黄土高原地区人工林营造——混交林模式生态效益研究

Study on the ecological benefits of a plantation mixed forest model in the Loess Plateau

为探讨不同类型人工林对土壤理化性质的改良能力,以兰州市南北两山5种典型林分类型(侧柏林、新疆杨林、刺槐林、侧柏刺槐混交林、新疆杨刺槐混交林)为研究对象,对0~80 cm土层的土壤理化性质进行了研究。结果表明:(1)不同林分类型混交林土壤容重、持水量、孔隙度、土壤含水量、渗透速率均好于纯林;两种混交林和侧柏林土壤pH低于刺槐林和新疆杨林;混交林土壤有机质、全氮、无机氮、全磷大于纯林;全钾、速效钾在不同林分类型之间差异不显著。(2)在0~80 cm土层范围内,各林分类型随着土壤深度的增加,土壤容重逐渐增加;土壤持水量、孔隙度逐渐降低;土壤含水量、土壤pH均在土层间无显著差异;土壤有机质、全氮、无机氮、速效磷、速效钾随土壤深度的增加逐渐降低,有表聚效应;全磷和全钾在土层间差异不显著。(3)土壤理化性质相关性分析发现:土壤有机质与土壤全氮、无机氮、全磷、持水量、孔隙度均呈极显著正相关,与土壤容重呈极显著负相关;土壤容重与土壤持水量、孔隙度均呈极显著负相关。混交林较纯林在改善土壤理化性质方面有更好的效果,建议该区域在今后人工林营造中以混交林为主,在现有纯林的抚育管理中可考虑将其改造为混交林。

To study the ability of different plantation types to enhance the physical and chemical properties of soil,soil physical and chemical properties at layer depths of 0-80 cm under five typical plantations-Platycladus orientalis plantation,Robinia pseudoacacia plantation,Populus alba var pyramidalis plantation,P.orientalis-R.pseudoacacia mixed plantation,and P.alba var pyramidalis-R.pseudoacacia mixed plantation-were analyzed based on the results of field sampling and laboratory testing.The study revealed that(1)In mixed plantations,the bulk density and the physical properties of the soil,including soil maximum water holding capacity,capillary water holding capacity,field water holding capacity,soil total porosity,capillary porosity,noncapillary porosity,soil water content,and soil penetrability,were clearly better than those in the pure plantations.The pH values in mixed plantations and the P.orientalis plantation were lower than those in the R.pseudoacacia plantation and the P.alba var pyramidalis plantation.In mixed plantations,the soil organic matter,total nitrogen,mineral nitrogen,and total phosphorus contents were significantly greater than those in the pure plantations,whereas there was no significant difference in total potassium and available potassium among the various plantations.(2)The bulk density increased as soil depth increased in the 0-80 cm soil layers,whereas the other soil physical properties soil maximum water holding capacity,capillary water holding capacity,field water holding capacity,soil total porosity,capillary porosity,and noncapillary porosity decreased as the soil depth increased:however,there were no obvious differences in soil water content related to soil depth.The soil chemical properties including soil organic matter,total nitrogen,mineral nitrogen,available phosphorus,and available potassium,all decreased as the soil depth increased,though there were no significant differences in the pH values and soil total phosphorus and total potassium contents with soil depth.(3)Correlation analysis of the physical and chemical properties of the soil revealed significant correlations between soil organic matter and soil nitrogen,mineral nitrogen,total phosphorus,soil maximum water holding capacity,capillary water holding capacity,field water holding capacity,soil total porosity,capillary porosity,and noncapillary porosity,whereas there was significant negative correlation with soil bulk density;There was significant correlation between total nitrogen and soil mineral nitrogen,soil maximum water holding capacity,capillary water holding capacity,field water holding capacity,soil total porosity,capillary porosity,noncapillary porosity,but had significant negative correlation with soil bulk density.There was significant negative correlation between soil bulk density and soil maximum water holding capacity,capillary water holding capacity,field water holding capacity,soil total porosity,capillary porosity,and noncapillary porosity.The findings revealed that mixed plantation improved soil physical and chemical properties to a greater extent than did pure plantation.Therefore,this study implies that mixed plantation should be the main part of plantation management in this area in the future and that managers of pure plantations should considered transforming them into mixed plantations.