岩溶区稻田土壤真菌群落结构及功能类群特征

真菌是土壤生物地球化学循环的重要驱动者，然而岩溶区土壤真菌群落结构和功能类群具有怎样的特征还未见报道.以桂林毛村岩溶试验场稻田耕层土壤为研究对象，采用高通量测序技术，比较岩溶区和非岩溶（红壤）区（对照）水稻生长季土壤真菌群落结构，并用FUNGuild对真菌进行功能预测.结果表明，毛霉菌门（Mucoromycota）在岩溶区的平均相对丰度为4.87%，显著低于其在非岩溶区的平均相对丰度（29.92%）；被孢霉纲（Mortierellomycetes）在岩溶区的平均相对丰度为3.36%，显著低于其在非岩溶区的平均相对丰度（29.15%），球囊菌纲（Glomeromycetes）、壶菌纲（Chytridiomycetes）和外担菌纲（Exobasidiomycetes）在岩溶区的平均相对丰度分别为0.91%、0.98%和0.23%，显著高于其在非岩溶区的平均相对丰度（0.47%、0.28%和0.04%）； Ramophialophora和翅孢壳菌属（Emericellopsis）在岩溶区的平均相对丰度分别为2.39%和1.25%，显著高于其在非岩溶区的平均相对丰度（0.05%和0.09%），而被孢霉属（Mortierella）在岩溶区的平均相对丰度为3.04%，显著低于其在非岩溶区的平均相对丰度（28.34%）.岩溶区优势OTUs为OTU141、99和192等32个OTUs；在优势OTUs和土壤理化性质相关性网络图中，岩溶区的OTU69（Emericellopsis terricola）和OTU138（Westerdykella globosa）与阳离子交换量、交换性钙离子和总磷的连接度较高.共生营养型和病理-腐生过渡型在岩溶区平均丰度分别为1.29%和1.50%，显著高于其在非岩溶区的平均丰度（0.08%和0.09%），而腐生-共生过渡型在岩溶区的平均丰度为10.81%，显著低于其在非岩溶区的平均丰度（63.69%）；岩溶区和非岩溶区最优势真菌分别是粪腐生-木质腐生菌和内生菌根-植物病原-未定义腐生菌，平均丰度分别占优势OTUs的9.73%和45.93%.以上研究表明，岩溶区稻田较高的阳离子交换量、交换性钙和总磷等土壤因子对优势真菌群落和功能类群的构建具有重要的作用.

Investigation of Soil Fungal Communities and Functionalities within Karst Paddy Fields

Fungi are important drivers of soil biogeochemical cycles. However, the characteristics of fungal community structures and functional groups within karst area (KA) soils remain understudied. Top soil samples were collected from paddy fields within a KA and non-karst area (NKA) containing red soil, in the Maocun karst experimental site of Guilin. The fungal community structure was analyzed via high-throughput sequencing, and FUNGuild was used to predict the function of fungi. The average relative abundance of Mucormycota in KA was 4.87%, which was significantly lower than that in NKA (29.92%); The average relative abundance of Mortierellomycetes in KA was 3.36%, which was significantly lower than that in NKA (29.15%). However, in KA, the average relative abundances of Glomeromycetes, Chytridiomycetes, and Exobasidiomycetes were 0.91%, 0.98%, and 0.23%, respectively, significantly higher than those in NKA (0.47%, 0.28%, and 0.04%). In KA, the average relative abundances of Ramophialophora and Emericellopsis were 2.39% and 1.25%, respectively, significantly higher than those in NKA (0.05% and 0.09%). However, the average relative abundance of Mortierella was 3.04% in KA, which was lower than that in NKA (28.34%). KA contained 32 dominant OTUs, including OTU141, 99, and 192. There was more connectivity between OTU69 (Emericellopsis terricola) and OTU138 (Westerdykella globosa) with the cation exchange capacity (CEC), exchangeable Ca²⁺, and total phosphorus (TP) in the correlation network. In KA, the average abundances of symbiotroph and pathotroph-saprotroph fungi were 1.29% and 1.50%, respectively, significantly higher than those in NKA (0.08% and 0.09%). The average abundance of the saprotroph-symbiotroph fungi in KA was 10.81%, which was significantly lower than that in NKA (63.69%). In KA, dung saprotroph-wood saprotroph fungi were dominant, with an abundance of 9.73%, whereas in NKA, endophyte-litter saprotroph-soil saprotroph-undefined saprotroph fungi were dominant, with an abundance of 45.93%. The above results suggest that the soil factors of KA, such as CEC, exchangeable Ca²⁺, and TP, alter the structures and functions of fungi.