Effects of soil chemical properties on trunk decay of Korean pine standing trees in Xiao Xing'an Mountains,northeastern China.

In order to study the relationship between soil chemical properties and decay of Korean pine standing trees, an investigation was carried out in Dailing Forest District of Xiao Xing'an Mountains of northeastern China. Eighteen rotten and nine healthy mature Korean pine standing trees were chosen as sample trees. One transverse section of each sample tree about 40 -50 cm above the ground was tested by Resistograph to determine its inner decay status. And soil of 200 g was obtained from root zones of each sample tree. Eight chemical indicators of soil including pH, organic matter, total N, hydrolyzed N, total P, available P, total K and available K contents were tested in soil analysis laboratory of Northeast Forestry University by chemical process. Relationship between standing tree trunk decay and the eight soil chemical indicators was analyzed using one-way analysis of variance and ordinary least square regression. The results indicated that decay degree of mature Korean pine standing trees had a significant positive correlation with organic matter content of soil (R2 = 0.615, P = 0.007), obvious non-linear correlation with pH of soil. Decay degree reached the maximum when pH equaled 5.58 and decreased when pH was far from this value. Total N, hydrolyzed N and available P contents of soil at the root zones of healthy standing trees were significantly higher than that of decayed standing trees because that an excess of N and P impeded the growth of wood decay fungi, and protected standing trees from being rotten. The optimal multi-variable linear regression equation included three soil indicators of pH, organicmatter and total N contents (R2 =0.758, P﹤0.01), showing a high degree of correlation and extremely significant relevance