Temporal and spatial changes in soil micronutrients in managed Nothofagus pumilio forest of Tierra del Fuego, Argentina

摘要

Soil organic components are important factors in the quality and productivity of forest ecosystems. Timber harvesting reduces plant cover and the amount of organic matter in forest floor layer, increases surface runoff, soil erosion and alters microclimatic conditions over large areas. These changes can have important implications for nutrient cycling dynamics and soil organic matter mineralization. Fueguian temperate forests of Nothofagus pumilio (lenga) have been intensely harvested for the last decades, mainly by shelterwood-cut silvicultural system. Harvesting removes nutrients contained in logs from the site, modifies light, temperature and soil humidity, constraining nutrient cycling process. In this study, we evaluate available copper (Cu-a), zinc (Zn-a), iron (Fe-a), and manganese (Mn-a) concentrations and reservoirs in stands that represent a chronosequence and their respective primary forests (controls): stands cut 1 year ago, stands cut 5-10 years ago, and stands harvested more than 50 years ago. Concentrations of Zn-a and Cu-a in primary forest were 39.9 and 2.6 mg/kg, and increased in harvested sites to 60.5 and 3.2 mg/kg, respectively. Fe-a and Mn-a concentrations showed similar ranges in both harvested and control sites. Recent harvested sites showed the highest Cu-a concentrations. Micronutrient reservoirs showed similar ranges in both harvested and primary forests. We concluded that micronutrient availability changes at short term after forest harvesting; thus, the inclusion of soil fertility assessment in forest management plans should be incorporated to preserve the fertility of lenga forests soils and ensure sustainability.