| The litter leaf is recognized as the critical pathways of organic matter and nutrient flux in forest ecosystems, and it is an important part of ecological functions of ecosystem. The research was carried out in the forest litter fall of the broadleaved-Korean pine mixed forest, the station as Liang shui national Nature Reserve during October 2008 to November 2009. Four N addition treatments in three replicates (three plots) were established:NO (0 kgNhm-2·a-1), N1(30 kgNhm-2·a-1),N2 (60 kgNhm-2·a-1) and N3 (120 kgNhm-2·a-1). The amounts, components and seasonal dynamics of the litter and decomposition rate, the characteristics of nutrient element release during their decomposition were investigated.The annual litter fall production in total was distinct between four N treatment plots. And their total litter fall production were estimated to be 3978.61 kg·hm-2 for the control (NO), 3689.71 kg·hm-2 for N1,3956.51 kg·hm-2 for N2 and 4357.12 kg·hm-2 for N3, respectively. The litter fall production decreased in the following order:N3>N0>N2>N1. Variance analysis showed that high levels of N deposition (N3) increased the amount of the litter fall, while the low to medium N loads (N1 and N2) reduced the quantities to some extents and both showed no statistically significant difference (P>0.05). Annual litter production in our research were within the range of Frigid Zone reported, while they were less than that of temperate zone, subtropical and tropic, which indicated that litter amount was characteristic of zonal. The amount of various components in the litter decomposition for the four plots and their proportion in the total litter production showed significantly different. Litter leaves were the primary composition. Seasonal rhythm of the total litter fall production showed "single peak type" patterns for N0, N1, N2 and N3 treatments, with its maximum occurring in October, while the litter fall production for different treatments showed no significant difference (P>0.05).Remaining rate of litter leaves decreased with the decomposition time for different levels of N deposition. Decomposition rate after 242 d during the litter decomposition is quicker than that of 242 d before. We found that decomposition coefficient was between 0.15 and 1.26 by Olson models. Time needed for the decomposition proportion in fifty percent and ninety-five percent in litter leaves was 0.71-4.82 a,2.54-20.37 a, respectively. The additional N treatments inhibited the decomposition rate of litter leaves to some extents but no statistically significant difference (P>0.05).Phosphorus release in litter leaves under different treatments had various patterns during the decomposition. It showed enrichment for Betulla costata for low N levels (N1), and release for the control, medium and high levels (N0, N2 and N3). All litter leaves represented enrich for Pinus koraiensis, Fraxinus mandshurica and mixed leaves during the decomposition except for mixed leaves for NO and N2 treatments, which displayed enrichment release pattern. Potassium concentration could be divided into two stages during the decomposition. Potassium concentration decreased at first and then increased. The release pattern for Betulla costata and mixed leaf showed enrichment and that for Fraxinus mandshurica displayed release-enrichment pattern except for NO treatment, while the litter leaves of Pinus koraiensis appeared complicated. Nitrogen of litter leaves for Betulla costata and Fraxinus mandshurica displayed release pattern finally under different N treatment, and that for Pinus koraiensis changed slowly for N0, N3 treatments, while it showed enrichment for N1 and N2 treatments. Nitrogen of mixed leaf changed slightly. C remaining rate of litter leaves declined continuously during the decomposition, displaying release mode in all treatments.C/N ratio of litter leaves decreased with decomposition time under different N treatments. The decomposition and remaining rate of the litter leaves, C/N ratio and release rate of dry matters (P<0.05) were negatively correlated (P<0.05).The results indicates that Carbon, and C/N ratio could be regarded as good indexes to judge the litter decomposition rate.
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