干旱区生态系统稳态转换及其预警信号——基于景观格局特征的识别方法

在日益加剧的气候变化和土地开垦、放牧等人类活动干扰下，具有多稳态特征的干旱区生态系统可能会经历从相对健康状态到退化状态的稳态转换，导致生态系统的功能下降。早期预警信号的识别是生态系统稳态转换研究的热点，也是管理实践中防止生态系统退化的关键环节。以往预警信号研究聚焦于通用信号如自相关性、方差等统计学指标，然而这些指标对于具有特定机制的干旱区生态系统可能并不适用。基于干旱区景观格局特征所发展起来的空间指标为生态系统稳态转换提供了独特的空间视角，对于理解干旱区生态系统退化过程和机理具有科学意义和实践价值。介绍了干旱区生态系统稳态转换现象及其转换机制；聚焦景观生态学的指标和方法，从空间视角总结基于干旱区景观格局特征的关键预警指标(植被覆盖度、植被斑块形态、植被斑块大小频率分布和水文连通性等),重点剖析这些关键指标的概念、量化方法、识别特征及其实践应用；最后针对指标的优势和局限性对未来的研究方向进行展望，包括发掘潜在景观指标，加强干旱区生态系统变化的多种驱动要素的相互作用机制研究，开展多时空尺度的实证研究，构建生态系统稳态转换预警信号的整体分析框架，以及加强指标阈值的量化研究等方面。

Regime shifts and early warning signals in dryland ecosystems-an identification method based on landscape pattern characteristics

Dryland ecosystems with alternative stable states may undergo a regime shift from a relatively healthy state to a degraded state under the increasing climate change and disturbances from human activities such as land reclamation and grazing, resulting in the decline of ecosystem functions. The identification of early warning signals is a hot topic in the study of ecosystem regime shifts and a key aspect of management practices to prevent ecosystem degradation. Previous studies on early warning signals have focused on generic signals such as autocorrelation, variance and other statistical indicators, however, these indicators may not be applicable to dryland ecosystems with specific mechanisms. The spatial indicators developed based on landscape pattern characteristics provide a uniquely spatial perspective for ecosystem regime shift identification, which has scientific significance and practical value for understanding ecosystem degradation processes and mechanisms in drylands. In this review, the phenomenon of regime shifts in dryland ecosystems and its characteristic mechanisms are first introduced. Then, focusing on the indicators and methods of landscape ecology, the key early warning indicators (vegetation coverage, vegetation patch morphology, vegetation patch size and frequency distribution and hydrological connectivity, etc.) based on the characteristics of landscape pattern in drylands are summarized from a spatial perspective, and the concepts, quantitative methods, identification characteristics and practical applications of these key indicators are analyzed. Finally, based on the advantages and limitations of indicators, the review points out the future direction of the research, including exploring potential landscape indicators, strengthening research on the interaction mechanisms of multiple driving factors of ecosystem change in drylands, carrying out empirical research at multiple spatial and temporal scales, constructing an overall analytical framework for early warning signals of ecosystem regime shifts, and strengthening the quantitative research on indicator thresholds.