A multi-proxy dendroecological analysis of two tropical species (Hymenaea spp., Leguminosae) growing in a vegetation mosaic
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- Locosselli, G.M., Buckeridge, M.S., Moreira, M.Z. et al. Trees (2013) 27: 25. doi:10.1007/s00468-012-0764-x
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Tree species use a variety of strategies to obtain resources. As a result, semi-deciduous forest species and cerrado species can grow in close proximity and in the same climate, while occupying very different vegetation types. The aim of this study was to understand the dynamic responses of Hymenaea courbaril, a forest species, and Hymenaea stigonocarpa, a cerrado species, to annual climatic variation and increasing atmospheric CO2 concentrations under the same macroclimatic conditions. To that goal, we constructed chronologies of tree-ring width, vessel area, and intrinsic water-use efficiency (calculated from tree-ring δ13C content) for Hymenaea trees growing in a mosaic of the two vegetation types. Our analyses revealed that both species responded to climatic variation in similar ways, but with different intensities and at different times of year. Climate models showed that precipitation had a stronger effect on tree-ring width and earlywood vessel area of H. courbaril and temperature was slightly more determinant for H. stigonocarpa. In addition, both species showed increasing intrinsic water-use efficiency over the last five decades, but only individuals with reduced growth rate presented this trend, suggesting that those specimens in favorable growth conditions do not respond to the atmospheric CO2 enrichment. Despite the trend in water-use efficiency found in some individuals, it did not reflect in a higher growth rate. The differences between the two species documented by us may be due to divergent sources of hydrological stress in the two vegetation types.