Study On Biomass Allocation And Response Mechanism Of Main Crops In Agro-pastoral Ecotone Of Inner Mongolia

The Inner Mongolia agro-pastoral ecotone is the ecological security barrier of northern China,the production base of grain and livestock products,and the focus of research on material circulation in terrestrial ecosystems.Its ecological balance is very important to the coordinated development of agriculture and animal husbandry and food security.The effects of environmental factors on crop biomass allocation in agro-pastoral ecotone were unclear under the spatial scale,land use mode(cropland of main crops,grassland)and fertilization measures.In this paper,the effects of land use patterns on soil factors on the whole region scale of agro-pastoral ecotone and four zones were studied by sampling transits,and the effects of environmental factors on crop biomass allocation were quantified.The effect mechanism of different fertilization measures on crop biomass allocation was analyzed through site experiments,and the mechanism of crop biomass allocation at different scales was tested by correlation growth model.The main results are as follows:1.Compared with grassland,the contents of soil organic carbon,total nitrogen,ammonium nitrogen,carbon nitrogen ratio,carbon phosphorus ratio and nitrogen phosphorus ratio were reduced in cropland,and the contents of soil electrical conductivity,total phosphorus,total potassium,nitrate nitrogen,available phosphorus and available potassium content and phosphorus potassium ratio were increased.At the whole regional scale,the number of ASVs in the soil microbial community of cropland was more than that of grassland,and the ratio of bacteria/fungi(ASVs)in the soil microbial community of cropland was higher than that of grassland.The soil microbial community structures of cropland and grassland were significantly different between regions,and the species diversity of cropland was more different than that of grassland.The results indicated that there was a geographical gradient between soil nutrient content and stoichiometric relationship in the study area,and human disturbance(planting different crops)had significant effects on soil nutrient,stoichiometric characteristics and microbial characteristics.2.On the whole regional scale,above-ground crop biomass was mainly affected by longitude,altitude,average annual temperature,average annual precipitation,soil p H,nitrogen and phosphorus ratio,and fungal species richness and diversity.The underground biomass was mainly affected by average annual sunshine hours,soil nitrate nitrogen,available phosphorus,available potassium content,nitrogen and potassium ratio,and bacterial species richness.The root-shoot ratio was mainly affected by longitude,latitude,annual average temperature,annual average sunshine duration,soil organic carbon,nitrate nitrogen,ammonium nitrogen,available phosphorus content and microbial species richness.3.Changes in soil electrical conductivity,bulk density and contents of organic carbon,available phosphorus,available potassium and nitrate nitrogen had significant effects on soil bacterial community structure,while changes in soil bulk density,p H and contents of total phosphorus,organic carbon,available potassium and nitrate nitrogen had significant effects on fungal community structure under fertilization measures.Soil p H,water content,total nitrogen,total phosphorus,total potassium,nitrate nitrogen contents and microbial diversity had significant effects on crop yield,above-ground biomass,subsurface biomass and root-shoot ratio.Compared with no fertilization,fertilization measures increased the relative abundance of Proteobacteria,Firmicutes and Ascomycota.Different fertilization measures significantly affected the relative abundance of bacteria involved in the oxidative decomposition of organic matter and nitrogen cycle in soil,and the fungal community was rich in Undefined Saprotroph,Endophyte and Plant Pathogen functional groups.4.The allocations of underground and aboveground biomass of main crops in the agro-pastoral ecotone of Inner Mongolia under different spatial scales and fertilization measures accorded with the hypothesis of isokinetic allocation,but the biomass allocation of crops without fertilization treatment was allometric allocation.The study defined the mechanism of main crops biomass allocation under spatial scales and fertilization measures in the agro-pastoral ecotone in Inner Mongolia,and provided basic parameters for the study of material cycle in cropland ecosystem.Which provided theoretical support for field managements and planting structure adjustment according to local conditions,and had important practical significance for the coordinated and sustainable development of agriculture and animal husbandry in this region.