Elevation and vegetation influences on soil properties in Chilean Nothofagus forests

Kelly L.M Decker,R.E.J Boerner

doi:10.4067/s0716-078x2003000300003

Kelly L.M Decker, R.E.J Boerner

Open Access

https://doi.org/10.4067/s0716-078x2003000300003

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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.

Highlights

Upon approaching tree line along latitudinal or elevational gradients in the northern hemisphere, there is a marked shift in woody plant composition from deciduous to evergreen species
We hypothesized that soil pH and available P would decrease with elevation while organic C content would increase with elevation
Soil pH did not vary in any ecologically significant manner with elevation, and significant changes in available P with elevation were limited to a decrease observed in P in soils taken under N. obliqua that accounted for only 25% of the variance in P among those samples

Summary

Introduction

Upon approaching tree line along latitudinal or elevational gradients in the northern hemisphere, there is a marked shift in woody plant composition from deciduous to evergreen species This shift in leaf life span has long been attributed to long term selection for nutrient conservation and carbon acquisition in marginal habitats, such as those near tree line. Deciduous species of Nothofagus do dominate the lower foothills and are replaced by evergreen species at mid elevations, it is the deciduous species N. pumilio or N. antarctica that predominantly dominate near tree line The combination of this unexpected pattern of species distribution with elevation (from a northern hemisphere perspective), and the close evolutionary relationship of the sympatric Nothofagus species of this region presents an ideal opportunity to test hypotheses concerning how differences in leaf lifespan relate to soil properties, without the confounding problem of comparing evergreen gymnosperms to deciduous angiosperms

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