Urbanization and fragmentation have opposing effects on soil nitrogen availability in temperate forest ecosystems
Urbanization and fragmentation have opposing effects on soil nitrogen availability in temperate forest ecosystems
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DOI：
10.1111/gcb.16611
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发表时间：
2023-01
影响因子：
11.6
通讯作者：
Stephen Caron;Sarah M. Garvey;Jonathan Gewirtzman;Kyle Schultz;Jennifer M. Bhatnagar;C. Driscoll;L. Hutyra;P. Templer
中科院分区：
文献类型：
--
作者：
Stephen Caron;Sarah M. Garvey;Jonathan Gewirtzman;Kyle Schultz;Jennifer M. Bhatnagar;C. Driscoll;L. Hutyra;P. Templer
近年来，在全球陆地生态系统中，相对于植物需求的氮（N）有效性一直在下降，这种现象被称为N寡营养化。美国东北部的温带森林生物可利用氮的下降特别急剧，预计气候变化将加剧这种情况。近几十年来，该地区也经历了快速的城市扩张，导致森林破碎化，目前尚不清楚这些变化是否以及如何影响林木的氮素供应和吸收。许多研究已经研究了城市化或森林破碎化对氮（N）循环的影响，但据我们所知，没有一项研究关注这些共同发生的环境变化的综合影响。我们研究了城市化和破碎化对橡树为主的（栎属）的影响。从波士顿到马萨诸塞州中部，森林沿着城市到乡村的梯度分布。在八个研究站点沿着城市化梯度，植物和土壤测量沿着90米的样带从发达的边缘到一个完整的森林内部。净氨化率，净矿化，和叶面氮浓度显着高于城市比农村网站，而净硝化作用和叶面C：N城市和农村森林之间没有差异。在城市站点，叶面氮和净氨化和矿化在森林内部相比，边缘，而净硝化和叶面C：N在农村森林边缘比内部更高。这些结果表明，在美国东北部的城市森林有更大的土壤氮的可用性和树木的氮吸收相比，农村森林，抵消了广泛的氮贫营养化的趋势，在温带森林在地球仪。然而，这种增加在森林边缘减少，表明森林破碎化的城市化对耦合N的可用性和需求的树木有相反的效果。
Nitrogen (N) availability relative to plant demand has been declining in recent years in terrestrial ecosystems throughout the world, a phenomenon known as N oligotrophication. The temperate forests of the northeastern U.S. have experienced a particularly steep decline in bioavailable N, which is expected to be exacerbated by climate change. This region has also experienced rapid urban expansion in recent decades that leads to forest fragmentation, and it is unknown whether and how these changes affect N availability and uptake by forest trees. Many studies have examined the impact of either urbanization or forest fragmentation on nitrogen (N) cycling, but none to our knowledge have focused on the combined effects of these co‐occurring environmental changes. We examined the effects of urbanization and fragmentation on oak‐dominated (Quercus spp.) forests along an urban to rural gradient from Boston to central Massachusetts (MA). At eight study sites along the urbanization gradient, plant and soil measurements were made along a 90 m transect from a developed edge to an intact forest interior. Rates of net ammonification, net mineralization, and foliar N concentrations were significantly higher in urban than rural sites, while net nitrification and foliar C:N were not different between urban and rural forests. At urban sites, foliar N and net ammonification and mineralization were higher at forest interiors compared to edges, while net nitrification and foliar C:N were higher at rural forest edges than interiors. These results indicate that urban forests in the northeastern U.S. have greater soil N availability and N uptake by trees compared to rural forests, counteracting the trend for widespread N oligotrophication in temperate forests around the globe. Such increases in available N are diminished at forest edges, however, demonstrating that forest fragmentation has the opposite effect of urbanization on coupled N availability and demand by trees.