Meinzer 9419500 Transpiration, or evaporation of water from the leaves of plants, is a biological process that has a large impact on our physical environment through its effects on soil water storage, atmospheric water content, and the distribution of rainfall. Little is known about how plant species in tropical forests partition and regulate their use of soil water in time and space, yet such information is critical for predicting the effects of deforestation and climatic fluctuations on the water balance of tropical as well as temperate regions. The overall goal of this research is to determine how water movement along a continuum from the soil through plants to the atmosphere is regulated in contrasting types of tropical forest plants such as upper canopy trees, characteristic of mature forests, and forest gap colonizing plants, which may be representative of regrowth after harvest. The project will be carried out at three sites operated by the Smithsonian Tropical Research Institute in Panama. The relative roles of external environmental factors and inherent plant traits in the regulation of water use will be characterized. The research will provide unique, detailed information about how soil water resources in a seasonally dry environment are shared in time and space among different types of plants. General patterns that emerge will be applicable to temperate zone forests and other plant communities as well as tropical forests. The findings will contribute to our ability to predict how water use by vegetation at the stand and regional scales is influenced by species composition and should constitute a valuable contribution to the data necessary to make informed decisions in watershed management.
