Paruelo, J. M., O. E. Sala, and A. B. Beltrán. 2000. Long term dynamics of water and carbon in semi-arid ecosystems: A gradient analysis in the Patagonian Steppe. Plant Ecology 150:133-143. (Abstract)

------We used a soil water simulation model and remote sensed data to study the long-term dynamics of transpiration, evaporation, drainage and net primary production across a precipitation gradient in Northwestern Patagonia (Argentina). The proportion of precipitation transpired, the precipitation use efficiency and the transpiration use efficiency were constant across the gradient. The proportion of water evaporated was higher than the proportion drained at the driest extreme of the gradient. The opposite pattern was observed at the wet extreme. The seasonal pattern of water losses was similar across the gradient. Seasonal evaporation and transpiration losses were negatively correlated. Transpiration peaked during spring when simultaneously water availability and leaf area index are high. Evaporation was maximum during winter when water availability in the upper layer of the soil is high. ------The relative variability of water losses and carbon gains showed an exponential decrease across the precipitation gradient. The coefficient of variation of transpiration, evaporation and ANPP was, in general, lower than the CV of annual precipitation. This pattern suggests a buffering capacity of the ecosystem. The ecosystem would be able to dump fluctuations in the availability of resources.