Biodiversity Of Arbuscular Mycorrhizal Fungi In Black Soil Region Of Northeast China And The Response To Soil Organic Carbon

The black soil region of northeast China is an important grain-producing area in China and has precious black soil resources.However,long-term cultivation has made the black soil degraded seriously,resulting in changes in the composition of soil microbial communities.In recent years,the severe global climate change has attracted the attention of countries around the world on reducing greenhouse gas emissions.As the largest carbon pool in terrestrial ecosystems,soil organic carbon pool plays an important role in the global carbon balance.Arbuscular mycorrhizal fungi（AMF）are widely present in terrestrial ecosystems and have a critical role in the agricultural ecosystem functioning.This study adopted Mi Seq sequencing to predict the AMF community distribution and diversities in 41 farmland sites from northeast China’s black land,the spatial and temporal distribution characteristics of AMF was analyzed and the difference of AMF diversities in different host plants or land use type was known.The effect of soil factors on AMF diversity and the correlation between glomalin and soil factors were discussed.Moreover,the pot experiment inoculated with AMF was used to explore the carbon sequestration mechanism of AMF on soil organic carbon（SOC）.The main conclusions are as follows:（1）All sequences in 41 soil sites were categorized as four orders,eight families,and night genera in the black land of China.Typically,order Glomerales（mean relative abundances of 58.03%）displayed the highest abundance,followed by Paraglomerales（18.45%）and Diversisporales（0.85%）,and Archaeosporales（0.26%）had the lowest abundance.The families Ambisporaceae,Archaeosporaceae,Acaulosporaceae,Diversisporaceae,Gigasporaceae,Glomeraceae,Paraglomeraceae,and Claroideoglomeraceae were detected in the samples,among which,the latter three displayed the highest relative abundances（41.73%,18.45%,and 6.14%,respectively）.The genera Paraglomus,Glomus,Archaeospora,Scutellospora,Gigaspora,Acaulospora,Claroideoglomus,Ambispora and Diversispora were detected.Glomus,Paraglomus and Claroideoglomus were the high levels taxa（41.72%,18.45%and6.14%,respectively）.There were differences in AMF species composition and Chao1index among the plots.（2）Spatially,different AMF community had different correlations with longitude and latitude,but AMF diversity was significantly positively correlated with latitude.Geographical distance had a significant effect on AMF communities,indicating spatial differences in AMF community composition.Eight identical sampling sites were selected for three consecutive years,and it was found that the AMF diversity in different years was significantly different,and the species composition of AMF gradually decreased over time.There was no significant difference in AMF diversity and species composition between maize and soybean host plants in black soil area.In farmland and woodland,Glomerales（50.9%）and Paraglomerales（64.9%）were observed as the most abundant order in farmland and woodland,respectively,reflecting the differences of AMF communities in farmland and woodland.（3）The edaphic factors in the black soil region of northeast China had spatial distribution characteristics.Soil p H was mostly neutral or weakly acidic.SOC content,total nitrogen content,acid phosphatase activity and invertase activity increased with the increase of latitude,while urease activity decreased with the increase of latitude.The total phosphorus content was more affected by longitude.Soil factors had a significant effect on AMF composition,and different factors had different correlations with different AMF taxa,indicating that the suitable soil environments for AMF species were different.The diversity of AMF increased with the increase of soil p H,SOC,total nitrogen and invertase activity,showing a significant positive correlation.Taken together,SOC and total nitrogen were important drivers of AMF community composition and diversity.（4）Glomalin-related soil protein（GRSP）is a protein secreted by AMF mycelial.The GRSP content of farmland soil in the black soil region of northeast China decreased along latitude gradient from north to south,showing the same spatial distribution characteristics as AMF diversity.GRSP content was significantly positively correlated with SOC,total nitrogen,total phosphorus and acid phosphatase,and significantly negatively correlated with urease,indicating the relationship between GRSP content and soil factors.（5）In the outdoor pot experiments,inoculation with AMF had no significant effect in the distribution of photosynthetic carbon to roots and soil by ¹³C isotope labeling.Inoculation of AMF could promote soil aggregate aggregation and the accumulation of soil microbial biomass carbon in soil with low organic matter content.After the straw was returned to the field,AMF had no significant effect on the ¹³C abundance of the straw,but it promoted the decomposition of cellulose,hemicellulose and lignin in the returned straw.In sum,the farmland soil in the black soil region of northeast China was rich in AMF community resources and diversity,and AMF diversity gradually increased from south to north along the latitude gradient.Edaphic factors played an important role in the composition and diversity of AMF,of which SOC and total nitrogen are the critical factors.AMF and its mycelial secretion GRSP could promote the accumulation of SOC and the aggregation of soil,which played an important role in the stability of ecosystems and soil carbon pool.Understanding AMF biodiversity and its influencing factors in the black soil region of northeast China and exploring the role of AMF in carbon sequestration of SOC,could provide an important theoretical basis and guidance for regional AMF diversity and the protection and sustainable use of farmland black soil.