黄土丘陵区典型植物群落根系垂直分布与环境因子的关系

Vertical distribution characters of typical communities root system in relation to environmental factors in the Hill-gully region of Loess Plateau

深入研究植被恢复过程中根系与环境因子的响应规律，对于当前西部地区的生态环境建设中有关林草措施的配置问题具有重要理论意义和实践价值。采用对应分析（CA）和典范对应分析（EtA）方法研究黄土丘陵区4种典型植物群落的根系垂直分布特征及其与环境因子的关系。结果表明，所选群落的根系生物量随土层深度增加而明显减小，0～40cm土层根系生物量超过总根量的85％。借助CA分析将根系的垂直分布特征分为T1、T2和T3，其中大多数群落属于T1型，即表层根量聚积型，0～20cm土层根量远高于其他层次；T2和T3型为深根与浅根型根系的组合类型，层次变化相对缓和。群落根系的垂直分布及变化受环境因子的综合影响，T1型分布在硝态氮含量较高且有机质和全氮含量较低的地段；T2和髓型的有机质和全氮含量较高，硝态氮含量较低；土壤水分含量、密度、硝态氮是影响退耕地典型植物群落根系垂直分布特征的主要环境因子。

In order to provide scientific basis for vegetation restoration and reconstruction of removal lands in the Hill-gully region of Loess Plateau, the effects of environmental factors on the vertical distribution of root system biomass were studied with the methods of CA and CCA analyses in four typical communities. The results showed that root system biomass of four communities decreased with the increase of soil depth in a similar manner, and 85% root system biomass were concentrated in surface soil layer of 0 - 40 cm. The distribution of root system in soil profile can be divided into three types ： T1, T2 and T3, and root system in most communities belongs to the T1 type in which the roots are concentrated in the top soil layer（0 - 20 cm）, far more than in the lower soil layers ; while root systems of types T2 and T3 are imbedded in both top and deep soil layers. Results showed that environmental factors compositively affected the distribution and variety of roots, among which soil water content, bulk density, nitrate nitrogen had main effects. The T1 type distributed in the areas which had more nitrate nitrogen, while the types T2 and T3 distrbuted in places with high content of organic matter and total nitrogen.