黄土高原子午岭辽东栎更新层与灌木层物种种间联结分析

Analysis on Interspecific Association of Quercus liaotungensis in Regenerated Layer with Shrub Species in the Ziwuling region of the Loess Plateau

辽东栎（Quercus liaotungensis）是黄土高原子午岭地区的主要优势树种之一，研究辽东栎幼苗及幼树与灌木层物种的种间关系，有助于揭示其自然更新的规律。利用联结系数（AC）和χ^2检验研究辽东栎幼苗及幼树与林下灌木层35个主要物种的联结；用典范对应分析法（CCA）分析灌木层主要物种分布和环境的关系。结果表明：①幼苗与灌木层物种种间联结不显著（χ^2〈3．841），联结系数均在-0．250～0．370之间，说明幼苗在群落中的存在是相对独立的；而幼树与灌木层物种存在显著（3．841≤χ^2〈6．635）或极显著（χ^2〉6．635）联结现象，这些物种对幼树生长发育有一定的影响。②土庄绣线菊（Spiraea pubescens）与辽东栎幼树为极显著正联结物种对，它们的分布反映出对环境要求相似；毛药忍冬（Lonicera serreana）、山楂（Crataegus pinnatifida）、湖北荚蒾（Viburnum hupehense）、木姜子（Litsea pungens）、樱桃忍冬（Lonicera fragrantissima）、漆（Toxicodendron vernicifllzltm）、沙株（Swida bretchneideri）、水枸子（Cotoneaster multiflorus）、短柄五加（Acanthopanax brachypus）、胡枝子（Lespedeza bicolor）、毛樱桃（Cerasus tomentosa）、鞘柄菝葜（Smilax starts）与辽东栎幼树为显著或极显著负联结物种对，它们的分布反映出对环境的要求不同。

Quercus liaotungensis is one of the dominant species in the Ziwuling region of the Loess Plateau, and it might be helpful for revealing the laws of natural regeneration of Q. liaotungensis to study the interspecific association of its seedlings and saplings with the shrub species. In this paper, χ^2 test and association coefficients （AC） are employed in testing the interspecific association of the seedlings and saplings of Q. liaotungensis with 35 main shrub species ; the relationship between the distribution of main shrub species and the environmental factors is analyzed by CCA. The results are as follows： ① The χ^2 values indicate that there is no significant association between the seedlings and the shrub species （χ^2 〈3. 841 ）, the association coefficient （AC） ranges from -0. 210 to 0. 370, the association degree is relatively low, and the seedlings are inclined to an independent survival in the community; however, the χ^2 values indicate that there is a significant（3. 841 ≤ χ^2 〈 6. 635 ） or highly significant （ χ^2 ≥6. 635 ） association between the saplings and some shrub species, the sapling growth is strongly affected by the shrub species; ② There is a significant positive association between the saplings and Spiraea pubescens, and thespecies pairs with significant positive association reveal that their adaptability to habitats is similar; there are significant negative associations between the saplings and Lonicera serreana, Crataegus pinnatifida, Viburnum hupehense, Litsea pungens, Lonicera fragrantissima , Toxicodendron vernicifluum , Swida bretschneideri , Cotoneaster multiflorus , Acanthopanax brachypus, Lespedeza bicolor, Cerasus tomentosa and Smilax starts, and the species pairs with the significant negative association reveal that their adaptability to habitats is different.