Environmental modulation of self-organized periodic vegetation patterns in Sudan
Environmental modulation of self-organized periodic vegetation patterns in Sudan
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DOI：
10.1111/j.1600-0587.2010.06694.x
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发表时间：
2011-12-01
期刊：
影响因子：
5.9
通讯作者：
Barbier, Nicolas
中科院分区：
文献类型：
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作者：
Deblauwe, Vincent;Couteron, Pierre;Barbier, Nicolas
在过去的十年中，干旱至半干旱地区的空间周期性植被模式激发了许多机械模型。所有这些都体现了自组织的共同原则，并对环境因素如何调节这些模式的形态特性做出一致且稳健的预测。这样一系列的预测仍需要通过大规模的共时和历时实地观测来证实。利用基于傅里叶的卫星图像纹理分析，我们客观地对苏丹广大地区的周期性图案的典型形态及其特征尺度（波长）进行了分类。然后，我们分析了不同日期的环境领域和模式形态的调制，以在单个综合和定量研究中测试理论预测。我们的结果表明，在取决于干旱水平的临界坡度梯度以下，模式形态在空间上随着年平均降雨量的减少而变化，其顺序与自组织模型的预测一致：间隙、迷宫和波长增加的斑点。此外，在 20 世纪 70 年代和 80 年代的萨赫勒干旱期间，随着时间的推移，观察到了相同的动态序列。对于给定的形态，干燥的影响是增加图案波长。在临界坡度梯度之上，我们观察到沿等高线定向的平行带图案（所谓的虎丛）。这些波段的波长与斜率呈松散的负相关。这些结果凸显了自组织理论在解释并可能预测这些受威胁生态系统的动态方面的相关性。
Spatially periodic vegetation patterns in arid to semi-arid regions have inspired numerous mechanistic models in the last decade. All embody a common principle of self-organization and make concordant, hence robust, predictions on how environmental factors may modulate the morphological properties of these patterns. Such an array of predictions still needs to be corroborated by synchronic and diachronic field observations on a large scale. Using Fourier-based texture analysis of satellite imagery, we objectively categorized the typical morphologies of periodic patterns and their characteristic scales (wavelength) over extensive areas in Sudan. We then analyzed the environmental domain and the modulation of patterns morphologies at different dates to test the theoretical predictions within a single synthetic and quantitative study. Our results show that, below a critical slope gradient which depends on the aridity level, pattern morphologies vary in space in relation to the decrease of mean annual rainfall in a sequence consistent with the predictions of self-organization models: gaps, labyrinths and spots with increasing wavelengths. Moreover, the same dynamical sequence was observed over time during the Sahelian droughts of the 1970s and 1980s. For a given morphology, the effect of aridity is to increase the pattern wavelength. Above the critical slope gradient, we observed a pattern of parallel bands oriented along the contour lines (the so called tiger-bush). The wavelength of these bands displayed a loose inverse correlation with the slope. These results highlight the pertinence of self-organization theory to explain and possibly predict the dynamics of these threatened ecosystems.