Environmental heterogeneity mediates plant diversity and ecosystem stability in mountain ecosystems of the Mediterranean Andes

Globally, mountains are highly diverse ecosystems that serve as natural laboratories for testing fundamental ecological theories, while also providing vital ecosystem services. The biodiversity of these ecosystems is largely attributed to their complex topography, which creates gradients of elevation and environmental heterogeneity. These gradients in turn influence the maintenance of ecosystem functions, such as vegetation productivity, over time. However, how topography influences ecosystem stability and its relation with different facets of biodiversity in mountain ecosystems remains relatively unexplored. Here, we evaluated the impacts of environmental heterogeneity and spatial autocorrelation on taxonomic and phylogenetic diversity, and the extent to which they mediate ecosystem stability in a mountain ecosystem. Using a highly-replicated fractal sampling design, we estimated plant taxonomic and phylogenetic diversity locally and across space. We estimated the temporal stability of vegetation productivity with a high-resolution, remotely-sensed vegetation productivity time series in the Mediterranean Andes forest of central Chile. We assessed the effects of topographic gradients as proxies for environmental heterogeneity and local phylogenetic and taxonomic diversity and turnover on ecosystem stability using generalized linear and structural equation models that account for spatial autocorrelation. Our results show that environmental heterogeneity, particularly that associated with topographic ruggedness and elevation, plays a key role in shaping plant diversity and ecosystem stability. While increasing topographic ruggedness and elevation increased taxonomic turnover, structural equation modeling indicated that it decreased taxonomic and phylogenetic