Study On Forest Structure Of Different Recovery Stages In Secondary Broad-leaved Forest On The Tiantai Mountain Of Western Sichuan Basin Border In China

In recent years, because of the deteriorating environment, the research on forest restoration and reconstruction had been paid progressively attention. The study of secondary succession community structure characteristics was valued to clarify community growth regularities and principles, and provide scientific basis for the restoration and reconstruction of degraded ecosystem in similar area. Taking 8 plots in the secondary broadleaved forest that located in Tiantai Mountain in the western margin of Sichuan basin as the study object with adopting spatial sequence instead of time successional sequence, we tried to explain the natural recovery and community development direction of the broadleaved forest in this area, and provide theoretical foundation to recover and reconstruct degenerating forest ecosystems in similar background. The results were shown below:(1)Based on main factors including shade tolerance, growth rate, the percentage of the actual average height and theoretical height, the community is divided into three recovery stages:Ⅰ:Acer franchetii Pax-Cornus controversa Hemsl.population;Ⅱ:Acer franchetii Pax-Ulmus castoneifolia Hemsl.population; Ⅲ:Acer franchetii Pax-Tilia nobilis Rehd.et Wils population.(2)The results of Tree species composition characteristics in different recovery stages showed that Species composition varies regularly with the overall performance of positive species gradual decrease and the neutral species gradual increase. With the recovery, the basal area per hectare increases steadily, and the stand density decreases before an increase.(3)The results of Diameter structure characteristics in different recovery stages showed that The diameter distribution in each phase is not strongly regulated, and there exists small fluctuations. The average diameter decreases before increases. The fitting effects of Weibull distribution function, the negative exponential distribution function and normal distribution function are not ideal. The Weibull model is more precise than the other models. Anthropogenic deforestation contributes to abnormal distribution of each high class and results in an uneven state, making the deviation increases beyond the error range of normal distribution testing.(4)The results of Tree height structure characteristics in different recovery stages showed that Forest tree height distribution tends to the unimodal distribution. With the succession, tree height changes regularly. The proportion of moderate height increases, while the percentage of maximum and minimum heights reduces.The stand average height increases gradually.The distribution curve moves to the left direction, kurtosis changes from positive to negative, and ultimately forms a wide and flat distribution. The fitting effects of Weibull distribution and normal distribution function to the tree height and stem number distribution are not ideal.(5)The results of Age structure characteristics in different recovery stages.showed that The proportion of saplings and mid-age trees reduces and the proportion of big trees rises.There is a tendency of developing from growth oriented community to the stable community.(6) The results of Spatial structure in different recovery stages showed that In terms of aspect of mingling intensity, the mingling of trees in the three stages is mainly moderate intensive or intensive. Mingling intensity increases first and then decreases. According to the layout view of the forest stand, the spatial distribution transits from clumped distribution to random distribution. From the view of comparison of space, no matter diameter or height, the number of tress in dominant status grows gradually. In order to explore deeper stand spatial structure, this study using bivariate distribution, Angle scale, mixed degree, two joint size score between the two. Results show that, with the recovery of mixed in strength and a random distribution proportion of tree number increases gradually, diameter at breast height and tree height in advantage state and well mixed forest tree number increased gradually, tree height and DBH in advantage state and the random distribution of forest plant increase gradually.