Land protection and timber harvesting along productivity and diversity gradients in the Northern Rocky Mountains

Understanding the complex and reciprocal ways in which ecosystem functions (such as productivity) and biodiversity interact may provide important insights into sustaining ecosystem services and protecting species diversity. Despite years of research, observed relationships between productivity and biodiversity have been varied and hypotheses explaining patterns are diverse and equivocal. The ways in which patterns of productivity-biodiversity relationships can inform conservation may depend on understanding how gradients in human land use map onto gradients of productivity and biodiversity. Here, we used diverse publicly available spatial datasets on ecosystem productivity, tree diversity, climate, and land cover to explore two broad questions in ecoregions of Montana: (1) what is the relationship between productivity and tree diversity and (2) are land use gradients (from timber harvesting to wilderness protection) related to gradients of productivity and diversity? We also investigated the possible climatic and topographic drivers of these ecological and anthropogenic patterns. We found the most productive ecoregions support greater numbers of tree species, which appears to be influenced by precipitation but not temperature gradients. The most productive and diverse ecoregions included greater amounts of timber harvesting disturbance and associated road densities. The amount of protected area within ecoregions was highest at intermediate levels of productivity and diversity and was strongly related to mean elevation of ecoregions. Our results suggest that climate-influenced productivity gradients may influence patterns of biodiversity and are related to patterns in human land use. Further, given the existing conditions and current distribution of protected areas, we recommend that the most altered productive and diverse ecoregions may offer opportunities both for additional protection and for holistic restoration programs.