Secondary afforestation method under interstitial forest of low-quality artificial pure forest and degenerated secondary forest

Abstract

The invention relates to a method for secondary afforestation under forest gaps of low-quality artificial pure forests and degenerated secondary forests, and relates to the technical field of forest cultivation, comprising the following steps: (1) selecting afforestation tree species; (2) configuration of afforestation tree species; (3) full life cycle design; (4) afforestation operation. According to the method, the forest stand value is remarkably increased, meanwhile, the development of soil microorganisms is promoted, and the overall quality of forest soil and an ecological system is improved. Compared with a pure forest, the method has the advantages that the accumulation growth amount of the operation forest stand reaches 19.7 m < 3 > / hm < 2 >. A, compared with a pure forest, the growth amount is increased by 3.14 m < 3 > / hm < 2 >. A, the growth amount of a single forest tree is increased by more than 3 times compared with that of a contrast forest, and under the condition that the sustainable operation basic principle that the yield is smaller than the growth amount on the forest stand level is met, the standing tree yield of 17.39 m < 3 > / hm < 2 > can be obtained every year, and the pure income is 7600 yuan / hm < 2 >. A.

Description

Technical Field

[0001] The invention relates to the technical field of forest cultivation, and in particular to a secondary afforestation method under forest gaps of low-quality artificial pure forests and degraded secondary forests. Background Art

[0002] For a long time, large-scale artificial pure forests of Masson pine, Chinese fir and other trees have been built in southern my country for the purpose of producing timber. Due to long-term large-scale continuous multi-generation management, problems such as productivity decline have emerged. In addition, due to human destruction and insufficient management, there are a large number of degraded natural secondary forests and secondary valley woodlands. At present, my country's forestry development has entered a new stage of both quantity and quality from quantitative growth. Some European countries with developed forestry, such as Germany, have carried out near-natural transformation of artificial pure forests in the middle of the last century and achieved remarkable results. In recent years, my country has also carried out preliminary explorations. The secondary afforestation technology under forest gaps in the near-natural transformation process is the primary issue and key technology. For this reason, how to construct forest gaps, select reasonable tree species and mixed planting methods, how to afforest and efficiently cultivate, and reduce operating costs have become urgent practical needs. In view of this, the present invention provides a secondary afforestation method under forest gaps of low-quality artificial pure forests and degraded secondary forests. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a secondary afforestation method in the forest gaps of low-quality artificial pure forests and degraded secondary forests. The purpose is to solve the problems of biodiversity decline, soil fertility decline, and poor ecosystem stability in pure Masson pine and Chinese fir forests or severely degraded forest ecosystems under traditional management models.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] A secondary afforestation method under forest gaps of low-quality artificial pure forests and degraded secondary forests comprises the following steps:

[0006] (1) Selection of tree species for afforestation:

[0007] The afforestation tree species are selected to grow mutually beneficially or compatibly with the tree species of the artificial pure forest or degraded secondary forest to be reforested, and the saplings of the afforestation tree species have the basic shade tolerance ability to grow from the understory to the main forest layer;

[0008] (2) Afforestation tree species configuration:

[0009] The afforestation tree species are planted in at least one of cluster planting and uniform planting;

[0010] (3) Full life cycle design:

[0011] The whole life cycle includes the mixed uneven-aged forest stage and the near-natural forest stage in sequence;

[0012] (4) Afforestation operations: Afforestation operations are performed according to step (1) afforestation tree species selection, step (2) afforestation tree species configuration, and step (3) full life cycle design.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] Furthermore, the afforestation tree species include at least one of precious native tree species and fast-growing broad-leaved tree species.

[0015] Furthermore, the precious native tree species include at least one of Castanopsis rubrum, Eupatorium chinense, Dalbergia odorifera, Parashorea chinensis, Phoebe nanmu, Teak, and Dalbergia cochinchinensis;

[0016] The fast-growing broad-leaved tree species include at least one of Myrica ovata, Quercus macrophylla, and Magnolia officinalis.

[0017] Furthermore, in step (3), the mixed uneven-aged forest stage is specifically as follows: carrying out tending thinning and / or intensive thinning on the artificial pure forest to be reforested or the degraded secondary forest to form forest gaps; replanting the afforestation tree species in the formed forest gaps, and carrying out tending and management on the replanted afforestation tree species and the remaining trees from the thinning of the artificial pure forest to be reforested or the degraded secondary forest to be reforested; when the average height of the replanted afforestation tree species is ≥15m, selecting target trees and cutting down interfering trees;

[0018] The near-natural forest stage is specifically as follows: when the target trees reach the target tree diameter at breast height, they are selectively felled; at the same time, target tree species entering the main forest layer are selected and cultivated as succession target trees, and the succession target trees are managed individually.

[0019] Furthermore, the thinning is specifically to create 60 to 90 gaps / hm2 with a diameter of 8 to 10 m. 2 ;

[0020] The intensive thinning specifically includes: setting the retention density of trees in the artificial pure forest or degraded secondary forest to be reforested to 8-10 trees / mu, and felling the remaining trees in the artificial pure forest or degraded secondary forest to be reforested.

[0021] Furthermore, for the artificial pure forest to be reforested, the full life cycle design in step (3) includes the following specific steps:

[0022] (3-1) Mixed uneven-aged forest stage: The mixed uneven-aged forest stage lasts from 1 to 15 years;

[0023] In the first year, the artificial pure forest of secondary afforestation is thinned and 60 to 90 gaps with a diameter of 8 to 10 m are constructed per hectare. 2; The following year, the precious native tree species are replanted in the formed forest gaps, 4 to 6 trees are replanted in each forest gap, and the spacing between trees is 2m×2~3m, such as 2m×2m or 2m×3m; or / and the artificial pure forest for secondary afforestation is subjected to intensive thinning, the tree retention density of the artificial pure forest for secondary afforestation is 8 to 10 trees / mu, and then the fast-growing broad-leaved tree species are evenly planted, and the afforestation spacing is 2m×2~3m, such as 2m×2m or 2m×3m; the precious native tree species or / and the fast-growing broad-leaved tree species are nurtured and managed, and the nurturing and management tools can be: growth felling is carried out every 5 years, and Masson pine or fir that affects the growth of broad-leaved trees is cut off; when the average height of the precious native tree species or / and the fast-growing broad-leaved tree species is ≥15m, target trees are selected, and the planting density of the target trees is 60 to 90 trees / hm 2 , cutting down interfering trees, including pruning the target trees, and removing side branches less than 3 cm at a height of 7 to 9 m; every 5 to 8 years, according to the growth of the target trees, cutting down interfering trees to protect and promote natural regeneration under the forest;

[0024] (3-2) Near-natural forest stage: The period of the near-natural forest stage is 16 to 40 years;

[0025] When the target tree's diameter at breast height reaches ≥50cm, selective felling is carried out, and at the same time, target tree species entering the main forest layer are selected and cultivated as succession target trees, and the succession target trees are managed individually.

[0026] Furthermore, for the artificial pure forest to be reforested, the full life cycle design in step (3) also includes the following steps:

[0027] (3-3) Forest maturity and secondary colonization stage: The forest maturity and secondary colonization stage is 41 years later:

[0028] Continue the individual tree management of the succession target trees, selectively cut down the succession target trees that have reached the target breast diameter in batches, and gradually form a multi-species and multi-age multi-layered near-natural forest with succession target trees as the main body; make the forest stand evolve towards the management target, cultivate large-diameter timber of precious native tree species, obtain maximum economic benefits, and at the same time form a more complex forest stand structure to stably perform the multiple functions of the forest.

[0029] Furthermore, for the degraded secondary forest to be reforested, the full life cycle design in step (3) includes the following specific steps:

[0030] (3-1) Mixed uneven-aged forest stage: The mixed uneven-aged forest stage includes the community establishment stage, competitive growth stage and quality selection stage;

[0031] The period of the group establishment stage is 1 to 6 years; in the degraded secondary forest to be reforested, target tree species with ecological and economic value cultivation potential are selected and marked, the target tree species are nurtured, the remaining tree species are cut down, and 45 to 60 forest gaps with a diameter of 8 to 10 meters are constructed per hectare. 2 ; Plant the precious native tree species in the formed forest gaps. The precious native tree species can be selected from 2-year-old fine seedlings (seedling height of more than 1.5m), 4 to 6 plants / forest gap, with a spacing of 2m×2m, and the precious native tree species are nurtured and managed; the nurturing and management can specifically include timely felling or pruning of the upper forest trees that affect the target tree species to provide a good growth environment for them;

[0032] The competitive growth stage lasts for 7 to 14 years; light felling or pruning is performed on the upper trees around the forest gaps, and vines are cleared in time to ensure the healthy growth of the target tree species and the precious native tree species planted in the supplementary planting;

[0033] The time period of the quality selection stage is 15 to 40 years: when the average height of the target tree species or the precious native tree species to be planted is ≥15m, target trees are selected, and the planting density of the target trees is 60 to 90 trees / hm2 2 , and at the same time, remove interfering trees; manage the target trees individually, with each management period lasting 5 to 8 years, selectively cut down interfering trees, and protect and promote natural regeneration;

[0034] (3-2) Near-natural forest stage: The near-natural forest stage is from 41 years onwards;

[0035] When the DBH of the target tree is ≥70cm, single tree selective felling is carried out; succession target trees are cultivated by selection or artificial replanting.

[0036] Furthermore, the degraded secondary forest to be reforested includes degraded natural secondary forest or gully woodland.

[0037] Furthermore, the afforestation operation in step (4) is specifically as follows: forest clearing operation, land preparation operation and planting operation are carried out in sequence according to step (1) afforestation tree species selection, step (2) afforestation tree species configuration and step (3) full life cycle design.

[0038] The present invention mainly carries out secondary afforestation in the gaps of low-quality artificial pure forests and degraded secondary forests through the following two aspects: (1) First construct the gaps: According to the actual conditions of different forest stands, the forest stand space is adjusted through artificial felling to form gaps of different sizes and their distribution. (2) Then select, configure and nurture the afforestation tree species: Forest growth is a long-term process, and the selection and configuration of afforestation tree species are particularly important. Through years of practice, the present invention has improved the key technologies such as the traditional afforestation tree species configuration, fully utilized natural forces, reduced the cost of afforestation, and achieved the precise improvement of the quality of artificial forests and sustainable management.

[0039] The beneficial effects of the present invention are:

[0040] The present invention is based on 13 years of observation data of the experimental demonstration forest, which shows that the mixed and uneven-aged forest pattern is rapidly formed under the promotion of management measures. The growth of the near-natural transformation forest is significantly higher than that of the control forest, and the growth of the forest is mainly concentrated in trees with larger diameters, which has significantly improved the value of the forest. At the same time, it has promoted the development of soil microorganisms and improved the overall quality of forest soil and ecosystem. The cumulative growth of the working forest reached 19.7m 3 / hm 2 a. Compared with the pure forest control, the growth rate increased by 3.14m 3 / hm 2 a. The growth of individual trees is more than three times higher than that of the control forest. Under the basic principle of sustainable management that "the harvest volume is less than the growth volume at the forest stand level", 17.39 m 3 / hm 2 The harvest of standing timber is equivalent to a net income of 7,600 yuan / hm2. 2 a. At the same time, it reduces human interference, improves forest biodiversity, achieves long-term maintenance and improvement of site productivity, and has good ecological benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The configuration of planting precious native tree species in clusters under a Masson pine forest gap of the present invention (left) and the actual scene of cluster planting of red cones in a Masson pine forest gap (right);

[0042] Figure 2 The configuration of evenly planting precious native tree species under the gaps of Masson pine forests (left) and the actual scene of evenly planting eucalyptus trees in the gaps of Masson pine forests (right) of the present invention;

[0043] Figure 3 The diagrams are the construction of gaps in degraded and inefficient natural secondary forests (left) and the planting of red cones in the gaps (right);

[0044] Figure 4 Figure 2 shows the construction of gaps in degraded and inefficient gully forest land according to the present invention (left) and the planting of teak in forest gaps (right). DETAILED DESCRIPTION

[0045] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0046] The present invention is mainly used for secondary afforestation in forest gaps during near-natural transformation of low-quality and low-efficiency artificial pure coniferous forests such as Masson pine and Chinese fir, degraded natural secondary forests, and secondary valleys. After felling and adjusting the forest stand space, forest gaps of different sizes are formed, and the afforestation tree species are selected according to their biological characteristics and economic value. Replanting is carried out in a clump, uniform, and random manner to adjust the tree species structure and forest stand density, improve forest productivity and ecological service functions, and achieve continuous forest coverage and sustainable management. The following is a detailed description with specific embodiments.

[0047] Example 1

[0048] The management objectives and target forest phases of the near-natural transformation of the low-quality and low-efficiency Masson pine artificial pure forest involved in this embodiment are as follows:

[0049] Management goal: Focus on cultivating large-diameter timber of precious broad-leaved tree species, while also considering small- and medium-diameter timber of Masson pine and Chinese fir. Large-diameter timber of precious broad-leaved trees (target DBH ≥ 60cm), target tree stock ≥ 250m 3 / hm 2 Optimize the tree species structure of the forest, improve the soil, and increase the biodiversity of the forest. Solve the problems of the decline of biodiversity, soil fertility decline, and poor ecosystem stability in pure Masson pine and Chinese fir forests under the traditional management model.

[0050] Target forest type: In the early stage, it is a mixed coniferous and broad-leaved forest with Masson pine and Chinese fir as the main tree species. In the later stage, it is mainly composed of precious native tree species. It is a near-natural forest with multiple tree species, multiple age classes and multiple layers, and is rich in natural regeneration and shrub and grass vegetation under the forest.

[0051] The near-natural transformation of low-quality and low-efficiency Masson pine artificial pure forests involved in this embodiment includes the following specific steps:

[0052] (1) Selection of tree species for afforestation: Precious native tree species mainly include Castanopsis rubrum and Castanopsis chinensis. The goal is to cultivate large-diameter timber of precious native tree species.

[0053] (2) Tree species configuration: The planting method of afforestation tree species is cluster planting.

[0054] (3) Full life cycle design: (3-1) Mixed coniferous and broadleaved forest stage (1 to 15 years). Select 15 to 20-year-old low-quality and low-efficiency pine and fir plantations, carry out thinning, and build 60 to 90 gaps / hm2 with a diameter of 8 to 10 m. 2 ; The next year, precious native tree species such as Castanopsis hystrix and Euphorbia cerasifera will be planted in the gaps, with 4 to 6 trees planted in each gap. When the average height of the precious native tree species planted is ≥ 15m, select the target tree (60 to 90 trees / hm2). 2), remove interfering trees, prune target trees, and remove side branches less than 3 cm at a height of 7 to 9 meters. Every 5 to 8 years, select interfering trees according to the growth of target trees to protect and promote natural regeneration under the forest. (3-2) Near-natural forest stage (16 to 40 years). After the target trees of Masson pine or Chinese fir have a breast diameter ≥50 cm, they are selectively cut down and utilized, and gradually withdraw from the forest stand. At the same time, target tree species entering the main forest layer are selected and cultivated as successor target trees, and single target tree management is carried out. (3-3) Forest maturity and secondary community establishment stage (41 years ~). Continue to manage single target trees, and selectively cut down target trees of precious native tree species that have reached the target breast diameter in batches, and gradually form a near-natural forest with multiple species and different ages dominated by precious native tree species, so that the forest stand evolves towards the management target, cultivates large-diameter timber of precious native tree species, obtains maximum economic benefits, and forms a more complex forest stand structure while stably exerting multiple functions of the forest.

[0055] (4) Afforestation methods: (4-1) Forest clearing. According to the actual situation of understory shrubs and herbs, block clearing is adopted: each block has a diameter of 8m to 10m, and 90 to 120 blocks / hm2 are used. 2 1. Strip clearing: width 3m~10m, length depends on the actual terrain, parallel to contour line and comprehensive clearing, generally completed in autumn and winter of the year before afforestation. (4-2) Land preparation. Artificial block land preparation is adopted, planting pit size is 50cm×50cm×30cm, plant spacing is 2m×3m or 2m×3m, planting pit distribution mainly includes gap insertion, uniform distribution, strip distribution or cluster distribution. (4-3) Planting operation. The main method of afforestation is seedling planting, using container seedlings of excellent seed sources, with a seedling height of more than 1.5m. Direct seeding is adopted in suitable afforestation areas with inconvenient transportation, and grass is cleared and land is prepared under the forest gaps. The size is 1m×1m, the depth is 5cm~10cm, and the spot seeding is direct seeding. The density is 833~1110 pieces / hm2. 2 ( Figure 1 and 2 ).

[0056] After afforestation under the canopy, the number of target tree species or target trees in the forest stand shall not be less than 450 trees / hm2 2 , evenly distributed, with no forest window with a radius greater than 1 / 2 of the average height of the main forest layer in the entire forest stand; do not damage the original seedlings and saplings in the forest stand. Try not to destroy the original understory vegetation and minimize soil disturbance. The survival rate of afforestation seedlings in the first year should reach more than 85%, and the preservation rate in three years should reach more than 80%.

[0057] Compared with the traditional method, the present invention

[0058] Based on the observation data of Masson pine forests under three management modes, namely, near-natural transformation, conventional management (rotational management) and no management activities, for 10 years (2008-2018) at the Tropical Forest Center of the Chinese Academy of Forestry, the cash flow and replacement cost methods were used to calculate the timber value of large-, medium- and small-diameter timber and the value of seedlings of replanted broad-leaved tree species, respectively. The economic feasibility and risk tolerance of the three management modes were evaluated through financial static and dynamic economic indicators and sensitivity analysis, and the economic benefits of the three management modes were comprehensively compared.

[0059] The results showed that: (1) the dynamic changes of Masson pine species structure under the three management methods were significantly different: in the past 10 years, the output of large-diameter timber in the near-natural transformation forest increased from 1.22m 3 Increased to 56.85m 3 , the output of medium-diameter timber increased from 23.34m 3 Increased to 79.57m 3 , the output of small-diameter timber increased from 69.79m 3 Reduced to 68.76m 3 ; The output of large-diameter timber in conventional forest management has increased from 0.29m 3 Increased to 38.97m 3 , the output of medium-diameter timber increased from 22.51m 3 Increased to 90.89m 3 , the output of small-diameter timber increased from 80.69m 3 Reduced to 78.83m 3 ; The output of large-diameter timber in the control forest increased from 0.25m 3 Increased to 27.97m 3 , the output of medium-diameter timber increased from 20.95m 3 Increased to 93.69m 3 , the output of small-diameter timber increased from 189.39m 3 Reduced to 181.98m 3 (2) During the 10 years, the net profit dynamics of the near-naturalized forest, conventionally managed forest and control forest all showed a monotonically increasing trend, and the investment profit rate dynamics showed a monotonically increasing trend, first increasing and then decreasing, and monotonically decreasing trend, respectively. In the 10th year, the net present value of the near-naturalized forest, conventionally managed forest and control forest were 594, 265, and 193, respectively, and the net profit was 87384.96, 85745.21, and 71935.09 yuan / hm2, respectively. 2, and the investment profit rates were 8.02%, 7.92% and 5.95% respectively. In the past 10 years, the value of seedlings of broad-leaved tree species planted under the canopy in the near-natural transformation method has continued to increase, and the proportion of seedling income in the total forestry income (W value) has shown a wave dynamic of increase, decrease, increase, and decrease. In the 4th to 6th year, native fast-growing tree species such as big-leaf oak and gray magnolia reached the medium and small diameter timber standards, and the W value decreased to 11.26%. In the 8th to 10th year, as precious tree species such as red cones, euphorbia pulcherrima, and cinnamomum sempervirens reached the small diameter timber standards, the W value dropped again to 11.93%.

[0060] In summary, all three types of management methods of Masson pine plantations are economically feasible investments. The initial afforestation cost of near-natural transformation is relatively high, but it is more conducive to cultivating large-diameter timber, promoting the subsequent development and utilization of local precious and fast-growing tree species resources, and meeting the needs of different markets; rotation management tends to cultivate a single tree species, pursuing fast growth and high yield and relatively intensive management; the proportion of large-diameter timber in stands without management measures is low, and natural regeneration is scarce, which is not conducive to the sustainable use of forest resources. Data reference: Zhang Kexin, Liu Xianzhao, Lei Xiangdong, Jia Hongyan, Tang Jixin, Guo Hong. Analysis of short-term economic benefits of different management methods of Masson pine plantations [J]. Journal of Beijing Forestry University, 2022, 44(5): 43-54.

[0061] Example 2

[0062] The near-natural transformation of low-quality and low-efficiency Masson pine artificial pure forest involved in this embodiment is compared with Example 1. In addition to adopting intensive thinning, the low-quality and low-efficiency Masson pine retains a density of 8-10 trees / mu, and the old and fast-growing tree species are evenly planted in the forest, with a afforestation row spacing of 2m×2m. The replanted broad-leaved tree species are nurtured and managed, and growth felling is carried out every 5 years, and the Masson pine or fir that affects the growth of broad-leaved trees is cut off. The rest is the same as Example 1.

[0063] The milaopai in this embodiment and the large-leaf oak and gray manglietia in embodiment 1 are all fast-growing broad-leaved tree species with similar growth and economic value. The difference is the planting method, so the management effect is also roughly the same as that in embodiment 1.

[0064] Example 3

[0065] The management objectives and target forest types for near-natural transformation of degraded natural secondary forests are as follows:

[0066] Management objectives: To promote the formation of forest ecosystems through artificial reconstruction and reasonable construction of severely degraded forest ecosystems, restore and optimize the economic value and ecological service functions of forest ecosystems, and gradually develop artificially reconstructed forest ecological communities in a near-natural direction, ultimately forming zonal forest climax communities.

[0067] Target forest phase: Near-natural forest with mixed species dominated by precious native tree species and other native tree species, with the dominant layer dominated by precious native tree species and the secondary forest layer dominated by natural regeneration of precious native tree species and native trees and shrubs, forming a plant community with complex structure and rich biodiversity. In the long term, it will eventually form a zonal forest climax community.

[0068] This embodiment involves the near-natural transformation of degraded natural secondary forests, including the following steps:

[0069] (1) Selection of afforestation tree species: Based on management objectives and production needs, select precious native tree species with high requirements for site conditions, high ecological niche and high economic value, mainly including teak, red cone, eucalyptus, Dalbergia odorifera, and parashorea chinensis.

[0070] (2) Tree species configuration: mainly cluster planting.

[0071] (3) Full life cycle design: (3-1) Establishment stage (1 to 6 years): In degraded natural secondary forests or valley woodlands, select and mark target tree species with ecological and economic value and other cultivation potential, nurture them to promote their growth, and cut down some low-value tree species. Create 45 to 60 gaps / hm2 in the forest 2 , the diameter of the forest gap is 8m~10m. Precious native tree species with strong natural regeneration ability are replanted in the forest gaps. Two-year-old good quality seedlings (seedling height above 1.5m) are selected, 4~6 trees / gap, and the spacing between plants is 2m×2m. Continuous nurturing and management are carried out after replanting, and the upper forest trees that affect the target tree species are timely felled or pruned to provide them with a good growth environment. (3-2) Competitive growth stage (7~14 years): According to the actual situation of the forest stand, the upper forest trees around the forest gap are light-cut or pruned, and tall shrubs or low-value non-target tree species are cut first, and vines are cleared in time to ensure the healthy growth of the target tree species. (3-3) Quality selection stage (15~40 years): When the average height of the selected target tree species or the dominant trees of the replanted precious native tree species is ≥15m, start to select target trees, and the target tree density is 60~90 trees / hm2. 2 , and remove interfering trees at the same time. Carry out individual tree management around the target tree with a management period of 5 years, remove interfering trees, and protect natural regeneration seedlings or saplings. (3-4) Near-natural stage (≥41 years): Continue to manage the target tree individually, and select interfering trees every 5 to 8 years as a management period to protect and promote natural regeneration. After the target tree has a breast diameter of ≥70cm, select and use individual trees. Cultivate successor target trees by selection or artificial replanting.

[0072] (4) Afforestation method: Same as above ( Figure 3 ).

[0073] The transition from secondary forest to secondary top community is a long process. If humans do not intervene, it generally takes 200 to 300 years. According to Kang Bing et al. (2006), after 26 years of natural succession, the population structure change law of the subtropical secondary forest community in Daqingshan, Guangxi, was found to be from the sun-loving evergreen broad-leaved forest to the mesophytic evergreen broad-leaved forest. The niche overlap values ​​of the original sun-loving dominant tree species, such as Quercus macrophylla and Melia azedarach, with other populations generally decreased, while the niche overlap values ​​of the mesophytic populations increased slightly, such as Eurya chinensis, Blood Gum Tree, Guangxi Pseudo-Myristica fragrans, etc. The niche overlap values ​​of the mesophytic partial shade populations increased significantly, and some species, such as Thick-leaved Qiongnan, Yangtong, and Hairy Yellow Machilus, became the community's founding species and dominant species. Nong You et al. (2015) observed in a 1-ha long-term monitoring plot set up in Daqingshan and found that in terms of species abundance, cross-sectional area at breast height and importance values, Quercus macrophylla and Rhizophora rustica were the co-dominant species in the community, with their number of individuals accounting for 30.8% of the total number of individuals. Acanthopanax chinensis, Phoebe guangdongensis and Camellia lanceolata were the main companion tree species in the community.

[0074] In summary, it is found that after nearly 30 years of natural recovery, low-value tree species such as large-leaf oak and rusty-haired shuttle fruit are still dominant species in the community, with low economic value, and it will take a long time to evolve into a secondary top community. The present invention adopts a method of artificial intervention to replant native precious tree species to accelerate community succession and improve the economic value of the forest stand. Observation found that the currently replanted precious tree species grow well, and the average annual growth of native precious tree species such as red castanea and loblolly wood: tree height 1.0m, breast diameter 1.0cm, and the future is promising. Other local practices have shown that the Institute of Tropical Forestry of the Chinese Academy of Forestry began to experiment with tree species suitable for replanting tropical secondary forests in Hainan Island as early as the late 1970s. It can now be seen that a large number of precious tree species can produce precious large-diameter timber after less than 30 years of growth. Artificially replanted red sandalwood has almost become a group-building tree species for secondary forests, and its biodiversity is much higher than that of natural secondary forests that have not been replanted.

[0075] References for the above data: [1] Kang Bing, Liu Shirong, Wen Yuanguang, Zhang Yuejin, Jiang Zaimin, Chang Jianguo. Population dynamics of subtropical secondary forest succession in Daqingshan, Guangxi [J]. Acta Plant Ecologica Sinica, 2006, 30(6): 931-940. [2] Nong You, Zheng Lu, Jia Hongyan, Lu Lihua, Huang Dewei, Huang Baihua, Lei Liqun. Community characteristics and spatial distribution patterns of major tree populations in secondary forests in Daqingshan, Guangxi [J]. Biodiversity Science, 2015, 23(3): 321-331. [3] Hou Yuanzhao, Chen Tongai. Strategic benefits of developing precious timber species in combination with secondary forest management in my country [J]. World Forestry Research, 2008, 21(2): 49-52.

[0076] Example 4

[0077] Compared with Example 3, the near-natural transformation of the secondary gully valley is the same as Example 3 except for the near-natural transformation of the secondary gully valley. Figure 4 ).

[0078] The precious tree species replanted in this embodiment are roughly the same as those in embodiment 3, and the growth amount and economic value are also similar. The difference is that the water and fertilizer conditions in the valley and mountainous areas are more superior than those in embodiment 3. Therefore, the management effect is better than that in embodiment 3.

[0079] In summary, the present invention mainly targets the problems existing in inefficient pine and fir artificial pure forests, degraded natural secondary forests and secondary valley woodlands. Guided by the theory of near-natural forest management, it explains in detail the management objectives, target forest phases, afforestation tree species selection, tree species configuration, full life cycle design, afforestation operation methods and success control indicators.

[0080] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests, characterized in that: The steps include: (1) Selection of tree species for afforestation: The afforestation tree species are selected to grow mutually beneficially or compatibly with the tree species of the artificial pure forest or degraded secondary forest to be reforested, and the saplings of the afforestation tree species have the basic shade tolerance ability to grow from the understory to the main forest layer; (2) Afforestation tree species configuration: The afforestation tree species are planted in at least one of cluster planting and uniform planting; (3) Full life cycle design: The whole life cycle includes the mixed uneven-aged forest stage and the near-natural forest stage in sequence; (4) Afforestation operations: Afforestation operations are performed according to step (1) afforestation tree species selection, step (2) afforestation tree species configuration, and step (3) full life cycle design.

2. The secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 1, characterized in that: The afforestation tree species include at least one of precious native tree species and fast-growing broad-leaved tree species.

3. The secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 2, characterized in that: The precious native tree species include at least one of Castanopsis rubrum, Eupatorium chinense, Dalbergia odorifera, Parashorea chinensis, Phoebe nanmu, Teak, and Dalbergia cochinchinensis; The fast-growing broad-leaved tree species include at least one of Myrica ovata, Quercus macrophylla, and Magnolia officinalis.

4. A secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 3, characterized in that: In step (3), the mixed uneven-aged forest stage specifically comprises: carrying out tending thinning and / or intensive thinning on the artificial pure forest to be reforested or the degraded secondary forest to form forest gaps; replanting the afforestation tree species in the formed forest gaps, and carrying out tending and management on the replanted afforestation tree species and the remaining trees from the thinning of the artificial pure forest to be reforested or the degraded secondary forest to be reforested; when the average height of the replanted afforestation tree species is ≥15m, selecting target trees and cutting down interfering trees; The near-natural forest stage is specifically as follows: when the target trees reach the target tree diameter at breast height, they are selectively felled; at the same time, target tree species entering the main forest layer are selected and cultivated as succession target trees, and the succession target trees are managed individually.

5. A secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 4, characterized in that: The specific thinning is to create 60 to 90 gaps / hm2 with a diameter of 8 to 10 m. 2 ; The intensive thinning specifically includes: setting the retention density of trees in the artificial pure forest or degraded secondary forest to be reforested to 8-10 trees / mu, and felling the remaining trees in the artificial pure forest or degraded secondary forest to be reforested.

6. The method for secondary afforestation in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 4, characterized in that: For the artificial pure forest to be reforested, the full life cycle design in step (3) includes the following specific steps: (3-1) Mixed uneven-aged forest stage: The mixed uneven-aged forest stage lasts from 1 to 15 years; In the first year, the artificial pure forest of secondary afforestation is thinned and 60 to 90 gaps with a diameter of 8 to 10 m are constructed per hectare. 2 ; The following year, the precious native tree species are replanted in the formed forest gaps, 4 to 6 trees are replanted in each forest gap, and the spacing between trees is 2m×2~3m; or / and the artificial pure forest for secondary afforestation is carried out with intensive thinning, the forest retention density of the artificial pure forest for secondary afforestation is 8 to 10 trees / mu, and then the fast-growing broad-leaved tree species are evenly planted, and the afforestation spacing is 2m×2~3m; the precious native tree species or / and the fast-growing broad-leaved tree species are nurtured and managed; when the average height of the precious native tree species or / and the fast-growing broad-leaved tree species is ≥15m, select the target tree, and the planting density of the target tree is 60 to 90 trees / hm 2 , remove interfering trees; every 5 to 8 years, according to the growth of the target trees, select and cut down interfering trees to protect and promote natural regeneration under the forest; (3-2) Near-natural forest stage: The period of the near-natural forest stage is 16 to 40 years; When the target tree's diameter at breast height reaches ≥50cm, selective felling is carried out, and at the same time, target tree species entering the main forest layer are selected and cultivated as succession target trees, and the succession target trees are managed individually.

7. The method for secondary afforestation in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 6, characterized in that: For pure plantations to be reforested, the full life cycle design in step (3) also includes the following steps: (3-3) Forest maturity and secondary colonization stage: The forest maturity and secondary colonization stage is 41 years later: Continue the individual tree management of the succession target trees, selectively cut down the succession target trees that have reached the target DBH in batches, and gradually form a near-natural forest with multiple tree species and different ages, with succession target trees as the main trees.

8. The method for secondary afforestation in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 4, characterized in that: For degraded secondary forests to be reforested, the full life cycle design in step (3) includes the following specific steps: (3-1) Mixed uneven-aged forest stage: The mixed uneven-aged forest stage includes the community establishment stage, competitive growth stage and quality selection stage; The period of the group establishment stage is 1 to 6 years; in the degraded secondary forest to be reforested, target tree species with ecological and economic value cultivation potential are selected and marked, the target tree species are nurtured, the remaining tree species are cut down, and 45 to 60 forest gaps with a diameter of 8 to 10 meters are constructed per hectare. 2 ; Plant the precious native tree species in the formed forest gaps, 4 to 6 trees per forest gap, with a spacing of 2m×2m between trees, and nurture and manage the precious native tree species; The competitive growth stage lasts for 7 to 14 years; light felling or pruning is performed on the upper trees around the forest gaps, and vines are cleared in time to ensure the healthy growth of the target tree species and the precious native tree species planted in the supplementary planting; The time period of the quality selection stage is 15 to 40 years: when the average height of the target tree species or the precious native tree species to be planted is ≥15m, target trees are selected, and the planting density of the target trees is 60 to 90 trees / hm2 2 , and at the same time, remove interfering trees; manage the target trees individually, with each management period lasting 5 to 8 years, selectively cut down interfering trees, and protect and promote natural regeneration; (3-2) Near-natural forest stage: The near-natural forest stage is from 41 years onwards; When the DBH of the target tree is ≥70cm, single tree selective felling is carried out; succession target trees are cultivated by selection or artificial replanting.

9. A secondary afforestation method in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 8, characterized in that: Degraded secondary forests to be reforested include degraded natural secondary forests or gully woodlands.

10. The method for secondary afforestation in forest gaps of low-quality artificial pure forests and degraded secondary forests according to claim 1, characterized in that: The afforestation operation described in step (4) specifically includes: performing forest clearing operations, land preparation operations and planting operations in sequence according to step (1) afforestation tree species selection, step (2) afforestation tree species configuration and step (3) full life cycle design.

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