Patterns Of Eupatorium Adenophorum Along Roadsides In Lincang Region, Yunnan Province, China

As the pivot of society and economic development, road networks distribute more extensively and develop more quickly than the other mankind constructive project. The road network and all kinds of vehicles bring enormous benefit, while their negative influences on natural and ecosystem increase continually. In the past years, the important effects of roads on exotic plants invasion have been concerned in the worldwide. But the relationship between the corridor effects of roads and the spread of exotic invasive species has been little known in China. Eupatorium adenophorum, one kind of international harmful weed has spreaded extensively. This weed takes serious threat to biodiversity and environment of human living. Currently, the most of researches on E. adenophorum focus mainly on the distribution, threat, biological characteristics, and chemical composition and prevention methods. But the invasive mechanisms have not been well studied, especially in the roads effects of this harmful weed invasive distribution. Therefore, to understand the roads effects of this typical exotic invasive plants is of an actual significance, and the results will provide a foundation for ecological safety and biodiversity conservation.We examined the distribution of E. adenophorum along roadsides and the relationship of its invasion to the distance from roads, road width, landscape, aspect and elevation and soil seeds bank in Lincang, Yunnan, China, where was the earliest and most serious area on this exotic plant invasion. Ten plots were established along 7 roads stratified by grade, surfacing material, road age and human disturbance. In the study of this exotic plant spread from roadsides into adjoining land, the distance of road effect for biomass and plant height was 24m away from road, and the number of individual was 34m. The influence of the 6m-wide road on the biomass and number of individual was most significant. This exotic plant invasion was more serious along roadsides where road age and human disturbance were greater. E. adenophorum most frequently occurred at two landscapes: abandoned land and secondary forest along roadsides. There were no significant differences in the biomass between the two landscapes, and in the plant height between aspects. The biomass and number of individual on south facing slopes was greater than that on west and east facing slopes. And the biomass increased with elevation, reached its greatest at 1700m, and then declined.The sprouting of E. adenophorum seeds in soil of roadsides was not significantly related to time, and the relationship between seed sprouting rates of soil layers and time was same nearly. A great number of E. adenophorum seeds was stored in soil. .Seed density varied from 150 ind.·m^-2 to 13488 ind.·m^-2,with the average of 3111 ind.·m^-2 . Seed density in the 0-2 cm soil layer was the highest,followed by the 2-5 cm layer, and that of 5-10 cm soil layer was the lowest.E. adenophorum seeds accounted for 62.7%, 23.8% and 13.5% of the total seeds in the three soil layers, respectively.The correlation analysis indicated that the density did not show a direct relationship with the maternal plant of E.adenophorum. It showed exogenous seed bank of E. adenophorum account for the larger contributions.Seed density in the 0-2 cm soil layer reached its greatest at 9m from the roadside and reached its another greatest at 100m ,then declined at 200m. Seed density in the 2-5 cm soil layer displayed fluctuation within 50m from roadside and reached its greatest at 100m. Seed density in the 5-10cm soil layer stably varied in different distance from roads. The 6.5m-roads were in Nangunhe nature reserve where there was good standing vegetation. Because it was good for seeds reserve, seed density in 6.5m-road was bigger than the other road. The density did show strong relationships with standing vegetation types.The average seed density in second forest was 4525ind.·m^-2 nearly twice of 1973ind.·m^-2 the seed density in abandoned land. There were no significant differences in seed density between aspects. Eupatorium adenophorum seeds bank density increases with latitude. And the seeds bank increased with elevation, reached its greatest at 1800m.