Enhancing ecosystem function through conservation: threatened plants increase local carbon storage in tropical dry forests

The role of plant diversity, particularly of rare species, in ecosystem functioning (e.g., carbon storage) has been mostly studied in temperate systems with little practical application to the conservation of tropical forests, where species rarity and species richness tend to be greater and more important for ecosystem functioning. We linked carbon storage pools with functional plant diversity, occurrence of rare species, and environmental (topographic) gradients in a species-rich seasonally dry tropical forest protected as a part of a Biosphere Reserve in northwestern Mexico. We estimated various functional diversity and carbon pool measures from in situ plant community and soil data. Soil and total ecosystem carbon storage decreased with slope steepness but increased with plant height. Above-ground carbon was negatively associated with elevation. Our data suggest that species identity matters to the functioning and productivity of seasonally dry tropical forests. Two long-lived and highly threatened rare plant species contributed considerably (10-20%) to the above-ground carbon storage pool. The functional roles of threatened plant species should be investigated and incorporated into the management plans of Biospheres Reserves and other closely coupled natural-human systems, where conservation plays a significant role in ecosystem functioning and human well-being.