Effects of summer grazing by caribou on composition and productivity of vegetation: Community and landscape level
Effects of summer grazing by caribou on composition and productivity of vegetation: Community and landscape level
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DOI：
10.2307/2261473
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发表时间：
1996-08-01
影响因子：
5.5
通讯作者：
Crete, M
中科院分区：
文献类型：
--
作者：
Manseau, M;Huot, J;Crete, M
1人口统计学的变化和对里维埃乔治驯鹿的身体状况的研究表明，其规模可能主要由夏季牧场上可用的饲料量来调节。2因此，我们记录了放牧和践踏对两种植物群落（灌木苔原和矮桦树林）的组成和生产力的影响，在此范围内，未放牧的地点很少见，但四个先前定位的小区域被用作对照点。3对于灌木苔原，在放牧地没有地衣垫，先前被地衣占据的地面要么是裸露的，被死地衣和苔藓的碎片覆盖，要么被早期演替的地衣物种覆盖。未被驯鹿吃掉的灌木的地被在放牧地低于未被放牧地，并且禾本科植物、饲用灌木和杂类草的覆盖度在放牧地和未被放牧地之间没有显著差异。腺桦的地被植物和叶生物量显著低于未放牧地。5整个夏季范围内饲料植物物种的生产力估计为22.5在未放牧的条件下，年（-1）为10.3 g m（-2），而在放牧的条件下，年（-1）为10.3 g m（-2）。北美驯鹿将灌木苔原和矮桦林的生物量减少到非常低的水平，从而使其食物资源的分布变得支离破碎。7迁徙有蹄类动物对其夏季活动区植物生产力的严重负面影响可以用以下特征来解释：植被和高承载能力的冬季相比，夏季范围。与植被有关的重要因素是其复原力和生产力低，以及除去地衣后维管植物没有反应。
1 Changes in demography and studies on physical condition of the Riviere George caribou Rangifer tarandus herd have suggested that its size may be primarily regulated by the amount of forage available on the summer range.2 We therefore document the impact of grazing and trampling on composition and productivity of two plant communities, the shrub tundra and stands of dwarf birch, within this range, Ungrazed sites were rare, but four previously located small areas were used as control sites.3 For the shrub tundra, the lichen mat was absent in grazed sites and ground previously occupied by lichens was either bare, covered by fragments of dead lichens and mosses or recolonized by early succession lichen species. Ground cover of shrubs not eaten by caribou was lower in grazed sites than in ungrazed sites, and coverage of graminoids, forage shrubs and forbs did not differ significantly between grazed and ungrazed sites.4 In stands of dwarf birch grazed by caribou, ground cover and leaf biomass of Betula glandulosa was significantly lower than in ungrazed sites.5 Productivity of forage plant species over the summer range was estimated at 22.5 g m(-2) year(-1) in an ungrazed condition compared to 10.3 g m(-2) year(-1) when grazed.6 At the landscape level, caribou have fragmented the distribution of their food resource by reducing biomass of shrub tundra and stands of dwarf birch to a very low level.7 The serious negative impact of migratory ungulates on plant productivity of their summer range may be explained by characteristics of the vegetation and the high carrying capacity of winter compared to summer ranges. Significant factors related to the vegetation are its low resilience and productivity and the absence of a response of vascular plants following removal of lichens.