林火对大兴安岭典型林型林下植被与土壤的影响

Impact of forest fire on understory vegetation and soil in typical forest types of Daxing'an Mountains,northeastern China

利用大兴安岭南瓮河保护区典型林型的样方调查资料,并采用灰色关联度分析,对不同强度林火干扰下草类--白桦林和草类--落叶松林林下植被的物种多样性、生物量和土壤因子的关联性进行研究。结果表明:1)所有调查样地林下植被的物种丰富度、Shannon指数和Simpson指数等物种多样性指数随着火烧强度增加而降低,表现出未火烧>中度火烧>重度火烧的趋势,而物种多样性指数年变化量均有明显的增加,其中林火干扰的林下植被物种多样性的增加明显高于未受林火干扰的林下植被物种多样性。2)随着火烧强度的增加,林下植被生物量总量降低;而林下植被生物量总量年增加变化量呈上升趋势,增加的程度随着火烧强度的增强而增大,与火烧强度成正比(重度火烧>中度火烧>未火烧);而标准木细根生物量在不同火烧强度间无明显变化,而是随着离树干的水平距离的增加而减少(1m>2m>3m)。3)火烧迹地土壤pH值和有机碳含量随火烧强度增加而增加,而土壤全氮和全钾含量则相反;在中度火烧情况下,土壤密度和全磷的含量更高。4)灰色关联度分析结果显示,林火干扰后,土壤密度、有机碳含量和全氮含量与林下植被物种多样性的相关性较高;而土壤密度、有机碳含量和pH值与林下植被生物量相关性较高。由于一定强度的林火干扰并未完全破坏林下植被,而是导致部分林下植被死亡,植被间形成林隙,为林下植被创造了生存空间和发展条件,同时土壤养分含量受林火干扰发生变化,为林下植被生长提供养分,一定程度上促进了林下植被的恢复。

The effects of forest fire on biomass and species diversity and soil physical and chemical properties in Betula platyphylla and Larix gmelinii forests were studied to analyze the correlation among them according to the sample survey and using grey sequence analysis. The results showed that the understory vegetation diversity index was descending with the increase of fire intensity ： unburned 〉 moderate fire 〉 serious fire, although the annual variation obviously increased. And the increasing amount in burned area was more than that in unburned area. The total biomass of understory vegetation was descending with fire intensity increasing, but the annual variation increased, and the increasing amount was increased with the increase of fire intensity： serious fire 〉 moderate fire 〉 unburned. The root biomass was irregular in different fire intensities, but it was descending with distance increasing from the trunk： 1 m 〉 2 m 〉 3 m. The pH value and organic matter content of soil increased with fire intensity increasing, but nitrogen and potassium content was opposite. The unit weight and phosphorus of soil reached the maximum in moderately burned area. In the grey sequence analysis, the unit weight of soil, organic matter content and pH value played leading roles on biomass, and the unit weight of soil, organic matter, and nitrogen content played leading roles in diversity index. The fire did not destroy all the understory vegetation so that some vegetation died, and some forest gap formed, which creates living space and development conditions for understory vegetation. Some soil nutrient content had changed to provide beneficialnutrients for understory vegetation, so to some extent, the forest fire promots the recovery of understory vegetation.