The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-four month research fellowship by Dr. Radika Bhaskar to work with Dr. Patricia Balvanera at UNAM in Mexico, and with Dr. Todd Dawson at the University of California, Berkeley in the US.
Due to their vulnerability and bio-complexity, tropical dry forests (TDFs) present a compelling system to assess functional diversity in the dry tropics and the effect of anthropogenic land use on ecosystem function. In TDFs, precipitation is strongly seasonal; within undisturbed stands, this temporal variability is associated with a highly diverse woody plant community with a wide spectrum of water use strategies accompanied by large variation in leaf phenology. This study addresses how land transformation and land-use history affect the loss and recovery of functional diversity, specifically related to plant water use and cycling. The objectives are two-fold: 1. To assess how land-use history influences community-level patterns of water use, and 2. To examine whether hydraulic trait variation is associated with leaf phenology and carbon gain. The research is conducted in and around the Biosphere Reserve in Chamela, Mexico, which contains well preserved TDF stands of high floristic diversity, as well as established research plots in abandoned agricultural fields representing regenerating forests at different ages since disturbance. In the first part of the study, traits related to water acquisition and use are measured from dominant species of mature stands and along a chronosequence of regenerating plots of 3 different ages. In the second study two aspects of functional diversity are examined in greater detail: hydraulic and leaf trait variation. This data is used to assess whether water use traits differ among leaf phenological groups, and how they correlate with photosynthesis. The hypothesis is that, rather than falling into distinct groups based on phenological functional types, interspecific variation in hydraulic traits will correlate with maximum seasonal water stress.
The proposed research will increase basic understanding of the coupling between hydraulic properties and leaf function, specifically leaf phenology and carbon gain. Instead of focusing on differences between phenological groups, this study will examine how species are arrayed along an axis of maximum seasonal water stress, and ask whether leaf traits co-vary. The little research that has been conducted in Chamela on the consequences of past land-use on abiotic resources has focused primarily on the changes to nutrient availability: its losses through soil erosion and through fire. This project focuses on another critical resource: water. These results will contribute to a general understanding of the functioning of tropical dry forest in terms of water storage and cycling and the effects of past-management on these key processes. Few studies have examined shifts in hydraulic traits in TDFs in relation to succession, and this project aims to fill this important science gap.
