Effects Of Nitrogen Deposition And Phosphorus Addition On Arbuscular Mycorrhizal Fungal Colonization,Spore Density And Glomalin-related Soil Protein Of Chinese Fir

The southern area of China has been faced with the problem of phosphorus limitation and increasing nitrogen deposition.Besides,the region is the main distribution area of Chinese fir（Cunninghamia lanceolata）.Although there have been many reports on the effects of nitrogen（N）deposition or phosphorus（P）addition on the physiological status of Chinese fir and ecological change of Chinese fir plantation,few studies about the effects of their on arbuscular mycorrhizal fungi（AMF）.Therefore,we take 10-year-old Chinese fir as the research object to study different levels of nitrogen deposition(N30: 30 kg·hm^-2·a^-1 and N60: 60 kg·hm^-2·a^-1)and phosphorus addition(P20: 20 mg·kg^-1 and P40: 40 mg·kg^-1)and their interactions on arbuscular mycorrhizal fungi colonization,spore density,and glomalin related soil protein.The results showed that :（1）In all four seasons（spring,summer,autumn,and winter）,low N addition significantly increased the AMF root colonization in Chinese fir plantations but did not significantly affect the spore density.In summer and autumn,N addition significantly increased the content of easily extracted glomalin-related soil protein and total glomalin-related soil protein.（2）In autumn and winter,P addition significantly increased the AMF root colonization,the content of easily extracted glomalin-related soil protein and total glomalin-related soil protein,but had no significant effect on spore density.（3）The effect of interaction between N and P addition can reduce the AMF root colonization in general,but the effect of interaction on spore density varied with seasons.In the four seasons,N30+P20 treatment significantly increased the content of easily extracted glomalin-related soil protein.The interaction of nitrogen deposition and phosphorus addition generally increased the content of total glomalin-related soil protein.The results suggested that（1）A certain degree of nitrogen deposition is conducive to the growth of arbuscular mycorrhizal fungi in Chinese fir plantation and the accumulation of glomalin related soil protein,thus contributing to the formation of soil aggregates which can effectively slow down the decomposition of organic carbon and mitigate the release of soil carbon.（2）The appropriate supplement of soil available phosphorus in soil can promote the growth of arbuscular mycorrhizal fungi,increase the content of glomalin-related soil protein in soil so as to improve the stability of soil.This experiment is helpful for us to understand the response of AMF root colonization,spore density,and glomalin-related soil protein to nitrogen and phosphorus addition in Chinese fir plantation.Thereby it provides a new reference for sustainable management of Chinese fir plantation under the background of nitrogen deposition.