1.College of Earth Science, Jilin University, Changchun;2.Institute of Geographical Sciences and resources, Chinese Academy of Sciences;3.College of Earth Sciences, Jilin University;4.Institute of Geographic Sciences and Natural Resources Research，Chinese Academy of Science
National Natural Science Foundation of China（41907036，42177447）；Strategic Priority Research Program of the Chinese Academy of Sciences（XDA23080302）
明确土壤真菌生物多样性的形成与维持机制是理解真菌生物地理分布格局的关键，但是目前对深层土壤真菌多样性的海拔分布格局及其影响机制知之甚少。本研究在西藏色季拉山3 300～4 600 m海拔梯度下采集表层（0～20 cm）及底层（40～60 cm）土壤样品，基于ITS rDNA高通量测序分析，揭示不同深度土壤中真菌多样性的海拔分布特征及其影响因子，并基于生态位属性计算探讨真菌群落的共存特征。研究表明，在表层土壤中，真菌丰富度及香农多样性均随海拔升高而显著降低。在底层土壤中，真菌丰富度随海拔升高而显著降低，而香农多样性则表现出先升高后降低的单峰模式。真菌群落组成的差异性（β多样性）在土壤表层及底层均随海拔梯度的增加而显著增加， pH和土壤湿度分别是表层和底层土壤真菌群落组成沿海拔梯度变化的关键驱动因子。对真菌群落生态位宽度（Bcom）和生态位重叠值（Oik）的计算结果表明，土壤真菌的环境适应性和代谢灵活性随海拔升高而降低，并且低海拔以及表层土壤中各真菌种群在资源利用或生境适应性上具有更高的相似度。以上研究结果揭示了环境过滤及种群共存特征对土壤真菌多样性海拔分布格局的关键影响，有助于深入了解青藏高原高寒生态系统中土壤真菌群落多样性形成和维持机制。
【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.
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, DOI:10.11766/trxb202109230511,[In Press]