对广西木论国家级自然保护区铁榄〔Sinosideroxylon pedunculatum (Hemsl.) H.Chuang〕群落优势种群的重要值进行了测定,并利用Levins和Hurlbert的生态位宽度指标及百分率相似性指数、Pianka和王刚的生态位重叠指数对这些优势种群的生态位进行了研究。结果表明,该铁榄群落中有11个优势种群,其中铁榄的重要值总和最大(319.27%),小栾树〔Boniodendron minus (Hemsl.) T.Chen〕、日本女贞(Ligustrum japonicum Thunb.)和广西密花树(Rapanea kwangsiensis Walker)的重要值总和也均在200%以上,掌叶木〔Handeliodendron bodinieri (Lévl.) Rehd.〕、朴树(Celtis sinensis Pers.)和榔榆(Ulmus parvifolia Jacq.)的重要值总和较小,均在70%以下。生态位宽度值较大的优势种群为铁榄、广西密花树、小栾树、红背山麻杆〔Alchornea trewioides (Benth.) Müll.Arg.〕及九里香(Murraya exotica L.Mant.),生态位宽度值最小的是掌叶木。用3种方法测得的生态位重叠结果基本一致;生态位重叠值较大的种对有铁榄-小栾树、小栾树-日本女贞及小栾树-广西密花树等;生态位重叠值较小的种对有掌叶木-朴树和掌叶木-榔榆等。研究结果显示,重要值大的优势种群生态位宽度通常较大,生态位宽度大的优势种群间通常生态位重叠较大,但喀斯特生境的高异质性也可使生态位宽度较小的种对间产生较大的生态位重叠;该铁榄种群中大部分优势种群的生态位相似值和重叠值较高,说明该铁榄群落优势种群间竞争较强,群落结构可能具有一定的不稳定性。 

The important value of dominant populations of Sinosideroxylon pedunculatum (Hemsl.)H.Chuang community in Mulun Nationa lNature Reserve of Guangxi was determined, and niches of these dominant populations werere searched by using Levins' and Hurlbert's niche breadths, percents imilarity index, Pianka's and Wang-gang's niche over lap indexes. The results show that there are eleven dominant populations in the S. pedunculatum community, among which, the total important value of  S. pedunculatum population is the highest (319.27%), that of Boniodendron minus(Hemsl.)T.Chen, Ligustrum japonicum Thunb. and  Rapanea kwangsiensisWalkeris also over 200%, but that of Handeliodendron bodinieri(Lévl.)Rehd., Celtis sinensis Pers. and Ulmus parvifolia Jacq. is smaller and below 70%. Populations of S. pedunculatum , R. kwangsiensis , B. minus, Alchornea trewioides(Benth.) Mǜll. Arg. and Murraya exotica L.Mant. have larger niche breadths and niche breadth of H. bodinieri opulation is the smallest. Determination results of niche over lap are basically identical by means of three methods. The species-pairs such as S. pedunculatum-B.minus,B.minus-L.japonicum andB.minus-R.kwangsiensis, etc have larger niche over laps,  while those such as H. bodinieri-C. sinensisand H.bodinieri-U.parvifolia, etc have smaller ones. It is suggested that the dominant populations with high important value usually have large niche breadths, and the similar trend exists between niche breadth and niche over lap in dominant populations, but the high environmental heterogeneity of karst habitat leads to the large niche over lap between some species-pairs with narrow niche breadth. The high niches imilarity and niche over lap of most dominant populations in S. pedunculatum  community show that the inter specific competition is intensive and the community structure is probably instable.