Climate change in Brazilian mountains: functional responses of native plants from campos rupestres and campos de altitude to extreme droughts

Abstract

Extreme climatic events are predicted to increase in frequency and magnitude, but their ecological impacts are poorly understood. Under this scenario, it is important that we understand the ecological responses and the vulnerability of tropical montane vegetation to climate change, such as the increase in frequency of extreme drought events. In the proposed research, we will investigate experimentally the tolerance thresholds and the capacity of morphophysiological adjustments of plants to drier climates in two biodiversity hotspots. Rainfall will be reduced in twenty-four 16 m2 trenched plots using rainfall exclusion structures that intercept incoming rain and transport this water outside of the plots in areas of campos rupestres and campos de altitude. We will use a combination of traditional methods (leaf gas exchange, monitoring of phenological events, growth and mortality rates), with innovative methods such as stable isotopes and sapflow monitoring. The stable isotope composition of carbon (´13C) and oxygen (´18O) of leaf cellulose will be used as an integrative tool to evaluate plant ecophysiological responses and will be used to describe changes in photosynthetic capacity and stomatal conductance of species in the rainfall-excluded plots. Sapflow monitoring in woody species will be used to integrate the response of the multiple components that determined whole plant water use (rooting depth, foliar phenology and stomata conductance). A more thorough understanding of the ecological strategies and responses of species from tropical montane ecosystems is key to foster more realistic simulations of vulnerable ecosystem functioning under climate change scenarios. (AU)