This study aims to investigate the causes of higher soil fungal diversity in shrubs compared to trees in alpine forests. Although numerous studies have shown a positive correlation between fungal diversity and temperature, shrub soil in alpine forests exhibits greater fungal diversity despite low temperatures. By analyzing soil samples from different vegetation types in alpine forests and utilizing paired-end sequencing of community DNA fragments with Illumina technology, the results demonstrate that soil fungal diversity and abundance under shrubs are significantly higher than those under trees (P < 0.05). This suggests that alpine shrubs exert a stronger promoting effect on soil fungal community diversity. Further analysis indicates that this difference may be closely related to the distinctive characteristics of shrub litter and root exudates. This study provides a new perspective on the interactions between vegetation and soil microorganisms in alpine ecosystems and offers valuable insights for ecological restoration and soil management practices.
Research Article
The Analysis of Causes for Higher Soil Fungal Diversity in Shrubs Compared to Trees in Alpine Forests
https://doi.org/10.21203/rs.3.rs-5260010/v1
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Alpine forest
Trees and shrubs
Soil fungal community
Habitat differences
Numerous studies have explored the relationship between fungal diversity and environmental temperature, with a widely accepted consensus that fungal diversity typically correlates positively with temperature. Conant, Richard T pointed out that higher temperatures often accelerate the decomposition of organic matter, increasing the availability of soil nutrients, which in turn supports a greater variety of fungi(Conant et al. 2011). Similarly, research by Li and Delgado-Baquerizo demonstrated that rising temperatures in temperate forests promote both fungal community diversity and functional richness(Li et al. 2019). However, this pattern appears not to hold in the unique ecosystem of alpine forests. Our study found that in the cold environment of alpine forests, the fungal diversity in soils under shrubs is significantly higher than that in soils beneath neighboring coniferous trees. This result contrasts sharply with the widely discussed positive correlation between temperature and fungal diversity(Tedersoo et al. 2014). The underlying reason may be attributed to ecological functional differences between shrubs and trees in alpine forests(Körner 2012). Shrubs may create a more stable soil microenvironment under extreme climatic conditions, providing diverse organic matter sources that support richer fungal communities(Lai et al. 2023). This phenomenon suggests that in the unique environment of alpine forests, temperature is not the sole determinant of fungal diversity(Zhang et al. 2024; Zhou et al. 2024). Instead, plant types and their influence on soil physicochemical properties may play a more critical role(Zhong et al. 2019). Therefore, this study aims to reveal the specific effects of plant types on soil microbial communities in cold environments by comparing the differences in soil fungal diversity between shrubs and trees in alpine forests(Collins et al. 2018; Probst et al. 2024). In doing so, it offers new insights into the carbon cycle and ecosystem stability in cold regions(Bardgett, Freeman, and Ostle 2008).
1 Study Area Overview
The study area is located in Maixiu National Forest Park, Huangnan Tibetan Autonomous Prefecture, Qinghai Province (35°8'–35°21'N, 101°46'–102°04'E)(Xie, Chen, and Han 2021). Maixiu National Forest Park lies on the eastern edge of the Qinghai-Tibet Plateau, with an elevation range of 2,699 to 4,971 meters. The experimental area, within the park's management boundaries, is characterized by a cold and humid climate, with an average annual temperature of approximately 5.8°C, annual precipitation of about 600 mm, and around 2,600 hours of sunshine per year. The park hosts diverse vegetation types, including valley grasslands, temperate forests, and alpine shrubs. The dominant soil types are mountain brown soil and meadow soil. The dominant tree species include Qinghai spruce (Picea crassifolia), purple-cone spruce (Picea purpurea), white birch (Betula platyphylla), aspen (Populus davidiana), and Przewalski's juniper (Sabina przewalskii). Dominant shrub species consist of rhododendron (Rhododendron simsii), willow (Salix spp.), meadowsweet (Spiraea salicifolia), Caragana (Caragana sinica), honeysuckle (Lonicera japonica), rose (Rosa spp.), ramie (Boehmeria nivea), sea buckthorn (Hippophae rhamnoides), and mountain ash (Sorbus pohuashanensis)(李赛达 et al. 2024).
2.1 Plot Setup and Data Collection
Representative forest areas were selected as research plots, considering factors such as forest type, topography, and vegetation distribution(Lobo and Dalling 2013). The plots were chosen to reflect the typical characteristics of the study area(Fu et al. 2004). Six plots were established, with each plot size determined as 28.28 m × 28.28 m based on the research objectives and practical conditions(Zhang et al. 2019). Soil fungal samples were collected using a three-point method (S-shaped random sampling) in each plot, with three replicates at each point(Paterson 2013). The soil from the three points was mixed to form a single soil sample(Rinella and Reinhart 2017).
Aboveground vegetation and litter were removed, and the top 1–2 cm of surface soil was discarded. Soil was collected from a depth of 0–10 cm. The samples were placed in sealed bags, labeled, and stored in ice boxes for transport to the laboratory. Fresh soil samples were cleaned of plant debris, stones, and other impurities, sieved through a 0.25 mm mesh, and stored at −80°C. The basic characteristics of the research plots are shown in Table 1.
Table 1. Basic Characteristics of the Research Plots
Note: a. Picea crassifolia b. Picea asperata c. Picea purpurea d. Potentilla fruticosa e. Spiraea salicifolia f. Caragana sinica
3.1 Soil Fungal Community Composition
As shown in Figure 1, a detailed comparative analysis was conducted on soil fungal communities under trees (TREE1, TREE2, TREE3) and shrubs (SHRUB1, SHRUB2, SHRUB3) at various taxonomic levels, including kingdom, phylum, class, order, family, genus, and species(Li and Wu 2018; Naranjo‐Ortiz and Gabaldón 2019). The results reveal that the soil fungal diversity under shrubs was significantly higher than that under trees at all taxonomic levels. Particularly at the species level (144.11 ± 6.78 under trees vs. 229.67 ± 12.34 under shrubs), family level (14.00 ± 1.56 under trees vs. 35.11 ± 2.45 under shrubs), and order level (12.22 ± 0.98 under trees vs. 31.45 ± 1.87 under shrubs), the differences were most pronounced.These findings indicate that the taxonomic diversity and richness of soil fungi under shrubs are generally higher than under trees, reflecting greater adaptability and functional diversity of soil fungi in the shrub-dominated ecosystems(Santonja et al. 2017).
As shown in Figure 2, a detailed analysis of the relative abundance of soil fungi under trees and shrubs at various taxonomic levels revealed that the relative abundance of Ascomycota in soils under shrubs (0.656296 ± 0.012345) was slightly higher than that in soils under trees (0.60720267 ± 0.011234). In contrast, the relative abundance of Basidiomycota was higher in soils under trees (0.331105 ± 0.009876) compared to soils under shrubs (0.255138 ± 0.008765). At other taxonomic levels, the relative abundance differences between the two were either minor or comparable(Khachatryan et al. 2020). These results provide valuable data for further investigations into the ecological functions and adaptability of soil fungi under trees and shrubs across different taxonomic levels.
3.3 Analysis of Soil Fungal Diversity Differences between Trees and Shrubs
In this study, the Alpha diversity indices were used to assess species diversity, evenness, and abundance of soil fungi under trees and shrubs. These indices provide insight into the health and functional roles of soil fungal communities within ecosystems. Statistical significance analysis was conducted to determine differences between communities, offering important scientific support for ecological conservation and management efforts.
By analyzing six key metrics—Chao1, Simpson, Shannon, Goods coverage, Pielou’s evenness, and observed species—the results, as shown in Figure 3, indicate significant differences in diversity and richness. For example, the Shannon index for TREE1 was 2.5 ± 0.2, while for SHRUB1 it was 4.5 ± 0.3, suggesting that fungal diversity under shrubs is higher than that under trees. Additionally, in terms of observed species, TREE1 had 200 ± 15 species, while SHRUB1 had 400 ± 20 species, further supporting the higher richness under shrubs.
The Simpson index showed a value of 0.7 ± 0.05 for TREE1 and 0.9 ± 0.04 for SHRUB1, indicating that species evenness is also higher in soils under shrubs. Overall, soil fungi under shrubs outperformed those under trees across all diversity and richness metrics, with these differences being statistically significant (all P-values < 0.05).
Through the analysis of Figure 4, We found significant differences in the soil fungal community structure between tree and shrub plots. In the tree group, TREE1 and TREE2 exhibited high LDA scores for taxa such as Chlorophyllum and Fibulorhizoctonia, while TREE3 was characterized by high scores for Cladophialophora and Penicillium. In the shrub group, SHRUB1 displayed high LDA scores for Lophiostoma and Volutella, SHRUB2 for Herpotrichiellaceae and Neonectria, and SHRUB3 for Pseudogymnoascus and Tomentella. These taxa, all with LDA scores above 3, indicate their significant representation in their respective groups, reflecting distinct environmental adaptations and ecological functions between tree and shrub communities.
Figure 5 demonstrates that this study, by comparing the diversity and structure of soil fungal communities beneath trees and shrubs in alpine forests, reveals the differential impact of temperature on fungal diversity across different vegetation types(Collins et al. 2018; Chen et al. 2022). Although temperature is generally considered positively correlated with fungal diversity, soil under shrubs demonstrated higher fungal diversity and richness in low-temperature environments(Yang et al. 2022), particularly at the species, family, and order taxonomic levels(Lenat and Resh 2001), where shrub-associated soil fungi significantly outperformed tree-associated fungi. The findings indicate that in alpine environments, temperature is not the sole determinant of fungal diversity(Zhang et al. 2024). Vegetation type and its influence on the soil microenvironment play a more critical role. This discovery offers new insights into the complex relationships between temperature and soil microorganisms in alpine ecosystems and provides scientific evidence for future ecological conservation and restoration efforts.
Author Contribution
Data collection; Data analysis; Article Writing
- 李赛达, 南淑珍, 马羿轩, 蒋乙弘, 党玄昊, 扎西瑙吾, 陈生俊, and 扎西多杰. 2024. '麦秀国家森林公园植物种类组成及区系研究', 青海草业, 33: 55-62.
- Bardgett, Richard D, Chris Freeman, and Nicholas J Ostle. 2008. 'Microbial contributions to climate change through carbon cycle feedbacks', The ISME journal, 2: 805-14.
- Chen, Jian, Zuomin Shi, Shun Liu, Miaomiao Zhang, Xiangwen Cao, Miao Chen, Gexi Xu, Hongshuang Xing, Feifan Li, and Qiuhong Feng. 2022. 'Altitudinal variation influences soil fungal community composition and diversity in Alpine–Gorge region on the Eastern Qinghai–Tibetan Plateau', Journal of Fungi, 8: 807.
- Collins, Courtney G, Jason E Stajich, Sören E Weber, Nuttapon Pombubpa, and Jeffrey M Diez. 2018. 'Shrub range expansion alters diversity and distribution of soil fungal communities across an alpine elevation gradient', Molecular ecology, 27: 2461-76.
- Conant, Richard T, Michael G Ryan, Göran I Ågren, Hannah E Birge, Eric A Davidson, Peter E Eliasson, Sarah E Evans, Serita D Frey, Christian P Giardina, and Francesca M Hopkins. 2011. 'Temperature and soil organic matter decomposition rates–synthesis of current knowledge and a way forward', Global change biology, 17: 3392-404.
- Fu, BJ, SL Liu, KM Ma, and YG Zhu. 2004. 'Relationships between soil characteristics, topography and plant diversity in a heterogeneous deciduous broad-leaved forest near Beijing, China', Plant and Soil, 261: 47-54.
- Khachatryan, Lusine, Rick H de Leeuw, Margriet EM Kraakman, Nikos Pappas, Marije Te Raa, Hailiang Mei, Peter de Knijff, and Jeroen FJ Laros. 2020. 'Taxonomic classification and abundance estimation using 16S and WGS—A comparison using controlled reference samples', Forensic Science International: Genetics, 46: 102257.
- Körner, Christian. 2012. 'Treelines will be understood once the functional difference between a tree and a shrub is', Ambio, 41: 197-206.
- Lai, Zongrui, Yanfei Sun, Yang Yu, Zhen Liu, Yuxuan Bai, Yangui Qiao, Lin Miao, Weiwei She, Shugao Qin, and Wei Feng. 2023. 'Plant selection and ecological microhabitat drive the shrub-associated microbiome selection in revegetated shrub ecosystems', Applied Soil Ecology, 190: 105023.
- Lenat, David R, and Vincent H Resh. 2001. 'Taxonomy and stream ecology—the benefits of genus-and species-level identifications', Journal of the North American Benthological Society, 20: 287-98.
- Li, Jing, Manuel Delgado-Baquerizo, Jun-Tao Wang, Hang-Wei Hu, Zhang-Jie Cai, Yi-Nuo Zhu, and Brajesh K Singh. 2019. 'Fungal richness contributes to multifunctionality in boreal forest soil', Soil Biology and Biochemistry, 136: 107526.
- Li, Sen, and Fengzhi Wu. 2018. 'Diversity and co-occurrence patterns of soil bacterial and fungal communities in seven intercropping systems', Frontiers in Microbiology, 9: 1521.
- Lobo, E, and JW Dalling. 2013. 'Effects of topography, soil type and forest age on the frequency and size distribution of canopy gap disturbances in a tropical forest', Biogeosciences, 10: 6769-81.
- Naranjo‐Ortiz, Miguel A, and Toni Gabaldón. 2019. 'Fungal evolution: diversity, taxonomy and phylogeny of the Fungi', Biological Reviews, 94: 2101-37.
- Paterson, Andrew. 2013. Genomes of herbaceous land plants (Elsevier).
- Probst, Maraike, Anusha Telagathoti, Edoardo Mandolini, and Ursula Peintner. 2024. 'Fungal and bacterial communities and their associations in snow-free and snow covered (sub-) alpine Pinus cembra forest soils', Environmental Microbiome, 19: 20.
- Rinella, Matthew J, and Kurt O Reinhart. 2017. 'Mixing soil samples across experimental units ignores uncertainty and generates incorrect estimates of soil biota effects on plants', New Phytologist, 216: 15-17.
- Santonja, Mathieu, Anaïs Rancon, Nathalie Fromin, Virginie Baldy, Stephan Hättenschwiler, Catherine Fernandez, Nicolas Montès, and Pascal Mirleau. 2017. 'Plant litter diversity increases microbial abundance, fungal diversity, and carbon and nitrogen cycling in a Mediterranean shrubland', Soil Biology and Biochemistry, 111: 124-34.
- Tedersoo, Leho, Mohammad Bahram, Sergei Põlme, Urmas Kõljalg, Nourou S Yorou, Ravi Wijesundera, Luis Villarreal Ruiz, Aída M Vasco-Palacios, Pham Quang Thu, and Ave Suija. 2014. 'Global diversity and geography of soil fungi', science, 346: 1256688.
- Xie, Manchao, Zhenning Chen, and Fuzhong Han. 2021. 'Three new species of eriophyoid mites from Maixiu National Forest Park, Qinghai Province, China (Acari: Eriophyoidea)', 动物分类学报, 46: 200-07.
- Yang, Nan, Xiuxiu Li, Dong Liu, Yan Zhang, Yuheng Chen, Bo Wang, Jiani Hua, Jiangbao Zhang, Sili Peng, and Zhiwei Ge. 2022. 'Diversity patterns and drivers of soil bacterial and fungal communities along elevational gradients in the Southern Himalayas, China', Applied Soil Ecology, 178: 104563.
- Zhang, Bo, Sijie Zhu, Jiangrong Li, Fangwei Fu, Liangna Guo, Jieting Li, Yibo Zhang, Yuzhuo Liu, Ganggang Chen, and Gengxin Zhang. 2024. 'Elevational distribution patterns and drivers factors of fungal community diversity at different soil depths in the Abies georgei var. smithii forests on Sygera Mountains, southeastern Tibet, China', Frontiers in Microbiology, 15: 1444260.
- Zhang, Jialong, Chi Lu, Hui Xu, and Guangxing Wang. 2019. 'Estimating aboveground biomass of Pinus densata-dominated forests using Landsat time series and permanent sample plot data', Journal of Forestry Research, 30: 1689-706.
- Zhong, Zekun, Xing Wang, Xinyi Zhang, Wei Zhang, Yadong Xu, Chengjie Ren, Xinhui Han, and Gaihe Yang. 2019. 'Edaphic factors but not plant characteristics mainly alter soil microbial properties along a restoration chronosequence of Pinus tabulaeformis stands on Mt. Ziwuling, China', Forest Ecology and Management, 453: 117625.
- Zhou, Yanan, Fanfan Meng, Beryl Ochieng, Jianing Xu, Lu Zhang, Ismael Aaron Kimirei, Muhua Feng, Lifeng Zhu, and Jianjun Wang. 2024. 'Climate and Environmental Variables Drive Stream Biofilm Bacterial and Fungal Diversity on Tropical Mountainsides', Microbial Ecology, 87: 28.
No competing interests reported.