Remote sensing of protected areas to derive baseline vegetation functioning characteristics

Abstract

Abstract: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 (fPAR), and the surface temperature (Ts), for the period 1981–1993. We extracted the following indices: NDVI integral (NDVI‐I), NDVI relative range (Rrel), NDVI maximum value (Vmax), date of maximum NDVI (Dmax) and actual evapotranspiration.Results: f PAR varied from 2 to 80%, in relation to changes in net primary production (NPP) from 83 to 1700 g.m‐2.yr‐1. NDVI‐I, Vmax and fPAR had positive, curvilinear relationships to mean annual precipitation (MAP), NPP was linearly related to MAP. Tropical and subtropical biomes had a significantly lower seasonality (Rrel) than temperate ones. Dmax was not correlated with the defined environmental gradients. Evapotranspiration 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.