Nitrogen Saturation of Terrestrial Ecosystems: Some Recent Findings and Their Implications for Our Conceptual Framework
Nitrogen Saturation of Terrestrial Ecosystems: Some Recent Findings and Their Implications for Our Conceptual Framework
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DOI：
10.1007/s11267-006-9103-9
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发表时间：
2007-02
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影响因子：
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通讯作者：
B. Emmett
中科院分区：
文献类型：
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作者：
B. Emmett
由于活性氮的持续或增加的高排放率，氮富集对陆地和淡水生态系统的影响在许多地区日益受到关注。在陆地生态系统中，各种概念框架和建模方法已经开发出来，这些方法增强了我们对与N可用性增加相关的变化序列的理解，并帮助我们预测其未来的影响。在这里，一些最近的调查结果进行了说明，并讨论了这些概念框架和建模方法的影响。它们分别是：（a）随着氮素有效性的增加，具有低氮条件特征的植物物种的早期损失，以及具有高氮素保持效率的物种的损失（所谓的N“过滤器”），（B）由于在N饱和的早期阶段增加的NH 4+可用性，抑制沉积的NO3-的微生物固定，（c）由于这些变化，NO3-浸出的早期发生（a和B）在植物和微生物功能方面，（d）在历史上氮沉降量高的地区，植被对氮添加的敏感性降低，（e）土壤C：N变化是由于净初级生产力增加和土壤有机质分解减少。提出了一些关于氮饱和度早期指标的建议（苔藓的出现;表层土壤中NH 4+：NO3−的比例），这些指标表明生态系统功能和/或结构发生了变化。
The consequences of nitrogen (N) enrichment for terrestrial and freshwater ecosystems are of increasing concern in many areas due to continued or increasing high emission rates of reactive N. Within terrestrial ecosystems various conceptual frameworks and modelling approaches have been developed which have enhanced our understanding of the sequence of changes associated with increased N availability and help us predict their future impacts. Here, some recent findings are described and their implications for these conceptual frameworks and modelling approaches discussed. They are: (a) an early loss of plant species that are characteristic of low N conditions as N availability increases and a loss of species with high N retention efficiencies (so called N ‘filters’), (b) suppression of microbial immobilisation of deposited NO3−due to increased NH4+availability in the early stages of N saturation, (c) the early onset of NO3−leaching due to these changes (a and b above) in both plant and microbial functioning, (d) reduced sensitivity of vegetation to N additions in areas with high historical N deposition, (e) delayed changes in soil C:N changes due to increased net primary productivity and reduced decomposition of soil organic matter. Some suggestions of early indicators of N saturation are suggested (occurrence of mosses; NH4+: NO3−ratio in surface soils) which indicate either a shift in ecosystem function and/or structure.