Soil Nitrogen Form of Xiaoxing’anling Forest

In the forest ecosystems, nitrogen is one of the most important factor to limit plant growth, and it has important influence on the succession of forest communities. Nitrogen also plays an important role in the maintenance of the stability of the top communities, and maintain a certain percentage of tree species composition, and so on. This paper treats the biggest area zonal soil-dark brown soil of XiaoXingAnLing forest as the research object based on the sum of previous studies, in which stratified-bit sampling is used, to systematically analysis the distribution of various forms of nitrogen in Korean pine and secondary natural birch forest, the relation with various forms of nitrogen, organic matter、pH value、the forest types and the level. The major findings are as follows:(1)In Xiaoxing’anling Cold Water forestry area, the ammonium of forest dark brown soil is 8.31-70.32μg/g, nitrate is proximately 0.58-58.92μg/g, which is higher than previous findings significantly. The content of ammonium in natural secondary forest was higher than the original Korean pine forest, while the content of nitrate in original Korean pine forest was higher than the nitrate content in natural secondary forest. The anova analysis of ammonium, nitrate and water content showed that there were significant correlation (p<0.05), and the changing trend of ammonium, nitrate are the same as the water content trend at all levels.(2)The acid hydrolysis nitrogen took up 28.98%, and non-hydrolisis took up 71.02%, which is different from the former research. They are possibly related with the rich biological organic matter of dark brown soil, and their regional influence is also very big. In various components of acid hydrolysis organic nitrogenous, the amino acid nitrogen and the ammoniacal nitrogen occupy the entire nitrogen the proportion to be big (respectively are 14.36%,6.83%), the aminosugar condition nitrogen and the acidolysis unknown nitrogen occupy the entire nitrogen the proportion to be small (respectively are 4.13%,2.95%). At p<0.01 level, the components of organic nitrogen analysis showed that, amino acid nitrogen content did not have significant difference(p=0.0603) between 0-15cm layer and rhizosphere soil, the other components were significantly differences in litter matter layer,0-15cm layer, rhizosphere soil layer. In the same layer, each component show different relativity, in the litter layer, there was not significant difference(p=0.285) between the ammoniacal nitrogen and acidolysis unknown nitrogen, but they had significant difference with amino sugar nitrogen and amino acid nitrogen respectively; in 0-15cm layer, it does not exist significant difference in amino acids and ammonia nitrogen, amino sugar N and hydrolysable unidentified nitrogen (p=0.028and0. 119,respectively), while there were significant difference between them. In rhizosphere soil, there were significant differences between acidolysis unknown nitrogen and amino acid nitrogen, ammonia nitrogen, amino nitrogen content of sugar (p=0.001,0.001 and 0.003, respectively), but the latter three had no significant difference. (3) Whether in the original Korean pine forest or natural secondary forest soils, soluble organic nitrogen (SON) content of various levels in sequence had its order:litter> rhizosphere> 0-15cm of soil. Compared the same level between different forest types we found that, in the litter layer, 0-15cm layer, the content of SON in the original Korean pine forest soil was higher than the natural secondary forest, but opposite in the rhizosphere soil. In each layer, the SON/TN value in the original Korean pine forest was higher than the natural secondary forest. SON/TN in the two types of forest soil layers has the same order as follows:rhizosphere soil> 0-15cm> litter.(4) In the original Korean pine forest, the TFAA content is in the order as follows:litter>0-15cm layer>rhizosphere soil, while in the natural secondary forest was:litter>rhizosphere>0-15cm, TFAA content in the litter was much higher than in the soil. Due to the impact of TSN, SON and ammonium significant stratification difference, TFAA content in hierarchical differences also emerged:the litter layer>rhizosphere>0-l 5cm. TFAA content had significant difference between the litter layer and the rhizosphere,0-15cm layer of soil respectively (P=0.0003,0.007 respectively), however in rhizosphere soil and 0-15cm layer, TFAA did not reach significant different levels (P=0.291). Statistics between different materials on the same level, we found that:it does not exist significant differences between TFAA and NH4+-N,SON and TSN (p=0.067,0.440), but there was significantly differences between TFAA and SON,TFAA and TSN(p=0.0006,0.001), there was significantly differences between NH4+-N and SON,TSN (p=0.001,0.0008).(5) The content of alkali-hydrolyzable nitrogen in 0-15cm layer was the lowest in the original Korean pine forest and natural secondary forest soils, highest in the litter layer. The content of alkali-hydrolyzable nitrogen in each layers of natural secondary forest was higher than the corresponding layers of original Korean pine forest.(6) There were significantly correlated between the various forms of nitrogen (p<0.01), and organic matter had significant correlation with the various forms of nitrogen (p<0.01). In the p<0.05 level, there was significant correlation between pH and TFAA, which showed significant correlation with other forms of nitrogen (p<0.01).