Responses of plant 15N natural abundance and isotopic fractionation to N addition reflect the N status of a temperate steppe in China. (19th November 2018)

• Record Type: Journal Article
• Authors: Sheng, Zhilu; Huang, Yongmei; He, Kejian; Borjigin, Narigele; Yang, Hanyue; Chen, Huiying; Li, Engui; Xu, Xia; Duan, Lei
• Is Part Of: Journal of plant ecology. Volume 12:Number 3(2019:Jun.)
• Page Start: 550
• Page End: 563
• Publication Date: 2018-11-19
• Subjects: N deposition -- 15N natural abundance -- temperate steppe -- N saturation; Plant ecology -- Periodicals; Phytogeography -- Periodicals; 581.705
• DOI: 10.1093/jpe/rty047
• Languages: English
• ISSNs: 1752-9921

Abstract

Abstract: Aims: Elevated anthropogenic nitrogen (N) deposition could alter N status in temperate steppe. However, threshold observations of N status change from N limit to N saturation by far are not conclusive in these ecosystems. Research on the natural abundance of 15 N (δ 15 N) could greatly help provide integrated information about ecosystem N status. The goal of this study was to investigate the suitability of measurements of δ 15 N of major ecosystem N pools and several key species, plant 15 N fractionation, together with key vegetation and soil indicators in response to N fertilization as a tool to identify the N status in a temperate steppe in Inner Mongolia. Methods: We carried out a N addition experiment during 2011–14 on a Stipa krylovii steppe in Inner Mongolia, Northern China. We investigated the response of several key N transformation processes, vegetation and soil properties to N addition. Aboveground biomass and belowground biomass (BGB) δ 15 N, root and foliar δ 15 N of three dominant species ( Artemisia frigida, S. krylovii and Leymus chinensis ), δ 15 N of soil total N and soil KCl-extractable NO3 − -N were determined. The responses of isotope fractionation during plant N uptake and reallocation to N addition were also determined. Important Findings: Our results suggest that the N addition rate of 5g N m −2 yr −1 could be regarded as threshold of early N saturation in this S. krylovii steppe as indicated by an increase in plant fractionation and a decrease in plant δ 15 N. When N input rate is >10 g N m –2 yr –1, increased N deposition can lead to an apparent reduction in species richness and BGB as well as an increase in NO3 − in extractable soil pools <30-cm soil profile. With N addition, S. krylovii and A. frigida undergo earlier N status shift from N limitation toward N excess compared with L. chinensis, contributing to L. chinensis out-competing other species. Overall, this study provides a better understanding of N status change in temperate steppe based on isotope evidence and several other functional variables and contributes to predicting the responses of temperate steppe to future global N deposition scenario.