Effects Of Agroforestry Pattern Of Camellia Oleifolia On Energy Flux Of Soil Food Webs

Soil food web is considered to be one of the most diverse biological networks on Earth,which affects the functions and processes of terrestrial ecosystems through complex interspecific interactions.The concept of food web energy flux integrates food web theory and biodiversity and ecosystem function theory,characterizing the energy flux rate between nodes,expressing the energy expenditure of different trophic groups,and describing the energy structure of communities.Therefore,it can be used to provide a standardized index of ecosystem versatility.Camellia oleifera(C.oleifera)is an important woody oil tree species in China and an economic tree species widely planted in typical ecologically fragile areas of southern China.In this study,the energy flux of food web under the agro-forest mode of camellia oleiferans was studied.Six treatments were set up,including monocrop and weeder(CK),monocrop and no weeder(CG),monocrop and peanut intercropping(CP),monocrop and Cassia seed intercropping(CS),monocrop and high nitrogen addition(HN),and monocrop and low nitrogen addition(LN).We analyzed the changes of soil physical and chemical properties,the diversity of soil arthropod community,and the structure of soil microbial community under the six treatments during the crop growth and harvest periods.A food web model was used to construct the energy flux network of soil food web under different treatments.We further analyzed the energy flux of soil food web under different treatments and its relationship with soil nutrients and microbial communities using univariate analysis,multivariate analysis,correlation analysis and redundancy analysis,to provide theoretical basis for evaluating the effects of cropping and nitrogen application during the young stage of C.oleifera on soil food web energy flux.The results showed that:(1)The responses of soil physical and chemical properties were different in different periods and treatments.The overall soil pH value of the experimental plot was slightly acidic.During the crop harvest,soil pH value in the intercropping legume treatment was significantly higher than that in the camellia oleifera monocropping treatment.Compared with the growing period,the pH value of all treatments decreased in the harvest period,but soil organic carbon and soil water content in the intercropped legume treatment increased significantly.In the growing phase,N application significantly reduced soil pH.Different from the changes in soil physical and chemical properties,soil microbial community structure did not change significantly among the treatments.Nitrogen application and intercropping of nitrogen-fixing plants did not affect the total PLFA content of soil microorganisms in the growing and harvest periods,but the ratio of Gram-positive and negative bacteria in each treatment in the harvest period was slightly higher than that in the growing period.(2)The composition and proportion of soil arthropods in the experimental plots were different at different stages.During the growth period,there were 19 arthropod groups in soil,with Scarabidae,Rhinotermitidae,and Formicidae being the dominant groups.There were 17 groups of soil arthropods in the harvest period,among which the dominant groups were Cydnadae,Lygaeidae,Clidicinae,and Formicidae.There were no significant differences in Shannon-weinner diversity index,Pielou index,Richness index and taxon number among the treatments under different agroforestry patterns.However,Shannon-weinner diversity index,Pielou index,Richness index and taxonomic number of soil arthropods were higher in harvest than in growing season.In the HN treatment,the biomass of plant-eaters was significantly higher than other treatments in the growing period,while in the CG treatment,the biomass of omnivores was significantly higher than other treatments in the harvest period.Compared with the growing period,the biomass of predators in all treatments showed an increasing trend in the harvest period.In terms of energy flux,the total energy flux,decomposition energy flux,herbivorous energy flux and intra-node predation energy flux in the CG treatment were much higher than those in the other treatments in the growth and harvest periods,indicating that the energy flux would decrease significantly in the treatment with excessive artificial intervention.In addition,compared with the N fertilizer treatment,the herbivorous energy flux of intercropping legumes was decreased,indicating that intercropping legumes may be more effective in inhibiting the growth of herbivorous pests.(3)In the growing period,pH and ammonia had a strong negative correlation with total energy flux,but nitrate and soil bulk density had a strong positive correlation with total energy flux and herbivory energy flux.However,available P in the harvest period had a strong negative correlation with total energy flux,primary predation energy flux,intra-node predation energy flux,and herbivory energy flux The energy flux was significantly positively correlated with Shannon diversity index and evenness in the growing season,the total energy flux was significantly positively correlated with Shannon-weinner diversity index and Richness index in the harvest season,and the primary predation energy flux was significantly positively correlated with Shannon-weinner diversity index and Richness index.There was a significant positive correlation between predation energy flux and Richness index within nodes.The decomposition of soil food web in the growing stage was significantly positively correlated with total bacterial PLFA and bacterial-fungal ratio.Total energy flux,primary predation energy flux phytophagous energy flux,and intra-node predation energy flux in soil food web were significantly positively correlated with total bacterial PLFA,total fungal PLFA,and total microbial PLFA at harvest stage.Only decomposition had no significant correlation with microbial community.In summary,the higher energy flux in intercropped legumes was more likely to enter predators and omnivores,while the high energy flux in the nitrogen fertilizer treatment was more likely to enter plant-eaters.Compared with the undisturbed CG treatment,the energy flux of decomposition in both intercropped legumes and nitrogen fertilizer treatments was much lower,suggesting that in the artificial underground agroforestry ecosystem,The trophic versatility of subsurface communities is compromised.