Quantitatively monitoring the resilience of patterned vegetation in the Sahel
Quantitatively monitoring the resilience of patterned vegetation in the Sahel
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DOI：
10.1111/gcb.15939
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发表时间：
2021-10-28
影响因子：
11.6
通讯作者：
Lenton, Timothy M.
中科院分区：
文献类型：
--
作者：
Buxton, Joshua E.;Abrams, Jesse F.;Lenton, Timothy M.
旱地植被的格局是局部反馈机制的结果。这种反馈也决定了生态系统的适应性，即从扰动中恢复的能力。因此，植被的格局被假设为是一个指标的弹性，也就是说，斑点是较低的弹性比芦苇。以前的研究已经建立了这种定性联系，并使用模型对其进行定量探索，但很少有定量分析可用数据来验证假设。在这里，我们提供了定量监测模式化植被的恢复力的方法，适用于40个网站在萨赫勒地区（以前确定的和新的混合）。我们发现，现有的量化植被格局的特征向量度量可以有效地区分差距，植被，斑点，和一个新的类别的斑点植被在其最大程度上，而NDVI没有。特征向量模式度量与平均降水量相关。然后，我们探讨了两种测量弹性的方法。首先，我们把雨季作为一个扰动，并研究了随后的衰减率的模式和植被指数作为可能的措施的弹性。这表明更快的腐烂率-传统上被解释为更大的毒性-与潮湿，更多的植被相关的网站。其次，我们的季节性周期和检查时间的自相关性和方差的残差作为可能的措施的弹性。自相关性和方差的模式度量增加平均降水量下降，与弹性损失。因此，干燥的网站出现弹性较低，但我们发现没有显着的相关性的平均值或最大值的模式度量（和相关的形态模式类型）和我们的弹性措施。
Patterning of vegetation in drylands is a consequence of localized feedback mechanisms. Such feedbacks also determine ecosystem resilience-i.e. the ability to recover from perturbation. Hence, the patterning of vegetation has been hypothesized to be an indicator of resilience, that is, spots are less resilient than labyrinths. Previous studies have made this qualitative link and used models to quantitatively explore it, but few have quantitatively analysed available data to test the hypothesis. Here we provide methods for quantitatively monitoring the resilience of patterned vegetation, applied to 40 sites in the Sahel (a mix of previously identified and new ones). We show that an existing quantification of vegetation patterns in terms of a feature vector metric can effectively distinguish gaps, labyrinths, spots, and a novel category of spot-labyrinths at their maximum extent, whereas NDVI does not. The feature vector pattern metric correlates with mean precipitation. We then explored two approaches to measuring resilience. First we treated the rainy season as a perturbation and examined the subsequent rate of decay of patterns and NDVI as possible measures of resilience. This showed faster decay rates-conventionally interpreted as greater resilience-associated with wetter, more vegetated sites. Second we detrended the seasonal cycle and examined temporal autocorrelation and variance of the residuals as possible measures of resilience. Autocorrelation and variance of our pattern metric increase with declining mean precipitation, consistent with loss of resilience. Thus, drier sites appear less resilient, but we find no significant correlation between the mean or maximum value of the pattern metric (and associated morphological pattern types) and either of our measures of resilience.