Nitrogen-15 signals of leaf-litter-soil continuum as a possible indicator of ecosystem nitrogen saturation by forest succession and N loads
Nitrogen-15 signals of leaf-litter-soil continuum as a possible indicator of ecosystem nitrogen saturation by forest succession and N loads
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DOI：
10.1007/s10533-010-9438-1
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发表时间：
2011-01-01
期刊：
影响因子：
4
通讯作者：
Luo, Yiqi
中科院分区：
文献类型：
--
作者：
Fang, Huajun;Yu, Guirui;Luo, Yiqi
理解森林碳循环对大气氮沉降的响应对于评估生态系统氮动态至关重要。氮 - 15的自然丰度（δN - 15）已被认为是监测氮库和通量的一种高效且非侵入性的工具。在本研究中，中国南方的三种演替森林接受了四种不同水平的氮添加处理。在每种处理中，我们测量了土壤氮矿化、硝化、N₂O排放和无机氮淋溶的速率，以及叶片、凋落物和土壤的氮浓度和δN - 15。我们发现成熟阔叶林的叶片氮浓度和δN - 15高于演替中的松林或混交林。连续三年的氮添加没有改变叶片氮浓度，但显著提高了叶片的δN - 15（p < 0.05）。此外，氮添加降低了贫氮的松林和混交林表层土壤的δN - 15，并显著提高了富氮阔叶林有机层和矿质层土壤的δN - 15（p < 0.05）。另外，土壤N₂O排放通量和无机氮淋溶速率随着氮添加量的增加而增加，并且与森林生态系统的N - 15富集因子（ε(p/s)）呈正相关。我们的研究表明，叶片、凋落物和土壤的δN - 15综合了有关植物种类、林分年龄、外源氮输入以及土壤氮转化和损失的各种信息，可用于监测未来因氮沉降增加而导致的森林生态系统中氮的有效性和氮动态。
Understanding forest carbon cycling responses to atmospheric N deposition is critical to evaluating ecosystem N dynamics. The natural abundance of N-15 (delta N-15) has been suggested as an efficient and non-invasive tool to monitor N pools and fluxes. In this study, three successional forests in southern China were treated with four levels of N addition. In each treatment, we measured rates of soil N mineralization, nitrification, N2O emission and inorganic N leaching as well as N concentration and delta N-15 of leaves, litters and soils. We found that foliar N concentration and delta N-15 were higher in the mature broadleaf forest than in the successional pine or mixed forests. Three-year continuous N addition did not change foliar N concentration, but significantly increased foliar delta N-15 (p < 0.05). Also, N addition decreased the delta N-15 of top soil in the N-poor pine and mixed forests and significantly increased that of organic and mineral soils in N-rich broadleaf forests (p < 0.05). In addition, the soil N2O emission flux and inorganic N leaching rate increased with increasing N addition and were positively correlated with the N-15 enrichment factor (epsilon (p/s)) of forest ecosystems. Our study indicates that delta N-15 of leaf, litter and soil integrates various information on plant species, forest stand age, exogenous N input and soil N transformation and loss, which can be used to monitor N availability and N dynamics in forest ecosystems caused by increasing N deposition in the future.