Shrub encroachment alters topsoil C:N:P stoichiometric ratios in a high-altitude forest cutover

Abstract

The effect of shrub encroachment on soil carbon (C): nitrogen (N): phosphorus (P) stoichiometric ratios are largely still unknown. We investigated this effect and the effect of shrub size in a high altitude forest cutover among four common shrub species: Cerasus trichostoma, Ribes glaciale, Rosa omeiensis and Salix sphaeronymphe. The difference in topsoil C:N ratio between meadows and shrub islands was greatly influenced by shrub species and plant sizes. Topsoil N:P and C:P ratios were always higher in shrub islands than in meadows, irrespective of shrub species and plant size. The expansion of shrubs merely increased the topsoil C:N ratio beneath Cerasus and Rosa, and increased the topsoil N:P and C:P ratios beneath the four shrub species. The increase in stoichiometric ratio followed an identical pattern among the four shrub species as shrub size increased. There were always higher topsoil C:P and N:P ratios beneath Ribes than under the other shrub species with the same plant size. This study clearly suggests that the effect of shrub islands on soil C:N:P stoichiometric ratios was dependent on shrub species and size. Our results are conducive to clarifying the currently confusion in secondary successional trends of soil C:N:P stoichiometry.