What can we learn from observational data about vegetation resistance to increasing aridity?

Natural ecosystems are under increasing pressure from environmental changes such as climate change, natural disasters, or anthropogenic disturbances. Prolonged droughts, heat waves and increasing aridity are generally considered major consequences of ongoing global climate change and are expected to produce widespread changes in key ecosystem attributes, functions and dynamics. Drylands are especially vulnerable to potential adverse consequences of climate change. Recent research documented the existence of three major thresholds in aridity associated with distinct changes in multiple ecosystem attributes and a gradual reduction in vegetation productivity when a threshold is crossed. We hypothesise that different environmental conditions such as climate, drought intensity and topography, as well as specific soil and plant related attributes impact the vegetation resistance to disturbances. Here, we define disturbance as a crossing of an aridity threshold and vegetation resistance as the inverse of the magnitude of disturbance, which is measured as a reduction in vegetation productivity when crossing the threshold.

We used a generalised linear model on observational data from the BIOCOM (Biotic community attributes and ecosystem functioning: implications for predicting and mitigating global change impacts) and BIODESERT (Biological feedbacks and ecosystem resilience under global change: a new perspective on dryland desertification) databases complemented with remote sensing-based data to test our hypothesis.

Generally, a field site’s slope, nitrogen content, soil texture and pH, as well as changes in rainfall are significantly related to the magnitude of disturbance. Preliminary results further suggest that the magnitude of disturbance is negatively related to drought intensity in years prior to crossing a threshold. Interactions of some soil properties with drought intensity may also play an important role in explaining the magnitude of disturbance.