砒砂岩沟坡沙棘根系分布特征及其对林下土壤的改良作用

沙棘是砒砂岩地区植被恢复的先锋树种,沙棘根系形态不但影响植物本身的生长,还影响其保土效果及改土效果。采用根系追踪法,研究砒砂岩地区同一坡面不同坡位、不同林龄沙棘根系的分布形态,测定沙棘林下土壤的理化性质,以裸坡地作为对照,分析沙棘林对土壤的改良作用。结果表明:1)砒砂岩沟坡沙棘根系在垂直方向上集中分布在0～40 cm深的土壤中,在水平方向分布可达137 cm。2)沙棘一级侧根的数量与小环境有密切关系,土壤水分条件越好,侧根数量越多,根长越短;沙棘根系的径粗与埋深呈反比,并且与距植株中心距离也呈反比。3)人工沙棘林在砒砂岩沟坡上,其根系分布表现为坡顶根系由于土层薄受到砒砂岩的限制,水平分布较发达,在坡底由于土壤厚度及肥力的充足,沙棘在垂直分布上明显深于坡顶。4)种植沙棘可增加土壤含水量和土壤孔隙度,同时还可以提高土壤中的速效N、P、K及有机质质量含量。

Characteristics of root distribution of Hippophae rhamnoides L. and its improving effect on the forest soil on the ditch slope of soft sandstone area

Hippophae rhamnoides L. is one of pioneer tree species in soft sandstone area. The distribution patterns of roots affect not only the growth of the plant itself, but also soil conservation and soil improving. The paper studied the root distribution patterns of different plantation age of Hippophae rhamnoides L. in three site conditions on slopes using roots tracing method. Through measuring the soil physical and chemical properties in Hippophae rhamnoides L. forests, and compared with that on bare slopes, the improving effect of planting Hippophae rhamnoides L. on forest soil was analyzed. The results of the study show that ： roots of Hippophae rhamnoides L. mainly distributed in the depth from 0 to 40 cm in soil on ditch slope in the soft sandstone area, in horizontal direction the roots could reach 137 cm. There was a close relationship between the numbers of first lateral root of Hippophae rhamnoides L. and microenvironment. If condition of soil moisture was better, the tiller ability of Hippophae rhamnoides L. root systems was stronger, and root was shorter. Root diameter of Hippophae rhamnoides L. decreased with soil depth and distance to standard strains. For the man-planted Hippophae rhamnoides L. forest on the soft sandstone slope, because is more developed. Since the soil distribution of root was apparently increase soil moisture content and of limit of soft sandstone the horizontal distribution of root on slope top thickness and fertility at slop bottom were good enough, the vertical deeper than that at slope top. Planting Hippophae rhamnoides L. could the soil porosity, and increase the mass fractions of available N, P, K and organic matter in soil.