Discriminating the biophysical signal from human‐induced effects on long‐term primary production dynamics. The case of Patagonia

IRISARRI, J. GONZALO N.; TEXEIRA, MARCOS; OESTERHELD, MARTÍN; VERÓN, SANTIAGO R.; DELLA NAVE, FACUNDO; PARUELO, JOSÉ M.

GLOBAL CHANGE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021 vol. 27 p. 4381 - 4391

1354-1013

The temporal trend of aboveground net primary production (ANPP) is frequently used to estimatethe human effect on ecosystems. In water-limited ecosystems, like most grazing areas in theworld, human effects act upon ANPP in combination with environmental variations. Our mainobjective was to quantify long-term (1981-2012) changes of ANPP and discriminate the causes ofthese changes between environmental and human at a subcontinental scale, across vast areas ofPatagonia. We estimated ANPP through a radiative model based on remote sensing data. Then,we evaluated the relation between ANPP and environmental interannual variations of twohierarchically related factors: ENSO, through the Southern Oscillation Index, SOI, andprecipitation. We described the human effect through the shape of the temporal trends of theresiduals of the environmental model (RESTREND) and quantified human relative impact throughthe RESTREND: ANPP trend ratio. ANPP interannual variation was significantly explained byENSO (through SOI) and precipitation in 65% of the study area. The Southern Oscillation Indexhad a positive association with annual precipitation. The association between ANPP and annualprecipitation was positive. RESTREND analysis was statistically significant in 92% of the areawhere the tested environmental model worked, representing 60% of the study area, and it wasmostly negative. However, its magnitude, revealed through the RESTREND: ANPP trend ratio,was relatively mild. Our analysis revealed that most of ANPP trends were associated with climateand that even when human density is low, its incidence seems to be mainly negative.