Remote sensing of protected areas to derive baseline vegetation functioning characteristics

Question: How can we derive baseline/reference situations to evaluate the impact of global change on terrestrial ecosystem functioning? Location: Main biomes (steppes to rain forests) of Argentina. Methods: We used AVHRR/NOAA satellite data to characterize vegetation functioning. We used the seasonal dynamics of the Normalized Difference Vegetation Index (NDVI), a linear estimator of the fraction of the photosynthetic active radiation intercepted by vegetation (f(PAR)), and the surface temperature (Ts), for the period 1981-1993. We extracted the following indices: NDVI integral (NDVI-I), NDVI relative range (R-rel), NDVI maximum value (V-max), date of maximum NDVI (D-max) and actual evapotranspiration. Results: f(PAR) varied from 2 to 80%, in relation to changes in wnet primary production (NPP) from 83 to 1700 g.m(-2).yr(-1). NDVI-I, Vmax and f(PAR) had positive, curvilinear relationships to mean annual precipitation (MAP), NPP was linearly related to MAP. Tropical and subtropical biomes had a significantly lower seasonality (R-rel) than temperate ones. D-max was not correlated with the defined environmental gradients. Evapo-transpiration ranged from 100 to 1100 mm.yr(-1). Interannual variability of NDVI attributes varied across the temperature and precipitation gradients. Conclusions: Our results may be used to represent baseline conditions in evaluating the impact of land use changes across environmental gradients. The relationships between functional, attributes and environmental variables provide a way to extrapolate ecological patterns from protected areas across modified habitats and to generate maps of ecosystem functioning.