林火干扰对兴安落叶松林下植被多样性和生物量的影响

Effects of Forest Fire on Understory Vegetation Diversity and Biomass of Larix gmelini Forest

以寒温带大兴安岭受林火干扰的兴安落叶松林下植被为研究对象,采用植物多样性测度方法和收获法,分析火烧强度和自然恢复年限对林下植被物种多样性和生物量的影响。结果表明：在不同火烧强度的影响下,林下植被物种多样性有所降低,Shannon-Wiener指数表现为随林火强度呈递减趋势,Margalef指数表现出未过火区〉中度火烧迹地〉轻度火烧迹地〉重度火烧迹地的规律;火烧降低了林下植被的总生物量,主要降低的是灌木生物量;重度火烧和轻度火烧后草本生物量有所提升,但提升量不足以改变总生物量降低的趋势。在自然恢复过程中,Margalef指数表现为先升高后降低的单峰变化趋势,而Pielou指数的变化趋势与之相反;恢复年限与植被生物量呈正相关关系,草本生物量在经过5 a恢复后逐渐达到一个稳定期,灌木生物量在1～10 a的自然恢复期内持续增长。

With larch boreal forest vegetation under interference of forest fire in Daxing＇ an Mountain, we used the plant diversity and harvesting methods to analyze the impacts of fire severity and age of spontaneous recovery on plant diversity and bio- mass. Understory plant diversity was reduced under different degrees of fire. However, from Shannon-Wiener index, the plant diversity had a decreasing trend with the intensity of fire. From Margalef index, the order of plant diversity from high to low was not burned area, moderate burned area, lightly burned area, and severe burned area. But Pielou index had not significant difference （P〉0.05）. As for biomass, fire reduced the total biomass of understory vegetation, especially shrub biomass. Although the herbaceous biomass was improved under severe burning and light burning, it was not enough to off- set the decreased total biomass. During the recovery, Margalef index （ 1-5 a） of understory vegetation had a growth trend with the longer recovery period, while a decreased tendency in 5-10 a. However, Pielou index had a contrary trend. The vegetation biomass was positively correlated with the recovery period. There is a stable period to herbaceous biomass after 5-a gradual recovery, and shrub biomass continues to grow in l-10-a recovery period.