云南山地尾叶桉类林引种对土壤物理性质的影响

The effect of Eucalyptus uraphylla spp.introduction on soil physical properties in a mountainous region of Yunnan

采用野外调查和室内分析相结合的方法,对澜沧县尾叶桉类林(Eucalyptus uraphylla spp.)、次生常绿阔叶林、思茅松林(Pinus kesiya)3种林型土壤物理性质进行研究,以揭示云南山地大面积引种尾叶桉类林对土壤物理性质的影响。结果表明:(1)尾叶桉类林取代次生常绿阔叶林和思茅松林后,土壤含水量分别下降了10.98%和9.55%,对土壤水分的消耗增加;土壤容重分别增加了10.14%和3.31%,土壤紧实度增加;土壤总孔隙度和毛管孔隙度分别下降了6.77%、3.15%和11.96%、4.09%,桉树(Eucalyptus)土壤吸持水分能力降低,保水性能变差。土壤非毛管孔隙度分别上升了7.07%和2.66%,土壤接纳降雨量、减少地表径流量的能力提高,但是桉树林表层土壤的非毛管孔隙却小于次生常绿阔叶林和思茅松林,涵养水源、消洪能力较弱;(2)尾叶桉类林的引种使土壤物理性质发生了一定的变化,变化大小与桉树引种前原用地类型关系很大。在第一轮伐期内,桉树林地土壤总孔隙度在50%左右,土壤松紧程度处于较适宜范围。以次生常绿阔叶林为原用地类型的桉树林地,土壤非毛管孔隙占总孔隙度的比例均在20%～40%,土壤通气性和持水性较好。而以思茅松林为原用地类型的桉树林地土壤非毛管孔隙占总孔隙度的比例均小于20%,土壤通气性和持水性相对较差。

The aim was to study the effects of large-scale introduction of Eucalyptus uraphylla spp. on the physical properties of the soil of a mountainous region of Yunnan. Field survey and laboratory analysis were employed. The original site was a secondary evergreen broad-leaved forest and a Pinus kesiya forest in Lancang County. The result showed that： after the Eucalyptus uraphylla spp. forest replaced the secondary evergreen broad-leaved and Pinus forests, the soil water content decreased by 10.98% in the evergreen broad-leaved forest and 9.55% in the Pinus forest. The consumption of soil moisture increased. The soil bulk deteriorated, soil bulk density increased by 10.14% in the evergreen broad-leaved forest, and by 3.31% in the Pinus forest. The total soil porosity and capillary porosity decreased by 6.77%, 3.15% and 11.96%, 4.09% respectively, which shows a low level of soil water absorption and holding capacity in the Eucalyptus uraphylla spp. forests. The soil non-capillary porosity increased by 7.07% and 2.26% respectively, which indicates a higher capacity of holding rainfall and reducing ground runoff flow in Eucalyptus uraphylla spp. forest. However, the minimum non-capillary porosity of Eucalyptus uraphylla spp. in soil surface layer shows a weak water conservation function. Eucalyptus uraphylla spp. can change physical properties of the soil, depending on the original land use. In the first cutting stage, the soil density under the Eucalyptus was within a suitable range, with porosity around 50%. As Eucalyptus replaced the secondary evergreen broad-leaved forest, the soil non-capillary comprised 20%-40% of total soil porosity, and the soil aeration and water retention improved. But where the Eucalyptus replaced Pinus kesiya, the level of soil non-capillary porosity was lower than 20% of the total soil porosity, and the soil aeration and capacity for water retention deteriorated.