火烧强度对大兴安岭林下植被的影响效应

Effect of fire severity on understory vegetation in Da Xing’anling Mountains,NE China

火干扰作为森林生态系统的重要干扰因子,对植被更新与演替有重要影响。本文以火后大兴安岭多年冻土区林下植被为研究对象,采用野外调查法,分析兴安落叶松(Larix gmelinii)林下植被群落物种组成、地上生物量、物种多样性和覆盖度在不同火烧强度后的变化特征。结果表明:1)火后14年轻度火烧区林下植被地上生物量最大;灌木地上生物量轻度火烧(235.65 g·m^(−2))>重度火烧(206.32 g·m^(−2))>未火烧(139.33 g·m^(−2));草本地上生物量轻度火烧(42.77 g·m^(−2))>未火烧(23.74 g·m^(−2))>重度火烧(8.07 g·m^(−2))。2)林火改变林下物种多样性指数;灌木层物种多样性指数在轻度火烧区最高,与重度火烧区呈显著差异(P<0.05);草本层物种多样性指数在重度火烧区最低。3)灌木和草本覆盖度变化特征相反;灌木覆盖度重度火烧(84.20%)>轻度火烧(69.20%)>未火烧(67.67%);草本覆盖度未火烧(43.50%)>轻度火烧(38.13%)>重度火烧(5.73%)。总体来看,轻度火烧一定程度上促进植物生长;重度火烧破坏严重,从维护物种多样性角度考虑应避免重度火灾发生。

As an essential disturbance factor in forest ecosystems,fire disturbance significantly impacts vegetation regeneration and succession.In this paper,the changes in species composition,aboveground biomass,species diversity,and coverage of the understory vegetation were analyzed using a field investigation method in the permafrost region of the Da Xing'anling Mountains,focusing on varying fire severities.The results showed that fourteen years after the fire,1)the aboveground biomass(AGB)of understory vegetation was the highest in the lightly burned area;the AGB of shrub was the highest in the lightly burned area at 235.65 g·m^(−2),followed by the severely burned area 206.32 g·m^(−2),and was the least in the unburned area 139.33 g·m^(−2).The herbaceous AGB was the highest in the lightly burned area,42.77 g·m^(−2),followed by the unburned area,23.74 g·m^(−2),and was the least in the severely burned area,8.07 g·m^(−2).2)Forest fire changed the species diversity index of the understory vegetation:the species diversity index of the shrub layer was the highest in the lightly burned area and was significantly different from that of the severely burned area (P < 0.05);the species diversity index of the herb layer was the lowest in the severely burned area. 3) The change characteristics of shrub and herb coverage were opposite: coverage of shrubs was the highest in the severely burned area (84.20%), followed by the lightly burned area (69.20%), and the least was in the unburned area (67.67%);herbaceous coverages was the highest in the unburned area (43.50%), followed by the light burn (38.13%), and was the least in the severely burned area (5.73%). Light burns promoted plant growth somewhat;severe burn damage was serious, and serious fire should be avoided while maintaining species diversity.