选择无地表火发生、当年发生地表火和地表火发生后12 a的天然樟子松林分,利用多尺度、面积1 000 m²改进的Whittaker样方,研究了地表火对呼伦贝尔沙地天然樟子松(Pinus sylvestris L. var. mongolica Litv.)林林下植被多样性的影响。结果表明,各林分所有林木的平均胸径(DBH)差异极显著(P<0.01)。在1 m²样方尺度上,3种林分的林下植被盖度有极显著差异(P<0.000 1),其中地表火发生后12 a的林分林下植被盖度最低(32.0%)。在面积1和10 m²样方尺度上,各林分林下植被的α多样性有显著差异(P<0.05),且以当年发生地表火的林分林下植被丰富度最高;不同功能群植物(包括木本植物、禾本科植物和非禾本科草本植物)的α多样性也仅在小尺度上有一定的差异。林下植被的β多样性随火后持续时间的延长不断增加,无地表火发生的林分β多样性最高。间接梯度分析(DCA)结果表明,当年发生地表火的林分中植物种类较多,林下植物均表现出从偏旱生到偏湿生、沿水分梯度分布的趋势。因此,樟子松林下植被多样性仅在小尺度上对地表火干扰产生响应,随着时间的推移其多样性趋于一致,表明天然樟子松林的林下植被具有抵御地表火干扰的能力。

The species diversity of understory plants of three stands including no surface fire, surface fire occurred in the current year and surface fire occurred 12 a ago in Pinus sylvestris L. var. mongolica  Litv. forest in Hulun Buir sandy land were investigated with multi-scale modified Whittaker plots(1 000m 2).  The results show that the DBH difference of all trees in each stand is very significant(P< 0.01).The understory vegetation cover age has extremely significant difference in the three stands at 1m ²scale(P<0.000 1) and that of the stand with surface fire occurred 12 a ago is the lowest (32.0%). At 1 and 10 m ²scales, the α diversity of understory plants exhibits significant difference (P < 0. 05), and the understory species richness of the stand with surface fire occurred in the current year is the highest. The α diversity of different functional groups, including woody plant, gramineous plant and forb has a little difference at small scales. The β diversity of understory plants increases continuously as time goes on and that of stand with no surface fire is the highest. The results of detrended correspondence analysis (DCA) show that there are more understory species in the stand with surface fire occurred in the current year and understory plants distribute from drought to hygrophytic habitat along water gradient. Therefore, it is suggested that the understory plant diversity of Pinus sylvestris var. mongolica forest only responses to surface fire significantly at small scales and trends to be uniform. as time goes on, and the understory vegetation has the ability to resist surface fire disturbance.