 16%下降到 2%和 9%下降到 2%。原生和次生森林的矿物土壤分别保留了 50%和 35%的 N，保留量随时间保持稳定。两种 N 形式的总生态系统保留量没有显著差异，但植物保留的 比 多，而有机土壤保留的 比 多。矿物土壤在 和 的保留方面没有差异。与温带森林相比，这些热带森林中更多比例的 N 分配到矿物土壤和植物中。总体而言，我们的结果表明，大气中沉积的 和 短期内（数月内）迅速损失，但此后在生态系统中被牢固保留，保留的 N 从有机土壤重新分配到植物和矿物土壤。这种长期的 N 保留可能有利于热带山地森林的生长，并增强生态系统的碳固存。
