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可将临界负荷概念用于确定生态系统能够忍耐的无显著毒害作用的沉积水平。本文总结了瑞典研究课题“跨界大气污染的削减策略(ASTA)”中北方针叶林氮的临界负荷评估工作。不论是瑞典北方低水平氮背景沉降地区的野外实验,还是大尺度的监测研究,结果都表明:少量增加氮剂量会引发重大的植被变化;并且停止氮输入后,植被恢复非常缓慢。数据表明,即便氮输入的速率低于目前建议的临界负荷(北方针叶林下层植被的经验值为10～15kg N/hm~2·a),生态系统的关键成分也会发生变化。根据这些数据,我们认为临界负荷应降为6 kg N/hm~2·a。
The concept of critical load can be used to determine the level of sedimentation that the ecosystem can tolerate without significant toxic effects. This paper summarizes the Swedish research project “Reduction Strategy for Transboundary Air Pollution (ASTA)” critical load assessment of nitrogen in coniferous forests in the north and north. Whether it is field experiments in the low-level nitrogen background subsidence area of northern Sweden or large-scale monitoring studies, the results show that a small increase in nitrogen dose can lead to major vegetation changes; and the vegetation recovery is very slow after nitrogen input is stopped. The data show that the key components of the ecosystem change even though the rate of nitrogen input is below the currently proposed critical load (10-15 kg N / hm2 · a for the lower conifer vegetation). Based on these data, we think the critical load should be reduced to 6 kg N / hm ~ 2 · a.