Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 8, issue 8
Biogeosciences, 8, 2341–2350, 2011
https://doi.org/10.5194/bg-8-2341-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Nitrogen and global change

Biogeosciences, 8, 2341–2350, 2011
https://doi.org/10.5194/bg-8-2341-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 26 Aug 2011

Research article | 26 Aug 2011

Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

L. Song1, X. Bao1, X. Liu2,1, Y. Zhang1, P. Christie3,1, A. Fangmeier4, and F. Zhang1 L. Song et al.
  • 1College of Resources and Environmental Sciences, Key Laboratory of Plant–Soil Interactions of the Ministry of Education, China Agricultural University, Beijing 100193, China
  • 2State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences (CAS), Urumqi 830011, China
  • 3Agri-Environment Branch, Agri-Food and Biosciences Institute, Belfast BT9 5PX, UK
  • 4Institute of Plant and Landscape Ecology, University of Hohenheim, 70593 Stuttgart, Germany

Abstract. Chinese grasslands are extensive natural ecosystems that comprise 40 % of the total land area of the country and are sensitive to N deposition. A field experiment with six N rates (0, 30, 60, 120, 240, and 480 kg N ha−1 yr−1) was conducted at Duolun, Inner Mongolia, during 2005 and 2010 to identify some effects of N addition on a temperate steppe ecosystem. The dominant plant species in the plots were divided into two categories, grasses and forbs, on the basis of species life forms. Enhanced N deposition, even as little as 30 kg N ha−1 yr−1 above ambient N deposition (16 kg N ha−1 yr−1), led to a decline in species richness. The cover of grasses increased with N addition rate but their species richness showed a weak change across N treatments. Both species richness and cover of forbs declined strongly with increasing N deposition as shown by linear regression analysis (p < 0.05). Increasing N deposition elevated aboveground production of grasses but lowered aboveground biomass of forbs. Plant N concentration, plant δ15N and soil mineral N increased with N addition, showing positive relationships between plant δ15N and N concentration, soil mineral N and/or applied N rate. The cessation of N application in the 480 kg N ha−1 yr−1 treatment in 2009 and 2010 led to a slight recovery of the forb species richness relative to total cover and aboveground biomass, coinciding with reduced plant N concentration and soil mineral N. The results show N deposition-induced changes in soil N transformations and plant N assimilation that are closely related to changes in species composition and biomass accumulation in this temperate steppe ecosystem.

Publications Copernicus
Download
Citation
Final-revised paper
Preprint