Shifting cultivation is the principle land use strategy in the Maya Forest of lowland Central America. This practice includes slash-and-burn forest clearance, followed by corn (milpa) cultivation. Next, fields are allowed to fallow before they are re-cleared and planted again. Shifting cultivation has been identified as a cause of tropical deforestation and, alternatively, as a sustainable agricultural strategy that is well adapted to tropical landscapes. This project combines methods from physical geography, aquatic ecology, and stable isotope biogeochemistry to evaluate the impact of shifting cultivation on ecosystem structure and function in the Temash River watershed, southern Belize. Remote sensing analysis of land use/land cover change will assess the spatial distribution of land uses in the watershed and the impact of shifting cultivation on land cover. A soil survey of forested areas, active cornfields, and fallow fields will examine hypotheses related to soil organic matter (SOM) sources and turnover, and the impact of changing forest cover on carbon dynamics within the SOM pool. Riverine particulate organic matter will be used to track the effect of forest-to-milpa conversion, with respect to organic matter transfer across the terrestrial-aquatic boundary. Finally, nutrient (nitrogen and phosphorus) concentrations will be measured in streams of undisturbed and cleared riparian regions of the watershed throughout the year. This comparison will provide insights into seasonal nutrient dynamics in these running waters, and whether humans alter aquatic nutrient dynamics through land use change.
This research will address how shifting agriculture impacts tropical aquatic ecosystems. It will also examine how land use changes affect carbon, nitrogen, and phosphorus dynamics in streams and rivers of the lowland tropics. The Temash River is located in the Sarstoon-Temash National Park, which is currently co-managed by inhabitants within the watershed. This research will provide a founding document for development of an aquatic ecosystem management plan for the national park. It will also inform residents about the impact of their land use practices on aquatic ecosystem structure and function with the Temash River watershed.
