Effects Of Soil Warming And Precipitation Exclusion On The Arbuscular Mycorrhizal Fungi Of Chinese Fir Plantation In Mid-subtropical China

Global climate change has a significant impact on terrestrial ecosystems forest carbon and nitrogen cycles.Subtropical evergreen broad-leaved forest in China is the world's important forest carbon sink area.Study the impact of climate change and subtropical forest ecosystem is very important.Our study is located at Sanming Research Station of Forest Ecosystem and Global Change,Fujian where Chinese fir(Cunninghamia lanceolata)young plantation was selected.Four treatments were used to simulate global climate change,viz.control,warming,precipitation exclusion and the interaction of warming and precipitation exclusion.We focus on the effects of temperature and precipitation changes on arbuscular mycorrhizal fungi in young Chinese fir plantation.Also,we investigated Chinese fir biomass and nutrient content.This study will benefit sustainable management of subtropical forests.In this paper,the main results were as follows:(1)Experimental study by warming and precipitation exclusion showed that warming and the interaction of warming and precipitation exclusion reduced microbial biomass carbon content.The highest value of soil microbial biomass nitrogen content occurred in August in all treatements.Soil microbial biomass nitrogen content in precipitation exclusion treatment was higher than that in other treatments.Compared with the control treatment,warming and the interaction of warming and precipitation exclusion reduced the total nitrogen content and total carbon content significantly.Plant growth was accelerated and root density increased,which may stimulate soil microbial activity,accelerate the decomposition of soil organic matter,and promote soil organic carbon and nitrogen mineralization.Each treatment had no obvious effect on soil phosphorus content.Under warming,the interaction of warming and precipitation exclusion treatments,soil available phosphorus content was significantly higher than in the control treatment.Soil acid phosphatase enzyme activity showed significant seasonal variation in all treatments,the highest value appeared in April,and lower in August.Soil enzyme activities have a certain appropriate temperature.High soil temperature may inhibit soil acid phosphatase activity.(2)A significant increase of arbuscular mycorrhizal fungi mycorrhizal colonization rate was found in the warming treatment,while significantly reduced under the interaction of warming and precipitation exclusion.The density of arbuscular mycorrhizal fungi spores increased significantly under warming and the interaction of warming and precipitation exclusion,but precipitation exclusion reduced soil arbuscular mycorrhizal fungi spores quantity.Easily extractable soil glomalin related protein content decreased under the interaction of warming and precipitation exclusion treatment.Effect of soil warming on contents of easily extract glomalin soil-related proteins was related to different seasons.Soil total glomalin was insoluble in water,not easily broken,so its changes were not obvious between treatments.(3)Warming and the interaction of warming and precipitation exclusion reduced arbuscular mycorrhizal fungal biomass significantly,while the effect of precipitation exclusion on arbuscular mycorrhizal fungi biomass was not significant.High-throughput sequencing results showed warming,precipitation exclusion and the interaction of warming and precipitation exclusion influence the relative abundance of arbuscular mycorrhizal fungi significantly.Warming and precipitation exclusion inhibited the arbuscular mycorrhizal fungi Ambisporaceae growth.Soil warming hindered arbuscular mycorrhizal fungi Gigasporaceae growth.(4)Warming and the interaction of warming and precipitation exclusion significantly reduced base diameter,tree height,diameter at breast height and root biomass of Chinese fir.But precipitation exclusion effects were not obvious.Carbon content of Chinese fir leaf had small changes.Warming increased leaf N and P contents of Chinese fir.Warming and the interaction of warming and precipitation exclusion significantly increased the nitrogen content of Chinese fir roots,but the phosphorus content in Chinese fir roots reduced in the two treatments.The increase of root N:P ratio indicated P limitation of Chinese fir growth.