Naiman Robert J, Melillo Jerry M
Woods Hole Oceanographic Institution, 02543, Woods Hole, MA, USA.
Marine Biological Laboratory, The Ecosystem Center, 02543, Woods Hole, MA, USA.
Oecologia. 1984 May;62(2):150-155. doi: 10.1007/BF00379007.
Beaver (Castor canadensis) influence stream ecosystems through their wood cutting and dam building activities. To quantify this influence we have used measured rates of nitrogen dynamics to construct a nitrogen budget for a section of a second order stream in eastern Québec and a beaver dam in that stream. The budget demonstrates the importance of sediment accumulations and an expanded wetted area to the annual nitrogen economy and to pathways of nitrogen cycling. Major changes after impoundment (per unit area) include a reduction in allochthonous nitrogen and an increase in nitrogen fixation by sediment microbes. Overall, the beaver-modified section accumulated ∼10 times more nitrogen than before alteration. The ecosystem implications of beaver activity suggest that current concepts of patterns and processes in running waters require modification.
海狸（加拿大河狸）通过砍伐树木和筑坝活动影响溪流生态系统。为了量化这种影响，我们利用测得的氮动态速率，为魁北克东部一条二级溪流的一段以及该溪流中的一座海狸坝构建了氮收支。该收支表明沉积物积累和扩大的湿润面积对年度氮经济和氮循环途径的重要性。蓄水后（每单位面积）的主要变化包括外源氮减少和沉积物微生物固氮增加。总体而言，海狸改造后的区域积累的氮比改造前多约10倍。海狸活动对生态系统的影响表明，当前关于流水生态系统中模式和过程的概念需要修正。
