修枝对杉木幼林生长和林下植物多样性的影响

在福建洋口林场4年生的杉木人工林建立固定试验标准地．选择修枝木，每年对其进行1次修枝，修枝强度为修去4种规定树干直径（6cm、8cm、10cm和12cm）以下的所有枝条．修枝试验后2年，随着修枝强度的增加，杉木的生长量明显降低．修枝强度为6cm（密度1200株·hm^-2）的修枝木的平均树高、平均胸径和平均单株材积增长量均显著低于不修枝木．修枝后2年，各修枝处理杉木林林下植物的覆盖度、生物量、总的物种数，灌木层、草本层和总体Shannon-Wiener指数均高于未修枝的对照，但藤本层植物在修枝时被大量劈除，其种类数量、多样性指数却低于对照．闽北生产力较高的4年生、密度1200株·hm^-2的杉木幼林进行修枝，推荐的修枝强度为10cm或12cm．

Effects of Pruning on the Growth and Species Diversity of Understory Plants in A Young Chinese Fir Plantation

An experiment was established in a 4-year-old Chinese fir plantation in Yangkou State Forest Farm, Fujian, China. Selected trees were pruned once a year to remove all branches to 4 predetermined stem diameters （6, 8, 10 and 12 cm）. Two years after the experiment was conducted, tree growth decreased apparently with the increase of pruning intensity. And the increments of mean tree height, diameter at breast height （DBH） and single tree stern volume of the pruned trees in the 6 cm pruning intensity treatment （stem density 1 200 trees·hm^-2） were all significantly lower than those of unpruned trees. Understory coverage, biomass, total species number, Shannon-Wiener index of shrub, herb layer and the total in the pruned sites of the Chinese fir plantation were higher than the unpruned control. Because quite a number of vine species were removed by pruning, plant species number and diversity of vine layer were lower than those of the control. For similar 4-year-old Chinese fir plantations with stem density 1200 trees·hm^-2 in northern Fujian, where the productivity of forests are relatively high, we recommend that the pruning intensity should be controlled at 10 or 12 cm.