Shifts in trait means and variances in North American tree assemblages: species richness patterns are loosely related to the functional space

摘要: One of the key hypothesized drivers gradients in species richness is environmental filtering, where stress limits which from a larger pool gain membership local community owing to their traits. Whereas most studies focus on small-scale variation functional traits along gradient, effect large-scale filtering less well understood. Furthermore, it has been rarely tested whether factors that constrain niche space limit total number coexisting species. We assessed role shaping tree assemblages across North America north Mexico by testing hypothesis colder, drier, or seasonal environments (stressful conditions for plants) trait diversity and thereby richness. geographic patterns relationships pattern using comprehensive set range maps. focused four plant reflecting major life history axes (maximum height, specific leaf area, seed mass, wood density) climatic variables (annual mean seasonality temperature precipitation). significant spatial shifts means variances null model approach. While we found species’ values at grid cells, cells did not deviate expectation. Measures harshness (cold, dry, climates) lower were weakly associated with reduction variance mass area. The height density was, however, opposite. These findings do support more stressful universally America. Environmental does, structure assemblage composition, selecting certain optimum under given conditions.