Empirically derived sensitivity of vegetation to climate across the globe
To predict the response of vegetation to climate change, we must understand the physiological processes controlling productivity across large spatial scales, and thus across climate space. To date there is not a fully empirical map of climate constraints on vegetation at the global scale. We use the response of satellite-based greenness (NDVI) to inter-annual climate variations in surface air temperature (from ERA-Interim) to derive the sensitivity of vegetation to temperature and infer mechanisms of climate constraint on vegetation as represented by greenness productivity across the globe.
We focus on how the sensitivity of vegetation to temperature varies and find that the actual climate constraint is a balance of resources. The majority of grid cells in simultaneously warm (above ~14 \degree C) and dry (below ~1000 mm/year rainfall) conditions have negative vegetation sensitivity to temperature (browner in warm years) while at places with cooler temperatures the vegetation sensitivity is generally positive (greener in warm years). At very high rainfall levels (beyond 3000 mm/year), even the hottest vegetated places on Earth have positive sensitivity to mean annual temperature. The mean annual temperature boundary between positive and negative sensitivities changes by 9 degrees C depending on how much rainfall a place receives, and at the highest rainfall rates vegetation never becomes constrained by high temperatures at all. The positive temperature sensitivity of these warm wet ecosystems suggests that they may actually benefit from near term warming on the scale of inter-annual variations of temperature, able to buffer against damaging maximum temperatures with their access to water.