A method for modeling volume of loblolly pine based on terrestrial laser scanning

Abstract

The application discloses a modeling method for timber volume of Taiwania flousiana based on ground laser scanning, and comprises the following modeling steps: S1, aerial photography of Taiwania flousiana forest panorama, selection of a research area and a test area, S2, collection of research data and test data of Taiwania flousiana respectively, S3, extraction of standing timber parameters, calculation of standing timber volume, S4, fitting of a volume equation, evaluation of fitting effect, and test of applicability of the volume table, wherein the Taiwania flousiana forest panorama is photographed before data collection, and according to the distribution of Taiwania flousiana, a peripheral area, a random middle area and a middle extension line corresponding area are selected as the research area, and trees in two extension line areas are reserved as the test area, so that the selected data is uniformly distributed, the inner and outer data are involved, the data collection efficiency is higher, the data is more abundant, the test data is selected through the extension line, subsequent test is facilitated, and subsequent modeling is more smooth.

Description

Technical Field

[0001] This invention relates to the field of forestry technology, specifically to a method for volume modeling of fallen fir wood based on ground laser scanning. Background Technology

[0002] Bald cypress is a deciduous tree species that is important for ecological protection, building materials, and landscaping. Since its introduction to Jiangsu in the last century, most of bald cypress trees have matured into forests and timber, providing significant ecological, economic, and social benefits. The bald cypress seed source introduction base in Linian Forest Farm, Donghai County, has been an important research subject for many years. Research and analysis over the past decade have shown that the 16 seed sources of bald cypress introduced to this area exhibit different growth characteristics. Some seed sources show excellent height growth, some show large volume growth, and some show large trunk taper. After nearly 10 years of management, the bald cypress trees in this experimental area have gradually entered the mature age. A volume table is a timber measurement table, a type of tree counting table. According to the object being measured, there are log volume tables, standing timber volume tables, and log volume tables. The use of bald cypress trees also needs to be monitored through the corresponding volume tables.

[0003] However, current volume models typically give little consideration to edge data when analyzing volume data. There are significant differences in the growth of trees at the edge of a forest compared to those in the middle, and they can only analyze the current volume of trees without analyzing subsequent volume trends. Summary of the Invention

[0004] This invention provides a method for volume modeling of *Pterocarya stenoptera* based on terrestrial laser scanning, which can effectively solve the problems of current volume models proposed in the background art, which usually give little consideration to edge data when calculating volume data, there is a large difference in growth between trees at the edge of the forest and trees in the middle, and can only analyze the current volume of trees without analyzing the subsequent volume trend.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for modeling the volume of *Cephalotaxus fortunei* based on terrestrial laser scanning, comprising the following modeling steps:

[0006] S1. Aerial view of the bald cypress forest to select the research and testing areas;

[0007] S2. Collect research data and test data of bald cypress separately;

[0008] S3. Extract standing timber parameters and calculate the standing timber volume;

[0009] S4. Fit the volume equation, evaluate the fitting effect, and verify the applicability of the volume table;

[0010] S5. Establish a cut model using the cut equation, and perform timber processing calculations based on the volumetric specifications;

[0011] S6. Create charts and graphs based on seed source data to study the data overview;

[0012] S7. Select the corresponding equation to obtain the univariate volume table, and verify the volume table to establish the volume model;

[0013] S8. Fit the selected cut equation, then calculate the yield and yield rate of the timber species, and establish the cut model;

[0014] S9. Summarize the volume model, predict volume trends, and optimize forestry management.

[0015] According to the above technical solution, in S1, firstly, a panoramic view of the bald cypress forest is taken by aerial photography, and photos of the top of the forest are taken from both vertical and horizontal planes to determine the distribution location of the bald cypress. The outer ring of the bald cypress forest is selected as the research area.

[0016] Then randomly select several 100m sections from the middle of the bald cypress forest. 2 The research area;

[0017] Finally, four straight lines were drawn outward from the center of the bald cypress forest. The areas covered by two of these lines were selected as the study area, and the areas covered by two more lines were selected as the test area.

[0018] According to the above technical solution, in step S2, based on the selected research object, the source and age of bald cypress in the research area are determined, the location of trees in the research area is collected using a scanner, and the ground diameter, diameter at breast height, upper diameter and tree height of the trees are measured using a measuring instrument as research data.

[0019] Then, a laser scanner is used to obtain the tree locations in the inspection area, and the diameter at breast height (DBH) and tree height are measured using measuring instruments as data for the inspection model.

[0020] According to the above technical solution, in step S3, the spatial location of the tree is determined by the tree location and tree height in the collected data, the three-dimensional structure of the tree is restored by the ground diameter, diameter at breast height and upper diameter, and the volume of a single standing tree is calculated.

[0021] According to the above technical solution, in step S4, commonly used volume equations are selected based on the collected research data, and a fitting is performed, and the correlation coefficient (R) is used to determine the volume equation. 2 ), average prediction accuracy (P), standard error of the estimate (S) EE Mean percentage standard error (M) PSE ), total relative deviation (T) RB ) and mean systematic deviation (M SB To evaluate the applicability of the volume table, data from six bald cypress trees in the test area that do not overlap with the study area were selected to test the applicability of the volume table.

[0022] According to the above technical solution, in S5, the taper equation describes the change in trunk shape and predicts the diameter at different tree heights. Using the diameter at breast height (D), tree height (H), and upper diameter (d) extracted from standing tree point cloud data, five taper equations are selected for modeling and parameter calculation. The model prediction effect is verified using a 10-fold cross-validation method. With the prediction model parameters already determined, all single-tree data used for modeling are randomly divided into n subsamples. One subsample is randomly selected as validation data and substituted into the subsequently fitted model for validation. The other n-1 samples are used for training. The validation is repeated 10 times, with each subsample validated once. The average of the n results is used to obtain the model estimate, and the correlation coefficient (R²) is used. 2 The optimal taper model is selected by using the residual sum of squares and Q-value as the selection criteria.

[0023] Based on the volume specifications, timber processing calculations were performed, and individual tree timber processing was conducted. The timber processing data of bald cypress was divided into four groups according to national standards: large-diameter timber, medium-diameter timber, small-diameter timber, and pulp timber.

[0024] According to the above technical solution, in step S6, the bald cypress trees in the study area are first classified according to their provenance, and the diameter at breast height, tree height and ground diameter of each provenance are recorded and compiled into a table.

[0025] Ground laser scanning was performed on standard trees in each provenance area to obtain standing points. Ground diameter, diameter at breast height, and tree height were extracted from the standing point cloud of bald cypress trees. The volume was calculated and summarized into a table according to the provenance.

[0026] A diameter distribution map was created for the diameter at breast height (DBH) of the standing trees in 5cm increments, and the DBH distribution of all standing trees showed a normal distribution.

[0027] A distribution map of the standing tree height was created based on a 2m tree height order, and the distribution of the total standing tree height showed a normal distribution.

[0028] Based on the measured diameter at breast height (DBH), the DBH of the bald cypress was extracted from the point cloud. The volume of each standing tree was obtained by the differential volume method and compared with the values ​​in the one-dimensional volume table of the main tree species in the data collection area.

[0029] According to the above technical solution, in step S7, the volume (V) calculated using point cloud data and the extracted diameter at breast height (D) are used to fit all candidate univariate volume equations. The fitting results are plotted into a chart, and the fitting effect, correlation coefficient, and relative deviation are analyzed. The corresponding equation is selected as the equation for constructing the univariate volume table of bald cypress, and the univariate volume table of bald cypress is obtained.

[0030] A univariate volume model was fitted to the standing data of bald cypress trees of the corresponding species. The volume table was tested using the analytical wood data. One analytical wood of each species was obtained. The data of the disk was consulted to calculate the bark-free volume of the felled trees at each age. The bark data of the disk was converted into the bark-inclusive volume of the corresponding diameter to complete the volume data. The volume data of the newly built bald cypress univariate volume table was retrieved and a scatter plot was drawn. The applicability F test of the model was performed and the test table was prepared.

[0031] According to the above technical solution, in S8, the bark diameter d, diameter at breast height D, and tree height H at any height h extracted from the point cloud of bald cypress trees are used to fit five taper equations, and the equation is selected as the taper equation of bald cypress based on the fitting results.

[0032] The cumulative length equation is derived from the established taper equation by fitting the curve of the univariate volume model, and the length of each diameter of timber in actual timber production is calculated. The volume of each diameter is derived by integration. The cumulative length, volume and yield of bald cypress timber produced by diameter class in the experimental area can be calculated using the above taper equation and the timber length and volume formulas of each timber species.

[0033] Using analytical wood data, the yield per tree of each species was calculated, the total yield within each species plot was calculated, and converted into the yield per unit area and the yield rate of each species.

[0034] According to the above technical solution, in S9, the model is verified by analyzing wood data, and the total timber yield and timber yield rate per unit area of ​​each seed source are calculated. Based on the comprehensive multi-trait research and analysis, the results can provide guidance for future afforestation, cultivation, logging and timber utilization.

[0035] We selected bald cypress trees of different ages from the same source, analyzed their volume, and plotted a volume curve and a scatter plot of the growth rate of timber output to analyze the volume.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. Before collecting data, a panoramic view of the bald cypress forest was taken. Based on the distribution of the bald cypress, the outer ring area, the random area in the middle, and the area corresponding to the extension line in the middle were selected as the study area. Trees in the two extension lines were reserved as test areas. This ensured that the selected data were evenly distributed and included both internal and external data, making the data collection more efficient and the data richer. The test data were selected by using the extension lines to facilitate subsequent testing and make the subsequent modeling process smoother.

[0038] 2. Summarize the timber volume of trees according to their age and draw timber volume curves and scatter plots of timber output growth rates. This allows us to understand the timber output of trees at different age stages and predict the timber output trend of younger trees. Based on the prediction of subsequent timber output, we can plan the timing of tree harvesting, achieve reasonable planning, and optimize the effectiveness of forestry management.

[0039] 3. Extracting standing tree structural parameters to establish a univariate volume model and taper model for bald cypress in the study area, compiling a univariate volume table and a species yield table, and harvesting one standard bald cypress tree of each source to produce analytical timber as test data. By establishing a suitable univariate volume table for the tree species, calculating the species yield, and calculating the diameter of the timber with the largest yield, combined with previous research results, we can determine the tree species that can be promoted, which will help to accurately manage the tree species and meet the current multi-purpose and multi-functional needs of forest resource monitoring. Attached Figure Description

[0040] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0041] Figure 1 This is a diagram showing the selected research area of ​​this invention;

[0042] Figure 2 This invention provides a table of the diameter distribution of standing trees;

[0043] Figure 3 This invention provides a table of the distribution of standing tree heights.

[0044] Figure 4 This invention provides a scatter plot of point cloud-extracted breast diameter and manually measured breast diameter.

[0045] Figure 5 This is a comparison chart of the volume of bald cypress logs and the volume of a single unit in this invention;

[0046] Figure 6 This is a fitting curve diagram of the one-dimensional volume model of the present invention;

[0047] Figure 7 This is a scatter plot of the wood data analysis used in this invention to verify the univariate volume table;

[0048] Figure 8 This is a graph showing the yield curve of this invention;

[0049] Figure 9 This is a scatter plot of the material output growth rate of this invention;

[0050] Figure 10 This is a flowchart of the modeling steps of the present invention. Detailed Implementation

[0051] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0052] Example: Figure 1 , 10 As shown, the present invention provides a technical solution, a method for modeling the volume of fallen fir wood based on ground laser scanning, comprising the following modeling steps:

[0053] S1. Aerial view of the bald cypress forest to select the research and testing areas;

[0054] The study area is located in Linian Forest Farm, Donghai County, Jiangsu Province. The experimental plot of *Cephalotaxus fortunei* involved 16 provenances, comprising 96 plots. Each plot had 4 rows, with 6 trees per row and a spacing of 2.0m × 3.3m. Container seedlings were used for planting. The afforestation was completed in 1993. Previous research in 2006 yielded conclusions regarding the growth characteristics of various provenances in the experimental area: provenances 6, 8, 9, 10, 12, and 13 showed better volumetric growth; all provenances had relatively large average taper, with provenances 4, 5, 14, 16, and 17 exhibiting particularly good taper characteristics; and aboveground biomass... The most abundant sources are 4, 6, 17, and 30. Based on this, this study focuses on pure stands of bald cypress trees from six sources (4, 8, 10, 14, 17, and 30). These six sources are from Arkansas OM National Forest, Mississippi RF, Mississippi No. 5 Tree, Louisiana NR, Tennessee HCO, and Jigongshan, Henan Province. First, a survey of all blocks was conducted. Tree factors for each source were measured in four plots using a diameter at breast height (DBH) measuring rod and height measuring instrument. One average standard tree was selected based on the average DBH.

[0055] First, take aerial panoramic photos of the bald cypress forest and vertical and horizontal photos of the top of the forest to determine the distribution of the bald cypress. Then, select the outer ring of the bald cypress forest as the research area.

[0056] Then, several 100m2 study areas were randomly selected from 96 plots of the bald cypress forest;

[0057] Finally, four straight lines were drawn outward from the center of the bald cypress forest. The areas covered by two of these lines were selected as the study area, and the areas covered by two more lines were selected as the test area.

[0058] S2. Collect research data and test data of bald cypress separately;

[0059] Based on the selected research subjects, the provenance and age of bald cypress trees in the research area were determined. The locations of trees in the research area were collected using a scanner, and the ground diameter, diameter at breast height, upper diameter and height of the trees were measured using measuring instruments as research data.

[0060] Tree age statistics are rounded off.

[0061] Then, a laser scanner is used to obtain the tree locations in the inspection area, and the diameter at breast height (DBH) and tree height are measured using measuring instruments to serve as data for the inspection model.

[0062] The scanner used was a RIEGLVZ-400i multi-echo terrestrial laser scanner with a scanning rate of 500,000 points / s. The scanned data underwent preprocessing such as stitching, noise reduction, normalization, and individual tree segmentation.

[0063] S3. Extract standing timber parameters and calculate the standing timber volume;

[0064] Point cloud data was used to reconstruct the structural status of living trees in three dimensions. Based on previous research results, the least squares method was used to extract the ground diameter, diameter at breast height (DBH), and upper diameter of the main trunk of bald cypress trees by fitting the center of the scattered points. The upper diameter was segmented at 1-meter intervals. The thickness of the cross-sectional slice of the point cloud was 0.1-meter. The tree height was obtained by extracting the difference between the maximum value and the minimum value of the z-axis of the tree's growth direction at ground level using FUSION / LDV software. Then, the volume of a single standing tree was calculated using the central cross-sectional area segmentation method. The central cross-sectional area was calculated from the upper diameter extracted from the point cloud. The 1-meter central cross-sectional area segmentation method was used, and the segments less than 1 meter were regarded as the top part. The volume of the standing tree was calculated by accumulating the segments.

[0065] S4. Fit the volume equation, evaluate the fitting effect, and verify the applicability of the volume table;

[0066] Based on the collected research data, commonly used volume equations were selected, fitted, and the correlation coefficient (R²) was used to determine the appropriate equations. 2 ), average prediction accuracy (P), standard error of the estimate (S) EE Mean percentage standard error (M) PSE ), total relative deviation (T) RB ) and mean systematic deviation (M SB To evaluate the applicability of the volume table, data from six bald cypress trees in the test area that do not overlap with the study area were selected to test the applicability of the volume table.

[0067] Table 1. Alternative Equations for One-Dimensional Volume Tables

[0068] Number NO. One-dimensional volume equation 1 <![CDATA[y=a0+a1x]]> 2 <![CDATA[y=a0+a1x+a2x 2 ]]> 3 <![CDATA[y=a0lnx+a1]]> 4 <![CDATA[y=a0x]]> 5 <![CDATA[y=a0e]]>

[0069] In the table, y represents volume, x represents diameter at breast height, and a0, a1, and a2 are parameters to be determined.

[0070] S5. Establish a cut model using the cut equation, and perform timber processing calculations based on the volumetric specifications;

[0071] Tapering equations describe changes in trunk shape and predict diameters at different tree heights, serving as a crucial basis for timber production calculations. This study utilizes standing tree point cloud data to extract diameter at breast height (D), tree height (H), and upper diameter (d), selecting five tapering equations (Table 2). Modeling and parameter determination are performed in DPS17.1 software. The model's predictive performance is validated using a 10-fold cross-validation method. With the model parameters already determined, all single-tree data used for modeling are randomly divided into n subsamples. One subsample is randomly selected as validation data and substituted into the subsequently fitted model for validation. The other n-1 samples are used for training. Validation is repeated 10 times, with each subsample validated once. The average of the n results is used to obtain the model's estimated value, and the correlation coefficient (R²) is used. 2 The optimal taper model is selected by using the residual sum of squares and Q value as the selection criteria.

[0072] Table 2 Alternative Equations for the Taper Equation Model

[0073]

[0074] The table shows the diameter of the tree trunk (with bark) at any position d, h is the height of d, D is the diameter at breast height (DBH), H is the tree height, and a0, a1, a2, and a3 are parameters to be determined.

[0075] The timber processing calculation is based on the volume specifications, following the principle of making the most of large timber, processing large timber first and then small timber, and making full use of the timber. The timber processing data of bald cypress is divided into four groups according to the timber species specifications of the People's Republic of China: large diameter timber, medium diameter timber, small diameter timber and pulp timber. The small end diameter of large, medium and small diameter timber is not less than 26.0, 20.0 and 6.0 cm respectively, and its length is not less than 2.0 m. The small end diameter of short timber is not less than 4.0 cm and not more than 12.0 cm, and its length is not less than 1.0 m and not more than 4.8 m.

[0076] S6. Create charts and graphs based on seed source data to study the data overview;

[0077] The survey data of 576 trees from 6 provenances of bald cypress in the study area, including 96 standing trees in 4 plots of each species, are summarized in Table 3.

[0078] Table 3 Summary of data on standing trees from 6 provenances in the study area

[0079]

[0080] Ground laser scanning was performed on standard trees in four plots of each provenance to obtain point clouds of five standing trees in each plot, for a total of 120 trees. Ground diameter, diameter at breast height (DBH), and tree height were extracted from the point clouds of bald cypress trees, and the volume was calculated and summarized by provenance as shown in Table 4.

[0081] like Figure 2As shown, a diameter distribution map was created for the diameter at breast height (DBH) of the standing trees in the table, with 5cm diameter steps. There are 5–10, 11–15, 16–10, 21–25, 26–30, and 31–35cm diameter steps. The DBH distribution of the entire standing trees shows a normal distribution, with the peak value in the 20–25cm diameter step.

[0082] like Figure 3 As shown, a distribution map of the standing tree height was created based on a 2m tree height order. The distribution of the total standing tree height showed a normal distribution, with the peak value between 9 and 11m.

[0083] Table 4. Overview of Tree Factors Measured by Point Cloud Analysis of Bald Cypress

[0084] Seed source mean diameter Average thoracic diameter Average tree height Average volume Seed source 4 38.60 23.4 11.20 0.230 Seed source 8 37.60 20.7 10.50 0.169 Seed source 10 37.20 23.5 10.30 0.213 Seed Source 14 35.27 22.4 12.50 0.223 Seed Source 17 35.90 22.6 10.70 0.203 Seed source 30 33.20 19.0 9.77 0.141

[0085] like Figure 4 As shown, the diameter at breast height (DBH) of 120 bald cypress trees extracted from point cloud data was verified based on the measured DBH. The intercept of the two sets of data was 0.141, the slope was 0.99, and the R² of the fitted line reached 0.922, indicating that the diameter extracted from the point cloud has good accuracy and can be used for subsequent modeling research. The volume of each standing tree was obtained by the discriminative volume method and compared with the values ​​in the one-dimensional volume table of major tree species in Jiangsu Province.

[0086] like Figure 5 As shown, there are significant deviations, with the total relative deviation (TRB) reaching 16.08%, the mean systematic deviation (MSB) at 33.23%, and the mean percentage standard error (MPSE) exceeding 41.17%. Using the existing volume table to calculate the volume for this experimental area results in overall data that are too large and not applicable to the actual situation. It is necessary to develop a single volume table suitable for the standing conditions of the experimental area.

[0087] S7. Select the corresponding equation to obtain the univariate volume table, and verify the volume table to establish the volume model;

[0088] like Figure 6 As shown, using the volume (V) calculated from point cloud data and the extracted diameter at breast height (D), all candidate univariate volume equations were fitted, and fitting curves were plotted. The fitting results are shown in Table 5. It can be seen from Table 5 that equation (2) has the best fitting effect, with a correlation coefficient R. 2 The relative deviation (T) is 0.969. RB Since the value is within 3%, equation (2)y = 0.0006x² - 0.0054x + 0.034 is chosen as the equation for constructing the univariate volume table of bald cypress, thus obtaining the univariate volume table of bald cypress.

[0089] Table 5. Fitting results of the univariate volume equation

[0090]

[0091] A univariate volume model (2) was fitted to the data of standing bald cypress trees from 6 different seed sources. As shown in Table 6 below, R... 2 The value was significantly increased to a maximum of 0.981 (source 4) and a minimum of 0.962 (source 8), and the volume table was verified using analytical wood data.

[0092] like Figure 7 As shown, one tree from each of the six source trees was obtained. The data from the data disk was consulted to calculate the bark-free volume of the felled trees at each age. The bark data from the data disk was converted into the bark-inclusive volume for the corresponding diameter to complete the volume data. The volume data was then retrieved from the newly established bald cypress univariate volume table and a scatter plot was drawn.

[0093] The model was subjected to an F-test for suitability, and the results are shown in Table 7.

[0094] At a confidence interval of 95%, there was no significant difference in variance between the two sets of data (F = 0.880), indicating that the difference between the theoretical and actual values ​​was not significant, and the established one-dimensional volume model met the applicability requirements.

[0095] S8. Fit the selected cut equation, then calculate the yield and yield rate of the timber species, and establish the cut model;

[0096] The bark diameter d, diameter at breast height D, and tree height H at any height h were extracted from the point cloud of bald cypress trees. Five taper equations were fitted, and the results are shown in Table 8. Among them, equation (8) R 2 The maximum value and the minimum residual sum of squares Q are selected as equation (8) as the taper equation for bald cypress.

[0097] Table 6. One-dimensional volume of six strains of *Cephalotaxus fortunei*: y = a0 + a1x + a2x 2 Model fitting results

[0098] Seed source <![CDATA[a0]]> <![CDATA[a1]]> <![CDATA[a2]]> <![CDATA[R 2 ]]> Seed source 4 0.0008 -0.0166 0.1467 0.981 Seed source 8 0.0005 -0.0164 0.1223 0.962 Seed source 10 0.0006 -0.0082 0.0768 0.974 Seed Source 14 0.0017 -0.0440 0.3987 0.972 Seed Source 17 0.0011 -0.0310 0.3489 0.972 Seed source 30 0.0010 -0.0298 0.2478 0.979

[0099] The cumulative length equation was derived from the established taper equation using the fitted curve of the univariate volume model. The lengths L26, L20, and L6 of large, medium, and small diameter timbers in actual timber production were calculated. The volumes of large, medium, and small diameter timbers were derived through integration. The relevant formulas are shown in Table 9.

[0100] Table 7 Analysis of Timber Volume and One-Dimensional Volume Tables: Results of Volume F Test

[0101] Confidence level CC / % upper limit lower limit F DF F critical value 95 0.636 1.219 0.880 146 0.442

[0102] Table 8. Fitting results for each taper equation

[0103]

[0104] Table 9 Formulas for different specifications of timber

[0105]

[0106] In the table, D is the diameter at breast height (DBH) with bark, H is the tree height, a1 is the parameter of the taper equation, and K = J1 / 40000.

[0107] Using the above taper equation and the formulas for timber length and volume for each timber species, the cumulative timber length, volume, and yield of bald cypress timber of different diameter grades in the experimental area can be calculated.

[0108] Using analytical wood data for timber production, bald cypress trees in the experimental area were processed. Timber production was summarized by diameter class for large, medium, and small diameter trees to verify the established timber yield table. The linear regression analysis results of the two sets of data are shown in Table 10. The linear regression slopes of both sets of data are close to 1, with the largest diameter trees showing the best regression accuracy. R0 2 Both are 0.99.

[0109] The yield per tree for each provenance was calculated, and the total yield within each provenance plot was converted into yield per unit area and yield rate. The results are summarized in Table 11 by provenance. Among the six provenances of *Cephalotaxus fortunei*, the largest yield per unit area was found in large-diameter timber (province No. 8, 187.57m). 3 ·hm -2 (With a yield of 51%), the order from largest to smallest is: Lot 8 > Lot 17 > Lot 14 > Lot 4 > Lot 10 > Lot 30, followed by small-diameter timber (Lot 17, 148.36m). 3 ·hm -2 The yield rate was 44%, and the seed sources were ranked from largest to smallest as follows: No. 17 seed source > No. 14 seed source > No. 8 seed source > No. 4 seed source > No. 10 seed source > No. 30 seed source.

[0110] Table 10 Timber Yield Table by Species - Analysis of Wood Data vs. Point Cloud Data

[0111]

[0112] Table 11 Calculation of Material Yield for Various Source Materials

[0113]

[0114] S9. Summarize the volume model, predict volume trends, and optimize forestry management;

[0115] Based on the 2006 research results, there were differences in the standing growth, timber accumulation, and trunk taper of the original 16 bald cypress seed sources. After more than ten years of cultivation, this study conducted further analysis on 6 seed sources. It can be seen that seed sources No. 8, No. 17, and No. 14, which showed excellent growth performance, are predicted to have better timber yield. In particular, seed sources No. 14 and No. 17, which originally had good taper characteristics, performed well (Table 11). The promotion and application of these two seed sources as timber species is consistent with the original research results. Further analysis of the original block experiments is needed.

[0116] The species with the highest yield per unit area is the large-diameter timber (source No. 8, 187.57m). 3 ·hm -2 The yield was 51%, followed by small-diameter timber (source No. 17, 148.36m). 3 ·hm -2 (The yield was 44%). Based on the comprehensive analysis of multiple traits, these results can provide guidance for future afforestation, cultivation, harvesting, and timber utilization.

[0117] like Figure 8-9 As shown, bald cypress trees of different ages from the same source were selected, and their volume was analyzed. A timber volume curve and a scatter plot of timber yield growth rate were plotted to analyze the volume.

[0118] The horizontal axis of both the timber yield curve and the timber yield growth scatter plot is tree age.

[0119] By plotting the timber yield curve and the timber yield growth rate scatter plot based on tree age, we can intuitively reflect the timber volume of different tree ages. This allows us to analyze the growth of younger trees, rationally plan the timing of tree harvesting, and optimize forestry management.

[0120] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for volume modeling of fallen fir trees based on terrestrial laser scanning, characterized in that: The modeling steps include the following: S1. Aerial view of the bald cypress forest to select the research and testing areas; S2. Collect research data and test data of bald cypress separately; S3. Extract standing timber parameters and calculate the standing timber volume; S4. Fit the volume equation, evaluate the fitting effect, and verify the applicability of the volume table; S5. Establish a cut model using the cut equation, and perform timber processing calculations based on the volumetric specifications; S6. Create charts and graphs based on seed source data to study the data overview; S7. Select the corresponding equation to obtain the univariate volume table, and verify the volume table to establish the volume model; S8. Fit the selected cut equation, then calculate the yield and yield rate of the timber species, and establish the cut model; S9. Summarize the volume model, predict volume trends, and optimize forestry management; In S1, firstly, a panoramic view of the bald cypress forest is taken from the air, and photos of the top of the forest are taken from both vertical and horizontal planes to determine the distribution location of the bald cypress. The outer ring of the bald cypress forest is selected as the study area. Then randomly select several 100m sections from the middle of the bald cypress forest. 2 The research area; Finally, four straight lines were drawn outward from the center of the bald cypress forest. Two of the lines were selected as the study area and two of the lines were selected as the test area. In step S4, commonly used volume equations are selected based on the collected research data, and a fit is performed. The correlation coefficient R is then used to determine the appropriate equations. 2 Average prediction accuracy P, standard error of the estimated value S EE Mean percentage standard error M PSE Total relative deviation T RB and average systematic deviation M SB To evaluate the applicability of the volume table, data from six bald cypress trees in the test area that do not overlap with the study area were selected to test the applicability of the volume table. In step S5, the taper equation describes the changes in trunk shape and predicts the diameter at different tree heights. Using the diameter at breast height (DBH) D, tree height (H), and upper diameter (d) extracted from standing tree point cloud data, five taper equations are selected for modeling and parameter calculation. The model's prediction performance is validated using a 10-fold cross-validation method. With the prediction model parameters already determined, all single-tree data used for modeling are randomly divided into n subsamples. One subsample is randomly selected as validation data and substituted into the subsequently fitted model for validation. The other n-1 samples are used for training. Validation is repeated 10 times, with each subsample validated once. The average of the n results yields the model's estimated value, which is then analyzed using the correlation coefficient R0. 2 Based on the sum of squared residuals and Q-value, the optimal taper model is selected; Based on the volume specifications, timber processing calculations were performed, and individual tree timber processing was conducted. The timber processing data of bald cypress was divided into four groups according to national standards: large-diameter timber, medium-diameter timber, small-diameter timber, and pulp timber.

2. The method for volume modeling of *Cephalotaxus fortunei* based on terrestrial laser scanning according to claim 1, characterized in that, In S2, based on the selected research object, the bald cypress seed source and tree age in the research area are determined, the location of trees in the research area is collected using a scanner, and the ground diameter, diameter at breast height, upper diameter and tree height of the trees are measured using measuring instruments as research data. Then, a laser scanner is used to obtain the tree locations in the inspection area, and the diameter at breast height (DBH) and tree height are measured using measuring instruments as data for the inspection model.

3. The method for volume modeling of fallen fir trees based on terrestrial laser scanning according to claim 1, characterized in that, In step S3, the spatial location of trees is determined by the tree location and tree height in the collected data. The three-dimensional structure of the tree is restored by the ground diameter, diameter at breast height and top diameter, and the volume of a single standing tree is calculated.

4. The method for volume modeling of *Cephalotaxus fortunei* based on terrestrial laser scanning according to claim 1, characterized in that, In S6, the bald cypress trees in the study area are first classified according to their provenance, and the diameter at breast height, tree height and ground diameter of each provenance are recorded and compiled into a table. Ground laser scanning was performed on standard trees in each provenance area to obtain standing points. Ground diameter, diameter at breast height, and tree height were extracted from the standing point cloud of bald cypress trees. The volume was calculated and summarized into a table according to the provenance. A diameter distribution map was created for the diameter at breast height (DBH) of the listed trees, with each 5cm diameter increment. The DBH distribution of all the listed trees showed a normal distribution. A distribution map was also created for the tree height of the listed trees, with each 2m tree height increment. The tree height distribution of all the listed trees showed a normal distribution. Based on the measured diameter at breast height (DBH), the DBH of the bald cypress was extracted from the point cloud. The volume of each standing tree was obtained by the differential volume method and compared with the values ​​in the one-dimensional volume table of the main tree species in the data collection area.

5. The method for volume modeling of fallen fir trees based on terrestrial laser scanning according to claim 1, characterized in that, In step S7, the volume V calculated using point cloud data and the extracted diameter at breast height D are used to fit all candidate univariate volume equations. The fitting results are plotted into a chart, and the fitting effect, correlation coefficient, and relative deviation are analyzed. The corresponding equation is selected as the equation for constructing the univariate volume table of bald cypress, and the univariate volume table of bald cypress is obtained. A univariate volume model was fitted to the standing data of bald cypress trees of the corresponding species. The volume table was tested using the analytical wood data. One analytical wood of each species was obtained. The data of the disk was consulted to calculate the bark-free volume of the felled trees at each age. The bark data of the disk was converted into the bark-inclusive volume of the corresponding diameter to complete the volume data. The volume data of the newly built bald cypress univariate volume table was retrieved and a scatter plot was drawn. The applicability F test of the model was performed and the test table was prepared.

6. The method for volume modeling of fallen fir trees based on terrestrial laser scanning according to claim 1, characterized in that, In S8, the bark diameter d, diameter at breast height D, and tree height H at any height h extracted from the point cloud of bald cypress trees are used to fit five taper equations, and the equation is selected as the taper equation of bald cypress based on the fitting results. The cumulative length equation is derived from the established taper equation by fitting the curve of the univariate volume model, and the length of each diameter of timber in actual timber production is calculated. The volume of each diameter is derived by integration. The cumulative length, volume and yield of bald cypress timber produced by diameter class in the experimental area can be calculated using the above taper equation and the timber length and volume formulas of each timber species. Using analytical wood data, the yield per tree of each species was calculated, the total yield within each species plot was calculated, and converted into the yield per unit area and the yield rate of each species.

7. The method for volume modeling of fallen fir trees based on terrestrial laser scanning according to claim 1, characterized in that, In S9, the model was verified by analytical wood data, and the total timber yield and timber yield rate per unit area of ​​each seed source were analyzed. Based on the comprehensive multi-trait research, the results can provide guidance for future afforestation, cultivation, logging and timber utilization. We selected bald cypress trees of different ages from the same source, analyzed their volume, and plotted a volume curve and a scatter plot of the growth rate of timber output to analyze the volume.

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