炼山造林后不同年龄杉木人工林林下植物多样性动态

Understory plant diversity dynamic of Chinese fir plantation with different forest ages after prescribed burning afforestation

以湖南省会同县炼山造林后4个不同年龄杉木人工林为对象,采用空间代替时间的方法,研究了炼山造林后杉木人工林林下植被多样性变化规律。结果表明:4个不同年龄杉木人工林林下植被多样性丰富,总物种数达到167种,分属于65科,127属;4个年龄阶段林下植被物种总数分别为74、85、76、68,草本的总数量在3 a时就达到最大值,平均高到7 a时,达到最大值;灌木的株数密度在7 a达到最大,随后开始降低,平均高则随林分年龄的增加而增大;林分中藤本的数量基本不变。随着林分年龄的增加,林下植被的物种相似性指数相对降低;菝葜Smilax china、狗脊蕨Woodwardia japonica、广东蛇葡萄Ampelopsis cantoniensis的重要值在所有样地中均大于5,是会同县杉木人工林的常见植物种;3 a时,五节芒Miscanthus floridulus的重要值最大,17a以后,杜茎山Maesa japonica和五叶地锦Parthenocissus quinquefolia的重要值最大。不同年龄阶段林下植被群落的Simpson指数在不同生活型中存在一定差异,灌木呈下降趋势,草本则表现出先升高后降低的特点,藤本波动较为明显,先降低后升高最后又降低。Pielou均匀度指数在藤本中变化较大;灌木Pielou均匀度指数在恢复初期增加,7 a时达到最高,随着林木分化和物种竞争,灌木均匀度下降;草本Pielou均匀度指数在炼山造林后17 a时达到最高,随后开始降低;表明炼山造林后杉木人工林群落的物种演替是一个漫长的过程,因此,炼山造林和幼林抚育时,建议多采用穴状整地和除草,以保持杉木人工林林内物种多样性。

By taking four different forest-ages Chinese fir plantations（three-year-old, seven-year-old, seventeen-year-old, twenty five- year-old） after controlled burning afforestation in Huitong county, Hunan province, as the studied objects, and by replacing time with space, the changing laws of understory plant diversity of Chinese fir plantations with different ages under controlled burning were investigated. The results show as follows. （1） Four different aged Chinese fir plantations all had rich plant diversity, the total species number of the four plantations was 167, and they belonged to 65 families, and 127 genera; The total numbers of under story plant species of four forest-aged were 74, 85, 76 and 68 respectively, the total number of herb layer species reached a maximum at 3-year-old, but the average height reached their maximum at 7-year-old; The density of tree numbers of bush layer reached a maximum at 7-yearold, and then began to reduce, but the average height of bush layer increased with the increase of stand age; The number of liana in the forest stand seldom changed; The similarity index of the undergrowth species relatively decreased with the increase of stand age. The indigenous species of the understory plants in Chinese fir plantations of Huitong county were Ampelopsis cantoniensis, Woodwardia japonica and Smilax china, whose important value （IV） were upon to 5 in each stand age. When the stand age was 3-year-old, the IV of Miscanthusfloridulus was the highest. The Maesajaponica and Parthenocissus quinquefolia had the highest IV, during 17-year- old and 25-year-old. The differences of the Simpson index among the 4 stand ages of understory plant community with different life forms were striking. With the stand age increasing, the Simpson index under bush layer was in a downtrend, and the index under herb layer increased at first, then declined, the index under Liana layer showed an obvious fluctuation （first declined, then rose and again declined）. The Pielou evenness index changed bigger on the Liana layer. Pielou evenness index in the shrub layer increased at the initial stage after afforestation, and reached their highest level at 7-year-old. But along with the tree differentiation and species competition, the Pielou evenness index of shrub layer decreased. Pielou evenness index of herb layer reached the highest value at 17-year-old, and then decreased. It was found that species succession and recovery of plantation community was a long process after controlled burning and afforestation. As a result, the suggestions were presented that cavernous ploughing and weeding should be used during the afforestation and young growth tending after controlled burning.