Exploring The Temperate Forests Of Northeast China Based On Bacterial Energy Flow Channels Influence Of Organic Carbon Input Patterns On Soil Micro-food Webs

Organic carbon input is of great significance to the stability of soil ecosystem carbon cycle,and the change of organic carbon input mode can directly change the soil ecosystem carbon pool on the one hand,and regulate the soil carbon budget and expenditure by changing the soil micro-food network on the other hand.As a fast energy flow turnover pathway in soil micro-food webs,bacterial energy flow channels are sensitive to organic carbon input patterns.Therefore,this study set up an experiment on root and litter organic carbon input control in the Maoershan forest in Northeast China to explore the response of various functional groups of bacterial energy flow channels to organic carbon input mode,in order to provide new ideas for in-depth exploration of soil carbon turnover changes in temperate forest ecosystems,and also provide data support for revealing the change mechanism of soil micro-food webs.The main results of this study are as follows:(1)The mode of organic carbon input had a significant impact on soil bacterial feeding nematodes.In terms of the number and composition of soil bacterivorous nematodes,a single organic carbon input reduced the total number of bacterivorous nematodes and reduced the relative biomass of Ba2 taxa,but increased the relative biomass of Ba3-5 taxa.In terms of the ecological function of energy and carbon turnover in bacterivorous nematodes,the root-only approach resulted in a reduction in the amount of energy received by bacterivorous nematodes from the environment,but an increase in the amount of energy transferred to higher predators.These results imply that the reduction in the amount of organic carbon input drives the nematode community towards more efficient bacterial energy turnover pathways(2)Soil bacterial communities differed significantly between organic carbon input methods.From the perspective of soil bacterial composition and diversity,the relative abundance of Proteobacteria of the phylum Proteobacteria decreased under the root-only and apoplastic organic carbon input methods,and the Shannon index,Pielous index and Observed index of the soil bacterial community all showed a decreasing trend,which was due to the fact that the removal of roots and apoplastic matter changed the physicochemical properties of the soil,causing the The reason for this is that the removal of roots and litter changes the physicochemical properties of the soil,causing the disappearance of less tolerant soil microbes.From the perspective of soil microbial ecological functions,the relative abundance of functions related to the nitrogen cycle decreases under a single organic carbon input.(3)Bacteria-feeding nematode feeding preferences are sensitive to the mode of organic carbon input.In this study,nematode gut microbes were used to represent the feeding preferences of nematodes.The observed and measured C-score values for the gut microbes of the bacterivorous nematodes differed significantly from each other,and the gut microbes of the bacterivorous nematodes differed significantly from the microbial community of the soil environment,suggesting that the bacterivorous nematodes have a unique feeding preference.The increase in the abundance of nitrogencycling microorganisms in the gut of the bacterivorous nematodes and the decrease in the relative abundance of nitrogen-cycling microorganisms in the soil environment under the treatment of a single organic carbon input may be an important factor in the change of soil nitrogen turnover function due to the increased selective feeding of nitrogen-cycling microorganisms by bacterivorous nematodes.This study revealed the effects of organic carbon input on the composition,diversity and ecological functions of various nutrient groups in bacterial energy flow channels in soil microfood webs,and explained the reasons for the changes in the ecological functions of eating bacterial nematodes and bacteria from the perspective of feeding preference.This study provides new ideas for the change of ecological functions of soil micro-food webs,and also provides data support for the indepth interpretation of the mechanism of soil carbon turnover changes.