Tropical dry forests (TDF) are known to be resource-limited due to a marked seasonality in precipitation. However, TDF are also shaped by factors such as solar radiation, wind speed, soil fertility and land-cover transformation. Together, these factors may determine gradients of environmental harshness, that are likely to drive changes in plant community attributes. Here we evaluated the effects of environmental harshness on plant community diversity and structure of Colombian TDF based on floristic and environmental data from 15 1-ha permanent plots. We also analyzed effects on groups of legumes species only (including deciduous and non-deciduous species), deciduous species only (including legumes and non-legumes species), and the whole community excluding either legumes or deciduous separately. Drier conditions and higher land-cover transformation had the strongest negative effects on species diversity, basal area and canopy height. Soil fertility, on the contrary, did not have a significant effects on any of the evaluated variables. Interestingly, legumes maintained their diversity and basal area along the climatic gradient, while deciduous species were negatively affected by drier conditions and an increase in secondary vegetation at the landscape level. Our results suggest that although TDF are limited by water availability, land-cover transformation strongly increases environmental harshness. Yet, both legumes group and deciduous group were differentially impacted by climatic and land transformation variables. Thus, to better understand TDF plant community attributes, it is necessary to consider these gradients and to disentangle their effects on different plant functional groups.