Effects Of Nitrogen Addition On Population Characteristics And Soil Nutrients Of Pedicularis Kansuensis

In recent decades,native invasive species Pedicularis kansuensis expanding rapidly in Bayanbulak Alpine grassland,which significantly affected the biodiversity,stability and ecological service function of grassland ecosystem,and seriously threatened the local livestock industry.The Bayingolin Mongol Autonomous government has invested a lot of manpower and financial resources to control it every year,but the effect is not ideal.Meanwhile,studies on the control of parasitic plant invasions in grassland ecosystems are very limited at home and abroad,especially native invasive species which has the root hemiparasitism character.As a result,the control measures for large-scale invasion of P.kansuensis are still in the exploration phase.Therefore,we set P.kansuensis which is a native invasive plant in Bayanbulak Alpine grassland as the research object in this study,and used the field short-term control experiment.We conducted the experiment by setting three different nitrogen gradients addition,and it contained control(0g/m~2),low nitrogen(3 g/m~2)and high nitrogen(9 g/m~2).Measured the soil nutrients of P.kansuensis population,community of P.kansuensis before and after nitrogen addition,and analyzed the effects of nitrogen addition on P.kansuensis invasionin Bayanbulak alpine grassland.The results are as follows:(1)Nitrogen addition in the first year had a certain promoting effect on height,coverage,density,aboveground biomass and underground biomass of P.kansuensis population in the Bayanbulak Alpine grassland,but the effect was not significant.In the second year,the height,coverage,density,aboveground biomass,underground biomass and root-shoot ratio of P.kansuensis population were significantly inhibited by nitrogen concentration in both addition treatments,and the effect of high nitrogen treatment was more significant,and P.kansuensis population almost disappeared.Nevertheless,nitrogen addition had no significant effect on specific leaf area of P.kansuensis.(2)It turned out nitrogen addition significantly increased coverage,aboveground biomass and underground biomass of gramineae and forbs in the community of P.kansuensis in the Bayanbulak Alpine grassland,especially in the second year.On the contrary,the coverage,aboveground biomass and underground biomass of leguminous plants in the community decreased significantly,and the inhibition effect was more significant under higher nitrogen concentration.Nevertheless,nitrogen addition had no significant effect on the distribution of underground biomass of the community.On the other hand,nitrogen addition reduced Simpson index,Shannon-Wiener index and Pielou index to a certain extent,but the effect was not significant.(3)The contents of available P and available K in 0-10 cm,10-20 cm and 20-30 cm soil layers were significantly increased in low concentration nitrogen addition,and the contents of C:N,total K and organic matter cotent in 0-10 cm and 10-20 cm soil layers were decreased,but not significantly.Compared with the control group,the contents of other nutrients in soil increased to a certain extent but did not change significantly.Higher nitrogen concentration addition significantly increased the content of available nitrogen and electrical conductivity in 0-10 cm soil layer,and total phosphorus content in 20-30 cm soil layer,but significantly decreased the content of total potassium in 10-20 cm soil layer.These results indicated that nitrogen addition could effectively inhibit the growth and development of P.kansuensis in the Bayanbulak Alpine grassland,especially at higher nitrogen concentration,P.kansuensis almost disappeared in the plant community.The main reason should be that be gramineae has the advantage of the nitrogen utilization and improve its coverage and aboveground biomass,and led to P.kansuensis at a disadvantage in light acquisition and utilization finally,eventually leading to P.kansuensis and gramineous plants on the obtain and make use of light at a disadvantage,and significantly inhibiting its growth in the end.This paper clarified the response characteristics of invasive native plant P.kansuensis to nitrogen addition,which is helpful to formulate effective management methods and control strategies for P.kansuensis invasion in Bayanbulak alpine grassland.