A shady business: Effects of pine afforestation on litter decomposition along a precipitation gradient in Patagonia, Argentina

ARAUJO P.I. Y A. T. AUSTIN

Congreso; Annual Meeting of the Ecological Society of America; 2012

ESA

Water availability is one of the primary regional controls on ecosystem processes in terrestrial ecosystems, and much attention has been paid to the observed linear relationship between mean annual precipitation and net primary production. Along spatial precipitation gradients, however, a lack of correlation with litter decomposition has been observed frequently and alternative controls have been postulated. Changes in plant life form, increased cover, and decreased incident solar radiation as precipitation increases may eclipse the direct effects of water availability on organic matter degradation. As these changes occur simultaneously along natural precipitation gradients, it is difficult to disentangle the relative importance of these controls. We took advantage of an unplanned natural experiment along a broad precipitation gradient (250-2200mm mean annual precipitation) in Patagonia, Argentina, where extensive areas of steppe and native forest have been converted to pine plantation of a single species (Pinus ponderosa). We established five paired sites, a natural vegetation site and a paired pine plantation of similar density and age. This particular design enabled us to explore how simultaneously changes in plant life forms and precipitation affect litter decomposition, but also, by disentangling these two factors, to isolate effects of precipitation and vegetation on C turnover. We conducted a litter bag experiment evaluating common litter substrates and in situ litter during two year period at all sites along the gradient.