北京石质山区不同水土保持措施对土壤物理性质及抗冲性的影响——以房山区蒲洼小流域为例

为评价北京山区多年来小流域综合治理的水土保持效果,也为以后小流域治理和植被重建提供理论支撑,以房山区蒲洼小流域为研究地,采用典型样地调查、野外抗冲性实验和室内样品处理的方法,对比分析不同水土保持措施的土壤物理性质、土壤质地和抗冲性.结果表明:随着土层加深,各类措施下土壤密度均呈现增大趋势,总孔隙度和毛管孔隙度呈现减小趋势,而非毛管孔隙度没有明显规律.不同水土保持措施下,土壤密度、总孔隙度和毛管孔隙度均有改善(侧柏林除外),改善程度由好到差依次为:辽东栎次生林＞油松落叶松混交林＞石坎梯田＞油松林＞落叶松林＞灌丛;各类措施下土壤颗粒均以细、中粉粒为最多,分形维数显示各类水保措施土壤通透性均较为良好;相比荒地,各类措施下土壤冲刷量显著减小,径流时间延长,冲刷量依次为油松落叶松混交林(0.82 kg/cm3)＜侧柏林(1.14 kg/cm3)＜落叶松林(1.30 kg/cm3)＜辽东栎次生林(3.91 kg/cm3)＜油松林(5.96 kg/cm3)＜荆条灌丛(10.88 kg/cm3),延缓径流冲刷时间由大到小依次为:辽东栎次生林(55.65 s/m)＞油松落叶松混交林(46.82 s/m)＞落叶松(28.19 s/m)＞荆条灌丛(22.39s/m)＞侧柏林(17.48 s/m)＞油松林(16.94 s/m).土壤抗冲性与细、中粉粒体积分数(正相关)、非毛管孔隙度呈显著(负相关)关系最为密切,由此推出大根径的根系穿插形成的非毛管孔隙对土壤抗冲性是负效应.综上,油松落叶松林混交林提升土壤蓄水持水性能、土壤抗冲性均显示出很大的优势;石坎梯田效果也较好,是小流域治理应首先考虑的2类措施.

Effects of soil and water conservation measures on soil physical properties and soil anti-scourability of Beijing mountainous area:A case study of the Puwa Watershed in Fangshan District

Background] In order to evaluate the effect of soil and water conservation in small watershed management in Beijing mountainous area for many years,and to provide theoretical support for small watershed management and vegetation reconstruction in the future,taking Puwa small watershed of Fangshan District in Beijing as research target,soil physical properties,soil texture,infiltration and soil anti-scourability of all major kinds of soil and water conservation measures were studied.Methods] The sample plots of 7 typical soil and water conservation measures was selected and investigated,and the data were acquired through typical plot survey,test of field soil anti-scourability,and method of single-ring.Results] The soil density increased and soil porosity decreased significantly with the increasing of the soil depth.The soil density,total porosity and capillary porosity varied with the measures consistently.The order of effects on improving soil structure were Quercus liaotungensis secondary forest ＞ Larix principis-rupprechtii and Pinus tabulaeformis mixed forest ＞ terraces with stone banks ＞ Pinus tabulaeformis forest ＞ Larix principis-rupprechtii forest ＞ vitex negundo shrub,while there was no significant effect for Platycladus orientailis forest.The soil particles in this area were mostly rich in powder,and the fractal dimension showed that the permeability of all kinds of soil and water conservation measures was promising.Compared with weed land,the scoured soil amount decreased significantly,the runoff time was prolonged,and the order of the scoured soil amount was as L.principis-rupprechtii and P.tabulaeformis mixed forest(O.82 kg/cm3) ＜ P.orientailis forest(1.14 kg/cm3) ＜ L.principis-rupprechtii forest(1.30 kg/cm3) ＜ Q.liaotungensis secondary forest(3.91 kg/cm3) ＜ P.tabulaeformis forest(5.96 kg/cm3) ＜ vitex negundo shrub (10.88 kg/cm3),and the order of runoff scouring time was as Q.liaotungensis secondary forest (55.65 s/m) ＞ L.principis-rupprechtii and P.tabuliformis mixed forest (46.82 s/m) ＞ L.principis-rupprechtii forest(28.19 s/m) ＞ vitex negundo shrub(22.39 s/m) ＞ P.orientailis forest(17.48 s/m) ＞ P.tabuliformis(16.94 s/m).The amount of soil loss showed a negative correlation with fine sand,medium silt,but a positive correlation with non-capillary porosity,indicating that the effect of non-capillary pore size formed by large diameter roots on soil erosion resistance might be negative.Conclusions] In summary,the soil and water conservation capacity of the mixed forest of L.principis-rupprechtii and P.tabulaeformis shows a great advantage followed by terraces with stone banks which should be the principal consideration of small watershed management.