Tree invasion into a mountain‐top meadow in the Oregon Coast Range, USA
Tree invasion into a mountain‐top meadow in the Oregon Coast Range, USA
复制标题
树木入侵美国俄勒冈州海岸山脉的山顶草甸
DOI：
10.2307/3235805
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
J. Antos
中科院分区：
文献类型：
--
作者：
Teresa K. Magee;J. Antos
位于俄勒冈州海岸山脉的玛丽峰山顶上的草地正被冷杉入侵，主要是沿着边缘。为了研究森林-草甸过渡带的植被和环境变化，并评估影响树木入侵的因素，在10个样地建立了样带。除趋势对应分析的环境瓦里与排序轴的相关性表明，站点分布沿着一个湿度梯度。虽然各地点的物种组成和环境差异很大，但树木入侵草甸的现象在所有地点都有发生。减少丰富的密集的草本植被的草甸之前，冷杉procera的幼苗可以成为建立。几乎所有的树木入侵草甸发生在狭窄的森林-草甸生态过渡带，因为森林边缘的树木减少了邻近草甸的草本植物的覆盖。在某些地点，高于平均水平的积雪进一步降低了草甸植被的活力，增加了树木的建立。在最干燥的地方，潮湿的夏天有利于树木的生长。罕见的火灾，消除火敏感的冷杉，可能需要扭转缓慢但持续的森林扩张趋势，并最终维持草甸。
The grassy meadow on the top of Marys Peak, in the Oregon Coast Range, is being invaded, primarily along the margins, by Abies procera. To examine vegetation and envi- ronmental changes across the forest-meadow transition and to evaluate factors affecting tree invasion, belt transects were established at 10 sites. Correlations of environmental vari- ables with ordination axes from Detrended Correspondence Analysis suggest that the sites were distributed along a mois- ture gradient. Although the sites varied considerably in spe- cies composition and environment, tree invasion of the meadow was occurring at all sites. Reduction in abundance of the dense herbaceous vegetation of the meadow is required before the small seedlings of Abies procera can become established. Almost all tree invasion of the meadow occurs in the narrow forest-meadow ecocline because trees at the edge of the forest reduce the cover of herbaceous plants in the adjacent meadow. On some sites, above average snow accumulations further reduce vigor of meadow vegetation and increase tree estab- lishment. On the driest sites wet summers facilitate tree estab- lishment. Infrequent fires, which remove the fire sensitive Abies procera, are probably required to reverse the slow but persistent trend of forest expansion and ultimately maintain the meadow.