Comparative Study On Competitive Ability Of Invasive Plant Xanthium Italicum Moretti And Two Economic Crops

Xanthium italicum Moretti is a global invasive weed of Compositae,which has caused serious ecological invasion and economic losses in many countries in Europe,Asia,Oceania and South America.The alien weed has strong adaptability,high interspecific competition,fast growth rate,and large body size.In farmland,its height reaches more than 2.5m usually,and the individual crown width of a single plant can reach 1.8m,so that the lower crops are not illuminated enough,which has seriously affected the development of global agriculture.Farmland of safflower and oil sunflower is one of the most common habitats invasive by the Italian cocklebur.Although the two economic crops and Italian cocklebur often present a mixed pattern in the farmland,the growth of the sunflower seems to be inhibited with thinner and dwarfer stems,smaller capitals.However,whether this result is caused by interspecific competition from the exotic Italian cocklebur is still unclear.In this study,the replacement experiments were adopted in this study to compare the interspecific competition intensity between Italian cocklebur and safflower or oil sunflower,to explore whether Italian cocklebur could inhibit the growth indexes,yield and quality of the two economic crops between single and mixed cropping patterns.This study compared the intraspecific competition in safflower and oil sunflower,and interspecific competition intensity between Italian cocklebur and two economic crops to explore whether Italian cocklebur could inhibit the yield and quality of the economic organs.Those will provide experimental evidence for the evaluation of invasion risk and invasion consequence of Italian cocklebur.Results are as follows:When Italian cocklebur coexisted with safflower and oil sunflower,the vegetative growth of safflower and oil sunflower were significantly inhibited.The main features are as follows: the plant height,crown width,underground biomass,aboveground biomass and total biomass of Italian cocklebur were significantly higher than safflower and oil sunflower.The Italian cocklebur individual growth indexes under single planting were significantly lower than mixed planting,while the individual growth indexes of safflower and oil sunflower under single planting were significantly higher mixed planting.Under the same planting pattern,with the increase of water and fertilizer supply level,the individual growth indexes of three plants increased significantly.When Italian cocklebur invaded safflower and oil sunflower fields,the reproductive growth of the two economic crops were significantly inhibited,and the yield and quality of their economic organs were significantly reduced.The main performances were that the average yield per plant,seed oil content,corolla yield(safflower),hydroxysafflor yellow A(safflower),seed length,seed width and 100 seed weight of safflower and oil sunflower under single planting mode were significantly higher than those under mixed planting mode.Under the same planting pattern,as water and fertilizer supply increased,the yield and quality of economic organs of safflower and sunflower increased significantly.When Italian cocklebur coexisted with safflower and oil sunflower,the intraspecific competition of Italian cocklebur was significantly greater than the intraspecific competition from the safflower and oil sunflower,while the intraspecific competition intensity of safflower and oil sunflower were significantly smaller than the intraspecific competition from Italian cocklebur.The interspecific competitiveness of Italian cocklebur was significantly greater than that of safflower and sunflower.With the increase of soil water and fertilizer supply,the competitive ability of Italian cocklebur to the adjacent plants of safflower oil sunflower became more intense.In summary,no matter in low water and low fertilizer environments or in high water and high fertilizer environments,the interspecific competition ability of Italian cocklebur was significantly higher than safflower and oil sunflower.Italian cocklebur not only had a significant inhibitory effect on the growth of the two crops which hindered their biomass accumulation,but also inhibited the e two crops reproductive growth.Under low water and low fertilizer supply condition,seed yield,oil content,corolla quality and hydroxysafflor yellow A(Chinese medicinal materials)reduced by 70%,30%,80% and 20%,respectively as it existed with Italian cocklebur.Oil sunflower seed yield and oil content decreased by 57.56% and20.00%.Therefore,Italian cocklebur dose have negative effects on the yield and quality of the two economic crops.