Geodiversity increases ecosystem durability to prolonged droughts

Interactions between biotic and abiotic factors dictate the response of ecosystems to varying conditions and disturbances. The importance of the relationship between these factors is demonstrated in the extensively studied interactions between water-limited vegetation and its ecosystem's physical components. Landscape geodiversity is often neglected in studies of vegetation dynamics and response to drought. Here, we combine field studies and mathematical modeling to elucidate the effects of geodiversity on shrub mortality following drought. In Israel's semi-arid northwestern Negev Desert, we found that homogeneous hillslopes, with little or no stoniness, experienced considerable shrub mortality following droughts, while neighboring slopes with higher stoniness showed little or no mortality. A mathematical model describing the dynamics of water-limited vegetation and accounting for landscape geodiversity predicted similar responses. The measurements and the model suggest that geodiversity increases the amount of water available for the shrubs, thereby increasing their durability. Future climate predictions of reduced precipitation and increased drought frequency in many regions make studies of ecosystem responses to water deficiency timely. Our findings suggest that future studies should account for landscape geodiversity in order to explain local differences in vegetation mortality and to better assess the possible impacts of climate fluctuations on ecosystem dynamics. In particular, geodiversity has a great effect on regime shifts and their nature.