The Chilean forestry industry is based on hundreds of thousands of hectares of Pinus radiata plantations that have been established in a variety of soil and climate conditions. This approach has resulted in highly variable plantation productivity even when the best available technology was used. Little information is known about the ecophysiology basis for this variability.We explored the spatial and temporal variation of stand growth in Chile using a network of permanent sample plots from Modelo Nacional de Simulación de Pino radiata. Wehypothesized that the climate would play an important role in the mmualvmiations inproductivity.To answer these questions we developed the following projects:1. Determination of site resource availability from historical data from automatic weather stations (rainfall, temperatures) anda geophysical model for solar irradiation,2. Detennination of peak annual leaf area index (LAI) for selected pem1anent sampleplots using remote sensing technologies,3. Analysis of soil, climate, canopy and stand factors affecting the Pinus radiataplantation growth and the use efficiency of si te resources.For project 1, we estimated solar irradiation using the r.sun, Hargreaves-Smnani (HS), andBristow-Campbell (BC) models and validated model estimates with observations fromweather stations. Estimations from a calibrated r.sun model accounted for 94 % of the variance (r2 = 0.94) in monthly mean measured values. The r.sun model performed quite well for a wide range of Chilean conditions when compared with the HS and BC models. Our estimates of global irradiation may be improved with better estimates of cloudiness as they become available. Our model was able to provide spatial estimates of daily, weekly, monthly and yearly solar irradiation.Por project 2, we estimated the inter-annual variation ofLAI (Leaf Area Index), using remote sensing technologies. We determined LAI using Landsat Thematic Mapper (TM) datacovering a 5 year period (2005-2009) for a network of permanent sample plots in Pinusradiata plantations in Chile. In 2009, we calculated LAI from ground measurements usingLI-COR LAI-2000 and TRAC instruments on each one hectare plot. These values of LAIwere regressed against Simple Ratio (SR), N01malized Difference Vegetation Index (NDVI)and Reduced Simple Ratio (RSR), derived from the TM 2009 data. Linear relationships werestrong with R2 values of 0.65 for SR, 0.61 for NDVI and 0.67 for RSR. Using the RSRrelationship, LAI values were estimated for the network of permanent sample plots of Pinus radiata plantations over the whole period.Por project 3, we examined enviromnental factors affecting growth rates of Pinus radiata in Chile. Water availability (as affected by precipitation, soil water holding capacity, and potential evapotranspiration) appeared to be the factor most limiting to leaf area and growth.Maximum growing season temperature also negatively affected growth. Sites with highest productivities had the lowest annual water deficits and the most productive sites used water and light more efficiently. Good si tes produced 1.6 as compared to 0.49 kg of wood per m3 of evapotranspired water for less productive sites. In addition, productive stands produced 0.5 as compared to 0.31 g ofwood per MJ for less productive sites.PFCHA-BecasDoctor en Filosofía157p.PFCHA-BecasTERMINADA