Effects Of Fungi On Coexistence Of Main Trees In Wild Fruit Forest On The Northern Slope Of Tianshan Mountains

Species coexistence is one of the most core issues in ecology,and the wild fruit forests on the northern slopes of Tianshan Mountain are rich in biodiversity,especially in wild plant resources,and are an important gene pool of biological resources in China.At present,most studies on the maintenance mechanisms of forest biodiversity have focused on such aspects as the determination of the number of above-ground organisms in abundance,while the interrelationships among plants and the effects of below-ground fungi on biodiversity are still unknown.The purpose of this study was to investigate the species diversity of arbuscular mycorrhizal fungi in the soil of a wild fruit forest and to explore the effects of soil microbial fungi(pathogens and arbuscular mycorrhizal fungi)on the growth of live seedlings.This study was conducted to test the potential mechanism of the Janzen-Connell hypothesis using the growth dynamics of live seedlings of Malus sieversii and Prunus padus in a wild fruit forest under natural conditions in the field.The main results of this paper are the following:(1)There are abundant arbuscular mycorrhizal fungal spores in the wild fruit forest soil.A total of 25 species of 5 families,6 genera and 25 species were isolated and identified from the sampled soil.Among them,One species of Claroideoglomus,Archeospora,Gigasporaceae accounted for 4 percent,four species of Scutellospora accounted for 16 percent,six species of Acaulospora accounted for 24 percent,and Scutellospora accounted for 24 percent,twelve species of Glomus accounted for 48 percent,of which Glomus was the dominant genus.(2)By observing and analyzing the dynamics of live seedlings in wild fruit forests,it was found that Pathogens cause death of conspecific live seedlings in wild fruit forest areas and provide a better survival space for heterospecific live seedlings;therefore,the Janzen-Connell hypothesis was valid in this experiment.Field investigations revealed that there were five causes of live seedling mortality,with leaf pathogens being the most important cause of mortality.In the summer months of June-August,leaf pathogenic fungi caused the highest mortality of live seedlings;in the autumn months of September-October,after the adults dropped its leaves,a certain light environment was provided,and under sufficient light,the arbuscular mycorrhizal fungi promoted the continued survival of the few remaining conspecific live seedlings and ensured the renewal of a small number of conspecific live seedlings.(3)The mean rate of infestation of the arbuscular mycorrhizal fungi in live seedlings of wild fruit forests was 74.44 percent.There was no significant difference in the infestation rate of mycorrhizal fungi in the root systems of different live seedlings under different adultss;the dry weight and relative growth rate of both conspecific and heterospecific live seedlings under different adultss were higher in heterospecific than in conspecific;the dry weight and relative growth rate of live seedlings were both proportional to the infestation rate of mycorrhizal fungi.In summary,the Janzen-Connell hypothesis holds true in this experiment,in which pathogenic fungi and tufted mycorrhizal fungi jointly influence the growth of live seedlings,and fungi,as key components of the soil microbial community,play a regulatory role in the coexistence of main trees.