Dynamics of soil inorganic nitrogen and their responses to nitrogen additions in three subtropical forests, south China

J Environ Sci (China). 2006;18(4):752-9.

Abstract

Three forests with different historical land-use, forest age, and species assemblages in subtropical China were selected to evaluate current soil N status and investigate the responses of soil inorganic N dynamics to monthly ammonium nitrate additions. Results showed that the mature monsoon evergreen broadleaved forest that has been protected for more than 400 years exhibited an advanced soil N status than the pine (Pinus massoniana) and pine-broadleaf mixed forests, both originated from the 1930's clear-cut and pine plantation. Mature forests had greater extractable inorganic N pool, lower N retention capacity, higher inorganic N leaching, and higher soil C/N ratios. Mineral soil extractable NH4(+)-N and NO3(-)-N concentrations were significantly increased by experimental N additions on several sampling dates, but repeated ANOVA showed that the effect was not significant over the whole year except NH4(+)-N in the mature forest. In contrast, inorganic N (both NH4(+)-N and NO3(-)-N) in soil 20-cm below the surface was significantly elevated by the N additions. From 42% to 74% of N added was retained by the upper 20 cm soils in the pine and mixed forests, while 0%-70% was retained in the mature forest. Our results suggest that land-use history, forest age and species composition were likely to be some of the important factors that determine differing forest N retention responses to elevated N deposition in the study region.

MeSH terms

  • Analysis of Variance
  • Carbon / analysis
  • Environmental Monitoring / methods*
  • Hydrogen-Ion Concentration
  • Nitrates / pharmacology*
  • Nitrogen / analysis*
  • Nitrogen / chemistry
  • Phosphorus / analysis
  • Soil / analysis*
  • Time Factors
  • Trees* / metabolism
  • Tropical Climate

Substances

  • Nitrates
  • Soil
  • Phosphorus
  • Carbon
  • Nitrogen
  • ammonium nitrate