| Solanum rostratum Dunal.and Xanthium spinosum L. are annual weeds. The former is belongs to the Solanaceae and is native to the southwestern United States. The later is belongs to the Asteraceae and is native to South America. Both have a strong ability for invasion, growing and reproducing quickly, and they are now widely distributed throughout much of the world. This paper was investigated about40(Cities) Counties ranging from the North to the South of Xinjiang where S. rostratum and X. spinosum probably occurred, and the distribution of S. rostratum and X. spinosum was recorded. We were also used the quadrates method to analyze the distribution range, community characteristic and effect on the local plants in communities that had been invaded. Our purpose is to provide basic data to control the expansion within the arid region. The main results were as follows:1. The distribution and community characteristics of two invasive plants in Xinjiang:(1) S. rostratum distributes in Uriimqi City (County), Changji City, Shihezi City, Turpan City and Toksun County of Xinjiang at present. The altitude of its distribution areas ranged from-12m～1325m. The types of its habitats include desert grassland, desert and oasis. X. spinosum distributes in Changji City, Yining City(County), Gongliu County, Tekes County, Xinyuan County, Chabuchar County, Huocheng County and Nileke County of Xinjiang at present. The altitude of its distribution areas ranged from597m～1834m. The types of its habitats include desert grassland and oasis.(2) We also observed and analyzed the abundance, frequentcy and importance value of these two species in the well-concentrated and select plots of different habitats. Our results indicated that, S. rostratum was the most abundant plant in the desert grassland, desert and oasis habitats, and X. spinosum was abundant in the desert grassland and oasis, and was at its highest abundance in the oasis. Thus, these two species considered as the most important plant in the invaded areas. Moreover, relative coverage of S. rostratum was the greatest of all the plants in its distribution areas. It had the highest relative coverage of in the oasis (54.27%)>desert grassland (35.07%)>desert (26.40%). Relative coverage of X. spinosum of was highest in the oasis (46.83%)>desert grassland(43.00%). These species had the highest of important value that indicated that the most comprehensive adaptability in different habitats, particularly in the oasis that it was invaded severely.2. Influence on local plant biodiversity of two invasive plants in Xinjiang:A survey was conducted of local plant species biodiversity with the square intercept method, selected S. rostratum in desert grassland and X. spinosum in oasis more areas distributed.20plots which were invaded by these two species, one plot which was none or few two invasive plants individuals selected as control plots with a distance of5m from others. The pattern of local community biodiversity was analyzed by Importance value, Simpson index and Pielou index. Our results indicated that:(1) There were total of6families and14species all plots that contained S. rostratum, but control plots had7families and29species. There were total of11families and31species all plots that contained X. spinosum, thus control plots had9families and23species, so the invasion by these two species is associated with a reduced number of species.(2) Compared with tested plots and controlled plots had the same plants of importance value, Most of native plants of importance value were lower, only Poly’gonum aviculare and Tribulus terrestris had slightly lower importance value invaded by S. rostratum and X. spinosum plots has Setaria vividis. Meantime, two invasive plants of Simpson index and Pielou index were lower than these in the control. This indicated that the invasion of S. rostratum and X. spinosum effect on native plants community structure and composition, and with a reduced species diversity. |
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