Method for transforming pure Xinjiang poplar forest in arid region into mixed Xinjiang poplar and robinia pseudoacacia forest

Abstract

The invention relates to the technical field of forest cultivation, in particular to a method for transforming a pure Xinjiang poplar forest into a Xinjiang poplar and robinia pseudoacacia mixed forest in an arid region. The method comprises the following steps: performing inter-row felling on a Xinjiang poplar forest stand with the canopy density greater than 0.7, deeply digging planting furrows in a vacant land after felling, complementarily planting robinia pseudoacacia saplings which are cultivated by seedling bags one year earlier in the planting furrows in an inter-row mixed manner, and when the ground diameter of trunks of the robinia pseudoacacia saplings reaches 3-4cm, felling residual Xinjiang poplar in the forest, and reserving one Xinjiang poplar coppice shoot. And performing conventional tending management until a stable populus bolleana and robinia pseudoacacia mixed forest is formed. According to the method, inter-row intermediate cutting, staggered rotation cutting and afforestation are combined, the degenerated pure Xinjiang poplar forest is efficiently transformed into the mixed forest of different ages through a progressive method by utilizing the mutual promotion relation of forest trees and adopting afforestation and tending and trunk repairing measures in different time periods, so that the protection forest in the arid region continuously plays ecological benefits, water and soil loss is reduced, and the economic benefit of the arid region is increased. The biodiversity is increased; and the forest stand is stabilized.

Description

Technical Field

[0001] The invention relates to the technical field of forest cultivation, and in particular to a method for transforming a pure Xinjiang poplar forest in an arid area into a mixed forest of Xinjiang poplar and black locust. Background Art

[0002] Xinjiang Populus Populusalbavar.pyramidalisBge. ) is a tree plant with a height of 15 to 30 meters, with morphological characteristics such as narrow cylindrical or spire-shaped crown, gray or blue-gray bark, smooth and few cracks. It is mainly distributed in Central Asia, West Asia, the Balkans of Europe and northern China. As a shelterbelt, Xinjiang Poplar has an irreplaceable role in preventing wind and sand, improving agricultural microclimate, etc., and plays a vital role in maintaining regional ecological balance. In arid areas, desertification is a serious problem, the land area is vast and the vegetation is sparse. Due to the long-term wind erosion and drought and high temperature conditions, the Xinjiang Poplar forest has gradually declined in tree growth and significantly reduced forest function. Under this environmental stress, Xinjiang Poplar has a series of low-quality and low-efficiency performances such as slow growth, bent trunks, sparse branches and leaves, and reduced wood quality, forming a large number of degraded forest stands.

[0003] In view of the current situation that there are a large number of low-quality and low-efficiency Xinjiang poplar pure forests in arid areas, some scientific and effective improvement measures are urgently needed. At present, most of the improvement measures are to replant Xinjiang poplar species, but because the original Xinjiang poplars have been planted for a long time, have a well-developed root system, and have a strong ability to obtain water resources, while the newly planted Xinjiang poplars have a shorter root system, they are restricted in terms of irrigation needs, root growth environment, and light requirements, resulting in poor or even no results in replanting. Therefore, it is of great significance to develop a method to effectively improve the low-quality and low-efficiency Xinjiang poplar pure forests in arid areas. Summary of the invention

[0004] In view of the technical problems existing in the above-mentioned prior art, the present invention provides a method for transforming pure Xinjiang poplar forests in arid areas into mixed forests of Xinjiang poplar and Robinia pseudoacacia. The method provided by the present invention can enable pure Xinjiang poplar forests in arid areas as shelter forests to continue to play ecological benefits, reduce soil erosion, increase biodiversity and stabilize forest stands.

[0005] A first aspect of the present invention provides a method for transforming a pure Xinjiang poplar forest in an arid area into a mixed forest of Xinjiang poplar and Robinia pseudoacacia, comprising the following steps: Fell the Xinjiang poplars in alternate rows, so that the spacing between the remaining Xinjiang poplars is 1m~2m and the row spacing is 4m~6m; Cultivate Robinia pseudoacacia saplings in seedling bags until the trunk height is 50cm~80cm; Dig planting trenches and plant the young Robinia pseudoacacia trees at a spacing of 2.5m to 3.5m; When the trunk diameter of the young Robinia pseudoacacia trees grows to 3cm~4cm, thin out the remaining Xinjiang poplar trees; Prevent the sprouts from the stumps after thinning, and cultivate a Xinjiang poplar sprout 1m~2m away from the stump; Targeted nurturing and management are carried out on Xinjiang poplar sprouts and Robinia pseudoacacia saplings until a mixed forest of Xinjiang poplar and Robinia pseudoacacia is formed.

[0006] Furthermore, the Xinjiang poplar pure forest is a Xinjiang poplar pure forest with a canopy density greater than 0.7.

[0007] Furthermore, the depth of the planting ditch is 75cm~85cm, the width of the planting ditch is 55cm~65cm; the distance between the planting ditch and the retained Xinjiang poplar is 1.9m~2.1m.

[0008] Furthermore, the method for preventing the sprouting of stumps after thinning is to apply herbicides or quicklime to the stumps by means of drilling holes for injection and / or applying the medicine.

[0009] Furthermore, the herbicide is glyphosate, paraquat or 2,4-D butyl ester.

[0010] Furthermore, the plant spacing of the Xinjiang poplar sprouts is 1.8m~2.2m, and the row spacing of the Xinjiang poplar sprouts is 2m~4m.

[0011] Furthermore, the cultivation and management includes irrigation, pruning and weeding.

[0012] A second aspect of the present invention provides an application of the above-mentioned method for transforming a pure Xinjiang poplar forest in an arid area into a mixed forest of Xinjiang poplar and Robinia pseudoacacia in restoring a degraded forest stand.

[0013] The beneficial effects of the present invention are: The present invention provides a method for transforming a pure Xinjiang poplar forest in an arid area into a mixed forest of Xinjiang poplar and Robinia pseudoacacia. (1) By thinning Xinjiang poplars in alternate rows, the spacing of the remaining Xinjiang poplars is 1m to 2m, and the row spacing is 4m to 6m. On the one hand, the ventilation and light transmission conditions in the forest can be improved. Light is the main factor affecting the growth of Robinia pseudoacacia. Thinning Xinjiang poplars leaves light and growth space for Robinia pseudoacacia saplings to ensure the normal growth of Robinia pseudoacacia saplings; on the other hand, excessive damage to the forest ecology is avoided. Since the ecological function of Robinia pseudoacacia saplings is relatively small in the early stage of transplantation, the retained Xinjiang poplars can still play a certain ecological function. (2) Robinia pseudoacacia saplings are cultivated in seedling bags until the trunk height is 50cm to 80cm. Cultivating Robinia pseudoacacia in seedling bags can be maximally free from the restrictions of climatic conditions in arid areas; Robinia pseudoacacia seedlings can be cultivated one year in advance, which can shorten the afforestation time of mixed forests and ensure that they have strong survival ability when planted, thereby improving the survival rate of planting. (3) Dig planting trenches to plant Robinia pseudoacacia saplings and control the spacing between plants to 2.5m~3.5m, so that the Robinia pseudoacacia saplings can take root and grow. The spacing of 2.5m~3.5m can make the Robinia pseudoacacia saplings fully utilize resources during their growth process and avoid overcrowding, which affects their growth. The reasons for cultivating Robinia pseudoacacia and Xinjiang poplar to form mixed forests are: Robinia pseudoacacia has strong drought tolerance and can survive in relatively harsh moisture conditions in arid areas, which is consistent with the characteristics of Xinjiang poplar in adapting to arid environments. The two can grow stably in the same area; the rhizobia of Robinia pseudoacacia can fix nitrogen in the air, increase soil fertility, improve the nutrient status of forest soil, provide more favorable soil conditions for its own growth and Xinjiang poplar growth, and promote the overall growth of mixed forests; the Robinia pseudoacacia branch and leaf morphology is different from that of Xinjiang poplar, and its crown distribution characteristics can complement Xinjiang poplar in space, improve the utilization efficiency of forest land for resources such as light, form a reasonable forest stand structure, and enhance the stability and ecological function of mixed forests. (4) When the trunk diameter of the Robinia pseudoacacia saplings grows to 3cm~4cm, the Xinjiang poplars that are retained are cut flat. At this time, the Robinia pseudoacacia has been able to adapt to the environment well and begin to play an ecological role. Thinning the Xinjiang poplars frees up more growth space for the Robinia pseudoacacia saplings transplanted earlier, promoting better growth of Robinia pseudoacacia. (5) Prevent the sprouts from the stump after thinning, and retain one Xinjiang poplar sprout by removing the weak and retaining the strong at a distance of 1m~2m from the stump. This can ensure that the new sprouts have sufficient growth space and nutrient sources, which is conducive to the formation of new high-quality Xinjiang poplar plants; at the same time, it can reduce the physiological age of Xinjiang poplars and avoid premature aging of mixed forest stands. (6) Finally, targeted care and management are carried out for Xinjiang poplar sprouts and Robinia pseudoacacia saplings, and targeted maintenance is carried out according to the growth characteristics of Robinia pseudoacacia and Xinjiang poplars, so as to form a stable and efficient Xinjiang poplar and Robinia pseudoacacia mixed forest as expected, and improve the stability and function of the forest ecosystem. The present invention efficiently and scientifically transforms pure Xinjiang poplar forests in arid areas into mixed forests of Xinjiang poplar and Robinia pseudoacacia through thinning and staggered rotation felling, cultivates Robinia pseudoacacia and Xinjiang poplar saplings in batches, and allows sufficient growth space for different tree species, thereby achieving the goal of not destroying the ecological function of the forest stand and enabling the forest land to continuously exert its ecological benefits.Especially in the desert areas on the edge of the oasis, the windbreak and sand fixation functions of the forest land will not be weakened, soil and water loss will be reduced, and the goals of mixed forest transformation and degraded forest restoration will be achieved.

[0014] The depth of the conventional planting ditch for cultivating Robinia pseudoacacia is generally 40cm~50cm. In the method of the present invention, the depth of the planting ditch for planting Robinia pseudoacacia saplings is 75cm~85cm. This is because, on the one hand, the mature Xinjiang poplar root system is widely distributed, and the planting ditch depth of 75cm~85cm can allow the roots of the Robinia pseudoacacia saplings to avoid the competition of the shallow Xinjiang poplar root system, better obtain water and nutrients in the soil, and improve the survival rate and growth potential of Robinia pseudoacacia; on the other hand, it can loosen the soil so that the roots of the Robinia pseudoacacia saplings can better grow and expand downward, so that the Robinia pseudoacacia saplings can take root deeper and more stably, and enhance their wind resistance and resistance to adverse environments such as drought. The present invention is based on the existing container seedling technology experience, combined with the climatic characteristics of arid areas, and uses seedling bags to cultivate Robinia pseudoacacia saplings in advance before afforestation, which not only shortens the afforestation time of alternating forests, but also improves the afforestation survival rate, and has good practicality; and Robinia pseudoacacia has great landscape benefits and economic value. After being mixed with Xinjiang poplar, it not only increases biodiversity and ecosystem stability, but also has the function of increasing forest stand ornamental value and improving soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The results show the effects of different light transmittances on the growth of Robinia pseudoacacia; Figure A, Figure B, Figure C and Figure D respectively show the daily changes in photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration of Robinia pseudoacacia in spring under different light transmittances.

[0016] Figure 2 The results show the effects of different light transmittances on the growth of Robinia pseudoacacia; Figure A, Figure B, Figure C and Figure D respectively show the daily changes in photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration of Robinia pseudoacacia in summer under different light transmittances.

[0017] Figure 3 The results show the effects of different light transmittances on the growth of Robinia pseudoacacia; Figure A, Figure B, Figure C and Figure D respectively show the daily changes in photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration of Robinia pseudoacacia in autumn under different light transmittances. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.

[0019] As a shelterbelt, Xinjiang poplar has an irreplaceable role in preventing wind and sand, improving agricultural microclimate, etc., and plays a vital role in maintaining regional ecological balance. However, the problem of desertification in arid areas is severe. Long-term wind erosion and high temperature and drought conditions have caused the growth of Xinjiang poplar to gradually decline, and the forest function has significantly decreased, forming a large number of low-quality and low-efficiency degraded forests. In view of the current situation that there are a large number of low-quality and low-efficiency Xinjiang poplar pure forests in arid areas, it is urgent to take some scientific and effective improvement measures. At present, most of the improvement measures are to replant Xinjiang poplar species. Because the newly replanted Xinjiang poplar has a short root system, it is restricted in terms of irrigation needs, root growth environment, light requirements, etc., resulting in poor or even no replanting results. Therefore, it is of great significance to develop a method to efficiently improve low-quality and low-efficiency Xinjiang poplar pure forests in arid areas.

[0020] The present invention provides a method for transforming a pure Xinjiang poplar forest into a mixed forest of Xinjiang poplar and Robinia pseudoacacia in an arid area. By performing inter-row felling on Xinjiang poplar forests with a canopy density greater than 0.7, deep planting trenches are dug on the clearing after felling, and Robinia pseudoacacia saplings cultivated one year in advance in a seedling bag are replanted in the deeper planting trenches in an inter-row mixed manner, and when the trunk diameter of the Robinia pseudoacacia sapling reaches 3 cm to 4 cm, the remaining Xinjiang poplars are felled, and one Xinjiang poplar sprout is retained, and conventional tending management is performed, so that a stable mixed forest of Xinjiang poplar and Robinia pseudoacacia can be formed.

[0021] Example 1: A method for transforming a pure Xinjiang poplar forest into a mixed Xinjiang poplar and Robinia pseudoacacia forest Cultivate Robinia pseudoacacia seedlings in advance: In early spring in the greenhouse nursery, put a 200mm diameter seedling bag into a PVC container (tube diameter 200mm, length 400mm), fill the bag with nutrient soil, then take the seedling bag filled with nutrient soil out of the PVC container and place it on the seedbed. The seedbed is 20 meters long and 5 meters wide, and ridges are built between the seedbeds. Sow Robinia pseudoacacia seeds in the middle of the seedling bag, cover with soil about 2cm, flood the seedling bed with water, so that the surface soil at the bottom of the seedling bag is completely soaked, and water again as needed until more than 85% of the cotyledons of Robinia pseudoacacia are unfolded. One year later, when the trunk of the Robinia pseudoacacia sapling is 50cm long, it can be used for transplanting and afforestation.

[0022] Felling Xinjiang poplars: select pure Xinjiang poplar forests with a canopy density greater than 0.7, and fell one row of Xinjiang poplars in the north-south direction every January, so that the spacing between the remaining Xinjiang poplars is about 1m, the row spacing is about 4m, and the roots are cleaned and felled.

[0023] Dig deep planting trenches: dig a row of planting trenches in the space between felled rows. The planting trench is 75cm deep and 55cm wide. The distance between the planting trench and the retained Xinjiang poplar is 1.9m.

[0024] Replanting Robinia pseudoacacia saplings: Replant the cultivated Robinia pseudoacacia saplings at the bottom of the planting ditch at a spacing of 2.5m, and irrigate with water in time. Wait about 20 days after the first watering before watering for the second time. Each irrigation must ensure that the soil water penetration depth is not less than 100cm.

[0025] Thinning Xinjiang poplar and stump treatment: After Robinia pseudoacacia has grown in the forest for one year, when the ground diameter of the main trunk reaches about 3 cm, the remaining Xinjiang poplars in the pure forest are cut down. At the stumps, 4 times the concentration of glyphosate, paraquat and 2,4-D butyl are applied by drilling and spraying. Then, plastic mulch is covered and soil is pressed to prevent the stumps from sprouting.

[0026] Cultivate Xinjiang poplar shoots: Cultivate Xinjiang poplar shoots at a distance of about 1.5m from the stump. According to the standard of plant spacing of about 2.2m and row spacing of about 4m, keep the strong shoots and remove the weak ones, retain only one Xinjiang poplar shoot, and carry out directional nurturing management.

[0027] Strengthen trunk pruning and care: timely prune the cultivated Robinia pseudoacacia and Xinjiang poplar saplings to promote ventilation and light transmission in the forest; the Xinjiang poplar trunk pruning method is: retain more than 2 / 3 of the trunk height, and remove all other side branches; Robinia pseudoacacia trunk pruning method is: timely prune the Robinia pseudoacacia saplings in May every year, cut off the side branches below 1 meter of the main trunk of the Robinia pseudoacacia saplings, and increase the trunk pruning height every year thereafter, and remove all side branches below 3 meters; the trunk pruning cuts should be smooth.

[0028] Strengthen water management: ensure irrigation during spring germination and autumn and winter each year, and at least 2 sufficient irrigations during the rest of the growing season.

[0029] Strengthen weed control in tree row planting ditches: Combine irrigation with manual weeding to inhibit weed growth; promptly remove weeds in planting ditches and around tree trays to reduce nutrient competition and provide a better growth environment for young Xinjiang poplar and Robinia pseudoacacia trees.

[0030] Example 2: A method for transforming a pure Xinjiang poplar forest into a mixed forest of Xinjiang poplar and Robinia pseudoacacia Cultivate Robinia pseudoacacia seedlings in advance: In early spring in the greenhouse nursery, put a 200mm diameter seedling bag into a PVC container (tube diameter 200mm, length 400mm), fill the bag with nutrient soil, then take the seedling bag filled with nutrient soil out of the PVC container and place it on the seedbed. The seedbed is 20 meters long and 5 meters wide, and ridges are built between the seedbeds. Sow Robinia pseudoacacia seeds in the middle of the seedling bag, cover with about 3cm of soil, flood the seedling bed with water, so that the surface soil at the bottom of the seedling bag is completely soaked, and water again as needed until more than 85% of the cotyledons of Robinia pseudoacacia are unfolded. One year later, when the trunk of the Robinia pseudoacacia sapling is 80cm long, it can be used for transplanting and afforestation.

[0031] Felling Xinjiang poplars: select pure Xinjiang poplar forests with a density greater than 0.7, and fell three rows of Xinjiang poplars in the north-south direction in February every year, so that the spacing between the remaining Xinjiang poplars is about 2m, the row spacing is about 6m, and the roots are cleaned and felled.

[0032] Dig deep planting trenches: dig 2 rows of planting trenches in the space between felled rows. The planting trenches are 85cm deep and 65cm wide. The distance between the planting trenches and the retained Xinjiang poplars is 2.1m.

[0033] Replanting Robinia pseudoacacia saplings: Replant the cultivated Robinia pseudoacacia saplings at the bottom of the planting ditch at a spacing of 3.5m, and irrigate with water in time. Wait about 20 days after the first watering before watering for the second time. Each irrigation must ensure that the soil water penetration depth is not less than 100cm.

[0034] Thinning Xinjiang Poplar and stump treatment: When the Robinia pseudoacacia grows to a ground diameter of about 4 cm in the forest, the remaining Xinjiang Poplars in the pure forest are cut down. At the stumps, 4 times the concentration of glyphosate, paraquat and 2,4-D butyl are applied by drilling and spraying. Then, plastic mulch is covered and soil is pressed to prevent the stumps from sprouting.

[0035] Cultivate Xinjiang poplar shoots: Cultivate Xinjiang poplar shoots at a distance of about 1.5m from the stump. According to the standard of plant spacing of about 1.8m and row spacing of about 2m, keep the strong shoots and remove the weak ones, retain only one Xinjiang poplar shoot, and carry out directional nurturing management.

[0036] Strengthen trunk pruning and care: timely prune the cultivated Robinia pseudoacacia and Xinjiang poplar saplings to promote ventilation and light transmission in the forest; the Xinjiang poplar trunk pruning method is: retain more than 2 / 3 of the trunk height, and remove all other side branches; Robinia pseudoacacia trunk pruning method is: timely prune the Robinia pseudoacacia saplings in July every year, cut off the side branches below 1 meter from the main trunk of the Robinia pseudoacacia saplings, and increase the trunk pruning height every year thereafter, and remove all side branches below 3 meters; the trunk pruning cuts should be smooth.

[0037] Strengthen water management: ensure irrigation during spring germination and autumn and winter each year, and at least 2 sufficient irrigations during the rest of the growing season.

[0038] Strengthen weed control in tree row planting ditches: Combine irrigation with manual weeding to inhibit weed growth; promptly remove weeds in planting ditches and around tree trays to reduce nutrient competition and provide a better growth environment for young Xinjiang poplar and Robinia pseudoacacia trees.

[0039] Example 3: Effects of different light transmittances on related indicators of Robinia pseudoacacia saplings under Xinjiang poplar in mixed forests The present invention further monitors the growth changes of morphological indicators and photosynthetic physiological indicators of Robinia pseudoacacia saplings under different light transmittances. The specific measurement method is as follows: In the pure Xinjiang poplar forest of Aksu Kekeshao Forestry Ecological Engineering Area, six normally growing Robinia pseudoacacia saplings with consistent growth were selected for the experiment. The plants and branches were fixed and marked, and the initial data were measured and counted. The growth conditions of the Robinia pseudoacacia saplings were regularly located and observed in spring, summer and autumn under different light transmittances of Xinjiang poplar, including the morphological characteristics of plant height, base diameter, and branch length (three standard branches were selected for each plant and their lengths were measured). At the same time, the diurnal changes in photosynthesis of the Robinia pseudoacacia saplings under two light transmittances were measured in spring (May 1), summer (August 8) and autumn (October 1) of the following year, and the measurement indicators included: photosynthetic rate, transpiration rate, stomatal conductance, and intercellular carbon dioxide concentration.

[0040] By monitoring the ground diameter and height of Robinia pseudoacacia saplings growing in Xinjiang poplars, monitoring was carried out according to the three growing seasons of spring, summer and autumn. The average light transmittance in the forest window was 84.74%, and the average light transmittance in the forest was 69.21%. The forest window was set as good light, and the forest was set as bad light. The Robinia pseudoacacia saplings in these two environments had a branch length (cm) increased by 49.67%, a base diameter (cm) increased by 91.67%, and a plant height (cm) increased by 34.78% under good light conditions compared to the Robinia pseudoacacia saplings under bad light conditions. The photosynthetic capacity of the Robinia pseudoacacia saplings under good light conditions was also higher than that of the Robinia pseudoacacia saplings under bad light conditions ( Figure 1~Figure 3 ).

[0041] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic inventive concept, they can make other changes and modifications to these embodiments, and these changes and modifications all fall within the scope of the present invention.

[0042] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention is also intended to include these modifications and variations.

Claims

1. A method for transforming a pure Xinjiang poplar forest into a mixed forest of Xinjiang poplar and Robinia pseudoacacia in an arid area, characterized in that: The following steps are involved: Fell the Xinjiang poplars in alternate rows, so that the spacing between the remaining Xinjiang poplars is 1m~2m and the row spacing is 4m~6m; Cultivate Robinia pseudoacacia saplings in seedling bags until the trunk height is 50cm~80cm; Dig planting trenches and plant the young Robinia pseudoacacia trees at a spacing of 2.5m to 3.5m; When the trunk diameter of the young Robinia pseudoacacia trees grows to 3cm~4cm, thin out the remaining Xinjiang poplar trees; Prevent the sprouts from the stumps after thinning, and cultivate a Xinjiang poplar sprout 1m~2m away from the stump; Targeted nurturing and management are carried out on Xinjiang poplar sprouts and Robinia pseudoacacia saplings until a mixed forest of Xinjiang poplar and Robinia pseudoacacia is formed.

2. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 1, characterized in that: The Xinjiang poplar pure forest is a Xinjiang poplar pure forest with a canopy density greater than 0.

7.

3. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 1, characterized in that: The depth of the planting ditch is 75cm-85cm, and the width of the planting ditch is 55cm-65cm.

4. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 1, characterized in that: The distance between the planting ditch and the retained Xinjiang poplar is 1.9m~2.1m.

5. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 1, characterized in that: The method for preventing the sprouts from the stumps after thinning is to apply herbicides or quicklime to the stumps by means of drilling holes, injecting medicine and / or applying medicine.

6. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 5, characterized in that: The herbicide is glyphosate, paraquat or 2,4-D butyl ester.

7. The method for transforming pure Xinjiang poplar forests into mixed Xinjiang poplar and Robinia pseudoacacia forests in arid areas according to claim 1, characterized in that: The plant spacing of the Xinjiang poplar sprouts is 1.8m~2.2m, and the row spacing of the Xinjiang poplar sprouts is 2m~4m.

8. Use of the method for transforming a pure Xinjiang poplar forest in an arid area into a mixed forest of Xinjiang poplar and Robinia pseudoacacia as described in any one of claims 1 to 7 in restoring degraded forest stands.

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