Seedling raising method for multi-layer mixed multifunctional ecological man-made forest of broad-leaved Chinese fir trees

Abstract

The invention discloses a seedling raising method for a Chinese fir broad-leaved tree multi-layer mixed forest, and belongs to the technical field of forestry seedling raising. Aiming at the technical problems that the fir and the broad-leaved tree have malignant competition and are difficult to form symbiotic relationship during mixed cultivation, a double-cavity integrated symbiotic cultivation container is adopted, a degradable isolating membrane is arranged in the container, and the fir and the broad-leaved tree are respectively placed in special functional matrixes of a main cavity and an auxiliary cavity for cultivation. Physical isolation is performed in the early stage of seedling raising, and the isolation film is degraded in the later stage to guide root system interweaving to form co-rooting lumps. According to the method, interspecific competition is effectively solved, and the survival rate and the growth amount of broad-leaved trees are remarkably increased through the cultivated integrated symbiotic seedlings.

Description

Technical Field

[0001] This invention belongs to the field of forestry seedling technology, specifically relating to a seedling cultivation method for multi-layered mixed and multifunctional ecological artificial forests of Chinese fir and broadleaf trees. Background Technology

[0002] Chinese fir (Cunninghamia lanceolata) is an important fast-growing timber species in southern my country, but long-term intensive management of monoculture forests has led to a series of problems such as soil degradation, reduced biodiversity, and fragile ecosystems. To enhance the stability and multifunctionality of forest ecosystems, constructing multi-layered mixed forests of Chinese fir with other valuable broad-leaved species such as Phoebe zhennan, Phoebe bournei, and Schima superba has become an inevitable trend in modern forestry development.

[0003] However, traditional seedling cultivation and afforestation practices face significant technical bottlenecks. When Chinese fir and broadleaf tree seeds are sown together in the same container, the Chinese fir seedlings, growing much faster than broadleaf trees, rapidly encroach on the growing space with their powerful root systems. Their canopies block sunlight, predatoryly absorb nutrients and water, and may even produce allelochemicals that inhibit the growth of broadleaf trees. This results in slow growth, weak morphology, and extremely low survival rates in the broadleaf seedlings—a phenomenon known as "suppression." To address this issue, the industry commonly employs a "separate-then-combine" model, cultivating Chinese fir and broadleaf trees separately in independent containers until the seedlings mature before mixing and planting them together.

[0004] However, this model also has its drawbacks: First, it merely avoids competition during the seedling stage and fails to establish a benign, mutually beneficial relationship between species in the early stages. After afforestation, the root systems and rhizosphere microbial communities of the two types of seedlings are unfamiliar with each other, requiring a long time to establish a synergistic relationship, resulting in a delay in the realization of the ecological functions of the mixed forest. Second, it neglects the construction of the underground micro-ecosystem. A healthy forest ecosystem relies on a complex underground mycorrhizal network, which promotes nutrient exchange and signal transduction among trees. Traditional isolated seedling cultivation cannot pre-construct this cross-species mycorrhizal network during the seedling stage. Third, traditional container seedling cultivation commonly suffers from the "root-entrapment" phenomenon, where the roots grow spirally along the inner wall of the container, making it difficult for them to penetrate deeper into the soil after transplanting, affecting the seedlings' drought resistance, wind resistance, and long-term growth potential.

[0005] Therefore, how to start from the seedling stage, effectively isolate the vicious competition in the early stage, actively induce the symbiotic relationship in the later stage, solve the root-binding problem, and cultivate an "integrated symbiotic seedling" with healthy roots, harmonious interspecific relationships, and the ability to quickly exert ecological functions after afforestation is a technical problem that urgently needs to be solved in the construction of multifunctional ecological artificial forests. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical defects in existing technologies, such as imbalance of interspecific competition during the seedling stage, lack of early symbiotic foundation, and root congestion in seedlings, and to provide a seedling cultivation method for multi-layered mixed and multifunctional ecological artificial forests of Chinese fir and broadleaf trees. This invention, through innovative container design, synergistic functional matrix formulation, and coupling of cultivation processes, achieves a spatiotemporal transformation from physical isolation to micro-ecological symbiosis, cultivating "integrated symbiotic seedling units" with interwoven roots and shared microbial communities, laying a solid foundation for the rapid construction of healthy and stable multi-layered mixed forests.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for cultivating seedlings of multi-layered mixed and multifunctional ecological plantations of Chinese fir and broadleaf trees includes the following steps: Step 1: Using biodegradable materials, a dual-cavity integrated symbiotic cultivation container is prepared by injection molding. The container consists of a main cultivation cavity and a secondary cultivation cavity. The main cultivation cavity is used to cultivate Chinese fir seedlings, and the secondary cultivation cavity is used to cultivate broad-leaved tree seedlings. The main cultivation cavity and the secondary cultivation cavity are separated by an isolation membrane. The inner wall of the container is provided with multiple root guide grooves distributed along the axial direction of the container. Step 2: Prepare the Chinese fir slow-release nitrogen-fixing substrate A for the main culture chamber and the broadleaf tree mycorrhizal growth-promoting substrate B for the secondary culture chamber; Step 3: Fill the main and secondary cultivation chambers of the symbiotic cultivation container with the slow-release nitrogen-fixing substrate A of Chinese fir and the mycorrhizal substrate B of broadleaf tree, respectively; select plump Chinese fir seeds and broadleaf tree seeds, and after disinfection and germination treatment, sow the Chinese fir seeds in the main cultivation chamber and the broadleaf tree seeds in the secondary cultivation chamber, with 1-2 seeds sown in each chamber and covered with 1cm of soil; carry out routine seedling management, control the ambient temperature at 20-28℃, the relative humidity at 75%-85%, and water regularly; the seedling cycle is 6-8 months; Step 4: 30 to 45 days before the seedlings are ready for transplanting, gradually reduce the watering frequency and shading rate; when the cedar seedlings reach a height of 30 to 40 cm and a ground diameter of ≥ 0.5 cm, and the broad-leaved seedlings reach a height of 20 to 30 cm and a ground diameter of ≥ 0.4 cm, and when the roots of both have penetrated the degraded isolation membrane and intertwined to form root balls, they can be transplanted for afforestation.

[0008] Preferably, the biodegradable material is a blend of polylactic acid and bamboo charcoal powder, wherein the mass ratio of polylactic acid to bamboo charcoal powder is (70-80):(20-30).

[0009] Preferably, the separator is made by mixing chitosan, sodium alginate and glycerol in a mass ratio of (3-5):(1-2):1, cross-linking with 0.5% (v / v) glutaraldehyde solution, and pressing it to a thickness of 0.2-0.4 mm.

[0010] Preferably, the slow-release nitrogen-fixing matrix A of Chinese fir comprises, by weight: 40-50 parts peat moss, 15-20 parts perlite, 10-15 parts vermiculite, 5-10 parts biochar, 10-15 parts decomposed pine needles, and 1-2 parts controlled-release fertilizer.

[0011] Preferably, the broadleaf tree mycorrhizal substrate B, by weight, comprises: 30-40 parts peat moss, 10-15 parts perlite, 15-20 parts vermiculite, 20-25 parts decomposed broadleaf soil, 1-2 parts superphosphate, 0.5-1 part potassium sulfate, 0.1-0.3 parts chitosan oligosaccharide, and additionally inoculated with a compound microbial agent.

[0012] Preferably, the compound microbial agent is a mixture of Trichoderma, arbuscular mycorrhizal fungi, and brown azotobacters in a mass ratio of 1:1:1; the effective viable count of the compound microbial agent is ≥2×10⁻⁶. 8 CFU / g; the inoculum amount of the compound microbial agent is 0.5% to 1.0% of the total weight of substrate B.

[0013] Compared with the prior art, the present invention has the following significant advantages: (1) Spatiotemporal coupling to realize the intelligent transformation from competition to symbiosis: The "dual-cavity integrated + time-degradable isolation membrane" structure designed in this invention effectively prevents the physical invasion and nutrient plunder of fast-growing fir roots in the early stage of seedling cultivation (0-3 months), providing an independent "safe haven" for slow-growing broad-leaved trees; in the middle and late stages of seedling cultivation (after 3 months), the isolation membrane gradually degrades, opening a "time window" for communication between the roots and mycelia of both sides. At this time, the roots of the broad-leaved trees have a certain competitiveness and can peacefully contact and intertwine with the roots of fir, realizing a clever transition from physical isolation to physiological symbiosis, solving the problem that existing technologies cannot take into account both isolation and symbiosis.

[0014] (2) Synergistic matrix function to construct a cross-species underground micro-ecological network: This invention does not use a universal matrix, but designs a synergistic matrix with complementary functions. The biochar and controlled-release fertilizer in the Chinese fir matrix A can slowly release nutrients and adsorb nitrogen-fixing bacteria, reducing the nutrient depletion of broad-leaved trees; the compound bacterial agent and chitosan oligosaccharide (inducer) in the broad-leaved tree matrix B can efficiently construct a strong rhizosphere micro-ecological system, and actively "export" beneficial mycorrhizal fungi and nitrogen-fixing bacteria to the Chinese fir roots through the degraded isolation membrane, constructing a cross-species underground mycorrhizal network, promoting the synergistic absorption of elements such as phosphorus and nitrogen by both parties, and producing a synergistic effect of 1+1>2.

[0015] (3) Structural innovation to cultivate "integrated symbiotic seedlings" with well-developed root systems: This method ultimately cultivates an "integrated symbiotic seedling unit" with interwoven roots and shared microbial communities. When transplanting such seedling units, the root ball remains intact and is not easily dispersed, greatly reducing the chance of root damage and transplant shock. At the same time, the root guide groove design on the inner wall of the container effectively avoids the "root-entrapment" phenomenon of root coiling, guiding the main root to grow vertically downwards. The cultivated seedlings have good deep root characteristics, and their drought and wind resistance are significantly enhanced after afforestation, solving a long-neglected potential problem in existing container seedling cultivation technology.

[0016] (4) Accelerate the formation of multi-layered forest stands and improve the efficiency of ecological construction: Since good interspecific synergy and healthy root system structure are established during the seedling stage, after afforestation, this "integrated symbiotic seedling" can adapt to the environment more quickly and grow synergistically. The growth rate and stress resistance of broad-leaved trees are significantly better than those of seedlings cultivated by traditional methods, thus enabling the formation of multi-layered mixed forests with stable structure and complete functions more quickly, shortening the forestation cycle and improving the efficiency and quality of ecological construction. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels or by existing known methods.

[0018] Example 1

[0019] A method for cultivating seedlings in multi-layered mixed forests of Chinese fir and Phoebe bournei.

[0020] Step 1: Preparation of a dual-cavity integrated root guide symbiotic culture container: A double-cavity, one-piece frustum-shaped container with an upper diameter of 12cm, a height of 15cm, and a lower diameter of 9cm was manufactured by injection molding using polylactic acid (PLA, grade 4032D, NatureWorks, USA) and bamboo charcoal powder (particle size 200 mesh) blended at a mass ratio of 75:25. The container's inner wall is evenly decorated with four vertical root guide grooves with a depth of 2mm, and a 1cm diameter vent hole is located at the bottom.

[0021] Preparation of biodegradable separator membrane: Dissolve 4g chitosan (90% deacetylation), 1.5g sodium alginate and 1g glycerol in 100mL deionized water, stir well, add 0.5mL glutaraldehyde solution (0.5% volume concentration) as crosslinking agent, pour into a plate, dry in an oven at 40℃ to form a biodegradable separator membrane with a thickness of 0.3mm, cut and install in the separator groove of the container.

[0022] Step 2: Prepare a synergistic functional special matrix: Chinese fir slow-release nitrogen-fixing matrix A: Take 45 kg of peat soil (imported, pH 5.5-6.5), 18 kg of perlite (particle size 3-5 mm), 12 kg of vermiculite (particle size 3-5 mm), 8 kg of biochar (made from bamboo through anaerobic pyrolysis at 500℃), 13 kg of decomposed pine needles, and 2 kg of controlled-release fertilizer (ICL's Osmocote series), and mix them evenly.

[0023] Broadleaf tree (Machilus chinensis) growth-promoting mycorrhizal substrate B: Take 35kg peat moss, 12kg perlite, 18kg vermiculite, 22kg well-rotted broadleaf soil, 1.5kg superphosphate, 0.8kg potassium sulfate, and 0.2kg chitosan oligosaccharide (molecular weight <3000Da), and mix them evenly. Then, take a compound microbial inoculant (Trichoderma, arbuscular mycorrhizal fungi, and brown nitrogen-fixing bacteria mixed in a mass ratio of 1:1:1, with a total effective viable count ≥2×10⁻⁶). 8 Mix 0.8 kg (CFU / g) evenly into the above matrix.

[0024] Step 3: Sowing and Co-cultivation Management: Substrate A and Substrate B are respectively loaded into the main and auxiliary chambers of the container and compacted to 2 cm from the container opening.

[0025] Select Chinese fir seeds with a thousand-seed weight of over 28g and Phoebe zhennan seeds with a thousand-seed weight of over 150g. Disinfect the Chinese fir seeds by soaking them in a 0.3% potassium permanganate solution for 30 minutes, and disinfect the Phoebe zhennan seeds by soaking them in 50℃ warm water for 24 hours.

[0026] The treated seeds were sown in their respective substrates, with Chinese fir seeds sown in the main chamber and Phoebe zhennan seeds sown in the secondary chamber, one seed per chamber, and covered with 1cm of soil.

[0027] Seedlings are raised in a smart greenhouse, maintaining a temperature of 25℃ and humidity of 80% for the first three months. After three months, the environment is gradually adjusted to a natural one. During the seedling stage, a 0.2% foliar fertilizer of potassium dihydrogen phosphate is sprayed every 15 days. The total seedling cycle is seven months.

[0028] Step Four: Seedling Hardening and Transplanting: By the beginning of the sixth month of seedling cultivation, the seedlings were moved out of the greenhouse and placed in a hardening-off shed with a 50% shading rate. Fertilization was stopped, and watering was reduced, allowing the soil to dry slightly between waterings. After 30 days, the shading netting was completely removed. At this time, the average height of the Chinese fir seedlings was 35.2 cm, and the ground diameter was 0.51 cm; the average height of the Phoebe zhennan seedlings was 25.8 cm, and the ground diameter was 0.45 cm. Upon digging up some seedlings for observation, it was observed that the roots of both species had penetrated the degraded insulating film, tightly intertwined, forming a complete root ball that was not easily loosened, with the main root pointing vertically downwards without any coiling.

[0029] Comparative Example 1 (Traditional mixed seedling raising): Using the same standard single-chamber container as in Example 1, substrate A and substrate B were mixed in a 1:1 ratio and filled into the container. One Chinese fir seed and one Phoebe bournei seed were simultaneously sown into the container. Other cultivation conditions were exactly the same as in Example 1.

[0030] Comparative Example 2 (Traditional Separation Seedling Raising): Two independent, conventional single-chamber containers, with volumes equivalent to the secondary chamber in Example 1, were used. One container was filled with substrate A and sown with Chinese fir, while the other container was filled with substrate B and sown with Phoebe bournei. All other cultivation conditions were identical to those in Example 1. The seedlings were delivered as two separate seedlings.

[0031] Comparative Example 3 (Simplified scheme: with isolation but no synergistic matrix): The same dual-chamber integrated container and isolation membrane as in Example 1 were used, but both chambers were filled with general-purpose nutrient soil (peat:perlite:garden soil = 2:1:1). Other cultivation conditions were exactly the same as in Example 1.

[0032] Test Example 1 Thirty seedlings each from Example 1 and Comparative Examples 1-3 were selected after 7 months of cultivation and the following performance tests were conducted. The average value of the results was taken.

[0033] (1) Seedling morphology index test: Test method: Use a ruler to measure the height of the seedling from the ground to the terminal bud (seedling height), and use an electronic vernier caliper to measure the diameter of the seedling at the ground (ground diameter).

[0034] (2) Biomass and root-shoot ratio test: Test method: Remove the seedlings intact and wash away the soil from the roots. Divide the plant into above-ground parts (stems and leaves) and underground parts (roots). Place each part separately in a 105℃ oven for 30 minutes to de-enzyme, then dry at 75℃ to constant weight. Weigh the dry parts using a 0.01% balance. Total biomass = above-ground dry weight + underground dry weight; Root-to-shoot ratio = underground dry weight / above-ground dry weight.

[0035] (3) Mycorrhizal infection rate test: Test method: Fresh fine roots of seedlings were taken and cut into 1cm long segments. Acid fuchsin staining was used. One hundred root segments were randomly selected under a microscope, and the number of segments infected by mycorrhizal fungi (showing vesicles or arbuscular structures) was observed and recorded. Mycorrhizal infection rate (%) = (number of infected root segments / 100) × 100%.

[0036] (4) Survey of survival rate and growth one year after afforestation: Test method: 30 seedlings were planted in each group in an experimental forest with identical site conditions. After one year, the number of surviving seedlings was counted, and the survival rate was calculated. The height and diameter at ground level of the surviving seedlings were measured, and the annual growth was calculated.

[0037] Table 1 Performance test results of Example 1 and Comparative Examples 1-3

[0038] Results analysis: As can be seen from Table 1: Compared to Comparative Example 1 (mixed sowing): The *Phoebe zhennan* seedlings in Example 1 showed significantly better performance than those in Comparative Example 1 in all indicators, including seedling height, ground diameter, and underground dry weight, with increases of 166%, 150%, and 483%, respectively. This demonstrates that the isolation measures of the present invention effectively solved the problem of strong inhibition of broad-leaved trees by *Cunninghamia lanceolata*. In Comparative Example 1, the growth of *Cunninghamia lanceolata* appeared optimal, but the broad-leaved trees almost failed to survive, resulting in the failure of the mixed sowing.

[0039] Compared with Comparative Example 2 (separate planting), the *Phoebe zhennan* seedlings of Example 1 outperformed Comparative Example 2 in all growth indicators, and the survival rate and annual growth (increased by 53%) one year after afforestation were also significantly higher. This proves that the "integrated symbiotic seedlings" cultivated in this invention have stronger transplant adaptability and later growth advantages compared with traditional separated seedlings, demonstrating the great value of building a symbiotic relationship during the seedling stage.

[0040] Compared with Comparative Example 3 (simplified scheme), the growth indicators of the *Phoebe zhennan* seedlings in Example 1 were comprehensively superior to those in Comparative Example 3, especially in underground dry weight and root-to-shoot ratio, demonstrating the powerful promoting effect of the synergistic functional matrix on root development. Meanwhile, the mycorrhizal infection rates of both *Cunninghamia lanceolata* and *Phoebe zhennan* in Example 1 reached the highest levels, proving the synergistic effect of the synergistic matrix in constructing cross-species mycorrhizal networks. This highlights that the synergistic functional matrix and root guide grooves in this invention are not simply superimposed, but rather achieve a synergistic effect greater than the sum of its parts.

[0041] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for cultivating seedlings in a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf trees, characterized in that, By weight, the following steps are included: Step 1: Using biodegradable materials, a dual-cavity integrated symbiotic cultivation container is prepared by injection molding. The container consists of a main cultivation cavity and a secondary cultivation cavity. The main cultivation cavity is used to cultivate Chinese fir seedlings, and the secondary cultivation cavity is used to cultivate broad-leaved tree seedlings. The main cultivation cavity and the secondary cultivation cavity are separated by an isolation membrane. The inner wall of the container is provided with multiple root guide grooves distributed along the axial direction of the container. Step 2: Prepare the Chinese fir slow-release nitrogen-fixing substrate A for the main culture chamber and the broadleaf tree mycorrhizal growth-promoting substrate B for the secondary culture chamber; Step 3: Fill the main and secondary cultivation chambers of the symbiotic cultivation container with the slow-release nitrogen-fixing substrate A of Chinese fir and the mycorrhizal substrate B of broadleaf tree, respectively; select plump Chinese fir seeds and broadleaf tree seeds, and after disinfection and germination treatment, sow the Chinese fir seeds in the main cultivation chamber and the broadleaf tree seeds in the secondary cultivation chamber, with 1-2 seeds sown in each chamber and covered with 1cm of soil; carry out routine seedling management, control the ambient temperature at 20-28℃, the relative humidity at 75%-85%, and water regularly; the seedling cycle is 6-8 months; Step 4: 30 to 45 days before the seedlings are ready for transplanting, gradually reduce the watering frequency and shading rate; when the cedar seedlings reach a height of 30 to 40 cm and a ground diameter of ≥ 0.5 cm, and the broad-leaved seedlings reach a height of 20 to 30 cm and a ground diameter of ≥ 0.4 cm, and when the roots of both have penetrated the degraded isolation membrane and intertwined to form root balls, they can be transplanted for afforestation.

2. The method for raising seedlings of a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf fir according to claim 1, characterized in that, The biodegradable material is a blend of polylactic acid and bamboo charcoal powder, wherein the mass ratio of polylactic acid to bamboo charcoal powder is (70-80):(20-30).

3. The method for cultivating seedlings of a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf fir according to claim 1, characterized in that, The separator is made by mixing chitosan, sodium alginate and glycerol in a mass ratio of (3-5):(1-2):1, cross-linking with 0.5% (v / v) glutaraldehyde solution, and pressing it to a thickness of 0.2-0.4 mm.

4. The method for raising seedlings of a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf fir according to claim 1, characterized in that, The slow-release nitrogen-fixing matrix A of Chinese fir includes, by weight: 40-50 parts peat moss, 15-20 parts perlite, 10-15 parts vermiculite, 5-10 parts biochar, 10-15 parts decomposed pine needles, and 1-2 parts controlled-release fertilizer.

5. The method for raising seedlings of a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf fir according to claim 1, characterized in that, The broadleaf tree growth-promoting mycorrhizal substrate B, by weight, comprises: 30-40 parts peat moss, 10-15 parts perlite, 15-20 parts vermiculite, 20-25 parts well-rotted broadleaf soil, 1-2 parts superphosphate, 0.5-1 part potassium sulfate, and 0.1-0.3 parts chitosan oligosaccharide, and is additionally inoculated with a compound microbial agent.

6. The method for raising seedlings of a multi-layered mixed and multifunctional ecological artificial forest of Chinese fir and broadleaf fir according to claim 5, characterized in that, The compound microbial agent is a mixture of Trichoderma, arbuscular mycorrhizal fungi, and brown nitrogen-fixing bacteria in a mass ratio of 1:1:1; the effective viable count of the compound microbial agent is ≥2×10⁻⁶. 8 CFU / g; the inoculum amount of the compound microbial agent is 0.5% to 1.0% of the total weight of substrate B.

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