Effects Of Warming On Arbuscular Mycorrhizal Fungal (AMF) Community In Alpine Meadow During Different Seasons

Arbuscular mycorrhizal fungi?AMF?is one of the most common and functional symbiotic fungi of terrestrial plants,and it is of great significance for plant nutrient absorption and resistance to pathogenic bacteria.However,there is currently relatively lack of researches on the influence of climate change on AMF communities,especially in the Qinghai-Tibet Plateau.Some research has shown that the Qinghai-Tibet Plateau is going to rapidly warming up in the future.Therefore,the alpine meadow ecosystem of the Qinghai-Tibet Plateau was investigated.We applied passive warming method–Open topped chambers?OTC?,which adopted by the International Tundra Experiment?ITEX?.Through combining field investigation with laboratory analysis,to discuss the change of plant community characteristics,soil physical and chemical characteristics and AMF community composition and diversity under warming treatment.The results are as follows:1.Warming increased gramineous biomass and coverage,but reduced the biomass and coverage of legumin,sedge,forb and litter.In addition,warming significantly reduced the species richness of plant communities?P<0.05?.2.Warming mainly affected the soil total nutrient content of alpine meadow.During the growing season,warming significantly reduced the soil total nitrogen?TN?content and soil nitrogen phosphorus ratio?N/P??P<0.05?,and aggravated the nitrogen limitation of alpine meadow plant growth?N/P=11.62,<14?;during the non-growth season,warming significantly increased the soil total carbon content?TC?,TN and total phosphorus content?TP?,then reduced the soil carbon phosphorus ratio?C/N??P<0.05?.3.The dominant genera of soil AMF community in alpine meadow were Acaulospora,Ambispora and Claroideoglomus during different seasons.Warming mainly affected the soil AMF community composition during the growing season.For instance,warming significantly increased the relative abundance of the Claroideoglomus genus and reduced the relative abundance of the Ambispora genus?P<0.05?;but there was no significant change of the soil AMF community composition during the non-growth season.The dominant genus of root AMF community were different between growing season and non-growth season.The dominant genus of root AMF community during growing season was Claroideoglomus and Rhizophagus,and the dominant genus of non-growing root AMF community was Acaulospora,Rhizophagus,Gigaspora genus.There was no significant change of root AMF community composition during growing season by warming.But warming increased the relative abundance of the Acaulospora and reduced the relative abundance of Gigaspora?P<0.05?.4.Alpha-diversity of soil AMF community in alpine meadow was not significantly affected by warming during different seasons.However,Beta-diversity of soil AMF community in different seasons was significantly changed by warming?P<0.05?.Temperature increase significantly reduced the Alpha-diversity of the root AMF community during the growing season?P<0.05?,but had no obviously effect during the non-growth season.In addition,warming significantly changed the Beta-diversity of the root AMF community during different seasons?P<0.05?.5.Redundancy analysis?RDA?results has showed that during the growing season,the composition of soil AMF community was significantly affected by the plant community Simpson diversity index,soil temperature?ST?and soil ammonium nitrogen?NH₄⁺?content?P<0.05?,while the composition of the root AMF community was significantly affected by leguminous coverage,forb coverage and soil nitrate nitrogen?NO₃^-?content?P<0.05?.During the non-growth season,the soil AMF community composition was significantly affected by soil moisture?SM?,and the root AMF community composition was significantly affected by soil TN?P<0.05?.6.The structural equation model?SEM?results has showed that:during the growing season,the soil AMF community diversity was significantly affected by the ST and soil available nutrient content?P<0.05?.During the non-growing season,the soil AMF community diversity was significantly affected by the soil p H,and the diversity of root AMF community was significantly affected by soil available nutrient content?P<0.05?.In summary,warming affects the composition and diversity of soil and root AMF communities mainly by changing plant communities and soil physicochemical characteristics in alpine meadows.The warming increased the nitrogen limitation of plant growth,resulting in the decrease of plants dependence on AMF,and the nutrients supply of AMF,thus the AMF life history strategies was transformed from the"tolerance-type strategies"dominated by Claroideoglomus and Rhizophagus during the growing season and dominated by Gigaspora during the non-growing season to the"weed-type strategies",which led by capable Acaulospora.The transformation of life history strategies was at the expense of some AMF community functions,such as the promotion of AMF to plant biomass during the growing season and carbon sequestration ability of AMF in the non-growing season declined.Moreover,warming promotes the decomposition of soil nutrients,while there were differences in species competition of soil and root AMF communities in different seasons.The increase of soil effective nutrient content during the growing season has a positive effect on the soil AMF community diversity,while has an adverse effect on the root AMF community diversity during non-growing season.Therefore,under the background of global warming,it is imperative to construct an ecological theory of plant-soil-AMF interaction relationship in alpine meadows.