Elevation and vegetation influences on soil properties in Chilean Nothofagus forests

Abstract

We measured net nitrogen mineralization, net nitrification, proportional nitrification, and total inorganic nitrogen, available phosphorus, and soil organic carbon in five Andean forested stands in an attempt to resolve the relative influence of elevation and forest canopy composition on soil organic matter and nutrient dynamics in this ecosystem type. Our five forested study sites were within a contiguous Nothofagus forest that ranged from 1,280 to 1, 700 m elevation in the central Chilean Andes. The five sites consisted of three single species stands, one each of the low elevation deciduous N. obliqua, the evergreen N. dombeyi, or the high elevation deciduous N. pumilio, as well as two mixed evergreen-deciduous stands. There was no statistically significant relationship of nitrogen mineralization or phosphorus with elevation. In contrast, there were statistically significant, though weak, negative relationships between elevation and net nitrification, proportional nitrification, soil pH and organic carbon. In general, soils from the N. obliqua stand had higher levels/rates of nitrification, soil organic carbon content, soil pH, and plant available phosphorus than soils form the other single species stands. In contrast, the N. dombeyi and N. pumilio stands had lower rates of nitrification and soil pH than did the N. obliqua stand. The evergreen-deciduous mixed stands tended to be intermediate in soil properties. These results demonstrate that vegetation, particularly the balance of evergreen and deciduous species, exerts stronger control over soil chemical and biochemical properties than the climate variations induced by 350 m in elevation, even where the evergreen and deciduous species are closely-related angiosperms.