Environmental controls of primary production in the Argentine pampas: an analysis based on wheat crops and remotely sensed data.

VERÓN, S.,; PARUELO J. M.; SALA, O.E; LAUENROTH, W.K.

ECOSYSTEMS (NEW YORK. PRINT)

SPRINGER

Lugar: Berlin; Año: 2002 vol. 5 p. 625 - 635

1432-9840

We studied the aboveground net primary productivity(ANPP) of wheat crops in the Argentine Pampas.Our specific objectives were to determine (a)the response of ANPP to changes in water availability(b) the regional patterns of ANPP and (c) theinterannual variability and environmental controlsof ANPP. We used ground and satellite data toaddress these questions. Wheat ANPP was calculatedas the ratio between grain yield and harvestindex. We developed a simple model that took intoaccount environmental and genetic improvementeffects upon harvest index. We used the normalizeddifference vegetational index (NDVI) as a surrogatefor ANPP at the county level. Straight-line regressionmodels were fitted to single-year and averagevalues of ANPP and precipitation to derive temporaland spatial models for wheat. For grasslands, weused spatial and temporal models already published.At any given site, there was no differencebetween modeled wheat and grassland averageANPP. The response of ANPP to changes in interannualwater availability decreased along the precipitationgradient when vegetation structure (forexample, species composition, density, and totalcover) was held constant (wheat crops). WheatANPP and total production variability, estimatedfrom remotely sensed data, decreased as mean annualprecipitation (MAP) increased. The percentageof soils without drainage problems was the variablethat explained most of the wheat ANPP spatial variabilityas shown by stepwise linear regression. Precipitationvariability accounted for 49% of wheatANPP variability. Remotely sensed estimates ofANPP variability showed lower and wheat ANPPhigher temporal variability than annual precipitation.