Eupatorium adenophorum is the most damaging invasive alien species in China and unbalances local ecosystems and threatens the survival of native species,thus,attracting increasing attention from all sectors of society.Exploring interspecific associations of E.adenophorum and the stability of companion species after invasion is an important starting point for studying the interaction of invasive and native species.To effectively predict and evaluate the level of E.adenophorum invasion,we investigated invaded areas in Liangshan Prefecture of Sichuan,using 2 × 2 contingency table analysis and x2and W tests to analyze interspecific associations,using the association coefficient (AC),percentage of cooccurrence (PC),Ochiai index (OI),Dice index (D I),Godron M method,of Xichang City and Huili,Huidong,Dechang,and Puge counties.There were 155 companion plant species in the E.adenophorum community in Liangshan Prefecture,including 86 herbaceous plants,34 shrubs,22 trees,10 vines,2 ferns,and 1 bryophyte.The x2and W tests results indicated that the variance ratio of overall association of major plants in the E.adenophorum community was 0.9677 ＜ 1,x20.95(50) ＜ W ＜x20.05(50),which indicates a non-significant negative correlation among the main species.Thex2 values among the various species were all lower than 3.841,indicating that the two main species were only slightly associated or even independent.Dominant species in the E.adenophorum community were similarly or equally adapted to the environment,and competition existed in the utilization of natural resources.Interspecific association analysis indicated that 20 pairs of species were positively correlated and that 22 pairs exhibited negative correlations or were completely independent.The percentages of co-occurrence of E.adenophorum with Bidens pilosa,Artemisia lavandulaefolia,Digitaria sanguinalis,and Physalis peruvianal ranged from 0.4 to 0.6,and the OI and DI indices were all over 0.6,which indicated that E.adenophorum had similar or identical ecological needs and adaptability to the environment,but also that B.pilosa,A.lavandulaefolia,D.sanguinalis,and P.peruvianal had strong resistance to the inhibitory properties of E.adenophorum.Community stability analysis indicated that the intersection point of the model equation and linear equation was 51/49,which was far from the stable intersection point 20/80,thus indicating that the E.adenophorum community was unstable.Therefore,we concluded that local plant communities in southwest China become relatively unstable after being invaded by E.adenophorum,interspecific segregation will occur to lower the competition intensity among the various species,thus the plant communities tends to be stable gradually.This conclusion could be referenced for predicting and evaluating the degree of invasion by E.adenophorum as soon as possible.%紫茎泽兰是中国危害最严重的入侵植物之一.为有效预测和评估紫茎泽兰入侵程度,基于2×2联列表,采用x2和W检验,联结系数(AC)、共同出现百分率(PC)、Ochiai指数(OI)、Dice指数(DI)的种间联结性分析和Godron M群落稳定性测定方法,以四川省凉山州危害最严重的入侵植物紫茎泽兰群落为研究对象,分析了西昌市、会理县、会东县、德昌县和普格县紫茎泽兰与其共生植物间的联结性及群落稳定性.结果表明:四川省凉山州与紫茎泽兰共生的植物共有155种,其中草本植物86种,灌木34种,乔木22种,藤本植物10种,蕨类植物2种,苔藓植物1种.x2和W检验发现,紫茎泽兰群落主要植物间的总体关联性VR(方差比率)为0.9677,小于1,检验统计量x20.95(50)＜x20.05(50),表明紫茎泽兰群落主要物种间总体表现为不显著负相关.种群间X2统计量均小于3.841,说明主要种对间联结性较低,甚至趋于独立,紫茎泽兰群落优势种群对环境的适应性相似甚至相同,但对资源利用存在竞争.种间联结性分析表明,紫茎泽兰群落中20个种对间表现出正相关性,22个种对间则表现出负相关性,或处于完全独立的状态.紫茎泽兰-鬼针草、紫茎泽兰-野艾蒿、紫茎泽兰-马唐和紫茎泽兰-灯笼草种对的共同出现百分率PC值均处于[0.4,0.6)区间内,OI指数和DI指数均大于0.6,一方面说明紫茎泽兰在一定时期内,与鬼针草、野艾蒿、马唐和灯笼草具有相同或相似的生态位需求和对环境的适应性,另一方面说明鬼针草、野艾蒿、马唐和灯笼草等物种对紫茎泽兰抑制其他物种生长特性的抵抗能力较强;群落稳定性分析可知,模型方程与直线方程的交点为51/49,距离稳定交点坐标20/80较远,说明紫茎泽兰群落处于不稳定状态.结论:紫茎泽兰入侵使四川省凉山州原有植物群落处于相对不稳定状态,种间会出现一定程度的分离,以降低竞争强度,从而逐步趋于稳定.该结论可为及早预测和评估紫茎泽兰入侵程度提供一定参考.
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