Mathematical Institute, Leiden University, 2300 RA Leiden, The Netherlands;
Mathematical Institute, Leiden University, 2300 RA Leiden, The Netherlands.
Proc Natl Acad Sci U S A. 2018 Oct 30;115(44):11256-11261. doi: 10.1073/pnas.1804771115. Epub 2018 Oct 15.
Spatial self-organization of dryland vegetation constitutes one of the most promising indicators for an ecosystem's proximity to desertification. This insight is based on studies of reaction-diffusion models that reproduce visual characteristics of vegetation patterns observed on aerial photographs. However, until now, the development of reliable early warning systems has been hampered by the lack of more in-depth comparisons between model predictions and real ecosystem patterns. In this paper, we combined topographical data, (remotely sensed) optical data, and in situ biomass measurements from two sites in Somalia to generate a multilevel description of dryland vegetation patterns. We performed an in-depth comparison between these observed vegetation pattern characteristics and predictions made by the extended-Klausmeier model for dryland vegetation patterning. Consistent with model predictions, we found that for a given topography, there is multistability of ecosystem states with different pattern wavenumbers. Furthermore, observations corroborated model predictions regarding the relationships between pattern wavenumber, total biomass, and maximum biomass. In contrast, model predictions regarding the role of slope angles were not corroborated by the empirical data, suggesting that inclusion of small-scale topographical heterogeneity is a promising avenue for future model development. Our findings suggest that patterned dryland ecosystems may be more resilient to environmental change than previously anticipated, but this enhanced resilience crucially depends on the adaptive capacity of vegetation patterns.
干旱地区植被的空间自组织是生态系统接近荒漠化的最有希望的指标之一。这一观点基于对反应扩散模型的研究，这些模型再现了航空照片上观察到的植被模式的视觉特征。然而，直到现在，由于缺乏对模型预测与真实生态系统模式之间更深入的比较，可靠的早期预警系统的发展一直受到阻碍。在本文中，我们结合了地形数据、（遥感）光学数据和来自索马里两个地点的原位生物量测量数据，生成了干旱地区植被模式的多层次描述。我们对这些观察到的植被模式特征与扩展 Klausmeier 模型对干旱地区植被模式的预测进行了深入比较。与模型预测一致，我们发现，对于给定的地形，具有不同模式波数的生态系统状态存在多稳定性。此外，观测结果证实了模型关于模式波数、总生物量和最大生物量之间关系的预测。相比之下，模型关于坡度角作用的预测与经验数据不符，这表明纳入小尺度地形异质性是未来模型开发的一个有前途的途径。我们的研究结果表明，有图案的旱地生态系统可能比以前预期的更能适应环境变化，但这种增强的弹性取决于植被图案的适应能力。
