Effects Of Warming,Nitrogen Addition And Fungicide On Foliar Fungal Disease In A Tibetan Alpine Meadow

The alpine meadow is the most important grassland vegetation type in the Qinghai-Tibet Plateau.It has important ecosystem services such as water conservation and climate regulation,and is an important green ecological barrier in China.However,in recent years,due to the intensification of human activities,alpine meadows are suffering from severe climate change processes(such as,warming and nitrogen concentration),and grassland plant diseases often occur.The plant diseases of the grassland ecosystem are mainly foliar fungal diseases.Environmental changes such as temperature increase and nutrient enrichment will directly affect the foliar pathogenic fungi,and indirectly affect the pathogenic fungi by affecting the host plant.Under the background of global changes in the future,it is not clear the foliar fungal diseases incidence of alpine meadows and the foliar fungi communities will change.This study based on a multi-factor control experiment of nitrogen addition,temperature increase and fungicide addition on the eastern edge of the Qinghai-Tibet Plateau.First,we determined the incidence of species’ leaves under different treatments.In addition,the most dominant species in the community,Kobresia capillifolia,was selected to conduct high-throughput sequencing on the foliar fungal community to further explore the effects of warming,nitrogen addition and fungicides on the foliar pathogenic fungus community.Finally,we collected the susceptible leaves of the main dominant species in the alpine meadow on the Qinghai-Tibet Plateau,and isolated and identified the leaf pathogenic fungi.The main types of disease fungi in this area are determined,which provides a theoretical basis for better prevention and control of plant diseases in alpine meadows.The main experimental results are as follows:1.The effects of warming,nitrogen addition and application of fungicides on the incidence of leaves of 9 plants were analyzed.Warming significantly reduce the foliar disease incidence of Thermopsis lanceolata and significantly increase the foliar disease incidence of Saussurea nigrescens and Anemone trullifolia;The application of fungicides significantly reduce the foliar disease incidence of Kobresia capillifolia;However,the foliar disease incidence of Elymus nutans,Aster alpinus,Anemone rivularis,Anemone obtusiloba and Ligularia virgaurea had no significant response to warming,nitrogen addition and fungicides addition.2.High-throughput sequencing of the dominant species of Kobresia capillifolia has identified 4 phyla,13 classes,36 orders,79 families,112 genera and 122 species of Kobresia foliar fungal communities.Among them,Stagonospora,Gibberella,Cladosporium,Didymella,etc.in the foliar fungal community are all plant pathogenic fungi.And through the analysis of the diversity of the Kobresia leaf fungus community,it can be seen that under the condition of nitrogen addition,warming significantly reduce intragroup heterogeneity.While fungicides addition significantly reduces the fungal community Alpha diversity and intragroup heterogeneity.After the application of fungicides,the percentages of Stagonospora,Gibberella and Cladosporium significantly decrease or even disappear,while the percentages of Vishniacozyma and Didymella increase and become the main components of the fungal community.3.The leaf pathogenic fungi of 9 dominant plants in the alpine meadow ecosystem were isolated and identified,a total of 29 fungi were isolated.According to molecular and morphological identification,they were identified as 12 genera and 12 species.This study explored the impact of global change factors on leaf incidence and leaf pathogenic fungi in alpine meadows on the Qinghai-Tibet Plateau,and isolated and identified the main types of local pathogenic fungi.It provides a theoretical basis for reducing plant fungal diseases,protecting pastures,formulating reasonable grassland management policies and protecting grassland ecological environment.