[Quantitative characteristics and distribution pattern of living and dead standing trees of secon-dary forest in Guandi Mountain, northern China].

Based on the survey data from a 4 hm secondary forest plot in the Pangquangou Nature Reserve, Guandi Mountain, Shanxi Province in 2010 and 2015, we analyzed the quantitative characteristics, distribution pattern, and correlation of living and dead standing trees during five years from four aspects, including species composition, diameter class structure, spatial pattern, spatial correlation between different diameter classes of living standing trees and dead standing trees, and intercorrelation between different diameter classes of dead standing trees. The results showed that there were 25811 living standing trees with DBH≥1 cm in the plot in 2010, belonging to 30 species, 22 genera, and 11 families. The distribution of individual diameter class was an inverted "L" type, and the number of individuals decreased in a fracture pattern with the increases of diameter class. During the five years (2010-2015), a total of 2145 dead standing trees were formed, involving 12 species, 10 genera, and 5 families. Most of the dead standing trees were distributed in diameter of 5-10 cm. At the scale of 0-50 m, the spatial distribution of living and dead standing trees was generally similar, indicating that the spatial pattern of dead standing trees was limited by that of living standing trees to some extent. The spatial correlation analysis of each diameter class of dead standing trees and living standing trees showed that with the increases of individual diameter class of trees, the intensified competition for space resources might be the main reason for the generation of dead standing trees. With the increases of diameter class of dead standing trees, the spatial correlation between living and dead standing trees was weakened to varying degrees, indicating that environment might be the key factor for the formation of large diameter class of dead standing trees. For the the dead standing trees, there was an obvious positive correlation between 5 cm≤DBH<20 cm dead standing trees and DBH<5 cm dead standing trees, between 10 cm≤DBH<20 cm dead standing trees and 5 cm≤DBH<10 cm dead standing trees, and between DBH≥20 cm dead standing trees and 5 cm≤DBH<20 cm dead standing trees. Our results indicated that dead standing trees would impact the subsequent dying of living standing trees.