| Road-region ecosystem has become an important channel which as a kind of special habitat and a landscape corridor of some invasion species, so roads are considered to be one of the main methods for the spread of invasion plants. In order to reveal the relationship between the road and the invasion plant, based on the main highway in Yunnan Province, Kunming-Mohan Expressway was selected as a study area in this paper, and we have researched the spatial distribution and the influence factors of Tithonia diversifolia which is an invasion plant spreads along this road through the field investigation and statistical analysis. The main results are obtained as following:(1) The distribution pattern of Tithonia diversifolia presents a heterogeneous distribution on Kunming-Mohan Expressway. There are3high concentration distribution areas (Yu-Yuan Road K142-165km Huanian-Yangwu; Si-Xiao Road K420-460km Manxieba-Puwen and Xiao-Mo Road K103-114km), and3gathering areas (Yu-Yuan Road K180-200km Honglongchang-Ganzhuang; Yuan-Mo Road K332to Mo-Si Road K385km Babian-Tongxin and Xiao-Mo Road K1-20km) with the main distribution form of largely dispersed in horizontal distribution and linear continuous spread in longitudinal distribution, in addition, the number of rare distribition area is4(Yu-Yuan Road K165-180km Yangwu Tunnel-Honglongchang; Yuan-Mo Road K264-306km Mojiang-Tongguan; Xiao-Mo Road K20-103km; Xiao-Mo Road K114-171km), the distribution pattern of the rest regions of this road shows single cluster or clusters.(2) The continuity and discontinuity of the distribution of Tithonia diversifolia has a certain inner link to the engineering structure of Kunming-Mohan Expressway, showing the discrete intervals of Tithonia diversifolia have high consistency with the structure of highways, especially with high proportion of the tunnels, bridges and ecological-curing slopes, maybe the rapid spread and diffusion of Tithonia diversifolia were obstructed by these project forms. According to the analysis, the more intensive of the tunnels, bridges and ecological-curing slopes’cohesion and coherence on the road, the less abundant of Tithonia diversifolia is.(3) There is no significant relationship between the abundance of Tithonia diversifolia and the composite index of soil fertility level or the elevation. The lowest and the highest altitude of Tithonia diversifolia’s distribution areas on Kunming-Mohan Expressway is540m and2010m, respectively. Moreover, the lowest and the highest of the soil integrated fertility index is0.498and0.001, respectively. The biggest base diameter (d=20.85cm) of Tithonia diversifolia’s soil integrated fertility index is0.161, which can explain that the habitat condition of the whole road is suitable for Tithonia diversifolia’s growth, also the soil fertility and the elevation gradient are not the key factors for its growth and proliferation.(4) The land use types and the mode of production on Kunming-Mohan Expressway have important effects on the spatial distribution of Tithonia diversifolia, large area of agriculture and forestry has greatly limited its habitat space and diffusion range on this road, and the dynamic diffusion process of Tithonia diversifolia largely depends on human disturbance which would compress or release the suitable space of Tithonia diversifolia.This study identifies the relevance level between the spatial distribution characteristics of Tithonia diversifolia and the factors included of elevation and soil fertility on the Kunming-Mohan Expressway system, which shows that the invasive plant Tithonia diversifolia has a wide adaptability, moreover, it also can say that the whole Kunming-Mohan Expressway system is the suitable establishment area, elevation and soil are not the main factors to limit its distribution. In some local scope, the more dominant factors on its diffusion are human disturbance and the way of land use. |
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