六盘山白桦群落乔木层主要物种生态位与种间联结

Niche and interspecific association of main species in arbor layer of Betula platyphylla community in Liupan Mountain,Ningxia

对六盘山自然保护区27个白桦(Betula platyphylla)群落乔木层、灌木层和草本层进行野外调查,采用生态位宽度、生态位重叠、方差比率(VR)、χ^(2)检验、Pearson相关系数、Spearman秩相关系数和点相关系数(PCC)等方法,对白桦群落乔木层进行生态位与种间联结性分析,结果显示:乔木层有植物17科28属47种;重要值与生态位宽度、生态位重叠指数存在差异。其中,白桦的重要值最大(22.55%),Levins指数(0.50)小于蒙古栎(0.55)和甘肃山楂(0.67),Shannon⁃Wiener指数(2.79)小于甘肃山楂(3.05)。此外,在乔木层优势种组成的190个种对中,生态位重叠指数大于0.5的仅16对,其中,白桦与山荆子、陕甘花楸的生态位重叠指数均在0.5以上。20个乔木层主要物种间总体联结性呈不显著正联结;χ^(2)检验显示群落中有4个种对间呈极显著联结,5个种对间呈显著联结;Pearson相关系数、Spearman秩相关系数和PCC检验结果均表明:白桦与多数树种的联结性不显著,仅与山荆子呈显著正联结。表明宁夏六盘山白桦群落乔木层的物种较单一,乔木层主要物种的种间联结较弱,各种类间呈独立分布格局。

Based on field investigation of the arbor layer,shrub layer and herbaceous layer of 27 Betula platyphylla communities in Liupan Mountain Nature Reserve,the ecological niche and interspecific association of the arbor layer were analyzed by methods of niche width,niche overlap,variance ratio,χ^(2) test,Pearson correlation coefficient,Spearman rank correlation coefficient and point correlation coefficient.The survey found 47 arbor species which belonged to 17 families and 28 genera with various rankings of im⁃portant value,niche width and niche overlap.Among them,B.platyphylla had the highest important value(22.55%),while its Levins index(0.50)was lower than those of Quercus mongolica(0.55)and Crataegus kansuensis(0.67)as well as smaller Shan⁃non⁃Wiener index(2.79)comparing to that of C.kansuensis(3.05).Among the 190 species pairs made up of the dominant arbor species,only 16 pairs had Pianka niche overlap indexes greater than 0.5,including the pairs of B.platyphylla with only 2 species(Malus baccata and Sorbus koehneana).Overall linkage analysis further showed insignificant linkage between 20 dominant arbor spe⁃cies,with only 4 greatly significantly related species pairs and 5 significantly related species pairs byχ^(2) test.Pearson correlation co⁃efficient,Spearman rank correlation coefficient and point correlation coefficient analysis confirmed insignificant association between most species pairs,and was the same to the pairs of B.platyphylla with dominant arbor species except for significant positive associ⁃ation with M.baccata.To summarize,the species in the arbor layer of B.platyphylla communities in Liupan Mountain in Ningxia were relatively single,with weak interspecific association and independent distribution pattern among various species.