中文摘要：

为探究秦岭林区松栎混交林群落乔木优势种的更新规律,通过典型样地调查,对油松（Pinus tabulifor-mis）、锐齿槲栎（Quercus aliena var.acuteserrata）和华山松（Pinus armandii）等3种优势乔木种群更新随林分密度、海拔、坡向、坡位等生态因子的变化规律进行了分析。结果表明：（1）林分密度、海拔、坡向、坡位等生态因子对3种乔木的天然更新均具显著影响;3种优势乔木树种幼苗密度均随林分密度增加而显著增加,林分密度从850株.hm-2增加到1 525株.hm-2时,3种幼树密度也逐渐增加,但林分密度为1 900株.hm-2时,3种幼树密度均显著降低;从海拔1 283m增至1 665m,锐齿槲栎和油松幼苗幼树密度均随海拔增加而显著增加,但海拔增至1 835m时,这两种幼苗幼树密度均显著降低。（2）华山松幼苗幼树密度一直随海拔升高而增加;从南偏西20°到75°,锐齿槲栎和华山松幼树密度逐渐降低,至北偏东40°（阴坡）时又显著增加,但3种乔木幼苗及油松幼树密度一直随坡向变化而增加;锐齿槲栎幼苗密度在下坡位显著高于中坡位和上坡位,但油松和华山松幼苗幼树随坡位由下到上逐渐增加。结果提示,处于中海拔、阴坡且密度适中的林分3种优势乔木更新最佳,对这类林分实施封禁将有助于松栎混交林优势乔木的天然更新。

英文摘要：

Regeneration characteristics of three dominant species in a pine-oak mixed forest were conducted in the Qinling Mountains. We analyzed the importance values for seedling and sapling,regeneration dynamics of dominant tree species under different site conditions,including stand density,slope aspect,slope posi tion,and altitude. Our results showed that the stand density, slope aspect, slope position,and altitude had significant effects on the seedling and sapling densities in pine-oak mixed forest. （1）The seedling and sap- ling densities of Quercus aliena var. acuteserrata and Pinus tabuliformis, respectively, were significantly increased at altitudes of 1 283 m to 1 665 m,whereas the seedling and sapling density decreased significant- ly at 1 835 m. The seedling and sapling density of P. arrnandii were significantly higher at altitudes of 1 283 m to 1 835 rn. （2）The sapling density of P. armandii and Q. aliena var. acuteserrata decreased gradu-ally from the southwest （20°-75°） in sunny conditions whereas it mcreasea onne smmy northeast （40°）. The seedling densities of three tree species and sapling density of P, tabuli,formi, in- creased gradually from the southwest （20°-75°） in sunny conditions and on the shady slopes to the north- east （40°）. The seedling densities of Q. aliena vat. acuteserrata on the lower slopes were much higher than the middle and upper slopes,whereas the sapling density did not differ. The seedling and sapling density of P. armandii and P. tabuliformis were significantly higher at slopes of lower to upper. The seedling and sapling densities of three tree species increased with the stand density （850 plant- hm to 1 525 plant hm 2） whereas the sapling density was significantly lower in stands （1 900 plant hm 2 ）. Thus, enclosing stands on middle altitudes,shady slopes at a moderate density are expected to promote the natural regeneration of pine oak mixed forest.