Effects Of AM Fungi And Phosphorus Additions On The Growth And Soil Of E. Japonica And P. Japonica With Different Competition Modes

The successful invasion and expansion of alien invasive plants usually lead to the withdrawal of native plants from their original habitats.There are abundant species diversity in karst habitats in Southwest China.However,in recent years,the intense invasion of alien plants has broken the ecological balance of karst habitat and seriously threatened the local species diversity and natural ecosystem stability.At present,the invasion of alien plants in karst areas has become a hot topic in ecological research,but the systematic exploration of the mechanism is still very limited.Arbuscular mycorrhizal(AM)fungi is a important functional microorganism,which can co-exist with many plants on land.AM fungi can activate soil nutrients,promote plant growth and influence competition among plants.It is found that AM fungi play a dual role of promotion and inhibition in regulating soil nutrients and influencing the successful invasion of alien plants.So how do different environmental resources,mycorrhizal fungi and competition interact to regulate the growth and soil properties of invasive plants and native plants to affect the invasion of alien species?Therefore,the invasive species Eupatorium adenophorum and native species Eupatorium lindleyanum DC were used as the test plant of competition treatment.Six planting methods were designed,including bare soil without plant treatment,single planting of E.adenophorum or E.lindleyanum,intraspecific competition of E.adenophorum or E.lindleyanum and interspecific competition of E.adenophorum and E.lindleyanum.The effects of AM fungi inoculation and phosphorus addition on the competitive growth of invasive and native plants and soil properties in karst habitats were analyzed,and the invasion mechanism of alien plants in Karst habitats was explored,so as to provide theoretical basis for biological invasion control in karst areas.This experiment is an indoor control experiment of four factors,including species,AM fungi,phosphorus addition and plants competition.After three months of plant growth,the biomass,phenotypic traits of plant organs and soil carbon,nitrogen,phosphorus and potassium were measured.The main findings are as follows:(1)Inoculation of AM fungi significantly increased the seedling height,ground diameter,biomass and root shoot ratio of invasive plant E.adenophorum and native plant E.lindleyanum under various phosphorus treatments.The biomass of E.adenophorum showed that the control and intraspecific competition was significantly higher than the interspecific competition;while for E.lindleyanum,the control treatment and the interspecific competition were significantly higher than the intraspecific competition.In general,the seedling height and biomass of E.adenophorum were significantly lower than that of E.lindleyanum.(2)Inoculation of AM fungi increased leaf thickness,leaf length,leaf width and leaf area of E.adenophorum and E.lindleyanum in different phosphorus treatments.The leaf size of E.adenophorum showed that the control was significantly larger than the interspecific competition;E.lindleyanum was the control treatment and the interspecific competition was significantly greater than the intraspecific competition.Compared with the leaf size of the two species,the leaf size of E.adenophorum was significantly lower than that of E.lindleyanum in interspecific competition.(3)AM fungi significantly promoted the growth and development of the root systems of the two species under various phosphorus treatments,showing that the inoculation of AM fungi significantly increased the root infection rate,root length,root surface area,root volume,average root diameter,and root average diameter,root tips,root branching points,and the specific root area in interspecific competition of E.adenophorum and E.lindleyanum.The root length,root surface area and root volume of E.adenophorum were significantly lower than those of E.lindleyanum.(4)Inoculation of AM fungi significantly increased soil AN in interspecific competition under the condition of phosphorus addition,soil SOC in single planting of the two species and in intraspecific competition of E.lindleyanum;significantly reduced soil AN in P₀ treatment,soil TK in single planting of the two species and soil AP and AK in intra-and inter-competition.The soil TP and TK in interspecific competition showed that the inoculated treatment was larger than the uninoculated treatment.The soil AP in single planting of the two species was significantly higher than the AP in their intraspecific and interspecific competition,and the soil AK for the planting treatment was significantly lower than the control treatment.(5)The results showed that the soil spore density,hyphal density,and EE-GRSP and T-GRSP in interspecific competition under all treatments were significantly increased by inoculation of AM fungi.Among them,the spore density,hyphal density and T-GRSP in P₀ treatment were higher than in high P₂₅ treatment,and the T-GRSP under the single planting treatment of E.adenophorum was significantly higher than that of the control treatment.In conclusion,AM fungi significantly promoted the growth and development of E.adenophorum and E.lindleyanum.Among them,the biomass of E.adenophorum was the highest under P₂₅ treatment,while E.lindleyanum was higher under P₀ and P₅treatments,and the total biomass of E.lindleyanum was significantly higher than E.adenophorum.AM fungi regulation increased soil spore and mycelium density,AN and T-GRSP under interspecific competition,and soil SOC under single planting treatment;reduced soil AP and AK under intraspecific and interspecific competition.With the increase of phosphorus concentration,soil AP gradually increased;but soil spores,mycelium,soil TK and AK in intraspecific competition of E.lindleyanum,soil SOC in single planting treatment,and soil T-GRSP in interspecific competition gradually decreased.