Unexpected high retention of 15 N-labeled nitrogen in a tropical legume forest under long‐term nitrogen enrichment
Unexpected high retention of 15 N-labeled nitrogen in a tropical legume forest under long‐term nitrogen enrichment
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长期富氮条件下热带豆科林中 N-15 标记氮的意外高保留
DOI：
10.1111/gcb.16005
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发表时间：
2021
影响因子：
11.6
通讯作者：
Mianhai Zheng
中科院分区：
文献类型：
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作者：
Jinhua Mao;Qinggong Mao;Per Gundersen;Geshere Abdisa Gurmesa;Wei Zhang;Juan Huang;Senhao Wang;Andi Li;Yufang Wang;Yabing Guo;Rongzhen Liu;Jiangming Mo;Mianhai Zheng
森林对氮沉降的响应在很大程度上取决于氮沉降在生态系统中的去向。固氮豆科植物广泛存在于陆地森林中，但在豆科植物占主导地位的森林中沉积的氮的去向仍不清楚，这限制了全球对氮沉积影响和碳固存反馈的评估。在这里，我们进行了第一个生态系统尺度的15 N标记实验，在一个典型的豆科植物为主的森林以及在附近的非豆科植物森林，以确定两种不同的森林类型之间的N沉积的命运，并探讨其潜在的机制。在两个森林的对照和氮添加（50 kg N ha− 1年− 1，10年）试验区，每两个月向森林地面喷洒15 N，持续1年。我们出乎意料地发现，豆科植物林具有很强的保留沉积氮的能力，在植物和土壤中回收了75 ± 5%的标记氮，高于非豆科植物林（56 ± 4%）。豆科植物林中较高的15 N回收率主要是由豆科植物的吸收驱动的，其中15 N回收率比附近的非豆科植物林高约15%。这表明豆科植物比非豆科植物对氮的需求更高。矿质土壤是沉积氮的主要库，豆科和非豆科森林分别保留了39 ± 4%和34 ± 3%的标记氮。此外，氮添加没有显着改变两种森林的15 N恢复模式。总体而言，这些研究结果表明，豆科植物为主的森林作为一个强大的汇沉积氮，无论长期大气氮沉降下土壤氮的高可用性，这表明有必要将豆科植物为主的森林纳入地球系统的N循环模型，以提高陆地N预算和全球N沉降效应的理解和预测。
The responses of forests to nitrogen (N) deposition largely depend on the fates of deposited N within the ecosystem. Nitrogen‐fixing legume trees widely occur in terrestrial forests, but the fates of deposited N in legume‐dominated forests remain unclear, which limit a global evaluation of N deposition impacts and feedbacks on carbon sequestration. Here, we performed the first ecosystem‐scale15N labeling experiment in a typical legume‐dominated forest as well as in a nearby non‐legume forest to determine the fates of N deposition between two different forest types and to explore their underlying mechanisms. The15N was sprayed bimonthly for 1 year to the forest floor in control and N addition (50 kg N ha−1year−1for 10 years) plots in both forests. We unexpectedly found a strong capacity of the legume forest to retain deposited N, with 75 ± 5% labeled N recovered in plants and soils, which was higher than that in the non‐legume forest (56 ± 4%). The higher15N recovery in legume forest was mainly driven by uptake by the legume trees, in which15N recovery was approximately 15% more than that in the nearby non‐legume trees. This indicates higher N‐demand by the legume than non‐legume trees. Mineral soil was the major sink for deposited N, with 39 ± 4% and 34 ± 3% labeled N retained in the legume and non‐legume forests, respectively. Moreover, N addition did not significantly change the15N recovery patterns of both forests. Overall, these findings indicate that legume‐dominated forests act as a strong sink for deposited N regardless of high soil N availability under long‐term atmospheric N deposition, which suggest a necessity to incorporate legume‐dominated forests into N‐cycling models of Earth systems to improve the understanding and prediction of terrestrial N budgets and the global N deposition effects.