大兴安岭典型针阔混交林区土壤持水效应

Soil Water Retention Effect in Typical Mixed Plantation of Broadleaf and Coniferous Leaf Forest Region of Daxingan Mountains

受地貌条件的影响,大兴安岭低山丘陵地区土壤的水、热性质出现分异,发育的土壤类型以及植被都表现出典型的高寒森林湿地中域景观特征。沿局部分水岭向河谷低漫滩发育4种土壤类型,依次为塔头苔草草甸土—灰色森林土—白浆土—暗棕壤。大兴安岭地区森林湿地存在明显的冻融过程,冻融作用的影响下森林湿地表层的水分数量和状态都发生明显的变化。在冻融过程中,位于地势较高的森林植被湿地仅表层储存大量水分,而位于低位的塔头苔草湿地整体土体的水分数量和状态都发生明显的变化。白浆土的水分特征曲线非常平缓,表明土壤水分变化微弱。大兴安岭地区山岭和山麓发育的土壤土层较薄,使得除了枯落物(O)层外其他土层土壤持水性能都弱,一旦该地区枯枝落叶层受到破坏,整个山岭表层的土壤将发生严重的水土流失。

As affected by the local topographical condition, soil moisture and thermal properties in the Daxingan Mountains varied largely, and soil types and vegetation in the region appeared to be the typical high-cold forest wetland with middle scale landscape feature. There were four types of soils from the local watershed divide to the low flood plain, i. e. , sedge meadow soil, gray forest soil, Baijiang soil and dark brow forest soil. Obvious freeze--thaw process occurred in the forest wetland of the Daxingan Mountains, whereby the soil moisture content and phase varied significantly. Large soil moisture storage was observed merely in the surface horizon of forest soil in high relief during the freezing period, whereas obvious change in soil moisture content and phase was observed in the meadow soil in low relief. The water retention curve of Baijiang soil is very smooth, suggesting minor water change. The thin soil horizon developed in the mountain ridge and foot leads to a weak water retention capacity, except the litter layer（O horizon）. When the litter layers are destroyed by human disturbances, serious soil erosion will occur.