Methods for regulating the diameter structure and plant distribution of high-density artificial pure forests

Abstract

The present invention relates to the technical field of forestry management, and specifically to a method for regulating the diameter-class structure and plant distribution of a high-density artificial pure forest, comprising three steps: first, obtaining plant data of a stand to be tended: establishing a rectangular coordinate system with a certain corner of the stand as the origin, investigating the breast diameter of each single plant in the stand to be tended and recording its position, and dividing the breast diameter into several diameter classes according to different sizes; then determining the number of thinning plants in each diameter class; calculating the total number of thinning plants based on the target density and existing density required by the stand, and allocating these thinning plants to each diameter class so that the number of plants remaining in each diameter class after thinning tends to be consistent; then determining the target plants to be cut and the retained plants in each diameter class. Thinning is performed according to the determined target plants to be cut, thereby achieving the purpose of regulating the diameter-class structure and plant distribution of a high-density artificial pure forest, so that the stand has a more reasonable age structure, diameter-class structure and vertical hierarchy, which is conducive to the sustainable management of forest resources.

Description

Technical Field

[0001] The present invention relates to the technical field of forest management, and in particular to a method for regulating the diameter-class structure and plant distribution of a high-density artificial pure forest. Background Art

[0002] As of 2021, my country's artificial forest area is 79.5428 million hectares 2 , is the country with the largest area of ​​artificial forests in the world. 85% of my country's artificial forests are pure forests. Due to the lack of relevant theoretical and technical support in the early stages of afforestation, the initial planting density is generally high, with most of the trees being 2,000-3,000 per hectare. 2 , some even higher. Furthermore, due to the uniform planting period, plantations have a highly homogenized age and diameter structure. With the increasing emphasis on ecological conservation, many timber stands have been gradually reclassified as ecological public welfare forests. Existing management practices no longer align with the functional role of these stands. Timber forests aim to maximize timber production, and common management practices include "removing weak trees and retaining strong ones," "removing small trees and retaining large ones," and "targeted tree management." This creates an impression of uniformity and consistent diameter classes. However, these management practices clearly overlook the original purpose of ecological public welfare forests, which should prioritize forest ecological services, ecosystem stability, and the sustainable use of forest resources. For example, the Pinus tabulaeformis and Larix gmelinii forests in Hebei Province, most of which were planted in the 1960s and 1970s, have reached maturity, but they commonly suffer from irrational diameter class structure, incomplete vertical stratification, poor natural regeneration capacity, and difficulty in forming a multi-aged, multi-layered structure. Controlling the diameter class structure and plant distribution of high-density plantations has become an urgent challenge in the current efforts to precisely improve forest quality. Summary of the Invention

[0003] In view of the technical problem, the present invention provides a method for regulating the diameter structure and plant distribution of high-density artificial pure forests, which solves the problem of unreasonable diameter structure of high-density artificial pure forests.

[0004] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0005] In a first aspect, the present invention provides a method for regulating the diameter structure and plant distribution of a high-density artificial pure forest, the regulating method comprising:

[0006] S1. Investigate and measure the DBH distribution of stand plants and record the distribution of plants

[0007] The diameter at breast height of the plants in the tended stand is measured and their positions are recorded. A plane rectangular coordinate system is established with a certain corner of the stand as the origin. The position of each plant is recorded as the vertical and horizontal coordinates in the rectangular coordinate system, and a database of the diameter at breast height and position coordinates of the stand plants is established.

[0008] The measured plant diameter at breast height is divided into several diameter classes, and the number of plants in each diameter class is counted N. i ;

[0009] S2. Determine the number of plants to be thinned for each diameter class

[0010] The total number of thinning plants N is calculated based on the target density and current density of the stand. Then, according to the principle that the remaining number of plants of each diameter class after thinning is close to the same, the total number of thinning plants N is allocated to each diameter class to obtain the number of plants m required to be thinned in each diameter class. i ,Σm 1→i =N;

[0011] S3. Determine the target plants for thinning at each diameter level. The principles for determination are as follows:

[0012] a. All other tree species associated with pure forests should be retained to promote the formation of mixed forests during stand succession;

[0013] b. Arrange the number of thinned plants required for each diameter class from largest to smallest, and determine the number of thinned plants for each diameter class in sequence;

[0014] c. Starting from the origin of the rectangular coordinate system, find the plant closest to the origin in a certain diameter class and set it as the reference tree. Draw a small circle with the reference tree as the center and r as the radius. Draw a large circle with the same radius as the diameter, and form a ring area between the large circle and the small circle. According to the distribution of plants of this diameter class in the small circle or the ring area, there are three types of judgment results:

[0015] c1. If there are plants of this diameter class on or within the small circle, but no plants of this diameter class in the annular area, then the reference tree and one plant on or within the small circle will be retained, and the rest will be identified as target plants to be felled;

[0016] c2. If there are plants of this diameter class on or within the small circle, and there is at least one plant of this diameter class in the ring area, all plants on or within the small circle other than the reference tree will be determined as target plants to be felled;

[0017] c3. If there are no plants of this diameter class on or within the small circle, skip the process;

[0018] Next, starting from the origin, find the tree closest to the origin in a certain diameter class and set it as the reference tree. The reference tree cannot be the target tree to be felled. Repeat the process from c to c3 and so on until all trees of the diameter class have been processed. If a tree was previously determined to be a retained plant, it will still be a retained plant if it is determined to be a target plant to be felled in subsequent calculations.

[0019] The initial value of r is calculated according to the following formula:

[0020]

[0021] Where S is the area of ​​the tended stand, n iLeft The number of plants retained for that diameter class is then adjusted based on the total number of target plants to be felled and the total number of thinned plants, N, so that the total number of target plants to be felled and the total number of thinned plants, N, are close to or equal. "Close" means that the difference between the total number of target plants to be felled and the total number of thinned plants, N, does not exceed 5 plants.

[0022] According to a preferred embodiment of the present invention, in S1, each tree in the tended stand with a DBH ≥ 2 cm is measured to determine its DBH. Plants with a DBH smaller than 2 cm and non-trees have little impact on the structure of the tended stand and therefore their DBH is not measured to save labor and time.

[0023] According to a preferred embodiment of the present invention, in S1, the measured plant diameter at breast height is divided into 4-10 diameter grades; the grading interval and the number of grades can be formulated according to actual conditions, and the grading interval is preferably 3-5 cm per grade; more preferably, the number of grades is preferably 4-7.

[0024] For example, the plant diameter at breast height can be divided into 6 diameter at breast height grades according to <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm.

[0025] According to a preferred embodiment of the present invention, in S2, the total number of thinned trees N is calculated as follows: N = (current density - target density) * S, where S is the area of ​​the tended stand.

[0026] According to a preferred embodiment of the present invention, in S2, the number of plants N of each diameter class is obtained by counting i Then, sort the plants in each diameter class from large to small according to the number of plants in each diameter class; on the premise of meeting the total number of thinned plants N, thin the plants in the first diameter class first. When the remaining number of plants after thinning to this diameter class is less than the number of plants in the second diameter class, thin the second diameter class instead, so that the remaining number of plants in the second diameter class is equal to the remaining number of plants in the first diameter class; thin the first and second diameter classes synchronously, and always keep the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class. When the remaining number of plants after thinning to the second diameter class is less than the number of plants in the third diameter class, thin the third diameter class instead, so that the remaining number of plants in the third diameter class, the second diameter class, and the first diameter class are all equal. Thin the first, second, and third diameter classes synchronously, and always keep the remaining number of plants in the first, second, and third diameter classes equal, and so on, until the total number of thinned plants N is reached; if it is eventually impossible to make the remaining number of plants in each diameter class strictly equal, then give priority to retaining plants in the small diameter class.

[0027] By the above method, the total number of thinned plants N is distributed to each diameter class, and the number of plants remaining in each diameter class after thinning is made consistent; if it is not completely consistent, thinning of plants of large diameter class is given priority.

[0028] For example, if the diameter ranges are divided into 6 categories according to <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm, and the number of plants in each diameter category is N1, N2, N3, N4, N5, and N6, and the number of thinnings in each diameter category is m1, m2, m3, m4, m5, and m6, then m1+m2+m3+m4+m5+m6=N must be satisfied, and the number of remaining plants in each diameter category (N i -m i ) are close to equal (achieving a uniform distribution of plants in each diameter class).

[0029] According to a preferred embodiment of the present invention, in step S3 c1, when retaining one plant on or within the small circle, priority is given to retaining the plant farthest from the reference tree; if the distances are the same, the plant with a larger difference in DBH from the reference tree is retained.

[0030] According to a preferred embodiment of the present invention, in step S3, if the total number of target plants to be cut according to the rule c1-c2 exceeds the number m of plants to be thinned to each diameter class allocated in step S2, i , then a reduction correction is performed on the calculated r value to determine the small circle and the large circle by reducing the corrected r value. The degree of correction is determined by the total number of target plants to be felled according to the rule of c1-c2 and the number of plants m required to be thinned at each diameter level determined in step S2. i Until they are close;

[0031] On the contrary, if the total number of target plants to be cut down according to the rule c1-c2 is less than the number m of plants to be thinned down for each diameter class allocated in step S2, i , then the calculated r value is increased and corrected to determine the small circle and the large circle by increasing the corrected r value. The degree of correction is determined by the total number of target plants to be felled according to the rule of c1-c2 and the number of plants m required to be thinned at each diameter level determined in step S2. i Until they are close.

[0032] The beneficial effects of the present invention are:

[0033] This invention addresses the challenges of high-density artificial pure forests, such as intense competition for space, an irrational diameter-class structure, incomplete vertical stratification, and difficulty forming a multi-layered structure with varying ages. By employing a series of technical measures, including measuring stand diameter and plant distribution, classifying trees at breast height (DBH) into different diameter classes, and determining the number of thinnings per DBH class and the number of plants to be thinned, this approach effectively addresses the issue of regulating the diameter-class structure in high-density artificial pure forests. Compared to traditional tending management methods, this method achieves a more rational age structure, diameter-class structure, and vertical stratification within the stand, contributing to the formation of a multi-layered stand structure with varying ages and a stable, sustainable forest ecosystem, ultimately achieving the sustainable utilization of forest resources. After investigating the forest stand diameter class and plant distribution, the present invention can realize computer intelligent programmed processing and calibration of the position (coordinates) of the plants to be felled without manual judgment, which not only saves a lot of time and manpower, but also ensures the control effect, avoids the errors caused by human experience-based processing, and improves the stability and repeatability of the control effect; in addition, the forest stand plant distribution database established when the present invention is first applied can be reused, and subsequent tending and thinning only requires measuring the breast diameter index, which is conducive to long-term tracking monitoring and timely tending of the same forest stand, and promotes the digitization of forest thinning plans.

[0034] The method of the present invention is implemented through a computer program. On the basis of determining the intensity of tending and thinning, the breast diameter and position are determined by measuring each tree in the forest stand, the breast diameter grades are divided according to certain intervals and quantities, the thinning quantity is allocated to different diameter grades according to the principle of uniform plant retention, and then the target plants that need to be thinned in each diameter grade are determined according to the principle of uniform spatial distribution. Practice has proved that the method of the present invention can effectively weaken the homogeneity of diameter grades, increase the vertical layers of the forest stand, promote the natural regeneration of the forest stand, gradually form a multi-layer structure of different ages, and play an important role in achieving the sustainable utilization of forest resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart for determining the number of thinning plants for each diameter grade during diameter grade regulation of the present invention.

[0036] Figure 2 These are three determination situations for the present invention when determining target plants to be felled within the same diameter class.

[0037] Figure 3 The present invention is a flow chart for determining target plants to be felled within the same diameter class.

[0038] Figure 4 This is a schematic diagram of the distribution of thinned plants and retained plants of the same diameter grade determined by the present invention.

[0039] Figure 5 This is the diameter distribution of Pinus tabulaeformis plantations obtained through investigation and statistics in a preferred embodiment.

[0040] Figure 6 The figure shows the location distribution of the investigated Chinese pine plantations in the preferred embodiment.

[0041] Figure 7 The diameter distribution of the Pinus tabulaeformis plantation after being regulated by the method of the present invention in a preferred embodiment is shown.

[0042] Figure 8 The distribution of selected plants for felling (i.e., target plants for thinning) in a Pinus tabulaeformis plantation is calculated by computer in a preferred embodiment.

[0043] Figure 9 The figure shows the distribution of Pinus tabulaeformis plantations after selective felling using the method of the present invention in a preferred embodiment.

[0044] Figure 10 This is a comparison of the diameter structure of the Chinese pine plantation before and after selective felling using the method of the present invention in the control example.

[0045] Figure 11 This is a comparison diagram of the plant distribution of the Chinese pine plantation before and after selective felling (thinning) by the method of the present invention in the control example. DETAILED DESCRIPTION

[0046] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0047] To address the serious problem of homogeneity in the age and diameter structure of plantations, this invention develops a scientific and rigorous computer-friendly method. Target plants for thinning are identified based on computer program calculations. This method improves diameter structure diversity, increases vertical stratification within the stand, creates a multi-layered structure with varying ages, and achieves sustainable forest resource development. This method is particularly suitable for the management of ecological public welfare forests.

[0048] The technical solution of the present invention mainly includes three steps. The first step is to obtain the plant data of the forest stand to be tended: a rectangular coordinate system is established with a certain corner of the forest stand as the origin, the breast diameter of each single plant in the forest stand to be tended is investigated and its position is recorded, and the breast diameter is divided into several diameter classes according to different sizes. The second step is to determine the number of thinning plants in each diameter class; the total number of thinning plants is calculated according to the target density and existing density required by the forest stand, and these thinning plants are allocated to each diameter class so that the number of remaining plants in each diameter class after thinning tends to be consistent; if it cannot be completely consistent, the plants of large diameter class are thinned first. The third step is to determine the target plants to be cut down and the plants to be retained in each diameter class. Finally, thinning is carried out according to the target plants to be cut down determined in the third step, so as to achieve the purpose of regulating the diameter class structure and plant distribution of high-density artificial pure forest, so that the forest stand has a more reasonable age structure, diameter class structure and vertical hierarchy, which is conducive to the sustainable management of forest resources.

[0049] The detailed description and preferred implementation of the scheme are as follows:

[0050] 1. Investigate and obtain data on plants in the forest to be tended

[0051] Each tree in the tended stand with a DBH ≥ 2 cm was measured to determine its DBH and position. Specifically, a rectangular coordinate system was established with a corner of the stand as the origin. While measuring the DBH of each tree, the tree's position coordinates were recorded to create a database of DBH and position coordinates for the stand.

[0052] The diameter-at-breast height (DBH) distribution of plants in a stand is divided into several DBH classes. For example, there are six DBH classes: <5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm, and >25 cm. The grading intervals and number of classes can be determined based on actual conditions. A grading interval of 3-5 cm and a number of 4-7 classes are appropriate. The number of plants in each DBH class is counted to determine the stand's diameter-at-breast height distribution. The distribution of plants in each diameter class is determined using the horizontal and vertical coordinates of a rectangular coordinate system.

[0053] 2. Determine the number of thinned plants for each DBH grade

[0054] The total number of thinned plants N is calculated based on the target density and existing density required by the stand. Based on the principle that the remaining number of plants of each diameter class after felling is close to the same, the total number of felled plants N is distributed to plants of each diameter class. The overall idea is to weaken the dominant diameter class with a large number of plants through thinning, so that the remaining number of plants in each diameter class range is close to the same as much as possible, so that different diameter classes can achieve uniform distribution control. The calculation formula is: N1-m1=N2-m2=N3-m3=……N i -m i .

[0055] The total number of thinnings, N, is calculated as: N = (current density - target density) * S, where S is the area of ​​the tended stand. The current density is determined based on surveys and measurements of the tended stand. The target density is a fixed parameter that can be determined according to existing technical regulations, field research, or based on water resource carrying capacity. For example, the optimal density of the current stand can be determined by referring to the method described in the applicant's prior patent application, publication number CN113919747A, "A Method for Determining Optimal Stand Density Based on Forest-Water Relationships."

[0056] The calculation process for determining the number of thinning trees for each diameter class is as follows: Figure 1 As shown (taking 6 diameter classes as an example): In the figure, N is the total number of thinned plants; Ni is the number of plants in the i-th diameter class, and N1 to N6 are sorted in descending order of plant number; mi is the number of thinned plants in the i-th diameter class, and the sum of the thinning numbers of each diameter class is N, that is, Σm 1→i = N. The range and number of diameter grades can be determined according to actual conditions.

[0057] For example, the diameter ranges can be divided into 6 categories: <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm. The number of plants in each diameter range is counted respectively, and then the number of plants in each diameter range is sorted from large to small. Assume that among the 6 diameter ranges, the number of plants in the >25cm diameter range is the largest, N1, followed by the number of plants in the 20-25cm diameter range N2, then the number of plants in the 15-20cm diameter range N3, the number of plants in the 10-15cm diameter range N4, and the number of plants in the 5-10cm diameter range N5. N5 and the number of plants with a diameter of less than 5 cm N6 are arranged from large to small as N1>N2>N3>N4>N5>N6. Therefore, when determining the number of thinnings, on the premise that the total number of felled plants meets N, first determine the number of thinnings from the plants with a diameter of >25 cm. When the number of remaining plants with a diameter of >25 cm is less than the number of plants with a diameter of 20-25 cm, start to determine a certain number of thinnings from the plants with a diameter of 20-25 cm, so that the remaining number of plants with a diameter of 20-25 cm is equal to the remaining number of plants with a diameter of >25 cm. At this time, if the total number of felled trees N has not been reached, the number of thinnings will continue to be determined from the two diameter classes of plants >25cm and 20-25cm. On the premise of keeping the remaining number of plants in these two diameter classes equal, the remaining number of plants will be compared with the number of plants in the 15-20cm diameter class. If the remaining number of plants is less than the number of plants in the 15-20cm diameter class, the number of thinnings will be determined from the 15-20cm diameter class, so that the remaining number of plants in the 15-20cm diameter class remains equal to the remaining number of plants in the two diameter classes felled previously. This process will be repeated until the sum of the thinning numbers determined for each diameter class is equal to the total number of thinnings N. At this time, the computer program will output the number of thinnings m for each diameter class. i .

[0058] If the final calculation result has a decimal, it will be rounded up after giving priority to retaining small-diameter plants. If it is not completely consistent, large-diameter plants will be harvested first, and small-diameter plants will be retained before rounding up.

[0059] 3. Determine the target plants for thinning at each diameter level

[0060] After determining the number of plants to be thinned in each DBH grade, the specific plants to be thinned will be determined through the following procedure.

[0061] (1) All other tree species that are associated with pure forests should be retained, which is conducive to the formation of mixed forests during the stand succession process.

[0062] (2) Arrange the number of thinned plants required for each diameter class in descending order, and determine the number of thinned plants for each diameter class in turn.

[0063] (3) Starting from the origin of the rectangular coordinate system, find the plant O1 that is closest to the origin in a certain diameter class and set it as the reference tree. Draw a small circle with the reference tree O1 as the center and r as the radius. Draw a large circle with the same radius as the diameter, and form a ring area between the large circle and the small circle. According to the distribution of plants of this diameter class in the small circle or the ring area, there are three types of judgment results:

[0064] Combine Figure 2-3 As shown:

[0065] The first case: If there are plants of this diameter class on or inside the small circle, but there are no plants of this diameter class in the circular area, then the reference tree and one plant on or inside the small circle will be retained, and the rest will be determined as target plants to be felled.

[0066] In this case, when retaining "one plant on or within the small circle", priority is given to retaining the plant farthest from the reference tree; if the distances are the same, the plant with a larger difference in DBH from the reference tree is retained.

[0067] The second case: If there are plants of this diameter class on and within the small circle, and there is at least one plant of this diameter class in the ring area, then all plants on and within the small circle other than the reference tree will be determined as target plants to be felled;

[0068] The third case: if there are no plants of this diameter class on or within the small circle, then skip and do not process. In summary, the reference tree is always the plant that is retained.

[0069] Reference Figure 3 As shown, then start from the origin and find the plant that is closest to the origin in a certain diameter class as the reference tree O2. The reference tree O2 cannot be the target plant to be felled. Repeat the process of drawing a small circle with the reference tree O2 as the center and r as the radius. Draw a large circle with a radius of 0.5, and form a ring area between the large circle and the small circle; then divide the distribution of plants of this diameter class in the small circle or the ring area into three judgment results for judgment. After the judgment is completed, start from the origin and find the plant of a certain diameter class that is third closest to the origin as the reference tree O3. Repeat the above method until all trees of this diameter class are processed.

[0070] The initial value of r is calculated according to the following formula:

[0071]

[0072] Where S is the area of ​​tended stands, n iLeft The number of plants retained for this diameter class is equal to N i -m i The r value is adjusted based on the total number of target plants to be felled and the total number of thinned plants N, so that the total number of target plants to be felled and the total number of thinned plants N are close to or equal. Wherein, close means that the difference between the total number of target plants to be felled and the total number of thinned plants N does not exceed 5 plants.

[0073] The method for correcting r is: considering that the distribution of plants may be very uneven in actual operation, it is very likely that the total number of target plants to be felled will exceed the number of plants to be felled calculated for that diameter class m i , at this time, the radius r needs to be reduced and the calculation is repeated until the total number of target plants to be felled in this diameter class is equal to the number of plants m that need to be thinned in each diameter class determined in step S2. i On the contrary, if the total number of target plants to be felled determined by the rule c1-c2 is less than the number m of plants to be thinned to each diameter class allocated in step S2, i , then the calculated r value is increased and corrected to determine the small circle and the large circle by increasing the corrected r value. The degree of correction is determined by the total number of target plants to be felled according to the rule of c1-c2 and the number of plants m required to be thinned at each diameter level determined in step S2. i Until they are close or even equal.

[0074] Figure 3 Where S is the area of ​​the forest to be tended, m i is the number of plants that need to be thinned for the i-th DBH grade, O is the origin of the rectangular coordinate system, O i For plants of a certain DBH grade, r determines the distance, and L determines the distance between other plants and O i The straight-line distance, D i Candidate thinning, B i With O i The farthest candidate for thinning. All plants marked as retained trees and thinning trees will no longer be considered as O i Relevant judgments will be made. Any plants previously marked as retained trees will be determined to be thinned trees in subsequent calculations and will still exist as retained trees.

[0075] Reference Figure 3 The method shown is used to determine target plants to be felled and plants to be retained, such as Figure 4 As shown, O1, O2, O3: there are 1 or more plants in the r circle, and there are ≠ 0 plants in the ring area. O1, O2, and O3 are determined to be retained plants, and all other plants in the r circle are determined to be target plants to be felled.

[0076] O4: There are multiple plants in the r circle, and there are 0 plants in the ring area. O4 and the farthest plant B4 are determined to be retained plants, and the rest are all determined to be target plants for felling.

[0077] O5: There are 0 plants in the r circle and ≠0 plants in the ring area, so O5 is judged as a retained plant.

[0078] O6: There is 1 retained tree B4 in the r circle, and ≠0 trees in the ring area. Originally, B4 should be identified as a target plant to be felled, but due to the priority principle, B4 still exists as a retained plant, and O6 is marked as a retained plant.

[0079] O7: 0 plants inside the r circle, 0 plants inside the ring area, O7 is marked as the retained plant.

[0080] The above solution is described below in conjunction with the preferred embodiments of the present invention.

[0081] This example was implemented in Xiaowutaishan National Nature Reserve in Hebei Province. The forest stand type was a Pinus tabulaeformis plantation, and the experimental plot size was 20 m×40 m.

[0082] 1. Determine the stand diameter and plant distribution

[0083] The stand was measured for each tree, and the diameter at breast height, coordinates, and associated tree species were measured. The current stand density was determined to be 1538 trees / hm2. 2 The average breast diameter is 14.8cm, accompanied by a very small number of young Larix principis-rupprechtii trees. It is divided into 6 breast diameter grades according to <5cm, 5-10cm, 10-15cm, 15-20cm, 20-25cm, and >25cm. The diameter grade distribution is shown in the figure. Figure 5 , the distribution of stand plants can be seen in Figure 6 .

[0084] 2. Determine the number of thinned plants for each DBH grade

[0085] (1) Determine the total number of thinnings. The number of thinnings can be calculated based on the thinning intensity required for the forest stand and the existing density. This embodiment uses "A method for determining a reasonable forest stand density based on forest-water relationship" (application number 202111319698.X) to determine the reasonable density of the current forest stand, thereby determining the total number of thinnings. Since this embodiment and the aforementioned patent embodiment belong to the same region and the same forest species, according to the aforementioned patent method, the "Management density table of each diameter class of Pinus tabulaeformis forest under different rainfall conditions" is queried. The current forest stand has an average breast diameter of 14.8 cm and the local average annual rainfall is 500 mm, and the reasonable density is 856-917 trees / hm2. 2 Due to the current high density and the high intensity of thinning, the target density was finally determined to be 900 plants / hm2. 2 After conversion, the number of trees retained in the experimental forest should be 72, the current number of trees is 123, and the total number of thinned trees is 51.

[0086] (2) Determine the number of thinned trees at different DBH levels. A total of 51 trees were thinned in the stand. Figure 1 The process is used to distribute the diameter of thinning trees, combined with Figure 5 As shown, the diameter classes that need to be thinned are 5-10cm, 10-15cm, 15-20cm, and 20-25cm. 4, 12, 33, and 2 trees are selected for thinning, respectively, for a total of 51 trees. The distribution results of different diameter classes after regulation are as follows Figure 7 shown.

[0087] 3. Determine the thinning plants for each DBH grade

[0088] First, retain the Chinese larch associated with the pure forest, and select thinning plants of four diameters at breast height (DBH) levels: 15-20cm, 10-15cm, 5-10cm, and 20-25cm according to the plant determination process. The screening results are as follows: Figure 8 The distribution of different diameter classes of Pinus tabulaeformis plantations after selective felling is shown in Figure 9 shown.

[0089] 4. Regulation results

[0090] Depend on Figure 6 and Figure 9 By comparison, the density is 1538 plants / hm2 2 The density of the Pinus tabulaeformis plantation with an average diameter at breast height of 14.8 cm was adjusted to 900 trees / hm2. 2 Afterward, the diameter structure becomes more ideal, with a relatively even distribution across diameter classes, weakening the dominant position of 15-20cm diameters at breast height. Controlling density and diameter class helps to preserve small and medium-sized plants under the forest floor, fosters the formation of a multi-layered forest structure, facilitates the harvesting and utilization of larger diameter plants, and promotes the replacement of large, medium, and small plants. This plays a crucial role in promoting the sustainable development of forest resources and balancing their protection and utilization.

[0091] Control Example

[0092] In parallel with the above experiment, a new experiment was conducted in the same area with a density of 838 plants / hm2. 2 The density of Pinus tabulaeformis plantations with a diameter at breast height of 19.2 cm was adjusted to 588 trees / hm2. 2 The test site size is 20m×40m, and the diameter-grade structure control results are as follows: Figure 10 The results of plant distribution regulation are shown in Figure 11 As shown in the figure. Although the diameter class structure has improved after regulation, it is still far from the reasonable structure. The main reason is that as the diameter at breast height increases, the dominant layer trees occupy the vast majority of water and heat resources, and the small and medium diameter trees under the forest are gradually eliminated and die, making the diameter class structure more concentrated, and the room for selecting and retaining plants during structural regulation is compressed. Figure 10 As can be seen, the diameter class is primarily concentrated between 15 and 25 cm, with very few plants under 10 cm in diameter at breast height, limiting the scope for retained plants. Furthermore, the natural decline in stand density has reduced the number of plants that can be regulated. These two factors combined have led to the current regulatory results. This suggests that regulation of plantation diameter structure should be carried out promptly and at the appropriate time. If this opportunity is missed, and regulation is carried out only when the diameter class structure in the dominant layer is more concentrated, the results will be less than satisfactory.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for regulating the diameter structure and plant distribution of a high-density artificial pure forest, characterized in that: The control method comprises: S1. Investigate and measure the DBH distribution of stand plants and record the distribution of plants The diameter at breast height of the plants in the tended stand is measured and their positions are recorded. A plane rectangular coordinate system is established with a certain corner of the stand as the origin. The position of each plant is recorded as the vertical and horizontal coordinates in the rectangular coordinate system, and a database of the diameter at breast height and position coordinates of the stand plants is established. The measured plant diameter at breast height is divided into several diameter classes, and the number of plants in each diameter class is counted N. i ; S2. Determine the number of plants to be thinned for each diameter class The total number of thinning plants N is calculated based on the target density and current density of the stand. Then, according to the principle that the remaining number of plants of each diameter class after thinning is close to the same, the total number of thinning plants N is allocated to each diameter class to obtain the number of plants m required to be thinned in each diameter class. i ,Σm 1→i =N; S3. Determine the target plants for thinning at each diameter level. The principles for determination are as follows: a. All other tree species associated with pure forests should be retained to promote the formation of mixed forests during stand succession; b. Arrange the number of thinned plants required for each diameter class from largest to smallest, and determine the number of thinned plants for each diameter class in sequence; c. Starting from the origin of the rectangular coordinate system, find the plant closest to the origin in a certain diameter class and set it as the reference tree. Draw a small circle with the reference tree as the center and r as the radius. Draw a large circle with the same radius as the diameter, and form a ring area between the large circle and the small circle. According to the distribution of plants of this diameter class in the small circle or the ring area, there are three types of judgment results: c1. If there are plants of this diameter class on or within the small circle, but no plants of this diameter class in the annular area, then the reference tree and one plant on or within the small circle will be retained, and the rest will be identified as target plants to be felled; c2. If there are plants of this diameter class on or within the small circle, and there is at least one plant of this diameter class in the ring area, all plants on or within the small circle other than the reference tree will be determined as target plants to be felled; c3. If there are no plants of this diameter class on or within the small circle, skip the process; Next, starting from the origin, find the tree closest to the origin in a certain diameter class and set it as the reference tree. The reference tree cannot be the target tree to be felled. Repeat the process from c to c3 and so on until all trees of the diameter class have been processed. If a tree was previously determined to be a retained plant, it will still be a retained plant if it is determined to be a target plant to be felled in subsequent calculations. The initial value of r is calculated according to the following formula: Where S is the area of ​​the tended stand, n iLeft The number of plants retained for this diameter class is adjusted according to the total number of target plants to be felled and the total number of thinned plants N, so that the difference between the total number of target plants to be felled and the total number of thinned plants N does not exceed 5 plants or is equal to each other.

2. The control method according to claim 1, wherein In S1, each tree plant with a breast diameter ≥ 2 cm in the tended stand was measured to determine the breast diameter.

3. The control method according to claim 1, characterized in that In S1, the measured plant diameter at breast height was divided into 4-10 diameter grades; the grading interval was 3-5 cm per grade.

4. The control method according to claim 1, characterized in that In S2, the total number of thinning trees N is calculated as: N = (current density - target density) * S, where S is the area of ​​the tended stand.

5. The control method according to claim 1, characterized in that: In S2, the number of plants of each diameter class N is obtained by counting i Then, sort the plants in each diameter class from large to small according to the number of plants in each diameter class; on the premise of meeting the total number of thinned plants N, first thin the plants in the first diameter class, and when the number of remaining plants after thinning to this diameter class is less than the number of plants in the second diameter class, switch to thinning the second diameter class, so that the remaining number of plants in the second diameter class is equal to the remaining number of plants in the first diameter class; when thinning the first diameter class and the second diameter class simultaneously, always keep the remaining number of plants in the second diameter class equal to the remaining number of plants in the first diameter class; when thinning the remaining number of plants after thinning to the second diameter class is less than the number of plants in the third diameter class, switch to thinning the third diameter class, so that the remaining number of plants in the third diameter class, the second diameter class, and the remaining number of plants in the first diameter class are all equal; when thinning the first diameter class, the second diameter class, and the third diameter class simultaneously, always keep the remaining number of plants in the first diameter class, the second diameter class, and the third diameter class equal, and so on until the total number of thinned plants N is reached; If it is ultimately impossible to make the number of remaining plants of each diameter class strictly equal, priority will be given to retaining plants of the smaller diameter class.

6. The control method according to claim 1, characterized in that: In step S3 c1, when retaining one plant on or within the small circle, the plant farthest from the reference tree is prioritized; if the distances are the same, the plant with a larger difference in DBH from the reference tree is retained.

7. The control method according to claim 1, characterized in that: In step S3, if the total number of target plants to be cut according to the rule c1-c2 exceeds the number of plants m to be thinned to each diameter class allocated in step S2, i , then a reduction correction is performed on the calculated r value to determine the small circle and the large circle by reducing the corrected r value. The degree of correction is determined by the total number of target plants to be felled according to the rule of c1-c2 and the number of plants m required to be thinned at each diameter level determined in step S2. i Until they are close; On the contrary, if the total number of target plants to be cut down according to the rule c1-c2 is less than the number m of plants to be thinned down for each diameter class allocated in step S2, i , then the calculated r value is increased and corrected to determine the small circle and the large circle by increasing the corrected r value. The degree of correction is determined by the total number of target plants to be felled according to the rule of c1-c2 and the number of plants m required to be thinned at each diameter level determined in step S2. i Until they are close.

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