LTREB: Evaluation of Landscape Patterns in Ecosystem Processes in Detrital-based Tropical Streams

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0075339PringleThe primary objective of this LTREB project is to understand the link between surface-subsurface water interactions and ecosystem processes in tropical streams in lowland Costa Rica. The focus is on how nutrient-rich groundwater affects microbially-mediated decomposition processes in streams where decomposing organic matter is the primary food source for higher trophic levels. The PI's will examine how landscape patterns in stream solute chemistry, resulting from variation in solute-rich groundwater inputs, affect patterns in growth and secondary production of stream-dwelling insects. First, the hypothesis that landscape-scale variation in insect secondary production is affected by inter-stream variation in the proportion of geothermally modified ground water will be tested. Second, to isolate the effects of phosphorus, a whole stream P enrichment study will be continued to evaluate phosphorus effects on insect growth rates, insect secondary production, rates of leaf decomposition, and microbial activity associated with leaf decomposition. Whether or not these processes become N limited as P availability increases will also be determined. The proposal studies will be the first to determine the long-term effects of nutrient enrichment in a detrital-based stream in the wet neotropics. In addition, this research will continue to build the only long-term data set on stream solute chemistry in primary lowland rainforest in Central America. Stream solute chemistry and ecosystem process-oriented data are of fundamental importance to understanding and management of tropical forest and in predicting effects of regional and potentially global environmental change on these threatened ecosystems. This long-term program has provided, and will continue to provide, critical information for other ecosystem studies, along with numerous opportunities for undergraduate and graduate research.