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Concentrations of different nitrogen forms in gaps of natural Pinus koraiensis mixed forest in Xiao Xing’anling Mountains.

JIANG Yi1, CHEN Li-xin1**, DUAN Wen-biao1, BU Fan1, SUN Shuang-hong1, LI Fan-fan1, XU Yi-fan2   

  1. (1College of Forestry, Northeast Forestry University, Harbin 150040, China; 2Heilongjiang Xinnong Agricultural Development Limited Company, Qiqihar 164800, Heilongjiang, China; 3Guilin University of Technology, Guilin 541004, Guangxi, China)
  • Online:2014-12-10 Published:2014-12-10

Abstract: The concentrations of different nitrogen (N) forms in soil (ammonium N (NH4+-N), nitrate N (NO3--N), total soluble N (TSN), soluble organic nitrogen N (SON), microbial biomass N (MBN) and total N (TN)) were investigated under gaps with different sizes in three Korean pine (Pinus koraiensis) mixed forests (i.e., TiliaKorean pine mixed forest, sprucefirKorean pine mixed forest, and birchKorean pine mixed forest) in Xiao Xing’anling Mountains. The results showed that organic N was the dominant form of TN, accounting for more than 98% of TN. Concentration of NO3--N was higher than that of NH4+-N, and SON concentration were higher than NH4+-N and NO3--N. Concentrations of NH4+-N, NO3--N, SON and MBN showed significant differences between large and small forest gaps and between forest gaps and closed forests. Especially, MBN was in the order of closed forests > small gap > medium gap > large gap, showing a significant negative correlation with gap size. NO3--N/TN and MBN/TN decreased with the increase of gap size in the three forests. NH4+-N/TN, TSN/TN and SON/TN decreased with the increase of gap size in the TiliaKorean pine mixed forest gaps and sprucefirKorean pine mixed forest gaps, but increased with the increase of gap size in the birchKorean pine mixed forest gaps. Significant correlations were observed between TSN and SON in forest gaps and closed forests. NH4+-N was significantly correlated with NO3--N and MBN in forest gaps, but such relationships were not found in the closed forests.

Key words: Potentilla fruticosa, subalpine meadow, spatial pattern, slope aspect, spatial correlation