云杉次生林林下植被、枯落物及土壤特征对林分密度的响应

Response of Understory Vegetation,Litter and Soil Characteristics to Stand Density in Picea Secondary Forests

以山西省庞泉沟自然保护区80年生云杉次生林为研究对象,通过样地调查、样品收集和实验室浸水实验,运用方差和多重比较等方法分析了不同林分密度云杉次生林林下植物多样性、枯落物和土壤水源涵养特征。结果表明:研究区域内林下植被物种较匮乏,林分密度越小,灌木层物种越丰富,灌木层以扶芳藤和苎麻为主;草本层物种多样性与林分密度关系不明显,草本层的苔草为绝对优势种。枯落物厚度随林分密度的增加而减小,且3个林分之间无明显差异。中密度时,枯落物生物量、最大持水量和有效拦蓄量均为最大,分别为36.56、81.50、31.58 t/hm^(2)。不同林分密度的土壤容重规律为:低密度>高密度>中密度,即中密度林分的平均土壤容重最小,为0.89 g/cm^(3)。总孔隙度表现为:低密度<高密度<中密度。中密度时,土壤层总持水量和土壤层总有效持水量均为最大,分别为3 945.61、364.00 t/hm^(2)。因研究区域位于黄土高原区,该区域森林的水源涵养功能更为重要,建议将山西省庞泉沟自然保护区80年生云杉次生林的合理林分密度控制在600~700株/hm^(2)。

Taking the 80-year-old Picea secondary forest in Pangquangou Nature Reserve of Shanxi Province as the research object,the understory vegetation diversity,litter and soil water conservation characteristics of the Picea secondary forest with different stand densities were analyzed by using the methods of variance analysis and multiple comparison through sample survey,sample collection and laboratory immersion treatment.The results showed that the smaller the stand density,the richer the species of shrub layer in the study area.The relationship between species diversity of herb layer and stand density was not obvious.The Euphorbia fortunei and Boehmeria nivea were the dominant species in the shrub layer,while Carex was the dominant species in the herbaceous layer.In general,the undergrowth vegetation species in the study area were relatively scarce.The litter thickness decreased with the increase of stand density,and there was no significant difference among 3 stands.At medium density,the biomass,maximum water holding capacity and effective storage capacity of litter were the largest,which were 36.56 t/hm^(2),81.50 t/hm^(2) and 31.58 t/hm^(2) respectively.The rule of soil bulk density was low density >high density > medium density,that is,the average soil bulk density of medium density stands is the smallest,0.89g/cm^(3).The total porosity,capillary porosity and non capillary porosity were low density < medium density < high density.When the total water holding capacity and total effective water holding capacity of soil layer of medium density forest were the largest,3 945.61 t/hm^(2) and 364.00 t/hm^(2) respectively.In conclusion,considering that the study area is located in the Loess Plateau,and the water conservation function of the forest in this area is more important,it is suggested that the reasonable stand density of 80-year-old Picea secondary forest in Pangquangou Nature Reserve of Shanxi Province should be controlled at about 600–700 plants/hm^(2).