不同密度人工云杉林土壤质量评价

Soil Quality Evaluation of Artificial Picea asperata Forest with Different Densities

以甘肃白龙江林区沙滩林场5个不同密度等级(800、1200、1600、1970、2400株·hm^-2)的人工云杉林为对象,对比分析各密度林分土壤物理指标、pH值、有机质及各养分元素含量等16个指标的差异,并基于主成分分析对土壤质量进行评价,旨在为该区域人工云杉林的合理经营提供理论依据。结果表明,在不同密度长期经营下人工云杉林林地土壤理化性质出现差异,并呈现一定的变化规律。在5个密度等级中,1600株·hm^-2时土壤含水率和孔隙度最大,容重最小,土壤物理性质最佳,土壤pH值随林分密度增大而逐渐减小,有机质及各养分元素含量随林分密度增大呈先增大后减小的变化趋势。相同密度下,表层土壤(0~20 cm)物理性质最佳,有机质及养分元素呈明显的“表聚”特征,即表层土壤理化性质最佳。对不同密度人工云杉林土壤质量进行评价发现,土壤质量指数随林分密度增大先增大后减小,在1600株·hm^-2时达到最大,为0.5664,土壤质量最高。说明适宜的密度能改善土壤质量,1600株·hm^-2为本区域人工林云杉的最适经营密度,因此今后本区域人工云杉林经营或间伐可以1600株·hm^-2为参考标准。

Picea asperata plantations with 5 densities(800,1200,1600,1970,2400 plant·hm^-2)were used as research objects that were in Shatan Forest Farm,Bailong forest region,Gansu Province.Sixteen indices,including soil physical indicators,pH,organic matter,and nutrients were analyzed comparatively.The soil quality evaluation was conducted based on principal component analysis.The objective of the study was to provide a theoretical basis and guidance for reasonable management of P.asperata plantations.The results showed there existed differences in soil physical and chemical properties between the soils with different stand densities under long-term management,and showed a certain law of change.Among the five densities,soil with the stand density of 1600 plant·hm^-2 presented the best soil physico-chemical properties:highest moisture content and porosity,and lowest soil bulk density.The soil pH gradually decreased with stand density,organic matter contents and nutrient elements increased first and then decreased with stand density.At the same density,the topsoil(0-20 cm)had the best physical properties,and soil organic matter and nutrients significantly accumulated in topsoil,resulting the best physical and chemical properties of topsoil.The evaluation of soil quality indicated that the soil quality index first increased and then decreased with the stand density,and it reached the maximum value at the stand density of 1600 plant·hm^-2,which was 0.5664,and the soil quality was the best,indicating that 1600 plant·hm^-2 was the optimal management density of P.asperata plantations in this region.