Structure and Functional Characteristics of Generalized and Specialized Species of Soil and Root-Associated Fungi in Pinus sylvestris var. mongolica Forests of the Hulunbuir Desert

CHENG Yanlin¹, WANG Jiayuan¹, GAO Guanglei¹,²,³,⁴,⁵, DING Guodong¹,³,⁴,⁵, ZHANG Ying¹,³,⁴,⁵, ZHAO Peishan¹, ZHU Binbin⁶

¹School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
²National Key Laboratory for Efficient Production of Forest Resources, Beijing 100083, China
³National Observation and Research Station of Yanchi Mu Us Desert Ecosystem, Yanchi 751500, Ningxia, China
⁴Engineering Research Center of Forestry Ecological Engineering, Ministry of Education, Beijing 100083, China
⁵Key Laboratory of State Forestry and Grassland Administration on Soil and Water Conservation, Beijing 100083, China
⁶Development Center of Forestry and Grassland in Hulunbuir, Hulun Buir 021000, Inner Mongolia, China

Abstract

This study investigated the community structure and functional characteristics of generalized and specialized fungal species (GFS and SFS) in soil and root environments of Pinus sylvestris var. mongolica forests and their relationships with soil physicochemical properties, aiming to reveal key microbial mechanisms influencing ecosystem functioning. Using high-throughput sequencing technology, we analyzed the community structure and functional group differences between GFS and SFS in both natural and plantation forests (24, 35, and 44 years old) of P. sylvestris var. mongolica in the Hulunbuir Desert. The results showed that: (1) Soil and root-associated GFS retained 169 operational taxonomic units (OTUs) in total, soil SFS retained 603 OTUs, and root-associated SFS retained 216 OTUs. Dominant genera in soil GFS included Tricholoma and Suillus, while root-associated GFS were dominated by Tricholoma, Suillus, and Cadophora. Soil SFS were dominated by Penicillium, and root-associated SFS by Acephala. (2) Symbiotic trophic fungi accounted for 28.49%–47.21% of soil GFS, with ectomycorrhizal fungi as the dominant functional group, showing a trend of increasing then decreasing with stand age. Saprophytic trophic fungi comprised 17.01%–40.01% of soil SFS. Compared with natural forests, plantations showed lower relative abundance of saprophytic fungi, which exhibited a decreasing then increasing trend with stand age. Root-associated SFS contained 43.25%–54.45% symbiotic trophic fungi, dominated by ectomycorrhizal fungi that increased with stand age and were more abundant in natural than plantation forests. (3) Natural forests had significantly higher soil organic matter and available phosphorus than plantations (P < 0.05). In plantations, soil organic matter, total phosphorus, available nitrogen, and available phosphorus increased significantly with stand age (P < 0.05), while pH decreased non-significantly (P > 0.05). GFS distribution correlated significantly with soil organic matter, ammonium nitrogen, and total potassium (P < 0.05). Root-associated SFS correlated significantly with these factors plus total nitrogen (P < 0.05), while soil SFS correlated significantly with total potassium, available nitrogen, and nitrate nitrogen (P < 0.05). The drivers of fungal community structure showed significant ecological niche differentiation. These findings enhance understanding of the ecological functions of soil and root-associated fungi in P. sylvestris var. mongolica forests and provide a scientific basis for sustainable forest management and conservation.

Keywords: soil fungi; root-associated fungi; habitat generalist; habitat specialist; community structure; ecological function; soil physicochemical properties

Introduction

Soil fungi are critical drivers of material and energy flow in soil ecosystems, participating in organic matter decomposition, nutrient cycling, and biodiversity maintenance. Their community structure and functional characteristics directly affect plant growth, development, and reproductive processes. Root-associated fungi colonize or spread into host root systems, enhancing plant nutrient and water absorption while obtaining photosynthates from the host as an energy source. To cope with invasive species competition and environmental changes, some fungi adopt generalist or specialist strategies to improve their survival capabilities. Generalist species exhibit broad ecological adaptability, can survive in diverse soil and habitat conditions, and play important roles in new species formation and ecosystem function maintenance and stability. Specialist species have strict requirements for specific resources, can utilize resources that other species cannot or rarely use, or use them more efficiently, and typically survive in only one or a few specific habitats. This characteristic gives them strong specificity and limitations in ecosystems, making them highly competitive in particular habitats and significantly influencing plant growth and stress resistance. The coexistence of these two functional groups is crucial for soil ecosystem health and plant growth and development.

From an ecological driving mechanism perspective, the distribution patterns of fungal generalists and specialists are jointly controlled by host plant characteristics and environmental factors. Fungal-plant symbiosis is a major driver of plant evolution, with both forming close interactions during long-term coevolution. Host plant preference determines fungal community composition and is a key factor influencing the community structure of generalists and specialists. At broad spatial scales, climate differences caused by geographic location—such as temperature, precipitation, humidity, and light intensity—are critical factors affecting the structure and function of generalist and specialist communities. At finer spatial scales, soil physicochemical properties including water content, porosity, and nutrient content influence community composition and functional characteristics. Additionally, research on forest ecosystems indicates that stand age is an important factor affecting changes in soil and root-associated fungal community functions. Stand age growth means plant root expansion, death, and renewal, which affects soil structure and organic matter accumulation, thereby influencing soil microbial community structure and function. Young stands typically allocate more energy to growth and development, while mature stands may allocate more resources to maintaining ecosystem stability and resilience. These differences in resource allocation affect root exudate quality and quantity, consequently influencing the composition and functional characteristics of fungal generalists and specialists in soil and roots.

Pinus sylvestris var. mongolica has strong adaptability, cold resistance, tolerance to poor soils, and well-developed root systems. It is the preferred species for windbreak and sand fixation as well as soil and water conservation in northern China's sandy areas, and is also an important economic and ornamental tree species. Existing research has primarily focused on the ecological adaptation strategies, evolutionary dynamics, and community assembly roles of single-niche generalists and specialists in forest ecosystems. Studies show that generalists have wider niches and stronger environmental adaptability, with their distribution mainly driven by stochastic processes, while specialists depend on specific environmental conditions and are dominated by deterministic processes. However, key scientific questions regarding the structural composition, dynamic response patterns, and functional synergies of generalists and specialists across different niches require further investigation. Therefore, this study used natural and plantation forests of P. sylvestris var. mongolica in the Hulunbuir Desert to compare and analyze the structural and functional characteristics of GFS and SFS in soil and root environments, and to explore their relationships with soil physicochemical properties, thereby providing a scientific basis for sustainable management and protection of P. sylvestris var. mongolica forests to ensure both ecological health and economic benefits.

1. Materials and Methods

1.1 Study Area

Natural and plantation forest sample plots were established in the Inner Mongolia Honghuaerji Pinus sylvestris var. mongolica National Forest Park (48°44′N, 120°01′E) and Inner Mongolia Hailar National Forest Park (49°12′N, 119°33′E) in the southeastern Hulunbuir Desert. The region has a mid-temperate semi-humid continental monsoon climate, with annual evaporation of 1100–1200 mm, mean annual temperature of -0.78°C, annual precipitation of 348.4 mm, and annual sunshine duration of 2500 h. The main soil type is sandy soil, with dominant tree vegetation being P. sylvestris var. mongolica and natural vegetation including Salix gordejevii, Artemisia desertorum, and Potentilla bifurca.

1.2 Sample Plot Establishment and Sample Collection

In August, during the peak growth period of P. sylvestris var. mongolica, sample plots were established in middle-aged (24 a), near-mature (35 a), and mature (44 a) plantation and natural forests with identical site conditions and management measures. Within each forest type, three 20 m × 20 m plots were established as replicates. Within each plot, all trees were measured for height, diameter at breast height, and canopy density. Three standard P. sylvestris var. mongolica trees were selected for sampling in each plot, with spacing >10 m between trees. Surface litter within a 50 cm radius of each standard tree was removed before excavating soil profiles. Soil samples (0–20 cm depth) were collected using soil cores, and fine roots were carefully extracted. Three fresh soil samples and three fine root samples were mixed separately per plot, placed in sealed bags, and stored in a portable incubator at 4°C. A total of 18 mixed fresh soil samples and 18 fine root samples were collected for molecular identification. Simultaneously, three mixed dry soil samples per plot were collected in sealed bags for soil physicochemical property determination.

1.3 Soil Physicochemical Property Determination

Soil water content was determined using the aluminum box drying-weighing method; soil porosity by the ring knife drying-weighing method; pH value using a pH analyzer (Shanghai Leici, China); total potassium content by flame photometry; soil organic carbon content by the potassium dichromate dilution-heat method, from which soil organic matter content was calculated; total phosphorus content by the molybdenum-antimony colorimetric method; total nitrogen content by the indophenol blue colorimetric method; available nitrogen content by the alkali-hydrolyzed diffusion method; available phosphorus content by sodium bicarbonate extraction and molybdenum-antimony colorimetric method; and nitrate nitrogen and ammonium nitrogen contents using a continuous flow analyzer (SEAL AA3, Germany).

1.4 Fungal Molecular Identification

Fine root tips were cut and ground in liquid nitrogen using a mortar and pestle. DNA was extracted from 0.25 g of fine root and fresh soil samples using the MoBio PowerSoil DNA Isolation Kit. The fungal universal primers ITS1F (5′-CTTGGTCATTTAGAGGAAGTAA-3′) and ITS2 (5′-GCTGCGTTCTTCATCGATGC-3′) were used to amplify the ITS1 region of rDNA. PCR products were purified using the Agencourt AMPure XP nucleic acid purification kit, detected by gel electrophoresis, and sequenced on the Illumina MiSeq PE300 high-throughput sequencing platform. After amplification sequencing, ASV (amplicon sequence variant) tables were generated. The platform normalized samples based on minimum total abundance, filtering low-abundance ASVs. Representative sequences were compared using BLAST. If similarity reached or exceeded 97%, identification to species level was possible; if similarity was 90%–97%, identification to genus level was possible. Dominant genera were defined as those with relative abundance ≥10%, and common genera as those with 1%–10% abundance. The Dispersal Niche Continuum Index (DNCI) was used to analyze community assembly processes. The Clamtest function in the Vegan package was used to classify fungi into GFS and SFS based on abundance patterns, with the Specialist-Generalist index further refining classifications to obtain the final GFS and SFS communities for soil and root environments.

1.5 Data Processing and Analysis

Relative abundance stacked bar charts and cluster heatmaps of GFS and SFS were generated. Based on FUNGuild analysis results, ecological functional categories of GFS and SFS were classified, retaining only "highly probable" and "probable" confidence levels. Trophic types were divided into three categories: symbiotrophic, saprotrophic, and pathotrophic, with other mixed-nutrition types classified as "other." The Ggcor module was used for Mantel tests between fungal communities and soil properties, and the Vegan package was used for redundancy analysis (RDA) between the top five dominant genera and soil properties.

2. Results

2.1 Community Structure Composition of GFS and SFS

In natural and plantation forests of P. sylvestris var. mongolica, GFS and SFS retained 169, 603, and 216 OTUs, respectively. At the phylum level, soil GFS were dominated by Ascomycota (16.71%–41.74%) and Basidiomycota (56.47%–82.37%). With increasing stand age, Ascomycota showed a decreasing then increasing trend, while Basidiomycota showed the opposite pattern. Root-associated GFS were dominated by Ascomycota (51.84%–89.92%) and Basidiomycota (9.95%–47.89%). Ascomycota increased with stand age, while Basidiomycota decreased. In GFS, the difference between natural and plantation forests was that natural forests had much higher relative abundance of Basidiomycota than Ascomycota. Soil SFS were dominated by Ascomycota (46.43%–80.39%), Basidiomycota (9.96%–42.81%), and Mortierellomycota (1.68%–8.42%). Natural forests uniquely had Mucoromycota as a dominant phylum (3.23%). With increasing stand age, Basidiomycota showed an increasing then decreasing trend, while Mortierellomycota showed the opposite pattern. Root-associated SFS were dominated by Ascomycota (52.71%–76.58%) and Basidiomycota (23.27%–46.20%). Ascomycota showed an increasing then decreasing trend, while Basidiomycota showed the opposite pattern. Overall, Basidiomycota abundance was greater than Ascomycota in GFS, while the opposite was true for SFS.

At the genus level, soil GFS had 7 dominant and common genera, accounting for 75.94%–85.19% of total sequences. Natural forests were dominated by Tricholoma and Suillus, middle-aged plantations by Suillus, near-mature plantations by Inocybe, and mature plantations by Tricholoma. Compared with natural forests, plantations showed significantly lower relative abundance of Suillus (P < 0.05) and significantly higher abundance of Inocybe (P < 0.05). With increasing stand age, Tricholoma showed a significant increasing trend (P < 0.05). Root-associated GFS had 8 dominant and common genera, accounting for 54.25%–73.66% of total sequences. Natural forests were dominated by Tricholoma, middle-aged plantations by Tricholoma and Cadophora, near-mature plantations by Suillus, and mature plantations by Tricholoma. Compared with natural forests, plantations showed significantly lower relative abundance of Mycena (P < 0.05) and significantly higher abundance of Inocybe and Cadophora (P < 0.05). With increasing stand age, Tricholoma showed a significant increasing trend (P < 0.05), while Inocybe and Cadophora showed significant decreasing trends (P < 0.05). Soil SFS had 9 dominant and common genera, accounting for 43.71%–75.14% of total sequences. Natural forests were dominated by Penicillium and Geminibasidium, middle-aged plantations had no dominant genus but the highest relative abundance was Penicillium (13.70%), and both near-mature and mature plantations were dominated by Penicillium. Plantations showed significantly lower relative abundance of Geminibasidium than natural forests (P < 0.05). With increasing stand age, Penicillium in plantations showed an increasing then decreasing trend. Root-associated SFS had 6 dominant and common genera, accounting for 54.25%–84.91% of total sequences. Natural forests were dominated by Acephala and Tricholoma, middle-aged plantations by Inocybe, near-mature plantations by Acephala, and mature plantations by Acephala. Middle-aged plantations showed extremely significantly lower relative abundance of Acephala than natural forests and other plantation ages (P < 0.01).

2.2 Ecological Functions of GFS and SFS

In P. sylvestris var. mongolica forests of the Hulunbuir Desert, soil GFS contained 28.49%–47.21% symbiotrophic fungi, 8%–32% saprotrophic fungi, and 4.31%–6.88% pathotrophic fungi. The dominant functional group was ectomycorrhizal fungi, which showed an increasing then decreasing trend with stand age. Root-associated GFS contained 53.88%–63.63% symbiotrophic fungi, 11.16%–28.14% saprotrophic fungi, and 1.62%–4.28% pathotrophic fungi. Other trophic fungi accounted for 0.00%–0.14%, with relative abundance increasing significantly with stand age (P < 0.05). The main difference between GFS and SFS was that SFS had significantly higher relative abundance of saprotrophic fungi (P < 0.05), with symbiotrophic fungi showing significantly lower abundance (P < 0.05). Pathotrophic fungi were most abundant in soil SFS.

Soil SFS contained 21.33%–40.01% symbiotrophic fungi, 17.01%–40.01% saprotrophic fungi, and 9.73%–30.83% pathotrophic fungi, with other trophic fungi accounting for 4.63%–20.48%. Compared with natural forests, plantations had significantly lower relative abundance of saprotrophic fungi (P < 0.05), which showed a decreasing then increasing trend with stand age, while symbiotrophic and pathotrophic fungi showed the opposite pattern. Root-associated SFS contained 43.25%–54.45% symbiotrophic fungi, 14.68%–31.80% saprotrophic fungi, and 1.62%–4.28% pathotrophic fungi, with other trophic fungi accounting for 0.04%–0.93%. The dominant functional group was ectomycorrhizal fungi, which increased with stand age and was more abundant in natural than plantation forests.

2.3 Correlations Between GFS/SFS and Soil Properties

Soil physicochemical properties of P. sylvestris var. mongolica forests are shown in [TABLE:2]. Natural forests had significantly higher soil organic matter and available phosphorus than plantations (P < 0.05), but significantly lower soil water content, pH, total potassium, and available nitrogen (P < 0.05). In plantations, soil organic matter, total phosphorus, available nitrogen, and available phosphorus increased significantly with stand age (P < 0.05), while pH decreased non-significantly (P > 0.05). Mantel test results ([FIGURE:4]) showed that soil GFS distribution correlated significantly with soil organic matter, ammonium nitrogen, and total potassium (P < 0.05). Root-associated GFS distribution correlated significantly with soil organic matter, pH, total nitrogen, total potassium, and ammonium nitrogen (P < 0.01). Soil SFS distribution correlated significantly with total potassium, available nitrogen, and nitrate nitrogen (P < 0.05). Root-associated SFS correlated significantly with soil organic matter, pH, total nitrogen, total potassium, and ammonium nitrogen (P < 0.01), and extremely significantly with total phosphorus (P < 0.01).

RDA analysis of the top five dominant genera and soil properties ([FIGURE:5]) revealed that soil GFS dominant genera Tricholoma and Suillus correlated significantly and positively with soil organic matter and total potassium (P < 0.01). Root-associated GFS dominant genera Tricholoma and Suillus correlated significantly and positively with soil organic matter, total nitrogen, total potassium, and ammonium nitrogen (P < 0.05). Soil SFS dominant genera Penicillium, Geminibasidium, and Suillus correlated significantly and positively with total potassium and ammonium nitrogen (P < 0.05), but significantly and negatively with pH (P < 0.05). Root-associated SFS dominant genus Acephala correlated significantly and positively with soil organic matter, total nitrogen, total potassium, and ammonium nitrogen (P < 0.05).

3. Discussion

3.1 Community Structure and Environmental Response of GFS and SFS

In P. sylvestris var. mongolica forests of the Hulunbuir Desert, both GFS and SFS were dominated by Ascomycota and Basidiomycota. GFS were dominated by Basidiomycota, while SFS were dominated by Ascomycota. This difference may relate to their ecological functions: Ascomycota have diverse nutritional modes, can decompose organic matter saprophytically, and form symbiotic relationships with P. sylvestris var. mongolica to promote host nutrient absorption, while Basidiomycota are primarily ectomycorrhizal fungi that build mutualistic relationships by expanding root absorption area. Previous studies have shown that Ascomycota can produce dormant structures to resist harsh sandy environments, while Basidiomycota have broader adaptation to various soil environmental factors. This study found that natural forests had higher relative abundance of Basidiomycota and ectomycorrhizal fungi in GFS communities, along with higher soil organic matter and available phosphorus, consistent with research on subalpine spruce forests.

At the genus level, Tricholoma dominated GFS in both natural and plantation forests, with its relative abundance increasing with stand age. RDA analysis showed that Tricholoma was widely distributed in habitats with high soil organic matter but limited in soils with high available phosphorus. This distribution pattern may result from several factors: as stand age increases, ecosystems mature, soil organic matter accumulates continuously, and soil structure and microenvironments become more stable and diverse, providing suitable habitats for Tricholoma; additionally, Tricholoma has efficient enzyme systems to decompose accumulated litter; finally, mature trees have well-developed root systems that form tighter symbiotic relationships with Tricholoma, which obtains more photosynthates from trees while helping them absorb nutrients and water, promoting its own proliferation.

Soil and root-associated SFS showed large differences in dominant and common genera composition, mainly due to ecological niche differentiation, selective screening by plant roots, and different microbial interactions. Spatially, the open soil environment provides diverse microhabitats at soil particle, pore, and organic-inorganic interfaces for fungal colonization and organic matter decomposition, while the relatively closed root environment requires fungi to adapt to plant root tissues and depend on host-provided nutrients. Plant roots strictly filter suitable fungal specialists through physical barriers, chemical signals, and symbiotic compatibility. Moreover, soil microbial communities are dominated by resource competition, while root-associated microbes tend to form cooperation relationships centered on plant needs. These factors collectively lead to composition differences at the common genus level. Penicillium dominated soil SFS communities, with its relative abundance increasing with stand age. RDA analysis showed its distribution was significantly affected by soil nutrients: positively correlated with total nitrogen, total potassium, ammonium nitrogen, and organic matter, but negatively correlated with available nitrogen, nitrate nitrogen, and pH. This pattern may occur because as stand age increases, more litter accumulates in forest ecosystems, and Penicillium can efficiently decompose complex organic components like cellulose and lignin. The negative correlation with available nitrogen and nitrate nitrogen may be because Penicillium prefers complex nitrogen compounds, and high levels of these nitrogen forms may alter soil chemistry or microbial competition relationships, inhibiting Penicillium growth. Notably, root-associated fungal dominant genera showed significant positive correlations with multiple soil nutrients (total nitrogen, total potassium, ammonium nitrogen, and organic matter), while specialists only correlated significantly with total potassium, ammonium nitrogen, and nitrate nitrogen, indicating that nitrogen forms in soil affect fungal community distribution patterns.

3.2 Ecological Functional Characteristics of GFS and SFS

During long-term evolution, fungi have developed diverse ecological adaptation strategies and nutritional modes to cope with environmental changes and competition. They can efficiently utilize resources, expand niches, flexibly adapt to environments, and enhance survival and reproduction capabilities. This study found that GFS and root-associated SFS were dominated by symbiotrophic fungi, while soil SFS were dominated by saprotrophic and pathotrophic fungi. Specifically, symbiotrophic fungi form mutualistic symbioses with plant roots, obtaining photosynthates while enhancing plant mineral nutrient and water absorption through extensive hyphal networks. Saprotrophic fungi act as key decomposers, playing central roles in soil organic matter transformation and nutrient cycling. Pathotrophic fungi infect host organisms, extracting nutrients from host cells for growth and reproduction. Overall, SFS had higher relative abundance of saprotrophic fungi than GFS, particularly in soil SFS, because soil environments provide abundant organic matter and pathogenic hosts, focusing on organic matter decomposition and host infection rather than mutualistic relationships with plants.

Compared with natural forests, plantations had lower saprotrophic fungal abundance, showing a decreasing then increasing dynamic with stand age. This trend may occur because early-stage plantations are dominated by single tree species, providing limited types and amounts of organic substrates that cannot meet the diverse needs of saprotrophic fungi. Additionally, afforestation practices such as tillage and fertilization disturb soil structure and microbial community stability, and saprotrophic fungi are sensitive to these changes, making initial adaptation difficult and causing early abundance declines. With increasing stand age, litter accumulation increases, soil microbial communities stabilize, ecosystem diversity improves, providing richer nutrient sources for saprotrophic fungi and promoting abundance recovery. However, because plantation ecosystem complexity and stability remain lower than natural forests, saprotrophic fungal abundance stays relatively low. The study also found that the proportion of symbiotrophic fungi in root-associated GFS decreased gradually with stand age, likely because mature trees have well-developed root systems with enhanced autonomous water and nutrient absorption capacity, reducing dependence on symbiotrophic fungi.

Fungi with different nutritional modes showed distinct distribution patterns in soil and root environments. When saprotrophic and pathotrophic fungal proportions increase, tree stress resistance continuously declines and disease risk increases. Pathotrophic fungi in soil SFS had the highest relative abundance, and as pathogenic fungi transform from pathotrophic to saprotrophic nutrition, host resistance to saprotrophic fungi is weaker than to pathotrophic fungi, slowing host recruitment of endophytes. Therefore, we speculate that P. sylvestris var. mongolica plantations are more susceptible to harmful fungal infections. As forest community succession progresses, soil and root-associated fungal communities become more complex and stable, organic matter accumulation provides abundant nutrients, diversified niches enhance interactions, and improved environmental conditions favor fungal growth. Through selective pressure adaptation, community structure becomes more stable and adaptive capacity to environmental changes improves.

4. Conclusion

Generalized and specialized fungal species in P. sylvestris var. mongolica forests of the Hulunbuir Desert show significant ecological differentiation. In terms of community structure, the two functional groups exhibit distinct differences. Both are dominated by Ascomycota and Basidiomycota, with GFS dominated by Tricholoma, Inocybe, and Suillus, soil SFS by Penicillium, and root-associated SFS by Acephala. These groups show varying degrees of significant correlation with soil physicochemical properties, with soil organic matter, available nitrogen, total nitrogen, and total potassium being key environmental drivers of community structure changes. Ecologically, during P. sylvestris var. mongolica growth, GFS primarily promote nutrient absorption and stress resistance through symbiotic relationships with hosts while improving rhizosphere microenvironments, whereas SFS participate in organic matter decomposition through saprotrophic nutrition, enhancing system material cycling efficiency. Notably, with increasing stand age, the two functional groups show a synergistic enrichment pattern: symbiotrophic fungi support rapid early tree growth, while saprotrophic fungi maintain ecosystem stability in mature stands by promoting organic matter transformation. This functional complementarity reflects the adaptive succession characteristics of microbial communities during forest development from establishment to maturity. Based on these results, regulating the ecological niche allocation of these two fungal groups to fully utilize the complementary functions of GFS in nutrient absorption and SFS in material decomposition can provide a theoretical basis for microbially-mediated sustainable forest management.

References

[1] Bastida F, Eldridge D J, García C, et al. Soil microbial diversity biomass relationships are driven by soil carbon content across global biomes[J]. The ISME Journal, 2021, 15(7): 2081-2091.

[2] Beck S, Powell J R, Drigo B, et al. The role of stochasticity differ in the assembly of soil and root associated fungal communities[J]. Soil Biology and Biochemistry, 2015, 80(1): 18-25.

[3] Dehling D M, Bender I M A, Blendinger P G, et al. Specialists and generalists fulfil important and complementary functional roles in ecological processes[J]. Functional Ecology, 2021, 35(8): 1810-1822.

[4] Sriswasdi S, Yang C, Iwasaki W. Generalist species drive microbial dispersion and evolution[J]. Nature Communications, 2017, 8(1): 1162-1168.

[5] Liu Hongtao, Hu Tianlong, Wang Hui, et al. Community assembly and functional potential of habitat generalists and specialists in typical paddy soils[J]. Acta Pedologica Sinica, 2023, 60(2): 546-557.

[6] Kennedy P G, Hill L T. A molecular and phylogenetic analysis of the structure and specificity of Alnus rubra ectomycorrhizal assemblages[J]. Fungal Ecology, 2010, 3(3): 195-204.

[7] Vilmi A, Gibert C, Escarguel G, et al. Dispersal niche continuum index: A new quantitative metric for assessing the relative importance of dispersal versus niche processes in community assembly[J]. Ecography, 2020, 44(3): 370-379.

[8] Chazdon R L, Chao A, Colwell R K, et al. A novel statistical method for classifying habitat generalists and specialists[J]. Ecology, 2011, 92(6): 1332-1343.

[9] Wei Xiaoshuai. Soil Characteristics and Root-Associated Fungal Communities of Pinus sylvestris var. mongolica Plantation in Hulunbuir Sandy Land[D]. Beijing: Beijing Forestry University, 2020.

[10] Zhao Peishan, Guo Mishan, Gao Guanglei, et al. Temporal and spatial variations in root-associated fungi of Pinus sylvestris var. mongolica in the semi-arid and dry sub-humid desertified regions of northern China[J]. Environmental Science, 2023, 44(1): 502-511.

[11] Liu Minghui, Liu Ye, Ren Yue, et al. Soil fungi co-occurrence network and its relationship with soil factors of Pinus sylvestris var. mongolica plantation in the Horqin Desert[J]. Acta Ecologica Sinica, 2023, 43(23): 9912-9924.

[12] Luo Mingxia, Hu Zongda, Liu Xingliang, et al. Characteristics of soil microbial biomass carbon, nitrogen and enzyme activities in Picea asperata plantations with different ages in subalpine regions of western Sichuan, China[J]. Acta Ecologica Sinica, 2021, 41(14): 5632-5642.

[13] Ma Yishu, Cao Yaxin, Niu Min, et al. Investigation of soil microbial characteristics during stand development in Pinus tabuliformis forest in Taiyue mountain[J]. Environmental Science, 2024, 45(4): 2406-2416.

[14] Wang Jiayuan, Yin Xiaolin, Ren Yue, et al. Diversity characteristics of ectomycorrhizal fungi associated with Pinus sylvestris var. mongolica in the Mu Us sandy land[J]. Microbiology China, 2020, 47(11): 3856-3867.

[15] Wei Xiaoshuai, Guo Mishan, Gao Guanglei, et al. Community structure and functional groups of fungi in the roots associated with Pinus sylvestris var. mongolica in the Hulunbuir Sandy Land[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2020, 56(4): 710-720.

[16] Liu Ye, Ren Yue, Gao Guanglei, et al. Distribution characteristics of soil carbon, nitrogen and phosphorus reserves in Pinus sylvestris var. mongolica plantation on sandy land[J]. Science of Soil and Water Conservation in China, 2021, 19(6): 27-34.

[17] Ren Yue, Gao Guanglei, Ding Guodong, et al. Species composition and driving factors of the ectomycorrhizal fungal community associated with Pinus sylvestris var. mongolica at different growth periods[J]. Chinese Journal of Plant Ecology, 2023, 47(9): 1298-1309.

[18] Zhang Dandan, Zhang Limei, Shen Jupei, et al. Soil bacterial and fungal community succession along an altitude gradient on Mount Qomolangma[J]. Acta Ecologica Sinica, 2018, 38(7): 2247-2261.

[19] Meng Zhaoyun, Li Min, Yang Xunjue, et al. Diversity, community composition and influencing factors of ectomycorrhizal fungi in typical forest types in cold temperate regions[J]. Acta Ecologica Sinica, 2023, 43(1): 38-47.

[20] Gao Haoying, Fu Shuangjia, Song Shiyu, et al. Soil enzyme stoichiometric characteristics of natural forest and plantation of subalpine spruce in western Sichuan[J]. Chinese Journal of Ecology, 2024, 43(6): 1531-1539.

[21] Yanan L, Anqi F, Tengzi Z, et al. Exogenous calcium improves photosynthetic capacity of Pinus sylvestris var. mongolica under drought[J]. Forests, 2022, 13(12): 2155-2155.

[22] Pan X, Sun S, Hua W, et al. Predicting the stand growth and yield of mixed Chinese fir forests based on their site quality, stand density, and species composition[J]. Forests, 2023, 14(12): 2315.

[23] Kang Xiaohu, Liu Xin, Liu Shanshan, et al. Distribution patterns and drivers of soil microbial communities at different spatiotemporal scales: A Review[J]. Soils, 2024, 56(4): 689-696.

[24] Chen Weili, Li Juan, Zhu Honghui, et al. A review of the regulation of plant root system architecture by rhizosphere microorganisms[J]. Acta Ecologica Sinica, 2016, 36(17): 5285-5297.

[25] Luo Qing, Peng Cheng, Ye Boping. New advances in research of the genus Penicillium[J]. Pharmaceutical Biotechnology, 2016, 23(5): 452-456.

[26] Ming T, Wenpeng H, Jiyi G, et al. Changes in bacterial community structure and root metabolites in Themeda japonica habitat under slight and strong karst rocky desertification[J]. Applied Soil Ecology, 2024, 195: 105227.

[27] Qiao Lijun, Zhou Sixuan, Wen Tingchi, et al. Diversity of endophytic fungi from Nothapodytes pittosporoides in Guizhou Province[J]. Mycosystema, 2018, 37(1): 43-51.

[28] Li Jiawen, Zhao Peishan, Gao Guanglei, et al. Root-associated fungal community structure and functional group of Pinus sylvestris var. mongolica in the desertified lands of Yulin in Shaanxi Province, western China[J]. Mycosystema, 2020, 39(10): 1854-1865.

[29] Li Dandan, Li Jiawen, Gao Guanglei, et al. Soil fungal community structure and functional characteristics associated with Pinus sylvestris var. mongolica plantations in the Horqin Sandy Land[J]. Journal of Desert Research, 2023, 43(4): 241-251.

[30] Zhu Lin, Huang Jian, Chen Tianyang, et al. Root and endophytic fungal community diversity in Xanthoceras sorbifolium plantations[J]. Journal of Northeast Forestry University, 2015, 43(5): 105-111.

[31] Peltoniemi K, Adamczyk S, Fritze H, et al. Site fertility and soil water table level affect fungal biomass production and community composition in boreal peatland forests[J]. Environmental Microbiology, 2020, 23(10): 5733-5749.

[32] Singavarapu B, Haq H, Darnstaedt F, et al. Influence of tree mycorrhizal type, tree species identity, and diversity on forest root-associated mycobiomes[J]. New Phytologist, 2024, 242(4): 1691-1705.