OOS 28

Functional, Phylogenetic and Genetic Dimensions of Forest Diversity and Change

Forests worldwide face multiple pressures because of shifts in temperature and precipitation, as well as deforestation and degradation due to land use change. Predicting how forest communities will be affected by future shifts in climate and land-use change remains a major challenge. The response of forests to climate change and land use will depend not only on species composition and diversity, but also on the functional diversity among species and the genetic variation within species. The talks in this session represent a major step towards a more mechanistic understanding of the drivers of tree species abundance, distribution, and demography across landscapes. Previous studies have focused on predicting how species distributions will be altered by global changes using niche based or climate-envelope models. However, current distributions may not reflect species' environmental tolerances. A more mechanistic approach is needed that uses information on individual or population-level variation in responses to environmental variables. This process-based approach is rare because it relies on detailed demographic or physiological data, which is lacking for most species. For example, in areas that will experience more frequent or severe droughts, shifts in species composition and diversity within communities will depend on the variation both among- and within-species in drought tolerance. Thus, an understanding of phenotypic plasticity and intraspecific genetic variation will more accurately predict the resilience of species and communities to changing climate. Session talks incorporate multiple dimensions of diversity that are key to predicting the resilience of forest communities to global change. Specific questions the talks will address include: (i) What functional traits underlie species' environmental tolerances and drive species’ distributions and dynamics? (ii) Does shared evolutionary history predict the distribution of functional traits among species and forest communities through space and time? (iii) How are species and functional diversity likely to shift under climate change? (iv) How much do functional traits and environmental tolerances vary among individuals within species, at both local and regional scales? And, to what extent is intraspecific functional variation due to phenotypic plasticity or genetic variation?