Effects of different soil management patterns on soil fungal community composition in a Castanea henryi orchard

Abstract:【Objective】Soil management is the key link of orchard production. Different soil manage- ment measures can directly or indirectly affect the growth and development of fruit trees by changing soil nutrients, microorganisms, and enzyme activities, thus affecting fruit quality and yield. Soil fungi are important parts of the soil ecosystem. Their diversity and community composition can be sensitive to the changes of soil under natural or human disturbance. The purpose of this study was to explore the effects of grass cropping, no-tillage, and clean tillage on soil fungal diversity and community composi- tion in the topsoil of a Castanea henryi orchard, so as to provide a theoretical basis for the selection of soil management measures in a C. henryi orchard in combination with the changes of soil available nu- trient content and enzyme activity.【Methods】The orchard with C. henryi trees in Jian’ou was taken as the research site. In October 2018, concentrated and contiguous experimental plots 10 hm2 with basical- ly the same site conditions were selected and divided into several experimental plots with an area of 0.3- 0.5 hm2. Randomized block design was used to construct Vulpiamyuros, Lolium perenne, and Vicia villo- sa and spraying glyphosate and clear tillage, with three replicates for each treatment. The sowing amount was 30 kg·hm-2, and the whole ground grass was planted. In October 2020, in every plot, three types of rootstocks (Corylus mandshurica Maxim.) were selected with‘Bailuzi’as a scion of, which were healthy, and tree height and DBH were basically the same. One meter away from the tree trunk, the litter on the surface was removed, and the soil was collected from 0-10 cm soil layer in four direc- tions: East, West, South, and North. After mixing the soil samples from the same plot, the roots and oth- er impurities were removed, and then the soil samples were put into a sterilization bag and brought back to the laboratory in an icebox. High-throughput sequencing technology was used to detect and analyze the soil fungal diversity and community composition in the 0-10 cm soil layer under different soil management conditions, and to combine with the number of OTUs to screen the specific bacteria genus.【Results】The results showed that the contents of hydrolytic nitrogen, available phosphorus and avail- able potassium in grass growing modes were significantly higher than those in clean tillage mode. How- ever, spraying glyphosate significantly reduced the contents of microbial biomass carbon, microbial bio- mass nitrogen, hydrolytic nitrogen, and available potassium contents, which were 0.64 g · kg- 1, 19.96 mg·kg-1, 47.10 mg·kg-1 and 176.37 mg·kg-1, respectively. The soil fungal Chao1 index, Observed-spe- cies index, Shannon index and Simpson index in the C. henryi orchard decreased after grass planting and glyphosate spraying, and the Chao1 index was lowest in the mode of V. villosa, which was 1 532.15; the Observed-species index and Simpson index of L. perenne mode were lowest, which were 1 343.33 and 0.88, respectively; the Shannon index of V. myuros mode was lowest, which was 6.39. The Unweighted UniFrac distance matrix indicated that soil fungal communities between V. my- uros and L. perenne modes were less different. At the genus level, the most dominant fungi with differ- ent soil management measures were different. Russula was the most dominant fungi in the modes of V. myuros, L. perenne and glyphosate spraying, and the relative abundance was 45.40% , 24.63% and 17.70%, respectively; the most dominant fungus in the cultivation mode of V. villosa was Mortierella, and its relative abundance was 11.65%; Laccaria was the most dominant fungus in clear tillage mode, and its relative abundance was 16.62. The similarity cluster tree analysis showed that the establishment of V. myuros, L. perenne and clean tillage modes could be classified into one category, the composition of soil fungal community among the three modes was similar, the establishment of V. villosa and spray- ing glyphosate modes could be classified into the other one. LEfSe difference analysis showed that the relative abundance of Russula fungi in the V. myuros mode was significantly higher than that in other modes; spraying glyphosate significantly increased the relative abundance of Clavaria (2.92%), while the relative abundance of Boletus in the clear tillage mode was significantly higher than that in other modes (3.08%). The results of redundancy analysis showed that the Alpha diversity index of soil fungi was negatively correlated with soil pH; Cat, Suc, and Ure’s activities and the hydrolyzed nitrogen con- tent were the main environmental factors affecting the composition of the soil fungal community. Through screening and comparison, it was found that Lachnum was a specific genus of V. myuros, which can secrete metabolites (such as A[(+)-mycorrhizin A]and A[(+)-chlormy-corrhizin A]) to kill nematodes. Cenococcum and Cylindrocarpon were the special genera in Lolium perenne mode, the for- mer can promote the growth of plants, while the latter may harm the fruit trees of C. henryi. The specific genus of V. villosa model was Monacrosporium, which could prey on nematodes through a three-di- mensional net. Hygrocybe and Orbiliawere were found in glyphosate spraying and clear tillage modes, respectively【. Conclusion】In this study, it was found that V. myuros could not only increase the content of soil available nutrients, but significantly promote the propagation of Russula fungi in the C. henryiorchard. Lachnum and Monacrosporium were found in the V. myuros and V. villosamodes, respectively, which were related to nematode control. Cylindrocarpon was found in the L. perenne mode, which was a potential pathogenic fungus. The composition of soil fungal community in the planting mode of V. my- uros and L. perenne was similar to that in the clean tillage mode, but different from that in the planting mode of V. villosa and spraying glyphosate mode. In conclusion, it is more suitable to build V. myuros in the C. henryi orchard, and the application of glyphosate should be reduced in production and management.