Influence of plant neighborhood on patch dynamics

Abstract

Patch dynamics in ecology have been useful for understanding the functioning of diverse biomes, focusing primarily on how processes maintain the vegetation mosaic. However, less is known about how the mosaic structure influences processes within each patch, completing the pattern–process feedback. We present a conceptual framework exploring the importance of neighborhood structure and composition on patch dynamics. We described the neighborhood for each focal patch based on the neighbor's distance (Voronoi area), the size of the neighbors, and the neighborhood species composition. We tested this model in grazed and ungrazed Patagonian steppes, where mosaic structure and patch dynamics are associated to shrub life stages. Using field data spanning 26 years, we evaluated how mosaic attributes influence the establishment, growth and mortality of long-lived dominant shrub species, while considering climate variability and the effect of grazing by domestic livestock. Our results show that larger neighborhood areas and lower intraspecific ratios reduced shrub establishment and growth, while increasing mortality. Therefore, the neighborhood structure and composition alter patch dynamics. Grazing had species-specific effects on establishment and growth but did not alter the relationship between neighborhood variables and focal shrubs. Our results demonstrate that shrub population dynamics – and thus patch dynamics – are influenced by the structure and composition of the vegetation mosaic. This long-term study enhances our understanding of the mosaic maintenance feedback involving patterns and processes in ecosystems where woody species play a significant role in its dynamics, and in a context of increasing environmental pressures.