Tropical dry forests are the most endangered tropical ecosystem. They are also poorly understood, particularly with regard to ecosystem structure, site productivity, nutrient cycling, and resilience following fire. This study will investigate biogeochemical mechanisms in intact, and cut and burn tropical dry forests at Chamela Biological Station, Mexico. The research will focus on pools, flows and losses of phosphorus, nitrogen and carbon, but with particular emphasis on phosphorus because of the distinctive role of phosphorus as the limiting element for plant growth in this system. The principal investigators hypothesize that: (1) a pattern of pulsed nutrient release occurs in soils under intact forest and that this pattern is substantially altered following fire, (2) soil organic reactions mediated by plant and microbial biological activity are fundamental for maintaining phosphorus availability in this system, (3) deforestation and fire cause substantial, and nearly irreversible net losses of phosphorus, nitrogen, and carbon from the system, and (4) repeated burning and/or very severe fires (high biomass consumption) will result in declining long-term site productivity. The researchers will quantify nutrient dynamics and experimentally manipulate both intact forest and fire severity to examine the mechanisms that control cycling and losses of these elements. Results of these studies will be used to validate and further develop simulation models. These models will be used in synthesis work, to examine long-term patterns of forest productivity, and to estimate the effect of fire caused phosphorus, nitrogen and carbon losses from this system. The principle investigators are well-qualified to do this work and the facilities are excellent.
