The stability of vegetation boundaries and the propagation of desertification in the American Southwest: A modelling approach
The stability of vegetation boundaries and the propagation of desertification in the American Southwest: A modelling approach
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DOI：
10.1016/j.ecolmodel.2007.04.010
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发表时间：
2007-11-10
影响因子：
3.1
通讯作者：
Parsons, Anthony J.
中科院分区：
文献类型：
--
作者：
Mueller, Eva Nora;Wainwright, John;Parsons, Anthony J.
一个基于过程的方法来空间分布，地表径流模拟，以评估在景观尺度上的水和养分再分配的影响所造成的短期，高强度的暴雨事件在美国西南部的半干旱生态系统的草地灌木植被边界。模拟情景表明，从灌木林到草地的模拟通量导致水资源的收益，但在草原地区的养分资源的损失接近边界。模拟的从草地到灌丛的通量并不导致水资源的增加，但增加了养分资源，因为灌丛离边界很近。在模拟结果的基础上，对美国西南部正在进行的荒漠化进程提出了一个新的假设。假设植被边界在以下两种情况下是稳定的：在现有环境设置中，草地的阻力较低，而灌木林的阻力较高：在边界附近的草地区，由地表径流作用引起的土壤养分的消耗与其他养分循环对草地的补充率是平衡的，草地从上坡灌丛中获得足够的水分资源。相比之下，植被边界可能变得不稳定时，草原收购的竞争劣势对灌木林的水效益和养分耗竭，由于地表径流动力学和一些外部力量，如广泛的过度放牧或气候变化的综合影响。模拟结果表明，景观联系，通过重新分配的水和土壤资源的植被过渡区在景观尺度和反馈动态的地表径流过程中发挥了重要作用，在美国西南部的土地退化的持续性。(C)2007 Elsevier B.V.保留所有权利。
A process-based approach to spatially distributed, overland-flow modelling is employed to as by assess the impact of water and nutrient redistribution at the landscape scale caused by short, high-intensity rainstorm e vents across grassland-shrubland vegetation boundaries of a semi-arid ecosystem in the south-western United States. The modelling scenarios showed that simulated fluxes from shrubland into grassland lead to a gain of water resources but to a loss of nutrient resources in the grassland areas close to the boundary. Simulated fluxes from grasslands into shrublands do not lead to a gain of water resources, but to an increase of nutrient resources for thee shrubland are as close to the boundary. On the basis of the modelling results, a new hypothesis for the on-going desertification process in the south-westesern United States is proposed. It is hypothesised that a vegetation boundary is stable when two conditions prevail to balance the lower resistance of grassland within the existing environmental setting with the higher resistance of shrubland: that the depletion of soil nutrients by the action of overland flow in the grassland zone close to the boundary is in balance with the replenishment rates of grassland by other nutrient cycling, and that the grassland gains enough water resources from the upslope shrublands. In contrast, a vegetation boundary potentially becomes unstable when the grassland acquires a competitive disadvantage towards shrubland regarding water benefit and nutrient depletion due to the combined effects of overland-flow dynamics and some external forces such as extensive overgrazing or climate change. The modelling results suggest that landscape linkages through the redistribution of water and soil resources across vegetation-transition zones at the landscape scale and feedback dynamics of overland-flow processes play a significant role in the persistence of land degradation in the US Southwest. (C) 2007 Elsevier B.V. All rights reserved.