Elevational Distribution Pattern of Fungal Diversity and the Driving Mechanisms at Different Soil Depths in Mount Segrila

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National Natural Science Foundation of China(41907036,42177447);Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23080302)

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    【Objective】 Unveiling the formation and maintenance mechanisms of fungal biodiversity is crucial to understand the biogeographic distribution pattern of soil fungi. However, knowledge of the elevational distribution pattern and its underlying mechanism of fungal communities in the deep layers of soil profile remains inadequate. 【Method】 In the present study, topsoil (0~20 cm) and subsoil(40~60 cm)samples were collected along an elevational gradient of 3 300~4 600 m from Mount Segrila, Tibet. The variations in fungal diversity and community composition with elevation in the topsoil and subsoil and the driving factors were investigated by Illumina MiSeq high-throughput pyrosequencing of the ITS rDNA. Changes in the coexistence characteristics of soil fungal communities among different elevations and between top-and subsoil were further explored based on the calculation of niche properties. 【Result】 We found that fungal communities collected from the topsoil and subsoil of Mount Segrila were dominated by Ascomycota (averaged relative abundance of 35%), Basidiomycota (46%)and Zygomycota (13%). Symbiotrophic fungi (62%) and saprotrophic fungi (33%) were identified as the major functional guilds by FUNGuild. In the topsoil, indices of fungal α-diversity (richness and Shannon diversity) decreased significantly with increasing elevation. In the subsoil, fungal richness decreased whereas Shannon diversity presented a hump-shaped pattern with increasing elevation. The dissimilarities in fungal community composition (β-diversity)increased significantly with increasing elevational distance in both topsoil and subsoil, suggesting a distance-decay pattern. The β-diversity of the fungal community was also positively correlated with environmental factors such as mean annual temperature (MAT), soil pH, the ratio of soil carbon to nitrogen, and soil moisture as suggested by the Mantel test. Results from distance-based redundancy analysis (db-RDA) suggested that pH was the driving factor for the variation in fungal community composition with elevation in the topsoil, whereas in the subsoil soil moisture was the most contributive factor. The community-level habitat niche breadth (Bcom) of soil fungi was significantly higher at 3 500 m and 3 689 m, indicating an increase in environmental fitness and a more metabolically flexible fungal community at lower elevations. However, the niche breadth of soil fungi became narrow at 4 420 m and 4 590 m, implying that soil fungi at higher elevations could be more vulnerable in response to climate change in the future. A greater degree of niche overlap (Oik > 8) between major fungal taxa was observed at lower elevations (3 356~3 689 m) and in the topsoil, whereas a lower degree of niche overlap (Oik ≤ 6) was observed at higher elevations (4 284~4 590 m) and in the subsoil. In addition, a greater degree of niche overlap was observed between Ascomycota, Basidiomycota and Zygomycota, suggesting fierce competition for resources or habitats among these taxa. The degree of niche overlap was lower between Glomeromycota, Chytridimycota and other taxa due to their symbiotic or parasitic relationships with plants. 【Conclusion】 Overall, our study shows that the elevational distribution pattern of fungal biodiversity is distinctive between topsoil and subsoil, which is strongly related to the effect of environmental filtering and coexistence characteristics of specific taxa. These results may thus provide novel insights into the diversity and coexistence mechanisms of soil fungal communities in the alpine ecosystems of the Tibetan Plateau.

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SUN Yuanyuan, XU Meng, LI Yuefen, ZHANG Xubo. Elevational Distribution Pattern of Fungal Diversity and the Driving Mechanisms at Different Soil Depths in Mount Segrila[J]. Acta Pedologica Sinica,2023,60(4):1169-1182.

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  • Received:September 23,2021
  • Revised:June 22,2022
  • Adopted:July 14,2022
  • Online: August 24,2022
  • Published: July 28,2023