Slow drying effects on woody vegetation cover along the Mediterranean rainfall gradient

Climate predictions, based on current emission scenarios, indicate unprecedented warming and drying in many places throughout the world. Novel climates and rapid change potentially influence Mediterranean woody species and ecosystems. Climate-driven tree mortality is just one extreme consequence of drying and warming. In most cases the consequences of climate change on local ecosystems and woody plant communities are gradual and result in slow changes in the composition, dominance and structure of woody ecosystems. These gradual changes are much harder to detect and foresee.

We evaluated whether woody ecosystems in Israel have been affected by recent climate history, by identifying trends in the climatic variables, and analyzing woody plant dynamics at decadal scales and differing spatial scales. Our analyses show that the dynamics of woody cover differ along the gradient of Mediterranean rainfall regime. At the dry-end of the Mediterranean rainfall gradient, we found a significant decrease in the cover of woody vegetation, whereas at the wet end of the Mediterranean rainfall gradient we found a significant increase in woody cover. These patterns were consistent at short-term local resolution to long-term satellite resolution. These observations of slow changes in climate and consequent changes in woody ecosystems suggests high vulnerability of dry-Mediterranean habitats, despite the assumed resilience of these habitats due to adaptation to large inter-annual variability. Since woody plants create the physical habitat that shape the diversity of a multitude of other organisms and ecosystem functions, changes in woody structure are expected to impact system function and biodiversity.