Climatic variability and plant functional traits in tropical montane cloud forest refugia along the Trans Mexican Volcanic Belt

Functional traits represent the adaptive responses of plant species to climatic changes. They are an integrative marker of the general environmental conditions at a location. Testing their patterns may help to understand how the functional traits would track these environmental changes of tropical montane cloud forests (TMCFs). These forests are characterized by the constant presence of clouds, and these are among the most threatened ecosystems by climate change worldwide. One of the main TMCF regions in Mexico is the Trans-Mexican Volcanic Belt (TMVB). This region has provided refugia during past climate-change events. We identify three current regions of distribution of TMCF in TMVB, Pacific, Center and Gulf. We used 60 years of climatic information, functional traits and plants databases. We proposed the following aims: to determine whether changes in climatic variation have occurred in the TMVB and how these changes can be related to functional trait variations for dominant tree species across the three TMCF regions, and to know the potential changes as a refuge of the TMCF of the TMVB. We found different rainfall and maximum temperature patterns among and within regions. We identified that the Pacific region forests were characterized by the lowest specific leaf area (SLA), wider leaf thickness and high leaf density, which indicates resources-conservative leaf economics and tolerance to low humidity. Center and Gulf forests were distinguished by the highest SLA, less leaf thickness, and higher leaf density values, which suggests that the leaves of dominant tree species tend to be resources-acquisitive rather than conservative-resources. Finally functional traits were associated with prevailing climatic conditions and suggested that SLA, leaf thickness and leaf density are the main functional traits that could be used to relate them to regional climate. Also, Central and Gulf regions could serve as a refuge for those species of trees demanding humidity.