| Strip clearcutting is a brand new method of moso bamboo forests logging,which has the advantages of high efficiency and low cost.The current research on bamboo forest strip cutting focuses on understory vegetation,soil physical and chemical properties,and the growth of new bamboo in the next year after logging.There are few studies on the spatial distribution and dynamic characteristics of bamboo forests after strip cutting.The spatial distribution greatly affects the growth,development and stability of the forest stand.Therefore,the research on the spatial distribution and dynamic characteristics of the bamboo forest after logging is of great significance to the evaluation of restoration of bamboo forests with strip logging.Compared with traditional moso bamboo forests survey methods,terrestrial laser scanning can efficiently,non-destructively and quickly obtain 3D point cloud data of moso bamboo forests.It provides a new method for bamboo forest investigation.Therefore,this article first uses the TLS technology to carry out the research on the extraction methods of the individual tree position,diameter at breast height,bamboo height,leaf area index and other parameters of the moso bamboo forest.On this basis,two major years data were used to clarify the spatial distribution characteristics and dynamic changes of five strip clearcutting(3m,5m,8m,12m,15m).It provides basic data support for the evaluation of the restoration of the strip clearcutting moso bamboo forests.The main conclusions of the study are as follows:1.Based on the plot-scale terrestrial laser scanning data,a new method based on morphological characteristics of Phyllostachys edulis for stem detection was developed with high accuracy.The accuracy of single wood detection is 100%,and the integrity of single wood detection can reach up to 91.93%.Compared with the two-dimensional curve and circle fitting(R~2=0.86),the cylindrical fitting according to the spatial distribution of the point cloud has a higher accuracy in fitting the diameter at breast height(R~2=0.91).TLS data was poor in estimating the height of Phyllostachys pubescara(R~2=0.70).Using terrestrial laser scanning data to extract the leaf area index of the Phyllostachys pubescens forest in the sample plot based on the voxel canopy analysis method,when the number of adjacent points n and the multiple of standard deviation K are set to 50 and 5,respectively,the voxel size is3cm×3cm×3cm When the time,the estimated leaf area index is the most accurate.2.Strip clearcutting affects the spatial distribution of moso bamboo.Four years after logging,the 3m,5m,12m,and 15m logging of moso bamboo were evenly distributed at small scales(under 0.25m).The 8m logging f moso bamboo was aggregated distributed at0.4m-0.9m scales,and moso bamboo in all logging at other scales is randomly distributed.From the first recovery period to the second recovery period,changes in the spatial distribution of moso bamboos in the logging.The 3m,8m and 15m logging of moso bamboo were uniformly distributed at small scales(under 0.25m),while the rest of the scales were randomly distributed;moso bamboo in the 5m logging changed from random distribution to uniform distribution at small scales(under 0.25m),and other scales remain unchanged;moso bamboo in the 12m logging was clustered at 0.2m-1.9m scales,and the other scales were consistent with the spatial distribution of the 3m logging.Moso bamboo in the 12m logging between the two major years has a positive correlation on the scale of 0.5m-0.6m,and the other logging have no obvious spatial correlation.3.The spatial distribution characteristics of diameter at breast height and biomass of moso bamboo in logging.The diameter at breast height and biomass of moso bamboo in the first recovery period of the 3m logging showed a discrete and random distribution pattern,and in the second recovery period and four years after logging showed a random distribution pattern.The diameter at breast height and biomass of moso bamboo in the first recovery period and four years after logging of 5m,8m and 12m logging showed an aggregated distribution pattern,and in the second recovery period showed a random distribution pattern.The biomass and DBH of moso bamboo in the first recovery period of the 15m logging showed a random distribution pattern,and in the second recovery period were clustered and randomly distributed.Four years after logging,the diameter and biomass of moso bamboo were distributed randomly and aggregated,respectively.4.The characteristics and changing trend of bamboo number,diameter at breast height,height,biomass and leaf area index of logging forests.Four years after logging,the number of moso bamboo in the order of which was 12m,15m,5m,8m,3m.The average diameter at breast height and bamboo height show a gradual decrease as the logging width increases.As the logging width increases,the biomass per unit area increases first,then decreases,and then increases.The average leaf area index of logging forests increased firstly and then decreased with the increase of the logging width,and the 8m logging was the largest.Compared with the first recovery period,the number of moso bamboo decreased,the average diameter at breast height and bamboo height increased significantly,and the difference in biomass per unit area was not significant in the second recovery period.This study proposes a new method for investigating moso bamboo resources,and illustrated the spatial distribution characteristics and dynamic changes of five strip clearcutting.The research results can provide a theoretical basis for the restoration and scientific management of the strip clearcutting moso bamboo forests. |
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