Sediment capture by vegetation patches: Implications for desertification and increased resource redistribution
Sediment capture by vegetation patches: Implications for desertification and increased resource redistribution
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DOI：
10.1029/2011jg001663
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发表时间：
2012-03-20
影响因子：
3.7
通讯作者：
Zou, Chris B.
中科院分区：
文献类型：
--
作者：
Field, Jason P.;Breshears, David D.;Zou, Chris B.
荒漠化影响很大比例的旱地，并可由各种气候和土地利用因素驱动。大多数关于沙漠化的概念模型都有一个基本的假设，即当草本覆盖减少时，光秃秃的斑块的侵蚀会重新分布到灌木树冠斑块上，从而形成自我强化的“肥沃岛屿”。然而，值得注意的是，这一基本假设尚未得到直接现场测量的明确验证。在这里，我们提供了在半干旱生态系统中，在模拟和自然沙尘事件以及对模拟干扰的响应中，进入和退出裸、草本和灌木为主的斑块类型的水平泥沙通量的直接测量。裸露斑块的水平输沙通量比草本斑块大约20%，比灌木斑块大约50%。植被斑块类型的差异表明，灌木斑块比草本斑块捕获更多的沉积物，重要的是，裸地斑块在扰动后成为放大的沉积物来源。我们的研究结果为普遍存在但未经检验的沙漠化再分配假设提供了明确的支持，强调了草地覆盖的丧失是一个复杂的问题，不仅增加了粉尘排放，而且还阻碍了捕获，并且可能与当前或潜在的沙漠化所带来的风险的耦合人类环境系统具有全球相关性。
Desertification impacts a large proportion of drylands and can be driven by a variety of climate and land use factors. Most conceptual models of desertification include the underlying assumption that when herbaceous cover is reduced, increased erosion from bare patches is redistributed to shrub canopy patches, resulting in self-reinforcing "islands of fertility." Notably, however, this underlying assumption has not been explicitly tested with direct field measurements. Here we provide direct measurements of horizontal sediment flux moving into and out of bare-, herbaceous-, and shrub-dominated patch types in a semiarid ecosystem for both simulated and natural dust events, as well as in response to simulated disturbance. Horizontal sediment flux out of the bare patches was approximate to 20% greater than the herbaceous patches and approximate to 50% greater than sediment flux out of the shrub-dominated patches. Differences among vegetation patch types indicate that shrub patches capture more sediment than herbaceous patches and, importantly, that bare patches serve as amplified sediment sources following disturbance. Our results provide explicit support for the pervasive but untested desertification redistribution assumption, highlighting that loss of grass cover is a compounding problem that not only increases dust emissions but also precludes capture, and may have global relevance for coupled human-environmental systems at risk due to current or potential desertification.