Carbon and Nitrogen Stable Isotope Abundance and Soil Stoichiometry of Zanthoxylum planispinum var. dintanensis Plantations of Different Ages

Abstract

Understanding the relationships between carbon; nitrogen, their stable isotopes δ13C and δ15N, and soil stoichiometry may further our understanding of the regulatory mechanisms of the soil quality index on the equilibrium on isotopic fractionation. Four plantations of Zanthoxylum planispinum var. dintanensis (5–7, 10–12, 20–22 and 30–32 years) in the karst plateau gorge area, Guizhou Province, China, were selected to determine the variation characteristics and interactions between leaves, leaf litter, soil carbon (C), soil nitrogen (N) and their isotopes with plantation age, and to explore the relationship between soil stoichiometry and the isotopes δ13C and δ15N. The results were as follows: (1) the δ13C in leaves, litter, and soil were −28.04‰ ± 0.59‰, −26.85‰ ± 0.67‰, and −19.39‰ ± 1.37‰, respectively. The contents of δ15N were 2.01‰ ± 0.99‰, 2.91‰ ± 1.32‰, and 3.29‰ ± 0.69‰, respectively. The contents of δ13C and δ15N were ranked in the order, soil > litter > leaf. (2) With increasing plantation age, the soil 13C decreased; the leaf and the litter δ15N increased first then decreased, and the litter δ13C and the soil δ15N did not vary significantly. (3) The litter layer was positively correlated with soil δ13C and negatively correlated to δ15N. (4) Redundancy analysis showed that the soil microbial biomass carbon (MBC) and the bacteria/fungi (BAC/FUN) were the dominant factors affecting the natural abundance of C and N isotopes