Study On The Interaction Between Wetland Plants And Arbuscular Mycorrhizal Fungi In South-Tibet River Basin

Arbuscular mycorrhizal fungi(AMF)are ubiquitous in terrestrial ecosystems and can form symbiotic associations with the roots of most vascular plants.The symbiotic relationship between AMF and plants can enhance the absorption of soil nutrients(especially nitrogen and phosphorus)by plant roots,increase the ability of host plants to cope with biotic and abiotic stress,and maintain plant community diversity.However,the ecological functions of AMF are closely related to their community structure and diversity.Therefore,understanding the community structure and diversity of AMF in ecosystems is of great importance.However,most previous studies have focused on terrestrial ecosystems,with few studies on the community structure of AMF in wetland ecosystems,and even fewer on AMF in high-altitude wetland ecosystems.The Qinghai-Tibet Plateau is the highest plateau in the world,known as the “Roof of the World”,it is also the source of many major rivers such as the Yangtze River,Yellow River and Brahmaputra,and is known as the “Water Tower of Asia”.The Qinghai-Tibet Plateau is one of Chinese important wetland distribution areas with rich wetland resources.However,previous studies have indicated that the wetland ecosystems on the Qinghai-Tibet Plateau are experiencing various degrees of degradation due to climate change and intensified human activities.Wetland plants,as an important component of the wetland ecosystem,are also significantly affected.The symbiosis of AMF and wetland plants can alleviate the degradation of wetland plants caused by water pollution and environmental stress,so as to maintain the biodiversity function of wetland in the ecosystem.Therefore,by investigating the AMF community in wetlands on the Qinghai-Tibet Plateau,clarifying the changing patterns of the interaction between AMF and wetland plants can help to better understand the variation rules of wetland plant communities under the global change background in the wetland ecosystems of the Qinghai-Tibet Plateau,and is of great significance for the protection and restoration of these ecosystems.This study focuses on the wetlands in the South-Tibet river basin,analyzing the distribution patterns of wetland plant communities,the structure of the AMF community,and the characteristics of the interaction network between wetland plants and AMF at different elevations.The main contents are as follows:(1)The phylogenetic diversity(PD)of wetland plant communities in the South-Tibet river basin is significantly positively correlated with plant species richness.The net relatedness index(NRI)and the nearest taxon index(NTI)both show an increasing trend with increasing elevation,indicating a phylogenetic clustering trend in wetland plant communities with elevation.Among the above three diversity indices,only NTI was found to be significantly correlated with the environmental indices(such as soil total phosphorus)measured in this study.(2)The diversity of AMF in wetland of the South-Tibet river basin is high,with 130 OTUs detected,belonging to 13 genera.The most abundant genus was Glomus(40.7%),followed by Paraglomus(17.5%),Scutellospora(15.0%),and Archaeospora(13.6%)and Ambispora(11.8%),with the remaining genera having an abundance of less than 1%.Of the 109 wetland plant root samples collected,nearly half(49.5%)were colonized by AMF,and the colonization rate of AMF in roots and the diversity of AMF in sediment both showed a decreasing trend with increasing elevation.(3)The variation in the composition of AMF communities in wetland in the South-Tibet river basin is mainly driven by species replacement processes,and the sediment-related indicators are the most important factors in comparison to plant and water-related indicators.This study found that the deterministic process dominated the AMF community construction in the wetlands of the South-Tibet river basin,which may be related to the extreme environmental conditions in the South-Tibet river basin,such as extreme low temperature.(4)In this study,structural characteristics of plant-AMF interaction networks in wetlands of the South-Tibet river basin were determined:indices of connectivity,nestedness,modularity,and specialization.Most of the network structural characteristics have significant correlations with elevation.The modularity and specialization showed an increasing trend with elevation,while the nestedness showed a decreasing trend with elevation,but the connectivity have no significant correlations with elevation.This suggests that wetland plants in the South-Tibet river basin tend to select more specialized AMF for more efficient mutualistic symbiosis with increasing elevation to cope with environmental stresses in wetlands at high elevation.