Study On Structure And Adjustment Of Larch And Spruce-Fir Stands

Larch-spruce-fir (Larix olgensis-Picea jezoensis-Abies nephrolepis) is a special forest with great importance in Changbai mountain area. Stand structure features of the forest were analyzed in the study. Results showed that tree species composition had some changes during 20 years. Larch has been dominant in stock volume and the number; spruce and fir was the second; and broadleaved tree species was the least. Proportion of stock volume for larch and fir was increased to 61% and 16% in 2006 from 56% and 14% in 1987, respectively. But the proportion of spruce was lowered to 7% from 9%. Other tree species presented little changes. The ratio of conifer to deciduous trees was changed to 0.87 from 0.83. The number of trees with large and medium diameter class was increased. Specifically, the proportion of large, medium and small diameter classes in volume were 0.12:0.61:0.27 in 2006 and 0.03:0.32:0.65 in 1987.Different distribution functions including normal distribution, Weibull distribution, Gamma distribution, Beta distribution and log normal distribution were calibrated for diameter distribution of the forest. Weibull distribution reported the best model performance. The q value was decreased to 1.36 from 1.48. The mean was 1.43.Spatial structure analysis showed that the stand was clumped distribution. Average mingling was 0.64, which was regarded as medium. Larch gave lowest spatial isolation but highest dominance whose value was 0.61. Conifer was dominant in diameter at breast height.Management objective and target structure of larch-spruce-fir forest was proposed according to stand structure characteristics and local requirements. Long-term target structure was planned as uneven-aged, multi-layer and mixed forest. The function was the combination of timber production and ecological service that produced timber with large diameter class. Indicators of stand structure were also discussed in detail based on current stand characteristics and research findings.Scenarios on stand structure transformation were developed in three stages for realizing target structure. Tree structure units will firstly be filtered through parameters on spatial structure, and then referenced trees will be judged as cutting or not with the basis of the status of referenced trees and neighbor trees. It is called the structure unit filter method for stand structure adjustment. Special cutting standards were put forward for dominant and planted larch. The study provided a basis for sustainable management of larch-spruce-fir forest.