Twentieth century changes of tree ring isotopes in Southeastern Brazilian forests: how do climate conditions influence growth and water use efficiency and thus enforce tree migration

Resumo

According to the Intergovernmental Panel on Climate Change the global surface temperature has continuously risen since 1861. Increasing temperatures combined with changing precipitation patterns result in a more active and more intense hydrological cycle. Combined with the continuously increasing atmospheric CO2 concentration, trees will undoubtedly be influenced. Tree-rings have shown to be very well suited for environmental reconstruction and represent a powerful tool to study ecophysiology of trees. They represent mostly annually resolved and widely distributed environmental archives and are easily sampled. Besides traditional tree-ring width analysis, isotopic ratio of stable elements, such as U13C and H180, have been established as valuable proxies for ecophysiological studies. The objective of this study is to quantify the natural long- term reactions of trees to a rising CO2 concentration and climate change patterns with regard to water use efficiency (WUE) and transpiration on a regional scale. The emphasis will be on a tropical transect across South-eastern Brazil. This should pave the way for elucidating the tree development of the past and for predicting tree dynamics in particular tree growth in a climatically changing world. To that aim, two tree species: Cariniana estrellesis and Hymenaea courbaril will be sampled in a transection of three sites in the State of Sao Paulo. Five trees per species will be sampled in each sampling site, always looking for the oldest individuals. Tree-rings will be dated, and a-celluloses will be extracted from each tree-ring to proceed 13C and 18C analysis. Long-term stable isotope patterns will be evaluated in yearly resolved chronologies. Intra-annual information will be accessed with a 12 parts tree-ring sampling. The intra tree-ring samples will be done in only two years of the chronologies constructed. (AU)