DeLuca Thomas H, Zackrisson Olle, Gundale Michael J, Nilsson Marie-Charlotte
Ecology and Economics Research Department, The Wilderness Society, 503 West Mendenhall, Bozeman, MT 59715, USA.
Science. 2008 May 30;320(5880):1181. doi: 10.1126/science.1154836.
Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ecosystem productivity. To date, no studies have documented the down-regulation of terrestrial nitrogen (N) fixation via an ecosystem-level feedback mechanism. Herein, we demonstrate such a feedback in boreal forests. Rapid cycling of N in early secondary succession forests yielded greater throughfall N deposition, which in turn decreased N fixation by cyanobacterial associates in feather moss carpets that reside on the forest floor. The forest canopy exerts a tight control on biotic N input at a period of high productivity.
生物反馈机制调节着基本的生态系统过程，并有可能调节生态系统生产力。迄今为止，尚无研究记录通过生态系统层面的反馈机制对陆地氮固定进行下调。在此，我们证明了北方森林中存在这样一种反馈。次生演替早期森林中氮的快速循环导致更大的穿透降雨氮沉降，这反过来又减少了森林地面羽藓地毯中蓝藻共生体的固氮作用。在生产力较高的时期，森林冠层对生物氮输入施加了严格的控制。
