The objective of this thesis was to identify the factors determining environmental harshness in Tropical Dry Forests (TDF) of Colombia and to study its influence on plant community attributes and functioning. Additionally, this thesis evaluated how the extreme “El Niño” Southern Oscillation drought of 2015 (ENSO2015) affected biomass dynamics of this ecosystem. Overall, we found that: (1) Colombian TDF are widely heterogeneous in their climate, soil, and land-cover transformation and that the interaction of these factors is what determines the environmental harshness in this ecosystem. (2) Environmental harshness drives changes in species composition, species diversity and forest structure, and trait community composition and biomass productivity of TDF. (3) TDF tree species are adapted to cope with environmental harshness via different functional trait combinations; nevertheless, all tree species seem to be sensitive to extreme droughts. Accordingly, extreme drought events cause negative net biomass balances, particularly for species having traits associated with high hydraulic efficiency and ‘cheap’ tissue investments. This dissertation provides new information about the drivers of environmental harshness and their ecological consequences on TDF diversity and functioning, with clear implications for a comprehensive management of the most threatened ecosystem in Colombia.
