Tree species screening method for high-altitude drought afforestation, afforestation method and application

Abstract

The invention provides a tree species screening method for high-altitude drought afforestation, an afforestation method and application, and belongs to the technical field of forest tree breeding and cultivation. According to the screening method, five physiological and biochemical indexes of soluble protein, malondialdehyde, proline, peroxidase and soluble sugar in the tree species are measured through a gradient drought stress experiment, and comprehensive scoring is performed by adopting a membership function, so that the drought-resistant tree species are scientifically screened. The tree species such as sophora moorcroftiana, rosa serrulata and amorpha fruticosa screened by the method are applied to afforestation in the high-altitude arid region, and the afforestation survival rate and preservation rate can be remarkably increased. The invention provides a reliable technical scheme for solving the long-term problem that the selection of tree species in the difficult site field lacks scientific basis.

Description

Technical Field

[0001] This invention belongs to the field of forest tree breeding and cultivation technology, specifically a method for tree species selection, afforestation method and application for high-altitude arid afforestation. Background Technology

[0002] The Tibet Autonomous Region and its surrounding areas are located in the central part of the Qinghai-Tibet Plateau, with an average altitude exceeding 3,600 meters. This region contains large areas of challenging sites, including arid river valleys, barren hillsides, desertified land, and the edges of degraded grasslands. These sites face harsh natural conditions, characterized by scarce and concentrated rainfall, extremely high evaporation rates, infertile soils with high gravel content, and very poor water and fertilizer retention capacity, accompanied by intense wind erosion. In such sites, severe water scarcity is the primary limiting factor for ecological restoration and afforestation. Currently, afforestation in high-altitude arid regions faces the serious challenge of a lack of scientific basis and significant haphazard selection of tree species. Species selection often relies on traditional experience or indiscriminate introduction, with a severe lack of systematic evaluation and screening targeting the physiological mechanisms of drought stress in high-altitude areas. For example, widely used tree species such as Pinus tabuliformis and Pinus bungeana exhibit significantly higher malondialdehyde (MDA) content under drought stress, directly revealing the severity of damage to their cell membrane systems. Simultaneously, these species generally exhibit low proline accumulation capacity and peroxidase activity, key drought resistance indicators, making it difficult for them to maintain basic physiological functions under water stress. This is the fundamental reason for low afforestation survival rates. Furthermore, existing drought resistance evaluation methods are also one-sided. Even when screening is conducted, it is often limited to a single indicator, lacking a scientific system that can comprehensively quantify the drought resistance of tree species. This one-sided approach fails to comprehensively weigh the synergistic response mechanisms of tree species in osmotic regulation, reactive oxygen species scavenging, cell membrane stability, and metabolic maintenance, resulting in incomplete stress resistance in the selected species and unstable performance under long-term or extreme drought conditions. Furthermore, existing drought-resistant afforestation technologies are mostly simple applications of single measures, failing to place the fundamental step of tree species selection at the core and systematically couple it with site conditions. As a result, on difficult sites where water is the primary limiting factor, all subsequent afforestation measures are inefficient due to the lack of a scientific tree selection basis centered on the physiological response to water stress.

[0003] Therefore, developing a method that can comprehensively evaluate and quantitatively screen multiple key indicators based on the physiological and biochemical responses of tree species, and thus scientifically select drought-resistant tree species that are truly suitable for high-altitude, arid, and difficult sites, has become a pressing technical challenge in this field. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a tree species selection method, afforestation method and application for high-altitude arid afforestation, so as to solve the technical problems of low survival rate and lack of scientific tree selection basis in high-altitude arid and difficult site afforestation.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for selecting tree species for afforestation in high-altitude arid regions, comprising the following steps: Provide candidate tree species and conduct gradient drought stress experiments on the candidate tree species; Five physiological and biochemical indicators of tree species after stress were measured: soluble protein content, malondialdehyde content, proline content, peroxidase activity, and soluble sugar content. The five indicators were comprehensively evaluated using the membership function method, and tree species with qualified drought resistance were selected based on the comprehensive score.

[0006] Preferably, the gradient drought stress experiment includes five gradients: control group, mild stress, moderate stress, severe stress, and recovery watering.

[0007] More preferably, the index data of the tree species measured on the 28th day under the three stress levels of mild, moderate and severe stress are used to construct membership functions, calculate membership degrees, and apply them to the comprehensive evaluation of the membership function method.

[0008] More preferably, the formula for calculating the comprehensive score is as follows: Positive index: U ij = (X ij -X j,min ) / (X j,max -X j,min ); Negative indicator: U ij =1-(X ij -X j,min ) / (X j，max -X j,min In the formula, U ij X represents the membership function value of the i-th tree species with respect to the j-th index. ij X represents the measured value of the j-th index for the i-th tree species. j,max and X j,min This represents the maximum and minimum values ​​of the j-th indicator among the candidate tree species; the positive indicators include soluble protein content, proline content, peroxidase activity, or soluble sugar content; the negative indicators include malondialdehyde content. Coefficient of variation: In the formula, This represents the average value of the j-th indicator for each variety. X ij V represents the measured value of index j for variety i. j This represents the standard deviation coefficient of the j-th indicator; The weights of the five physiological and biochemical indicators are as follows: In the formula, W jThis represents the weight of the j-th indicator; Membership function comprehensive score: D i = ； The D i The value range is 0-1.

[0009] More preferably, the screening criterion is that tree species with a comprehensive score ≥ 0.55 are qualified for drought resistance.

[0010] The present invention also provides a method for afforestation in arid high-altitude areas, using drought-resistant tree species selected by the screening method for afforestation.

[0011] Preferably, the afforestation method further includes the following steps: selecting afforestation areas, preparing the land, constructing a water collection funnel system, planting the selected drought-resistant tree species, and implementing subsequent supporting management measures.

[0012] The present invention also provides an application of the drought-resistant tree species combination screened by the screening method in ecological restoration, soil and water conservation or desertification control in high-altitude areas.

[0013] The present invention also provides a drought-resistant tree species combination for afforestation in high-altitude arid areas, wherein the tree species combination is a combination of at least three drought-resistant tree species with a comprehensive score ≥0.55 obtained by the screening method.

[0014] More preferably, the drought-resistant tree species combination includes trees and shrubs, and the ratio of the number of trees and shrubs is (30%-40%): (60%-70%).

[0015] Compared with the prior art, the present invention has the following advantages: This invention discloses a comprehensive scoring method based on five physiological and biochemical indicators and assigned membership function values, shifting tree species selection from experience-based judgment to scientific quantification. Using this system, this invention successfully screened 10 core drought-resistant tree species with a comprehensive score ≥0.55 from 28 candidate species. Comparative results show that the traditionally commonly used tree species, *Pinus tabuliformis*, performs significantly worse than the screened species under this evaluation system due to its high malondialdehyde content (87.05 nmol / g) and low peroxidase activity (151.93 U / g), revealing the fundamental reason for its low afforestation survival rate from a physiological perspective. The tree species screened by this invention exhibit excellent and balanced performance in key drought resistance indicators. For example, *Sophora alopecuroides* has a peroxidase activity as high as 66028.96 U / g, possessing a strong reactive oxygen species scavenging ability; *Amorpha fruticosa* has a malondialdehyde content of only 30.23 nmol / g under severe stress, demonstrating excellent cell membrane system stability; and *Sapindus mukorossi* accumulates 7291.28 μg / g of proline, exhibiting outstanding osmotic regulation ability. This synergistic effect across multiple pathways, including antioxidant, membrane stabilization, and osmotic regulation, ensures the survival of seedlings under extreme drought conditions. Practical applications show that afforestation sites using the tree species and configuration schemes of this invention achieve a survival rate of 88%-95% in the first year and a three-year survival rate as high as 85%-92%, which is 30-50 percentage points higher than traditional methods. Attached Figure Description

[0016] Figure 1 The growth of the extremely drought-resistant tree species *Sapindus mukorossi* after 28 days of different levels of drought stress is shown in the figure. From left to right, the figures represent the control group, mild stress, moderate stress, severe stress, and recovery watering. Figure 2 The growth of the drought-resistant tree species *Sophora alopecuroides* after 28 days of different levels of drought stress is shown in the figure. From left to right, the figures represent the control group, mild stress, moderate stress, severe stress, and recovery watering. Figure 3 The growth of the drought-resistant jujube tree species after 28 days of different levels of drought stress is shown in the figure. From left to right, the figures represent the control group, mild stress, moderate stress, severe stress, and recovery watering. Figure 4 The growth of the drought-resistant tree species *Caragana korshinskii* after 28 days of different levels of drought stress is shown in the figure. From left to right, the figures represent the control group, mild stress, moderate stress, severe stress, and recovery from watering. Detailed Implementation

[0017] This invention provides a method for selecting tree species for afforestation in high-altitude arid regions, wherein the method preferably includes the following steps: Provide candidate tree species and conduct gradient drought stress experiments on the candidate tree species; Five physiological and biochemical indicators of tree species after stress were measured: soluble protein content, malondialdehyde content, proline content, peroxidase activity, and soluble sugar content. The five indicators were comprehensively evaluated using the membership function method, and tree species with qualified drought resistance were selected based on the comprehensive score.

[0018] In this invention, the gradient drought stress experiment includes five gradients: control group, mild stress, moderate stress, severe stress, and recovery irrigation. Membership function values ​​are calculated for the index data of the tree species measured on day 28 under the mild, moderate, and severe stress gradients, and used for comprehensive evaluation using the membership function method. Data from the control group (CK) and recovery irrigation (F) treatments are used to observe basic condition and recovery potential, but are not included in the comprehensive membership function score calculation for drought resistance. To scientifically evaluate the drought resistance of tree species, a gradient drought stress experiment is conducted for each candidate tree species. In a specific embodiment of this invention, the experiment sets mild, moderate, and severe drought stress to simulate different degrees of drought adversity, and the experimental period lasts at least 28 days. To scientifically quantify and compare the drought resistance of tree species, a comprehensive evaluation model based on the membership function method is constructed, with the following specific steps: (1) Data integration: For each candidate tree species i, the raw data of five physiological and biochemical indicators were obtained on day 28 of the gradient drought stress experiment under three treatments: mild stress (L), moderate stress (M), and severe stress (H). The arithmetic mean of the measured values ​​of each indicator under the three treatments was calculated to obtain the representative value X of the indicator for that tree species. ij Where i is the tree species number (i=1,2,...,m, where m is the total number of candidate tree species), and j is the index number (j=1-5, representing soluble protein, malondialdehyde, proline, peroxidase, and soluble sugar respectively).

[0019] (2) Data standardization (calculating membership degree U) ij Based on the direction of the indicators' response to drought stress, the indicators are divided into positive and negative indicators. The positive indicators include soluble proteins, proline, peroxidase, and soluble sugars; a higher value for this positive indicator indicates stronger drought resistance. The negative indicator is malondialdehyde (MDA); a lower value for this negative indicator indicates stronger drought resistance. The membership function value U for each indicator j is calculated using the following formula. ij Positive indicator: U ij = (X ij -X j,min ) / (X j,max -X j,min ); Negative indicator: U ij =1-(X ij -X j,min ) / (X j,max -Xj,min ), where X ij X represents the measured value of the j-th index for the i-th tree species. j,max and X j,min This represents the maximum and minimum values ​​of the j-th index among all candidate tree species.

[0020] (3) Determine the indicator weight W j The standard deviation coefficient method is used to objectively determine the weight of each indicator in order to reflect the relative importance of the evaluation values ​​of each indicator among different tree species. a) Calculate the standard deviation coefficient of each indicator. In the formula, This represents the average value of the j-th index across all candidate tree species; b) Calculate the weight of each indicator: .

[0021] (4) Calculate the membership function comprehensive score D i The overall drought resistance score D of the i-th tree species i Calculate using the following formula: D i = (5) Result determination: D i The value ranges from 0 to 1, with higher values ​​indicating stronger overall drought resistance of the tree species. A threshold is set to screen out tree species that meet the drought resistance criteria.

[0022] In this invention, the positive indicators include soluble proteins, proline, peroxidase, and soluble sugars. Soluble proteins reflect the cell's ability to maintain metabolic stability under stress, and their accumulation helps reduce cell damage. Proline, as a key osmotic regulator, effectively maintains cellular osmotic balance and prevents water loss. Peroxidase, as a key antioxidant enzyme, directly reflects the plant's ability to scavenge reactive oxygen species and mitigate oxidative damage. Soluble sugars have both osmotic regulation and energy supply functions. The negative indicator is malondialdehyde, the end product of membrane lipid peroxidation, whose content directly indicates the degree of damage to the cell membrane system.

[0023] In this invention, based on the calculation results and analysis of a large amount of tree species data, a comprehensive score ≥ 0.55 is set as the threshold for screening drought-resistant tree species. Tree species that reach or exceed this threshold indicate that they perform well in multiple key drought-resistant physiological pathways and possess the physiological basis for successful afforestation in arid and challenging high-altitude sites. In this invention, a comprehensive score ≥ 0.55 for qualified tree species represents a high degree of synergy and stability in key drought-resistant pathways such as osmotic regulation, antioxidant protection, membrane system stability, and metabolic maintenance. For example, *Xanthoceras sorbifolium* (0.7314) and *Sophora alopecuroides* (0.6857) not only excel in individual indicators but also exhibit excellent balance across all indicators. Tree species that do not meet the standard have a comprehensive score < 0.55, often indicating significant physiological shortcomings. For example, although some tree species may have high proline accumulation, their peroxidase activity may be low; or their malondialdehyde content may be high, indicating that their drought-resistant mechanisms are incomplete and they are at high risk of failure under long-term or combined stress. In this invention, the tree species screened by the screening method include shrubs or trees.

[0024] In a specific embodiment of the present invention, the drought-resistant tree species is selected from at least one of the following: *Vernicia fordii*, *Sophora alopecuroides*, *Rosa latifolia*, *Amorpha fruticosa*, *Caragana korshinskii*, *Myrica spp.*, *Ziziphus jujuba*, *Caragana korshinskii*, *Berberis thunbergii*, and *Elaeagnus angustifolia*.

[0025] The present invention also provides a method for afforestation in arid high-altitude areas, using drought-resistant tree species selected by the screening method for afforestation.

[0026] In this invention, the afforestation method further includes the following steps: afforestation area selection, land preparation, construction of a water collection funnel system, planting of the selected drought-resistant tree species, and subsequent supporting management measures. In this invention, the preferred criteria for selecting the afforestation area are: choosing challenging sites at an altitude of 3200-4000m, including arid river valleys, barren hillsides, desertified land, and the edges of degraded grasslands; requiring a slope of ≤35°, a soil layer thickness ≥30cm, a soil pH of 6.5-8.5, and a groundwater level at least 2m below the surface; a site condition survey must be conducted before afforestation. The afforestation area selection criteria of this invention are not universal standards, but rather suitable site conditions determined based on the physiological and ecological characteristics and tolerance boundaries of the selected tree species. The aim is to precisely deploy tree species that have been physiologically proven to have excellent drought resistance within the geographical and soil environment range where they can realize their potential, avoiding the negation of their physiological advantages due to severe mismatches in site conditions.

[0027] The preferred specifications and methods for land preparation are as follows: Land preparation should be carried out in spring (March-April) or after the rainy season (September-October); pit planting should be used, with dimensions ranging from 60cm×60cm×50cm to 80cm×80cm×60cm; or fish-scale pit planting, with a pit diameter of 80-100cm and a depth of 40-50cm; the spacing between trees should be 2-3m×2-3m, and shrubs 1.5-2m×1.5-2m; during land preparation, topsoil and subsoil should be piled separately, the bottom of the pit should be loosened to a depth of 15cm to break up the plow pan, and 0.6kg of well-rotted organic fertilizer should be applied to each pit and mixed with the topsoil to form a 15-20cm fertile soil layer. Backfill soil should be slightly higher than the ground level to form a mound. This invention, by increasing the volume of planting pits and applying organic fertilizer, aims to improve the rhizosphere soil structure in the early stages of planting, increase water and fertilizer retention space, and provide a favorable starting point for the early recovery and extension of the root system of drought-resistant tree species.

[0028] The preferred method for constructing the water collection funnel system includes: a) a tree basin water collection ditch: excavating a circular water collection ditch centered on the tree pit, 30-40cm wide and 15-20cm deep, 50-80cm from the center of the tree pit; constructing a 15-20cm high earthen embankment on the inner side of the ditch and compacting it; leveling and compacting the bottom of the ditch; b) a moisture-retaining covering layer: laying a 2-5cm particle size, 5-8cm thick layer in the tree basin with a diameter of 1-1.5m and within the water collection ditch. c) Slope drainage: Dig a 40-50cm wide, 30-40cm deep intercepting ditch with a longitudinal slope of 0.3-0.5% above the afforestation site. Every 3-5m, set up a 20-30cm wide, 15-20cm deep, 5-8% slope diversion ditch to guide water to the planting hole. Build a 20-30cm high earthen embankment outside the intercepting ditch.

[0029] In this invention, the preferred planting time for the selected drought-resistant tree species is from mid-April to early May in spring or from late June to mid-July during the rainy season. Container seedlings can also be replanted in late autumn or early winter, choosing cloudy days, evenings, or overcast days. The preferred treatment for the seedlings includes: soaking the roots in 50-100ppm ABT1 rooting powder or 50-200ppm indolebutyric acid (IBA) for 2-4 hours before planting, or quickly dipping them in 1000-2000ppm for 5-10 seconds; spraying an antitranspirant of 300-500 times dilution of humic acid evenly on both sides of the leaves until moist but not dripping; the preferred planting method is: the seedling roots are spread out without any gaps, the planting depth is based on the original soil mark, and trees can be planted 3-5cm deeper, with soil filled in layers and compacted in layers, and a water storage basin is built after planting. Immediately after planting, water thoroughly. Add 50-100ppm of ABT1 rooting powder or 50-200ppm of indolebutyric acid (IBA) and 50-100g of water-retaining agent to the water. Use slow-flow irrigation to water thoroughly in 2-3 applications. After the water has seeped in, promptly cover the soil with 3-5cm of fine soil to retain moisture. Water a second time after 5-7 days, depending on the soil moisture.

[0030] In a preferred embodiment of the present invention, the drought-resistant tree species is at least three of the following: *Xanthoceras sorbifolium*, *Sophora alopecuroides*, *Rosa latifolia*, *Amorpha fruticosa*, *Caragana korshinskii*, *Myrica spp.*, *Ziziphus jujuba*, *Caragana sinica*, *Berberis thunbergii*, and *Elaeagnus pungens*. When planting, the *Xanthoceras sorbifolium* seedlings (4-5 years old, container-grown) should reach a height of 80-120 cm and a ground diameter ≥ 1.2 cm; the *Sophora alopecuroides* seedlings (3-4 years old, large container-grown) should reach a height of 50-80 cm and a ground diameter ≥ 0.8 cm; the *Rosa latifolia* seedlings (2-3 years old, container-grown) should reach a height of 30-60 cm and a ground diameter ≥ 0.6 cm; the *Amorpha fruticosa* seedlings (2-3 years old, container-grown) should reach a height of 60-100 cm and a ground diameter ≥ 0.8 cm; and the *Caragana korshinskii* seedlings (2-3 years old, container-grown) should reach a height of 30-60 cm. The following seedlings are required: * **Berberis vulgaris:** 2-3 year old seedlings, 40-70 cm tall, with a ground diameter ≥ 0.6 cm; * **Ziziphus jujuba:** 2-3 year old container seedlings, 50-80 cm tall, with a ground diameter ≥ 0.8 cm; * **Hedysarum heterotropoides:** 2-3 year old container seedlings, 40-60 cm tall, with a ground diameter ≥ 0.8 cm; * **Berberis thunbergii:** 3-4 year old seedlings, 50-70 cm tall; * **Elaeagnus pungens:** 2-3 year old container seedlings or seedlings with soil balls, 50-80 cm tall, with a ground diameter ≥ 1.0 cm. All seedlings must be robust, with well-developed root systems, and free from pests and diseases. The priority given to native species and container seedlings must be strictly adhered to to ensure the survival rate and ecological adaptability of afforestation under the special site conditions of the plateau.

[0031] In this invention, the preferred tree species configuration is a combination of trees and shrubs, or a mixed coniferous and broadleaf species, with trees accounting for 30-40% and shrubs accounting for 60-70%. Tree species are selected according to slope aspect: coniferous species are chosen for sunny slopes and windy areas, while broadleaf species are chosen for shady slopes and valleys. The preferred proportion of the tree layer is 30%-40%. This tree layer serves as the community framework, constructing the upper canopy and playing a key ecological role in long-term carbon sequestration, windbreak, and the formation of a microclimate within the forest. Its deep root system can absorb and utilize deep soil moisture and nutrients. The preferred proportion of the shrub layer is 60%-70%. As a crucial understory vegetation, the shrub layer effectively covers the ground surface, suppresses competition from weeds, and directly reduces ineffective soil moisture evaporation. Its dense stems, leaves, and roots effectively intercept slope runoff, promote infiltration, and retain topsoil, acting as the first line of defense against soil erosion. Simultaneously, the shrubland provides habitat for soil animals and microorganisms, promoting nutrient cycling.

[0032] In this invention, post-planting management measures are provided to improve the survival rate of afforestation. These post-planting management measures preferably include the following: a) Application of water-retaining agent: Apply 100-200g / plant of water-retaining agent to the root distribution layer of the planting hole, mix thoroughly with the soil, and cover 0.1-0.2% of the soil volume in the root layer, which can increase soil water holding capacity by 30-50%; b) Mulching: Use black or biodegradable mulch film, 0.008-0.01mm thick, covering an area of ​​1-1.5m². 2a) Set up windbreaks: Set up windbreaks in windy or windy areas, using materials such as straw mats and windbreak nets, 1-1.5m high, 30-50cm upwind of the seedlings, which can reduce wind speed by more than 50%; b) Watering in the later stages: Water 2-4 times during the growing season depending on rainfall; Water before freezing in early November; c) Loosen the soil and weed: Loosen the soil 2-3 times during the growing season, to a depth of 5-10cm, and thoroughly remove weeds; d) Topdressing: Topdress once in April of the second year, using 100-150g of compound fertilizer (N:P:K=15:15:15) per plant, applied in a circular trench 30-40cm away from the main trunk; g) Pruning and shaping: Prune and shape the seedlings in the spring of the second year. First pruning: Remove diseased, insect-infested, overly dense, and competing branches; cultivate trees into single-trunk or multi-leader shapes. h) Pest and disease control: Regularly inspect and promptly treat any pests or diseases found. Common diseases are controlled with carbendazim or thiophanate-methyl, and common pests with imidacloprid or abamectin. i) Winter protection: In the first winter, from late November to early December, mound soil around the roots to a height of 20-30 cm; whitewash the trunk to a height of 1-1.2 m; or wrap it with straw rope to a height of 0.8-1 m, removing it the following spring. j) Quality inspection: Conduct the first inspection 15 days after planting and promptly replant any dead seedlings. In October-November of the same year, conduct a survival rate survey; a survival rate ≥85% is considered qualified, and ≥90% is excellent. In the autumn of the third year, conduct a retention rate survey; a retention rate ≥80% is considered qualified, and ≥85% is excellent.

[0033] The present invention also provides an application of the drought-resistant tree species combination screened by the screening method in ecological restoration, soil and water conservation or desertification control in high-altitude areas.

[0034] This invention also provides a drought-resistant tree species combination for afforestation in high-altitude arid areas, wherein the tree species combination is a combination of at least three drought-resistant tree species with a comprehensive score ≥0.55 obtained by the screening method. As a preferred embodiment, the drought-resistant tree species combination consists of at least three species selected from *Xanthoceras sorbifolium*, *Sophora alopecuroides*, *Rosa latifolia*, *Amorpha fruticosa*, *Caragana korshinskii*, *Myrica spp.*, *Ziziphus jujuba*, *Caragana korshinskii*, *Berberis thunbergii*, and *Elaeagnus angustifolia*.

[0035] In this invention, the drought-resistant tree species combination includes trees and shrubs, and the ratio of the number of trees and shrubs is (30%-40%): (60%-70%).

[0036] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0038] Example 1: Screening Experiment for Drought-Resistant Tree Species To scientifically select afforestation tree species suitable for high-altitude, arid, and difficult sites, a systematic comprehensive evaluation experiment on the drought resistance of 28 major native and introduced tree species in Lhasa and surrounding areas of the Tibet Autonomous Region was conducted.

[0039] 1. Materials and Methods (1) Experimental materials: 2-3 year old healthy container seedlings or cuttings of 28 tree species (see Table 1) were selected, and 12 seedlings of the same growth were prepared for each tree species for stress experiment.

[0040] (2) Experimental Design: The experiment was conducted in a plastic greenhouse. Twelve seedlings of each tree species were thoroughly watered and then divided into four treatment groups for precise water control: T0 (control, CK): 3 seedlings, maintaining soil field capacity (FC) at approximately 80% (sufficient water supply). T1 (mild stress, L): 3 seedlings, maintaining FC at 50%-60%. T2 (moderate stress, M): 3 seedlings, maintaining FC at 30%-40%. T3 (severe stress, H): 3 seedlings, maintaining FC at 15%-25%. Soil moisture content was monitored every two days using a soil moisture meter, and supplemental watering was used to strictly control the soil moisture content of each treatment group within the aforementioned range. The stress treatment lasted for 28 days. After the 28th day, all treatment groups were re-watered and entered the recovery period for observation.

[0041] (3) Sample collection and index determination: Leaf samples were collected from 10:00 to 12:00 AM on day 0 (start), day 14, day 28 (end of stress) and day 7 after rehydration (day 35). The samples were immediately treated indoors, and five key physiological and biochemical indicators were determined: soluble protein content, malondialdehyde (MDA) content, proline (PRO) content, peroxidase (POD) activity, and soluble sugar content. Data used for comprehensive evaluation were taken from day 28 of stress in three treatment groups for each tree species: mild stress (L), moderate stress (M), and severe stress (H).

[0042] 2. Construction and selection of comprehensive scoring model (1) Data standardization and calculation: Data on five indicators of all tree species on day 28 under three stress levels (mild stress (L), moderate stress (M), and severe stress (H) were collected and comprehensively scored according to the membership function. D i Calculate the membership function values ​​respectively.

[0043] (2) Screening Results: Based on the distribution of the calculation results, a comprehensive score ≥ 0.55 was set as the screening threshold for "highly drought-resistant tree species". The comprehensive scores of 10 tree species, including *Xanthoceras sorbifolium*, *Sophora alopecuroides*, *Rosa latifolia*, *Amorpha fruticosa*, *Caragana korshinskii*, *Myrica spp.*, *Ziziphus jujuba*, *Caragana korshinskii*, *Berberis thunbergii*, and *Elaeagnus pungens*, ranged from 0.5545 to 0.7314, significantly higher than other tree species, and were established as the core drought-resistant tree species recommended by this invention (see Table 2). This invention provides the growth status of four representative tree species under different stress treatments, such as... Figure 1-4 .

[0044] Table 1. Actual measured values ​​of five indicators for 28 tree species under different stress treatments. Table 2. Overall scores of 28 tree species

[0045] Comparative Example 1 The commonly used but ineffective tree species for afforestation in difficult sites in Lhasa, namely *Pinus bungeana* and *Juniperus chinensis*, were analyzed using the same five-index measurement method as in Example 1. The results, shown in Table 3, indicate that their overall scores were far below the threshold of 0.55. Specifically, the malondialdehyde content of *Pinus tabuliformis* (87.05 nmol / g) was approximately 2.3 times that of *Juniperus sabina* (38.41 nmol / g), a tree species screened in this invention, while its peroxidase activity (151.93 U / g) was less than 0.3% of that of *Sophora japonica* (66028.96 U / g).

[0046] Table 3. Indicators of commonly used tree species in Lhasa

[0047] Note: Based on data from a survey conducted in August 2024 regarding the effectiveness of afforestation on Gala Mountain in Lhasa five years later. Example 2: Application of afforestation in difficult sites in Duilongdeqing District, Lhasa City 1. Experimental area and conditions (1) Location: South-facing sunny slope of Duilongdeqing District, Lhasa.

[0048] (2) Site conditions: The elevation is about 3650 meters, the slope is about 25°, the soil is barren, the gravel content is high, and it is a typical arid and difficult site.

[0049] (3) Objective: To carry out drought-resistant afforestation on 5 mu of land, quickly restore vegetation, and control soil erosion.

[0050] 2. Implementation Steps (1) Tree species selection and configuration: 1) Tree species: From the core tree species library screened in Example 1, 264 *Hedysarum heterotropoides* (trees or semi-trees), 132 *Elaeagnus pungens* (trees), 132 *Sophora alopecuroides* (shrubs), and 132 *Rosa latifolia* (shrubs) were selected for combination configuration.

[0051] 2) Configuration pattern: A combination of trees and shrubs is adopted, with trees or semi-trees (Caragana korshinskii, Elaeagnus angustifolia) accounting for 40% and shrubs (Sophora alopecuroides, Rosa laevigata) accounting for 60%. The spacing between plants and rows is 2m×2.5m.

[0052] (2) Fine land preparation and water collection system construction: 1) Land preparation: Use fish-scale pits for land preparation, with dimensions of 90cm long diameter, 80cm short diameter, and 45cm depth. Separate the topsoil from the subsoil, and when backfilling, apply 0.6kg of well-rotted organic fertilizer to each pit and mix it evenly with the topsoil.

[0053] 2) Water collection funnel system: With the tree pit as the center, dig a ring-shaped water collection ditch (30cm wide and 20cm deep) and compact the inside of the ditch; cover the tree basin and the ditch with gravel with a particle size of 3-5cm, about 5-8cm thick, to suppress evaporation; dig a simple intercepting ditch above the slope to divert the runoff to the planting pit.

[0054] (3) Seedling treatment and planting: 1) Seedling specifications: Select robust container seedlings that are 3-4 years old, and whose specifications meet the design requirements.

[0055] 2) Treatment: Before planting, soak the roots in ABT1 rooting powder (100ppm) for 2 hours and spray the branches and leaves with an antitranspirant (humic acid).

[0056] 3) Planting: Plant on a cloudy day in late April 2021. Straighten the seedlings, spread out the roots, and backfill with soil in layers, tamping it down so that the root collar is slightly higher than the original soil mark. Construct a water-retaining basin after planting.

[0057] 4) Rooting water: Immediately water each plant thoroughly with water, adding 50g of water-retaining agent to the water.

[0058] (4) Post-construction maintenance: 1) Water management: Water once 7 days after planting. During the growing season (May-September), water 2-3 times depending on soil moisture. Water before the ground freezes in early November.

[0059] 2) Nurturing and management: Loosen the soil and remove weeds in a timely manner. In the spring of the second year after planting, perform trunk pruning and apply compound fertilizer. 3) Winter protection: Whitewash the tree trunks in the winter and mound soil around the root collar for frost protection.

[0060] 3. Implementation Results Fifteen days after planting, the survival rate was 98%. In the autumn of the same year (October), the survival rate of the afforestation was 94%. In the autumn of the third year after planting (October 2023), a retention rate survey was conducted, and the results showed that the retention rate reached 89%. The average annual height growth of trees exceeded 35cm, the crown width of shrubs expanded significantly, the vegetation coverage increased rapidly, and soil erosion was effectively controlled, which was significantly better than that of surrounding afforestation plots using traditional tree species and methods.

[0061] Example 3: Comparative Experiment with Conventional Afforestation Methods 1. Experimental Design Two comparative experiments were set up in adjacent areas on the same slope (3620m above sea level), each covering 5 acres.

[0062] This invention group: adopts the afforestation scheme described in Example 2. Regular group: Tree species selection and arrangement: Based on experience, Pinus tabuliformis (tree) and Hippophae rhamnoides (shrub) that are commonly used locally were selected for planting. The arrangement method is simple inter-row mixed planting, with the planting ratio of Pinus tabuliformis to Hippophae rhamnoides being 1:1, with approximately 330 trees of each species planted.

[0063] Land preparation and planting: Use small pits for land preparation, with pit dimensions of approximately 40cm (length) × 40cm (width) × 30cm (depth), and plant at the same spacing of 2m × 2.5m.

[0064] Water management: No water collection and moisture retention measures are implemented. Approximately 10 kg of water is applied per planting hole at the time of planting to help the roots establish. After that, watering is done solely by natural rainfall, and no artificial watering is required during the growing season.

[0065] Post-treatment management: No targeted soil loosening, topdressing, or winter protection measures are implemented; only a simple weeding is carried out once in the autumn of the first year.

[0066] 2. Result Comparison The results of comparing the data from the third year after planting are shown in Table 4: Table 4 Comparison of planting data of the present invention and conventional afforestation after 3 years.

[0067] As shown in Table 4, this invention combines scientific tree species selection, proactive water collection and moisture conservation projects with systematic management and maintenance, forming a complete technical solution for the core limiting factors of high-altitude drought. It significantly outperforms conventional afforestation methods in terms of afforestation survival rate, preservation rate, tree growth and ecological benefits, providing reliable technical support for solving the problem of difficult site afforestation in this region.

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for screening of tree species for afforestation in high altitude arid region, characterized by, Includes the following steps: Provide candidate tree species and conduct gradient drought stress experiments on the candidate tree species; Five physiological and biochemical indicators of tree species after stress were measured: soluble protein content, malondialdehyde content, proline content, peroxidase activity, and soluble sugar content. The five indicators were comprehensively evaluated using the membership function method, and tree species with qualified drought resistance were selected based on the comprehensive score.

2. The tree species screening method of claim 1, wherein, The gradient drought stress experiment included five gradients: control group, mild stress, moderate stress, severe stress, and restoration of irrigation.

3. The tree species screening method of claim 2, wherein, Membership functions were constructed, membership degrees were calculated, weighted processing was performed, and a final comprehensive evaluation was conducted on the index data of the tree species measured on day 28 under the three stress gradients of mild, moderate and severe stress.

4. The tree species screening method of claim 3, wherein, The calculation formula of the comprehensive score is as follows: positive index: U ij = (X ij -X j,min ) / (X j,max -X j,min ); negative index: U ij = 1- (X ij -X j,min ) / (X j,max -X j,min ); wherein, U ij represents the membership function value of the i th tree species for the j th index, X ij represents the measured value of the j th index of the i th tree species, X j,max and X j,min represent the maximum value and the minimum value of the j th index representative value in the candidate tree species; the positive index includes soluble protein content, proline content, peroxidase activity or soluble sugar content; the negative index includes malondialdehyde content; Standard deviation coefficient: ; wherein denotes the average value of the jth indicator of each variety, X ij denotes the measured value of the jth indicator of the i variety, V j denotes the standard deviation coefficient of the jth indicator; The weights of the five physiological and biochemical indexes are: ; in the formula, W j represents the weight of the jth index. Membership function comprehensive score: D i = ； The D i The value range is 0-1.

5. The tree species selection method according to claim 4, characterized in that, The selection criteria are that tree species with a comprehensive score ≥ 0.55 are qualified for drought resistance.

6. A method for afforestation in high-altitude arid regions, characterized in that, The drought-resistant tree species selected by the screening method described in any one of claims 1-5 are used for afforestation.

7. The afforestation method according to claim 6, characterized in that, The afforestation method also includes the following steps: afforestation area selection, land preparation, construction of water collection funnel system, planting of the selected drought-resistant tree species, and subsequent supporting management measures.

8. The application of drought-resistant tree species combinations screened by the screening method of any one of claims 1-5 in ecological restoration, soil and water conservation or desertification control in high-altitude areas.

9. A combination of drought-resistant tree species for afforestation in high-altitude arid regions, characterized in that, The tree species combination is a combination of at least three drought-resistant tree species with a comprehensive score ≥0.55 obtained by the screening method described in any one of claims 1-5.

10. The drought-resistant tree species combination according to claim 9, characterized in that, The drought-resistant tree species combination includes trees and shrubs, and the ratio of trees to shrubs is (30%-40%): (60%-70%).

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