Plant community strategies responses to recent eruptions of Popocatepetl volcano, Mexico

Questions What are the mechanisms operating behind the plant community structure changes over time after lahars activity of Popocatepetl volcano? We hypothesize that functional diversity matters more than species richness and that, after major disturbances, the pioneer plant community will first show a ruderal composition, that subsequently changes into successional stages in which competitive and stress-tolerating species become dominant life-forms. We expect this process to be revealed by the community's functional signature. Location Popocatepetl volcano in Mexico (19 degrees 1 ' 0 '' N, 98 degrees 37 ' 0 '' W) which has undergone large eruptive activity that has caused lahars formation. Methods In 2002, survey plots were established in the bottom of the Huiloac gorge. Species composition and abundance data were thereafter collected for 10 years. In 2013, data on three functional traits leaf area (LA), leaf dry matter content and LA of 67 species were obtained and each species was assigned to a strategy according to the CSR (Competitive, Stress-Tolerant or Ruderal) scheme. A community-functional signature was calculated for each year. Also, a parallel ordination of plots strategies composition in time was performed to confirm functional shift trends. Results Initial successional phases were dominated by ruderal and competitive species. Thereafter, the communities went through a phase of increasing heterogeneity of strategies, which was followed by dominance of competitive and stress-tolerant strategists in the later years. Parallel ordination confirmed the gradient of functional differentiation through time. Conclusions The change from ruderal/competitive to stress-tolerant and competitive species with time suggests that the most recent lahar event played a major role in sorting species according to their tolerance for disturbances. Thereafter, a major trend has been the gradual shift from ruderal to stress-tolerant species (conifers and alpine grasses).