Plant and soil δ13C and δ15N are linked to community biomass, litter production, and litter turnover rate in mature subtropical forests

Abstract

The natural abundance of 13C and 15N can integrate information on the dynamics of C and N, respectively. This study tested whether and how δ13C and δ15N of the plant and soil samples (including leaf, forest floor litters, fine roots, and 0–15 cm mineral soil) can detect local variations in community biomass, litter production, and litter turnover rate were explored in eight mature subtropical forests in southern China. Community biomass, litter production, and litter turnover rate were significantly positively correlated with each other and revealed similar correlations with other plant and soil parameters. Leaf δ13C was significantly negatively correlated with litter production, suggesting the stomatal regulation of leaf gas exchange. Similar correlations were also observed for δ13C of the mineral soil and other plant materials. Leaf and forest floor litters δ15N were positively correlated with community biomass, litter production, and litter turnover rate. Such correlations were significantly positively mediated by soil availability of P rather than N, as demonstrated by the multiple regression analysis. In contrast, fine roots δ15N was not related significantly to community biomass, litter production, or litter turnover rate. Significant differences in δ13C and δ15N among forests were related to the species composition, topography conditions, and land use history. Our results suggest that δ13C and δ15N of most plant and soil samples can indicate local variations in community biomass, litter production, and litter turnover rate in mature subtropical forests. Better understanding of these linkages could significantly improve our knowledge of C and N dynamics in forest ecosystems.