间歇性降水和空间阿勒效应驱动半干旱生态系统中不规则植被模式
Intermittent precipitation and spatial Allee effects drive irregular vegetation patterns in semiarid ecosystems
AI总结：
本研究通过整合间歇性降水与本地阿勒效应，揭示随机降雨如何塑造半干旱生态系统中不规则植被模式及持续性。
摘要：
半干旱生态系统中的植被经常组织成空间异质的斑块，这些斑块调节生态系统的功能、生产力和韧性。这些模式源于本地生物相互作用，包括相邻植物之间的促进作用和对限制性资源的竞争。经典理论方法将这种组织归因于规模依赖的反馈，预测出规律的空间模式和突然的崩溃过渡。然而，越来越多的实证和理论证据表明，环境变异和种群随机性可以从根本上重塑空间组织，驱动不规则的聚类、动态斑块以及渐进而非灾难性的植被衰退。在干旱地区，降水的变异是环境驱动的主要来源：降水通常以短而不规则的脉冲形式出现，短暂地增强存活和招募，然后竞争性相互作用再次主导。接近持续阈值时，生态系统的动态不仅由平均气候条件决定，还由有利事件的时间和空间重叠决定。在这些条件下，正密度依赖和本地促进作用可以决定植被斑块是否持续、扩展或崩溃。在此，我们开发了一个基于个体的模型，整合间歇性降水与本地阿勒效应，以研究随机降雨如何塑造空间组织和持续性。我们表明，脉冲资源可用性和密度依赖生存的相互作用生成不规则的聚类结构，并强烈调节灭绝风险，韧性源于本地空间协方差和邻近密度，而非总生物量本身。这些结果突显了个体层面随机过程在决定生态系统韧性中的重要性。
英文摘要：
Vegetation in semi-arid ecosystems frequently organizes into spatially heterogeneous mosaics that regulate ecosystem functioning, productivity, and resilience. These patterns arise from local biological interactions, including facilitation among neighboring plants and competition for limiting resources. Classical theoretical approaches have attributed such organization to scale-dependent feedbacks, predicting regular spatial patterns and abrupt transitions to collapse. However, growing empirical and theoretical evidence reveal that environmental variability and demographic stochasticity can fundamentally reshape spatial organization, driving irregular clusters, dynamic mosaics, and gradual rather than catastrophic vegetation declines. In drylands, rainfall variability is a dominant source of environmental forcing: precipitation typically occurs in short, irregular pulses that transiently enhance survival and recruitment before competitive interactions again dominate. Near persistence thresholds, ecosystem dynamics are therefore governed not only by average climatic conditions but also by the timing and spatial coincidence of favorable events. Under these conditions, positive density dependence and local facilitation can critically determine whether vegetation patches persist, expand, or collapse. Here, we develop an individual-based model that integrates intermittent precipitation with local Allee effects to examine how stochastic rainfall shapes spatial organization and persistence. We show that the interaction between pulsed resource availability and density-dependent survival generates irregular cluster structures and strongly modulates extinction risk, with resilience emerging from local spatial covariance and neighborhood density rather than from total biomass alone. These results highlight the importance of individual-level, stochastic processes in determining ecosystem resilience.
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