Abstract:

Objective: The univariate and bivariate distribution characteristics of stand space structure were studied, and the stand stability in the mixed oak-pine forest under structure-based forest management was also analyzed, in order to provide the scientific basis for the implementation and evaluation of structure-based forest management in Quercus aliena var. acuteserrata mixed forest. Methods: The natural mixed oak-pine forest in Daganzigou, Baihua forest Farm, Xiaolongshan nature reserve, Gansu Province, as object was studied. In 2012, one 50 m×50 m, two 30 m×30 m and three 20 m×20 m fixed plots were established, the total station (TOPCON-GIS-602AF) was used to locate each tree with a diameter of more than 5 cm in all plots and investigate its species, diameter, height and crown. After those, one 50 m×50 m and two 30 m×30 m plots were used for structure-based forest management, and others plots were used for without any management as control. In 2017, the characteristics of stand spatial structure in managed and unmanaged plots were compared by the stand spatial structure parameters, such as uniform angle, dominance and mingling. The nine indicators of mixed oak-pine forest were selected as the parameters to construct the stability evaluation system, and stand stability was evaluated by the new rule of π value method of optimal stand state. Results: 1) The stand trees of managed plots before operation were close to aggregated distribution, and the stand trees of managed plots after five years of operation were randomly distributed, however, the stand trees of unmanaged plots were always presented an aggregated distribution. Simultaneously, the proportion of highly mixed by species in managed forest after five years of operation was increased by 10.4% compared with the managed forest before operation, the proportion of highly mixed by species in unmanaged forest grown for five years was increased by 5.5% compared with the unmanaged forest before five years. 2) Bivariate distribution of spatial structural parameters showed that the proportion of micro-structure that was the four or three neighbours were of different species to the reference tree and had a random distribution pattern in managed stand was higher than unmanaged stand, and the proportion of micro-structure that was the reference tree was dominant and surrounded by different species in managed stand was higher than unmanaged stand, on the whole, the proportion of micro-structure that was dominant and four neighbours had a random distribution pattern was not obviously different between unmanaged and managed stand. 3) Unit circle analysis of stand status showed that the ω value of managed forest after five years of operation was increased 27.09% compared with the managed forest before operating, the stand status was from poor to good, while theωvalue of unmanaged forest grown for five years was increased 13.24%, but the stand status was always poor. Conclusion: The trees of structure-based managed stand has a reasonable distribution and highly mingling, and dominant wood in highly mixed. Meanwhile, stand status of structure-based forest managed presented at a good level, which shows higher stand stability.

Key words: spatial structure, rule of π value, stand state, mixed oak-pine forest, Xiaolongshan