Phenology and growth responses of evergreen shrubs and deciduous trees in the dry forest of central Argentina.

LERNER, P. D.; DORNES, P.F.; CARBONELL SILLETTA, L. M.; GALLIA M.C.

Milwaukee

Conferencia; Phenology 2012 Conference; 2012

University of Wisconsin

Significant alterations in phenology and growth have been related to increasing temperatures and rainfall changes of the recent decades, and most of these evidences come from the Northern Hemisphere regions. Climatic projections predict increases of 1.7 - 3.9 °C in the mean temperatures and in the summer rainfalls over this century for the south-eastern South America. In the dry forests of central Argentina, responses to temperature and rainfalls may be different between the expanding evergreen shrub Condalia microphylla and the deciduous tree Prosopis caldenia, typical dominant of these forests. It is presented preliminary results of a long term study having as main goal to assess the effects of temperature and precipitation dynamics on phenology and growth of evergreen and deciduous plants in two sites of dry forest of P. caldenia trees with high densities of C. microphylla shrubs. At each site, phenology and growth of new stems were monitored every 15-30 days in 10 plants, from leaf-unfolding to the end of the most active growing period during 2011-2012 season. Leaf-unfolding onset, leaf peak date, flowering onset, flowering peak date and relative growth rates for different periods were estimated and their relationships with temperature and precipitation data measured in each study site were analyzed. The maximum intensity of leaf production was related with rising temperatures of spring in both species, although C. microphylla had another two peaks related with cumulative summer rainfalls and temperature around 20 ºC. Flowering peak intensity was higher in C. microphylla (90%) than in P. caldenia (3%). With increasing cumulative summer rainfalls, relative growth rates were higher in C. microphylla than in the P. caldenia. Dry conditions and high temperatures restricted stem growth and produced dieback of many C. microphylla stems. Plants with contrasting life strategies may respond with different sensitivity to the drivers of global change impacting on the dry forests of central Argentina and have consequences for community structure and functioning of the ecosystems.