秦岭山地锐齿栎次生林幼苗更新特征

分析了秦岭山地锐齿栎次生林群落乔木及木本幼苗物种特征值、更新生态位宽度及不同影响因子下（包括林分密度、坡向、海拔等）乔木更新动态。结果表明，乔木层物种有25种，锐齿栎占有明显地优势，重要值为149.18%。其次为华山松(Pinus armandii)和千斤榆(Carpinus cordata)等；更新层共有木本植物41种，其中乔木种有28种，占所有木本植物总数量的68%，优势种有青蛙皮槭(Acer grosseri)、木姜子(Litsea pungens)等。林下有丰富的幼苗库，径级及龄级比较小。更新方式以实生为主；分析了10种更新优势乔木种群的生态位宽度，同种幼树种群生态位宽度均大于幼苗种群生态位宽度。幼苗种群生态位宽度从大到小依次为榛子(Corylus heterophylla)、锐齿栎、青蛙皮槭等。幼树种群生态位宽度从大到小依次为榛子、青蛙皮槭、锐齿栎等；林分密度对林下乔木幼苗和幼树数量影响不同。当林分密度（株?hm-2）从720增加到1460时，幼苗密度逐渐增大。随后随着林分密度的增加，又呈现出减少的趋势。而幼树密度随着林分密度增加一直呈现出减少的趋势。坡向对锐齿栎次生林林下乔木幼苗和幼树的影响各异，阳坡（南偏西3）均利于幼苗和幼树的更新。南偏西45林分内，幼苗密度急剧减少。随着坡向转为阴坡，幼苗密度又逐渐增加。而幼树密度逐渐减少。当海拔从1083 m增加到1547 m时，幼树密度逐渐增加。随后，随着海拔增加到1882 m，幼树密度则逐渐减小。而幼苗密度随着海拔的增高一直呈现减小的趋势。

Characteristics of seedlings regeneration in Quercus aliena var. acuteserrata secondary forests in Qinling Mountains

We analyzed important value of tree and woody seedlings species, regeneration niche breath, tree regeneration dynamics under different factors, including stand densities, slop direction, altitude in Quercus valiena var. acuteserrata secondary forests in Qinling Mountains. The results showed there were 25 species in tree layer. Quercus valiena var. acuteserrata occupied dominant status in community,its important value was 149.18%. The subdominant species was Pinus armandii, Carpinus cordata,ect. There were 25 tree species among 41 woody species in regenerational layer, occupying 68% of total amount. The dominant species was Acer grosseri , Litsea pungens,ect.The seedlings bank was abundent ,the height class and age class were lower. The main regeneration type was seedling. We analyzed 10 kinds of dominant regeneration tree population . The regenerational niche breath of saplings population was higher than that of seedlings population for same tree species .The niche breath sequences from high to low of seedlings population was Corylus heterophylla, Quercus valiena var. acuteserrata,Acer grosseri,ect.while that of saplings population being Corylus heterophylla, Acer grosseri , Quercus valiena var. acuteserrata,ect. The effect of stand density on saplings or seedlings density was different ,the saplings and seedlings density was increased with the stand density from 720 trees?hm-2 up to 1460 trees?hm-2 ,then decreasing with the stand density increasing. The saplings density decreased continuously with the stand density increasing. There were various effects of slop direct on the seedlings or saplings. The sunny slop (SW 3)direct was benificial to saplings or seedlings.The seedlings density decreased sharply. As changing direction to shady slop, the seedlings density increased. The saplings density decreased nevertheless. The saplings density increased as altitude from 1083 m up to 1547 m, then decreasing with altitude up to 1882 m. The seedlings density increased from lower altitude to higher altitude.