Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (3): 563-569.DOI: 10.3773/j.issn.1005-264x.2009.03.015

• Research Articles • Previous Articles     Next Articles

EFFECTS OF NITROGEN ADDITION ON NET NITROGEN MINERALIZATION IN LEYMUS CHINENSIS GRASSLAND, INNER MONGOLIA, CHINA

ZHANG Lu1,2, HUANG Jian-Hui1, BAI Yong-Fei1, HAN Xing-Guo1,*()   

  1. 1Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2008-09-08 Accepted:2009-01-15 Online:2009-09-08 Published:2009-05-31
  • Contact: HAN Xing-Guo

Abstract:

Aims Our objective was to examine the response of soil nitrogen mineralization in natural grassland to N addition, which is pertinent to global N deposition and grassland fertilization management.

Methods We began a long-term N addition experiment in 2000 in typical steppe, Leymus chinensis community, in Inner Mongolia of China, at four N addition levels: control (N0), 5 g NH4NO3·m-2 (N1.75), 30 g NH4NO3·m-2 (N10.5) and 80 g NH4NO3·m-2 (N28). In 2002, soils were collected from two adjacent sites ― A and B (fenced since 1979 and 1999, respectively), with simultaneous fertilization. The soils were incubated under optimal temperature (25 °C) and moisture (60% of water holding capacity (WHC) ) in the laboratory to examine effects of nitrogen addition on the potential net N mineralization in 5 weeks by using a periodically leaching method.

Important findings Nitrogen addition significantly influenced accumulated mineralized nitrogen (Nm) in all plots of the two grassland sites. The highest N addition level (N28) was associated with the lowest Nm, whereas the N1.75 had the highest Nm among the four nitrogen addition levels. Accumulated nitrate nitrogen in N0 and N1.75 was higher than ammonium nitrogen, but that was not the case at the higher N addition levels (N10.5, N28). N addition significantly decreased soil pH value, but no significant correlations were found between Nm and soil pH value, total organic C or total N. N addition causes higher Nm at site A (fenced from 1979) than at site B (fenced from 1999).

Key words: net nitrogen mineralization, nitrogen addition, Leymus chinensis community, Inner Mongolia, land use history