Dr. Lara-Peña, Carlos

This study assessed natural variation in the macroinvertebrate assemblages (MIB) and water quality in one of the main basins with the largest agricultural activities in Chile (Aconcagua River Basin). We sampled throughout the annual cycle; nine sampling sites were established along the basin, classifying according to agricultural area coverage as least-disturbed, intermediate, and most-disturbed. We collected 56 macroinvertebrate taxa throughout the entire study area. Multivariate analysis shows significant differences among the three disturbance categories in different seasons, both water quality variables and the MIB structure. Distance-based linear model (DistLM) analysis for all seasons explained more than 95.9% of the macroinvertebrate assemblages, being significantly explained by chemical oxygen demand, pH, total coliforms, nitrites, elevation, and water temperature. ANOVA test revealed significant differences in the proportion of noninsect individuals, macroinvertebrates density, and the number of taxa among the three disturbance categories (p < 0.05). In general, water temperature, conductivity, chemical oxygen demand, ammonium, nitrites, and nitrates increased their values downstream in the basin. Our results indicate that the elevation gradient and increment in agricultural land use in the basin had a strong influence on water quality and MIB. A better understanding of these ecosystems could help conservation and integrated watershed management.

Using 19 years of remotely sensed Enhanced Vegetation Index (EVI), we examined the effects of climatic variability on terrestrial vegetation of six protected areas along southwestern South America, from the semiarid edge of the Atacama desert to southern Patagonia (30∘S–51∘S). The relationship between satellite phenology and climate indices, namely MEI (Multivariate ENSO Index), PDO (Pacific Decadal Oscillation) and SAM (Southern Annular Mode) were established using statistical analyses for non-stationary patterns. The annual mode of phenological activity fluctuated in strength through time from the semiarid region to the border of southern Patagonia. Concomitantly, enhanced synchrony between EVI and climatic oscillations appeared over interannual cycles. Cross correlations revealed that variability in MEI was the lead predictor of EVI fluctuations over scales shorter than 4 months at lower latitudes and for the most poleward study site. The PDO was correlated with EVI over lags longer than 4 months at low latitude sites, while the SAM showed relationships with EVI only for sites located around 40∘S. Our results indicate that the long-term phenological variability of the vegetation within protected areas along southwestern South America is controlled by processes linked to climate indices and that their influence varies latitudinally. Further studies over longer time scales will be needed to improve our understanding the impacts of climate change on vegetation condition and its effect over phenological variability.