Abstract: 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.

Key words: Low temperature stress, Garcinia hanburyi, Growing irradiances, Fluorescence characteristics, Active oxygen metabolism