Long term dynamics of water and carbon in semi-arid ecosystems: an analysis in the Patagonian steppe

PARUELO J. M.; SALA, O.E; BELTRÁN, A.B.

PLANT ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2000 vol. 150 p. 133 - 143

1385-0237

We used a soil water simulation model and remotely 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 useefficiency were constant across the gradient that covered a range of 150 to 600 mm. The proportion of waterevaporated was higher than the proportion drained at the driest extreme of the gradient. The opposite relationshipwas observed at the wet extreme.Two important characteristics of arid-semiarid systems dominated by winter precipitation emerged from ouranalyses: the importance of drainage losses and the asynchrony between evaporation and transpiration fluxes. Thesecharacteristics of the water dynamics influence the relative abundance of plant functional types and are crucial togenerate heterogeneity at the landscape level. The coefficient of variation (CV) of transpiration, evaporation andANPP was, in general, lower than the CV of annual precipitation. This pattern suggests a buffering capacity of theecosystem. The ecosystem would be able to damp at the functional level inter-annual changes in the availability ofresources.