Direct and indirect effects of climate on decompositionin native ecosystems from central Argentina

PÉREZ HARGUINDEGUY, NATALIA; DÍAZ, SANDRA; VENDRAMINI, FERNANDA; GURVICH, DIEGO EZEQUIEL; CINGOLANI, ANA MARÍA; GIORGIS, MELISA ADRIANA; CABIDO, MARCELO

AUSTRAL ECOLOGY

Año: 2006 vol. 32

1442-9985

Climate affects litter decomposition directly, through temperature and moisture, determining the ecosystem potential decomposition, and indirectly, through its effect on plant community composition and litter quality, determining litter potential decomposition. It would be expected that both direct and indirect effects of climate on decomposition act in the same direction along gradients of actual evapotranspiration (AET). However, studies from semiarid ecosystems challenge this idea, suggesting that the climatic conditions which favours decomposer activity, and in consequence ecosystem potential decomposition, do not necessarily lead to litter easier to decompose. We explored the decomposition patterns of four arid to sub-humid native ecosystems with different AET in central-western Argentina and we analysed if ecosystem potential decomposition (climatic direct effect), nutrient availability and leaf litter potential decomposition (climatic indirect effect) all increased with AET. In general, the direct effect of climate (AET) on decomposition (i.e. ecosystem potential decomposition), showed a similar pattern to nutrient availability in soils (higher for xerophytic and mountain woodlands and lower for the other ecosystems), but different from the pattern of leaf litter potential decomposition. However, the range of variation in the ecosystem potential decomposition was much higher than the range of variation in litter potential decomposition, indicating that the direct effect of climate on decomposition was far stronger than the indirect effect through litter quality. Our results provide additional experimental evidence supporting the direct control of climate over decomposition, and therefore nutrient cycling. For the ecosystems considered, those with the highest AET are the ecosystems with the highest potential decomposition. But what it is more interesting; our results suggest that the indirect control of climate over decomposition through vegetation characteristics and decomposability does not follow the same trend as the direct effect of climate. This finding has important implication in the prediction of the effects of climate change on semiarid ecosystems.