干旱区生态环境知识资源中心

Aims The aim of this study was to analyse the main drivers of compositional and distributional changes of xerophytic shrub communities at different spatial scales. We also assess whether the ecological dynamics of these communities comply with the Clementsian and/or Gleasonian paradigms of community assembly.

Methods We study the influence of environmental variables and human impacts at different scales on three xerophytic scrub communities growing on inland sand dunes. In 70 plots we sampled shrub cover, herb presence, soil characteristics and human disturbance. PCA and NMS were used to describe environmental and species variations. The effects of main drivers were assessed through Mantel tests, taking spatial structure into account. GAMs were used to model the scrub dynamics across environmental gradients.

Results We found that local and regional environmental factors drive the patchy distribution of the xerophytic scrub communities. The gradient found from Stauracanthus genistoides to Ulex australis-dominated communities depends on nutrient availability, probably through species interactions, namely facilitation and competition. In turn, the gradient from S. genistoides to Juniperus navicularis-dominated communities follows an aridity gradient associated with human disturbance, namely agriculture.

Conclusions We propose that the three studied scrub communities are the extremes of two successions. The S. genistoides to U. australis-dominated communities’ succession is driven by local edaphic factors, following Clementsian principles while the S. genistoides to Juniperus navicularis-dominated communities’ succession responds to local-disturbance-and regional-aridity-processes, following both Clementsian and Gleasonian principles. This implies that only dynamic management approaches directed to ensure a natural functioning of this landscape can be successful for their long-time preservation.