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首页> 外文学位 >Habitat changes and successional trends over a 20-year period within the upper Santa Ana River floodplain.
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Habitat changes and successional trends over a 20-year period within the upper Santa Ana River floodplain.

机译：圣安娜河上游洪泛区20年内的生境变化和演替趋势。

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摘要

Different stages of succession within the floodplain of the upper Santa Ana River have been documented by previous studies, predicting an eventual shift away from the sandy, sparsely vegetated conditions of the younger sites in the absence of future flooding. These habitat conditions are necessary for the endangered subshrub, the Santa Ana River woolly-star (Eriastrum densifolium ssp. sanctorum), as it does not survive on older surfaces due to competition with annual and woody perennial species.;This study was conducted in order to determine the changes that have occurred in this habitat over a 20-year period, and to assess the implications any changes may have on the persistence of the woolly-star. Small-scale habitat changes were determined by comparing annual plant data from 1989 and 2009. Large-scale habitat changes were determined by comparing perennial plant data from 1987 and 2009.;The results of this study suggest that annual species, lichen crust, and dead shrubs are increasing, and that bare ground and live shrubs are decreasing. The older sites are also increasing in annual grass cover. It appears that successional changes may have occurred over the past 20 years, although these changes are gradual and on a continuum, precluding a sharp distinction between different stages. The data appear to support previously predicted sucessional rates indicating ultimate maturity within at least 100 years. The continuation of these habitat changes will likely contribute to the decline of the woolly-star population, particularly during future drought periods.
机译：先前的研究已记录了圣安娜河上游洪泛区中不同的演替阶段，并预测在没有未来洪水的情况下，最终地点将从年轻地区的沙质稀疏植被转移。这些栖息地条件对于濒临灭绝的亚灌木灌木-圣安娜河毛星（Eriastrum densifolium ssp。sanctorum）是必不可少的，因为由于与一年生和多年生木本多年生物种的竞争而无法在较旧的表面生存。确定该栖息地在过去20年中发生的变化，并评估任何变化可能对毛恒星的持久性产生的影响。通过比较1989年和2009年的年度植物数据确定小规模的栖息地变化。通过比较1987年和2009年的多年生植物数据确定大规模的栖息地变化。研究结果表明，一年生物种，地衣结壳和死亡灌木在增加，裸露的地面和活动灌木在减少。较旧的地点的年草覆盖率也在增加。似乎在过去的20年中发生了连续的变化，尽管这些变化是逐渐的并且是连续的，从而排除了不同阶段之间的明显区别。数据似乎支持先前预测的成功率，表明成功率至少在100年内。这些栖息地变化的持续进行可能会导致羊毛明星数量的下降，特别是在未来的干旱时期。

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  • 作者

    Lucas, Shannon Desiree.;

  • 作者单位

    California State University, Fullerton.;

  • 授予单位 California State University, Fullerton.;
  • 学科 Biology Ecology.;Physical Geography.
  • 学位 M.S.
  • 年度 2010
  • 页码 66 p.
  • 总页数 66
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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