| Plant litter is the linkage of energy flow and material recycle in terrestrial ecosystem,and the litter decomposition process is great significance to the carbon sequestration and nutrients turnover in grassland ecosystem.Water-soluble compounds,which is released in the earlier stage of litter decomposition,can have allelopathic effect on the environment around.In this study,simulated experiments were designed based on physical extraction from Bothriochloa ischaemum,Leymus secalinus and Melissilus ruthenicus.Then we explored the effects of leachates from litters on the growth of seedlings,soil physical and chemical properties,and microbial structure and functional diversity of rhizosphere soil.The results are as follows:（1）The compounds in the extracts of plant litters were different at different sampled time.Soluble organic acids,straight-chain alcohols,aliphatic aldehydes and ketones;terpenoids,steroids and simple unsaturated lactones were the main substances.（2）The litters extract had a significant inhibitory effects on seed germination and seedling growth.The extract of litters from Bothriochloa ischaemum showed a certain promoting effect on the root growth of its own seedlings,and the extract concentration of 0.025 g·mL-1 significantly promoted the root growth.The extracts of litters fromLeymus secalinus and Melissilus ruthenicus significantly inhibited the growth of the roots of its seedlings,and the inhibition was improved with the increase of the concentration.The extracts of the tested plants litters also had different effects on the activity of antioxidant enzymes including SOD,POD,CAT,as well as the content of MDA.Under the treatment of 0.1 g·mL-1 extract,activity of SOD,POD and CAT of the tested plants was significantly reduced,and the content of MDA in plants was increased.（3）Different degrees of response of physical and chemical properties of soil to the treatments were observed: the addition of litters leaching solution of Bothriochloa ischaemum not only made SOC and TP content decrease first and then increase with the increase of concentration,but also reduced soil TN and pH.The addition of litters leaching solution of Leymus secalinus had no significant effect on soil SOC and TP,but it could increase soil TN and reduce pH.The addition of litters leaching solution of Melissilus ruthenicus could increase the TP content of soil,but had no significant effect on SOC,TN and pH.However,the soil microbial community structure showed that the leaching solution could increase the relative abundance of Proteobacteria and Basidiomycota,and decrease the relative abundance of Actinobacteria and Ascomycota.（4）The effects of extract concentration on the metabolism of 31 carbon substrates were as follows: along with the incubation,the microbial metabolic intensity between treatments became significantly different.At the end of the incubation（144 h）,AWCD values of rhizosphere soil reached the highest,among which the0.10 g·mL-1 extract from Bothriochloa ischaemum was the highest,55.35% higher than that of the control.In contrast,Leymus secalinus and Melissilus ruthenicus treated with 0.05 g·mL-1 were the highest concentration,21.41% and 534.85% higher than that of the control,respectively.In addition,principal component analysis showed that the carbon sources of polymerized sugars,amino acids and esters were the main reasons for the differences in the metabolic activities of the three soil microorganisms.In summary,the leachates from tested plant litters can affect the seedling development and soil properties,such as physical and chemical properties,rhizosphere soil microbial structure and function. |
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