Exotic grass competition in suppressing native shrubland re-establishment
Exotic grass competition in suppressing native shrubland re-establishment
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DOI：
10.1046/j.1526-100x.1997.09729.x
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发表时间：
1997-09-01
影响因子：
3.2
通讯作者：
Allen, EB
中科院分区：
文献类型：
--
作者：
Eliason, SA;Allen, EB
加州南部沿海鼠尾草灌丛的破坏导致了本地灌木被外来的一年生草广泛取代。从灌木林到异国草原的初始转换通常与激烈放牧，高火灾频率或机械植被去除所造成的干扰有关。虽然原生灌木已被证明在某些条件下使一年生草地退化，但其他一年生草地是持久的，没有灌木退化的证据。本研究探讨了机制，一年生草可能会排除本地灌木和持续释放后的干扰。在试验田中操纵草密度以达到一系列规定的密度。加州蒿，占主导地位的本地灌木，播种或种植到地块和草密度处理的反应进行了测量，在两个生长季节。A.加州草的发芽率、第一季生长量和存活率均与邻近一年生禾草的密度呈负相关。第一季生长和存活减少的最可能机制是草耗尽土壤水分。研究了几种牧草对A.加州在第二季中不再重要。这项研究的结果表明，地中海一年生禾草减少补充，并可以通过抑制干扰后建立的A。加州从种子。虽然继承本身可能不会返回干扰的一年生草地，他们以前的灌木丛组成，结果表明，恢复可以通过使用容器种植或草去除，然后播种。
Disturbance of coastal sage scrub in southern California has led to extensive displacement of native shrubs by exotic annual grasses. The initial conversion from shrubland to exotic grassland is typically associated with disturbance caused by intense grazing, high fire frequency, or mechanical vegetation removal. While native shrubs have been shown to recolonize annual grasslands under some conditions, other annual grasslands are persistent and show no evidence of shrub recolonization. This study examined the mechanisms by which annual grasses may exclude native shrubs and persist after release from disturbance. Grass density was manipulated in experimental plots to achieve a series of prescribed densities. Artemisia californica, a dominant native shrub, was seeded or planted into the plots and responses to the grass density treatments were measured over two growing seasons. A. californica germination, first season growth, and survival were all negatively related to the density of neighboring annual grasses. The most probable mechanism underlying the reduction of first season growth and survival was depletion of soil water by the grasses. The effects of the grasses on A. californica were no longer significant in the second season. The results of this study indicate that Mediterranean annual grasses reduce recruitment and can persist by inhibiting post-disturbance establishment of A. californica from seed. Although succession alone may not return disturbed annual grasslands to their former shrubland composition, the results suggest that restoration can be achieved by using container plantings or grass removal followed by seeding.