Intraspecies competition among Chinese pine(pinus tabulaeformis)in a level terraced forest of China's hilly and gully loess plateau

Forests with level terracing in Wuqi were chosen to study intraspecies competition among Chinese pine(pinus tabulaeformis)trees using an improved individual competition model. Results indicated the following: (1)within the pine plantation, the optimal growth distance was 2. 8m, which of 0-2cm lower diameter size was 4. 0m, but it did not change obviously with the diameter size increasing; (2)as the spacing increased, the number of neighbor trees became more and the total intraspecies competition intensified, but the trend of intensified became weaker. Model of the total competition intensity and interference zone was: Cl=a+bL-1; (3)The competition intensity decreased gradually with the DBH increasing, the model was Cl=aD-b. The competition between the pines was greatest among trees with diameters of up to ~2cm. Findings indicated that trees in this size range should thinned to a spacing pattern of approximately 2. 8m, which will improve the health and stability of the pine forest.