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arXiv 1703.01280nlin.PSq-bio.PE
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沙漠化通过前传播?

Desertification by Front Propagation?

Yuval R. Zelnik, Hannes Uecker, Ulrike Feudel, Ehud Meron

摘要:

了解荒漠化如何在不同的生态系统中发生,是试图预测和防止这种转变的重要一步。旱地生态系统往往呈现出斑块状植被,在若干模型研究中,这已被证明是干旱地区可能发生的状况转变的一个重要因素。特别是,由于干旱地区生态系统的空间异质性,无论是通过锋面传播发生的逐渐转移,还是植被斑块立即消失的突然转移,都是可能的。然而,最近的理论研究表明,荒漠化的最后一步-从斑点植被到裸露土壤的转变-只是作为一种突然的转变而发生的,但这一结果的普遍性及其根本原因仍然不清楚。我们调查了两个模型,详细的旱地植被的动态使用一个显着不同的功能结构,并发现,在这两个模型中,荒漠化的最后一步只能是突然的。使用仔细的数值分析,我们表明,这种行为是与有限的斑点图案域的消失作为固定状态,并确定这种行为的数学起源。我们的研究结果表明,在这些和类似的模型中,由于前沿传播过程而导致的逐渐荒漠化到裸露的土壤不会发生,并提出了这些动态是否可以在自然界中发生的问题。

英文摘要:

Understanding how desertification takes place in different ecosystems is an important step in attempting to forecast and prevent such transitions. Dryland ecosystems often exhibit patchy vegetation, which has been shown to be an important factor on the possible regime shifts that occur in arid regions in several model studies. In particular, both gradual shifts that occur by front propagation, and abrupt shifts where patches of vegetation vanish at once, are a possibility in dryland ecosystems due to their emergent spatial heterogeneity. However, recent theoretical work has suggested that the final step of desertification - the transition from spotted vegetation to bare soil - occurs only as an abrupt shift, but the generality of this result, and its underlying origin, remain unclear. We investigate two models that detail the dynamics of dryland vegetation using a markedly different functional structure, and find that in both models the final step of desertification can only be abrupt. Using a careful numerical analysis, we show that this behavior is associated with the disappearance of confined spot-pattern domains as stationary states, and identify the mathematical origin of this behavior. Our findings show that a gradual desertification to bare soil due to a front propagation process can not occur in these and similar models, and opens the question of whether these dynamics can take place in nature.

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