黄土高原退耕草地植被根系动态分布特征

Dynamic distribution characters of herbaceous vegetation root systems in abandoned grasslands of Loess Plateau.

采用土钻法研究了黄土高原不同退耕年限和天然草地植被根系的垂直分布特征.结果表明,样地上不同采样点间的根系分布不存在显著差异,根系指标的合并计算结果可以代表立地上植被根系的分布特征.植被根系生物量、根系长度等指标的垂直分布特征均表现出随着深度增加而减少的趋势;随着退耕年限的增加,植被根系的生物量、根系长度等指标逐渐增加,一般在退耕年限超过20年后,植被根系的分布特征接近天然草地的根系分布特征.随着退耕年限的增加,根系消失系数从0.98逐渐降低到0.96,说明植被在深层土壤中的相对含量逐渐减少,根系逐渐集中在0～40cm的表层土壤中.退耕植被根系分布特征的改善提高了土壤理化性质,有利于新物种入侵和植被演替进行.

The investigation on the vertical distribution characters of herbaceous vegetation root systems in abandoned and natural grasslands of Loess Plateau by the method of soil auger showed that there were no significant differences in root system distribution patterns between different sampling points,and the related root indexes could be used to indicate the vertical distribution characters of vegetation roots.The main root indexes including root biomass and root length were decreased with increasing soil depth,but increased with increasing abandoned years.After abandoned for more than 20 years,the root distribution characters of abandoned grassland were approached to that of natural grassland.The root extinction coefficient decreased with increasing abandoned years,indicating that more and more roots were concentrated in surface soil layer with the increase of abandoned time,which was helpful to the improvement of soil physical and chemical properties,and beneficial to the new species intrusion and vegetation succession.