UPPERMOST SOIL HORIZONS OF NOTHOFAGUS PUMILIO FORESTS FROM THE ECOTONE AREA OF TIERRA DEL FUEGO (ARGENTINA) AS NUTRIENT RESERVOIRS

SUSANA PEÑA-RODRÍGUEZ; XABIER PONTEVEDRA-POMBAL; NATALIA ORO; ALICIA MORETTO; JOSÉ RACEDO; JULIO ESCOBAR; EDUARDO GARCÍA-RODEJA GAYOSO; JUAN CARLOS NÓVOA-MUÑOZ

Santiago de Compostela

Congreso; MANAGED FORESTS IN MANAGED FORESTS IN FUTURE LANDSCAPES FUTURE LANDSCAPES: IMPLICATIONS FOR WATER AND CARBON CYCLES; 2011

SOCIEDAD ESPAÑOLA DE CIENCIAS DEL SUELO

The study of available macro- and micronutrients in the uppermost soil horizons of Nothofagus pumilio (lenga) forests is an issue scarcely addressed compared to C storage, although these nutrients influence the growth of young lenga trees after forest management and their loss should be avoided. Litterfall is the main source of nutrients to lenga soils and the stored amount depends on tree density and age, madurity, height, etc., which define the stand quality site (Martínez-Pastur et al., 1997). This study assess available macro- (C, N, P, K, Ca, Mg) and micronutrients (Fe, Mn, Cu, Zn)contents in uppermost soil horizons of four lenga stands differing in site quality. A comparison between organic (Oi+Oe+Oa) and uppermost mineral horizons (A) in terms of available nutrients content is checked to show the relevance of organic horizons as nutrient reservoirs. The effects of forest site quality in nutrient storage are also assessed. In organic horizons, ranges of total carbon and nitrogen were 170-295 and 6.6-11.4 g kg-1 respectively, approximately 3 and 4 times higher than in A horizons. Calcium is the most abundant exchangeable base cation in organic (35-44 cmolckg-1) and A horizons (10-16 cmolckg-1). Exchangeable K mean values in organic horizons (1.7-2.3 cmolckg-1) were two times higher than in A horizons (0.7-1.1 cmolckg-1). Available Zn and Mn mean contents were 10 and 5 times higher in organic than in A horizons, whereas available Cu was approximately twice in organic regard mineral horizons and no differences were found for available Fe. A Student t-test showed that all nutrients, unless available Fe, were significantly higher (p=0.01)in organic than in mineral horizons supporting the role of organic horizons of lenga soils as nutrient reservoirs, strengthening the importance of their conservation when natural regeneration is expected after forest management. An ANOVA test showed that nutrient contents did not differ significantly among standa with different forest quality site as defined by Matínez-Pastur et al. (1997). Thus, for a sustainable management, practices on soil nutrient conservation are recommended in any forest independently of their potential productivity.