陕北黄土丘陵区三种林地根系分布特征

Root Distribution Characteristics of Three Kinds of Forest Lands in Loess Hilly Region of Northern Shaanxi

植被根系在黄土丘陵区水土流失防治中发挥重要作用。采用分层挖掘法获取陕北黄土丘陵区三种林地根系,仿照群落生态学研究方法,利用根系生态位指数分析该区三种林地根系的分布特征,结果表明:三种林地根系生态位指数随深度的增加呈现较明显的下降趋势,但也有明显的差别,山杨林地中,根系生态位指数最大值是1.37,为最小值的6.95倍,而油松林地中最大值是1.07,为最小值的2.41倍,灌木林地中最大值是0.76,为最小值的2.75倍,三种林地中,相同深度的根系生态位表现为:山杨林>油松林>灌木林。山杨林地和油松林地根系生态位径级分布呈明显的不等高U型特征,林地根系为细-粗混合型,灌木林地为明显的反J型,为细根型群落根系。就群落根系生态位指数来看,山杨林地为5.40,油松林为4.41,灌木林为3.09。

Root system of vegetation in loess hilly region plays an important role in the prevention and control of soil erosion.Hierarchical excavation method is used to obtain the root system of three kinds of forest lands in loess hilly region of northern Shaanxi.Modeled on the research method of community ecology,the distribution characteristics of the root system of three kinds of forest lands in the region is analyzed by using the root ecological niche index（RENI）.The result shows that the root ecological niche index in three kinds of forest land declines obviously with the increase of depth of soil,but there are obvious differences.The maximum value of the root ecological niche index in populus davidiana land is 1.37,which is 6.95 times the minimum value.But the maximum value in pinus stabulaeformis land is 1.07,which is 2.41 times the minimum value.the maximum value in shrub land is 0.76,which is 2.75 times the minimum value.The root ecological niche index in the three forest lands with the same depth soil shows that：populus davidiana〉pinus stabulaeformis〉shrub.The distribution of the？root ecological niche index by root diameter in populus davidiana and pinus stabulaeformis lands are the characteristic of the U type.This indicates that the root system of the two woodlands is fine-coarse mixing type.That in shrub is the inverse J type.This indicates that the root system of shrub land is fine root type.As far as the ecological niche index of community root is concerned,populus davidiana forest land is5.40,pinus stabulaeformis forest land 4.41 and shrub forest land 3.09.