Litter decomposition and nutrients dynamics in Nothofagus antarctica forests under silvopastoral use in Southern Patagonia.

HA BAHAMONDE; PL PERI; R ALVAREZ; A BARNEIX; A MORETTO; G MARTÍNEZ PASTUR

AGROFORESTRY SYSTEMS

SPRINGER

Año: 2012 vol. 84 p. 345 - 360

0167-4366

The litter decomposition and its subsequent nutrient release are fundamental process in nutrient cycles (Lambers et al., 1998). Nutrients release-immobilization in decomposing organic matter is affected by micro environmental factors (temperature and humidity of air and soil) as well litter quality (chemical composition) and organisms availability (Swift et al., 1979). Different forests uses may alter the nutrient flows, and therefore their productivity in the long term (Imbert et al., 2004). In Patagonia, ñire (Nothofagus antarctica (G. Forster) Oerst.) forests have been used mainly as silvopastoral systems where thinning increase understorey forage production by increasing available photosynthetic active radiation (PAR). There are evidences reporting that canopy opening modified micro environmental factors as air temperature (Chen et al., 1999), soil temperature (Morecroft et al., 1998), soil humidity (Schroth and Sinclair, 2003), physicochemical characteristics of soil (Ostertag and Hobbie, 1999; Hobbie and Gough, 2004) and these may modify the litter decomposition process. Furthermore Peri et al. (2008) reported that in N. antarctica forests under silvopastoral use decreased litter fall compared to primary forest, and consequentely modify the amount of humus in the forest soil. In this system, the litter quality is modified by changing the proportion of ñire leaves (decrease) and understorey species (increase) annually incorporated into the soil with contrasting chemical elements such as carbon, nitrogen and lignin which have been related to differences in rates of litter decomposition (Swift et al., 1979; Melillo et al., 1982; Aerts, 1997). There are antecedents of litter decomposition in Nothofagus pumilio forests with different structures (Caldentey et al., 2001), altitudinal gradients (Frangi et al., 2005), and for Nothofagus oblicua, N. pumilio and N. dombeyi leaves decomposition and nutrient release in Chilean Andes (Decker and Boerner, 2006).