Landscape-scale effects of geomorphological heterogeneity on variability of oak forest structure and composition in a monogenetic volcanic field

Background: Eruptive events in monogenetic volcanic fields create mosaics of lava fields that result in different successional times and stages, and environmental conditions. Such geomorphological heterogeneity may be related to patterns of vegetation structure, diversity, and composition across a landscape.

Aims: To examine landscape-scale effects of geomorphological heterogeneity on the spatial variability of oak forest structure and composition in a monogenetic volcanic field.

Methods: We sampled oak forests in six geomorphological units within a monogenetic volcanic field in El Tepozteco National Park and carried out redundancy analyses to relate environmental variables to forest composition and structure.

Results: Geomorphological heterogeneity explained 28.8 and 25.7 % of the variation in canopy structure and composition, respectively, and 21.6% of the variation in understorey composition. Exposed rock was the most important predictor of understorey composition and canopy structure, while elevation was a better predictor of canopy composition. The role of chronic human disturbance as a driver of forest composition and structure was minor compared to that of geomorphological heterogeneity.

Conclusions: The geomorphological heterogeneity created by volcanic activity in this landscape drives oak forest variability; however, considerable unexplained variation in vegetation traits remains, which could be associated with unmeasured dimensions of environmental heterogeneity, neutral processes, and the effects of long-term human activity in the area.