Nitrogen oligotrophication in northern hardwood forests
Nitrogen oligotrophication in northern hardwood forests
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DOI：
10.1007/s10533-018-0445-y
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发表时间：
2018-12-01
期刊：
影响因子：
4
通讯作者：
Templer, Pamela H.
中科院分区：
文献类型：
--
作者：
Groffman, Peter M.;Driscoll, Charles T.;Templer, Pamela H.
尽管过去30年来的许多研究都集中在过量氮对森林及其相关水生生态系统的有害影响上，但最近大气氮沉降量的下降和这些生态系统氮出口的莫名其妙的下降引发了人们对氮营养不足、森林生产力的限制以及森林对干扰和环境变化做出动态反应的能力的新的担忧。在这里，我们展示了来自美国新罕布夏州哈伯德布鲁克实验森林长期生态研究的多个数据流，表明森林土壤中N的寡养化是由大气中通过土壤的碳流增加所驱动的，这刺激了微生物对N的固定，并减少了植物的有效N。土壤中有效氮的减少会导致树木对氮的吸收增加，从而减少土壤中的凋落物氮输入，进一步限制有效氮的供应，导致土壤氮素有效性的进一步下降。此外，气候变化增加了生长季的长度，并在冬季和春季通过矿化减少了有效氮的生产，这可能加剧了氮的营养不足。这些结果表明，有必要重新评估温带森林氮循环的性质和程度，并评估变化的条件将如何影响森林生态系统对全球环境变化的多重动态压力的反应。
While much research over the past 30years has focused on the deleterious effects of excess N on forests and associated aquatic ecosystems, recent declines in atmospheric N deposition and unexplained declines in N export from these ecosystems have raised new concerns about N oligotrophication, limitations of forest productivity, and the capacity for forests to respond dynamically to disturbance and environmental change. Here we show multiple data streams from long-term ecological research at the Hubbard Brook Experimental Forest in New Hampshire, USA suggesting that N oligotrophication in forest soils is driven by increased carbon flow from the atmosphere through soils that stimulates microbial immobilization of N and decreases available N for plants. Decreased available N in soils can result in increased N resorption by trees, which reduces litterfall N input to soils, further limiting available N supply and leading to further declines in soil N availability. Moreover, N oligotrophication has been likely exacerbated by changes in climate that increase the length of the growing season and decrease production of available N by mineralization during both winter and spring. These results suggest a need to re-evaluate the nature and extent of N cycling in temperate forests and assess how changing conditions will influence forest ecosystem response to multiple, dynamic stresses of global environmental change.