Comparison Of Interspecific Competitive Ability Between The Invasive Plant Xanthium Italicum Moretti And The Native Plant Glycyrrhiza Uralensis Fisch

Invasive plant Xanthium italicum Moretti is an annual herb of the Compositae family,native to North America and now widely distributed in the middle latitudes of the eastern and western hemispheres.Its strong ability of adaptability,resource competitiveness,reproduction and seed dispersal makes it become a worldwide malignant invasive weed.The roots and rhizomes of Glycyrrhiza uralensis Fisch contain a large amount of triterpenoids and flavonoids,which is one of the most commonly used medicinal materials.The stems and leaves of G.uralensis have high crude protein content,which is an excellent forage grass and widely used in animal husbandry.The extremely high value makes it an important cash crop in northwest in China.During the field investigation,we found that the X.italicum had invaded the farmland of the G.uralensis farmland,and the two formed a mixed pattern,but this phenomenon has not received any attention,the relative competitiveness of the invasive plant X.italicum and the native plant G.uralensis is not clear,and the results of the competition between the two plants are still unclear.Therefore,in this study,the allelopathic inhibitory potential of X.italicum on G.uralensis was explored by the Petri dish method and pot cultivation method under strictly controlled conditions.The replace experiment method was used to design the experiment,and the pot experiment was used to simulate the soil water and fertility conditions of different regions licorice farmland,and to explore the resource-based interspecific competition results and competition relationship between X.italicum and G.uralensis under different water and fertilizer management conditions.From the perspective of plant interference competition and resource-based utilization competition,we carried out research on the ability of the invasive plant X.italicum to compete with the native plant G.uralensis,to provide a preliminary experimental reference for the evaluation of the invasion ability and consequences of Italian cocklebur invading licorice farmland.The main results were as follows:1.Allelopathic inhibition potential of different organs of X.italicum to G.uralensisThe roots,leaves and fruits extracts of X.italicum had allelopathic inhibitory on the seed germination of G.uralensis,and the leaf extract has the strongest inhibitory effect,compared with the control,the seed germination rate of 25,50,75 g·L^-1and 100 g·L^-1leaf extracts treatments were reduced by 19.51%,43.9%,56.1%and 69.51%,respectively.The leaves and fruits extracts can significantly inhibit the seedlings growth of G.uralensis at various concentration.Compared with the control,the stem length of G.uralensis seedlings treated with 100 g·L^-1leaf and fruit extracts decreased by 65%and 70%,and the fresh weight of seedlings decreased by 87%and 72%,respectively.The extract of root and stem significantly inhibited the growth of G.uralensis seedlings at high concentrations(75 g·L^-1and 100 g·L^-1).The increase of the powder quality of the roots and stems of X.italicum in the soil promoted the SOD,POD and CAT activities of G.uralensis.When the quality of the leaves and fruits powder in the soil increased,the three protective enzymes activity showed a trend of first increased and then decreased.The effects of various organs powder of X.italicum on the photosynthetic capacity of G.uralensis showed a trend of decreasing P_n,T_r,G_sand C_iof G.uralensis with the increase of powder content.These results indicated that the X.italicum has a strong allelopathic inhibitory effect on G.uralensis.2.Effects of mixture between X.italicum and G.uralensis on their growth and developmentThe mixture of X.italicum and G.uralensis has a serious inhibitory effect on the growth and development of G.uralensis.The plant height,crown width,root biomass,stem biomass,leaf biomass,rhizome number and bud number of G.uralensis under the mixture treatment were lower than those of the monoculture treatment.Under the high water and high fertilizer conditions,the compared with the monoculture treatment,the above indicators decreased by 34.7%,53.5%,85.9%,85.7%,88.9%,100%and93.4%respectively;Under the high water and low fertilizer conditions,compared with the monoculture treatment,the indicators decreased by 38%,57.7%,85.1%,87.1%,91.2%,100%and 72.1%,respectively;Under the low water and high fertilizer conditions,compared with the monoculture treatment,the reductions were 39.3%,53.6%,87.7%,91%,87.8%,100%and 66.2%,respectively;Under the low water and low fertilizer conditions,compared with the monoculture treatment,the reductions were 47%,57.7%,83.6%,88.2%,93.8%,100%and 66.7%,respectively.However,the growth and development of the X.italicum in the mixed treatment is obviously superior to that of the native G.uralensis.under the conditions of four water and fertilizer supply conditions（High water and high fertilizer,high water and low fertilizer,low water and high fertilizer,low water and low fertilizer treatments）,the plant heights of the mixture treatment of X.italicum are 1.15,1.20,1.25 and 1.18 times that of the monoculture treatment groups,respectively;Its crown width was 1.90,1.56,1.13 and 1.82 times that of its monoculture treatment,respectively;its total biomass was 2.15,1.34,1.36 and 2.24 times that of its monoculture treatment;The number of seeds was 1.29,2.16,1.33 and 1.32 times that of the monoculture treatment,respectively.3.Effects of mixture between X.italicum and G.uralensis on the yield and quality of economic organs of G.uralensisUnder the conditions of high water and high fertilizer,high water and low fertilizer,low water and high fertilizer,low water and low fertilizer,the yield of mixed treatment G.uralensis as forage and medicinal material decreased significantly.Compared with monoculture treatment,under the four water and fertilizer supply conditions,the forage yield of mixture G.uralensis decreased by 87.7%,85.7%,88.1%,and 86.6%;the yield of medicinal materials decreased by 87.4%,88.5%,87.4%,91.1%.The competition between X.italicum and G.uralensis severely inhibits the quality of G.uralensis.Compared with the monoculture treatment,under the condition of high water and high fertilizer,the contents of total flavonoids,glycyrrhizic acid,glycyrrhetinic acid,liquiritin,liquiritigenin,isoliquiritigenin and glabridin in the mixture treatment of G.uralensis were decreased 39.3%,54.7%,80%,51.2%,43.3%,81.5%and35.3%,respectively;Under the condition of high water and low fertilizer,the contents of this seven medicinal components decreased by 24.4%,46%,29.4%,35.2%,36.4%,54.6%and 22.6%,respectively;Under the condition of low water and high fertilizer,The contents of this seven medicinal ingredients decreased by 14.7%,29.4%,66.7%,56%,37.2%,87%and 44.4%respectively;Under the low water and low fertilizer condition,the contents of this seven medicinal components decreased by 25.4%,46.1%,69.2%,52.1%,15.9%,86.5%and 44%,respectively.4.Study on the competition relationship between X.italicum and G.uralensisIn the monoculture treatment group,under the condition of high water and high fertilizer,high water and low fertilizer,low water and high fertilizer,and low water and low fertilizer,the plant height of X.italicum was 3.38,3.33,3.65 and 3.24 times that of G.uralensis,respectively.But when the two plants were mixed cultivation,the differences were increased by 5.96,6.45,7.53 and 7.21 times,respectively.Under the four water and fertilizer supply conditions,the differences in the total biomass of the two species were 3.66,3.10,3.96 and 4.06 times respectively when planted alone.The expansion was 64.72,50.46,72.16 and 63.91 times in mixed cultivation.This means that from the perspective of the competition results,the X.italicum has a more competitive advantage in the competition between the two plants.The relative yield（RY）values of G.uralensis under the condition of high water and high fertilizer,high water and low fertilizer,low water and high fertilizer,low water and low fertilizer were 0.25,0.31,0.26 and 0.31,all less than 1.The RY values of X.italicum were 4.36,4.61,4.98 and 4.2 respectively,which were all significantly greater than 1.This means that G.uralensis is mainly affected by interspecific competition from X.italicum,while X.italiana is mainly affected by competition from the same plant from neighboring.The relative competition intensities（RCI）of G.uralensis were 0.88,0.85,0.87 and 0.85,respectively,and the Aggressivity（A）values of G.uralensis were all less than 0,which were-4.11,-4.3,-4.72 and-3.89,respectively.While the RCI of X.italiana were-1.18,-1.31,-1.49 and-1.1 respectively,and their A values were all greater than 0,which were 4.11,4.3,4.72 and 3.89,respectively.This shows that the competitiveness of the X.italicum is stronger than the G.uralensis,and the X.italicum has an advantage in the competition.