SOIL ORGANIC MATTER IN AN ALTITUDINAL GRADIENT, pp. 347-356
Authors: (Bente Foereid, Kim Harding, The Macaulay Institute, Craigiebuckler, Aberdeen, UK)
Abstract: The question of how climate change will affect carbon storage in grasslands is important, as it could lead to tipping points in the climate system. Most of the carbon in grasslands is stored in the soil, and this is also the most permanent store. The main question is how temperature affects soil organic matter development and decomposition. Some authors have found no effect, but this may be because the temperature under which the soils developed needs to be taken into account when assessing the temperature sensitivity of soil organic matter decomposition. Temperature decreases rather uniformly with altitude, and we used an altitudinal gradient as a temperature gradient. We sampled soils from an altitudinal gradient in four heath and grass covered Scottish mountains. Soil carbon content, carbon to nitrogen ratio and isotope ratios were correlated to altitude, plant cover and other soil parameters. The soils were then incubated for a year, and the change in these parameters over the incubation period where measured again and related to altitude and other factors. The results show that the most important environmental factors for the soil carbon and nitrogen content and isotope ratios were altitude and soil phosphorous. Plant species composition appeared unimportant. The changes over the course of the incubation were small, but they give weak support for the hypothesis that soils developed at low temperatures were least developed to start with, and therefore changed the most.