Variations of Nitrogen-15 Natural Abundance in Three Plants and Soils from the Typical Karst Peak Cluster Depression, South Guizhou, China

Abstract

The stable nitrogen (N)isotope ratio (δ15N) of soils and plants is a powerful indicator to reflect synthetical information of ecosystem N process. In this article, we study the δ15N values of soils and plants in the typical karst peak cluster depression, South Guizhou, China. The composition of stable N isotope as well as N content in the samples were determinated. The results presented that plant N content followed the order: stem N < branch= root < litter < leaf, and the N content of soil in the sampling site II(0.06%) was significant lower than the sampling siteI(0.10%)and III (0.08%).The natural 15N isotope distribution pattern was overall consistent in all tested plant species, and for δ15N values of plant tissues, litter = leaf < branch = root < stem. The δ15N values (6.1) in 0-30cm soils were the lowest than those in 30-60cm (11.3) and 60-90cm (11.6) soils. With soils and plants N content increasing, their δ15N values significantly decreased (P < 0.001). Our results suggested that the three plant species may have a similar mechanism of δ15N storage and utilisation, however, different tissues showed obvious difference for N process.