A conceptual framework for understanding semi-arid land degradation : ecohydrological interactions across multiple-space and time scales.

Abstract

Land degradation is a problem prolific across semi‐arid areas worldwide. Despite being a complex process including both biotic and abiotic elements, previous attempts to understand ecosystem dynamics have largely been carried out within the disparate disciplines of ecology and hydrology, which has led to significant limitations. Here, an ecohydrological framework is outlined, to provide a new direction for the study of land degradation in semi‐arid ecosystems. Unlike other frameworks that draw upon hierarchy theory to provide a broad, non‐explicit conceptual framework, this new framework is based upon the explicit linkage of processes operating over the continuum of temporal and spatial scales by perceiving the ecosystem as a series of structural and functional connections, within which interactions between biotic and abiotic components of the landscape occur. It is hypothesized that semi‐arid land degradation conforms to a cusp‐catastrophe model in which the two controlling variables are abiotic structural connectivity and abiotic functional connectivity, which implicitly account for ecosystem resilience, and biotic structural and function connectivity. It is suggested therefore that future research must (1) evaluate how abiotic and biotic function (i.e. water, sediment and nutrient loss/redistribution) vary over grass–shrub transitions and (2) quantify the biotic/abiotic structure over grass‐shrub transitions, to (3) determine the interactions between ecosystem structure and function, and interactions/feedbacks between biotic and abiotic components of the ecosystem.