Abstract:

The spatial distribution of fine root biomass, specific root length(SRL), root length density(RLD), the root surface area index of the 10-year-old Robinia pseudoacacia plantation were investigated in hilly Loess Plateau region, and relationships between these root parameters and the soil environment factors(e.g. soil moisture content, soil temperature and soil bulk density) were analyzed. The results showed that, 1) the amount of fine roots decreased with depth of soil from 0 to 180 cm (the soil was divided into five layers; a, b, c, d and e layer). The change of the fine root biomass, RLD and the root area index with the depth could be described by a negative exponential function. The roots distributed mainly in the 0-60 cm soil layers and the peaks of the three parameters all appeared in the 0-20 cm, accounted for 42.72%, 44.44% and 47.14% of those amounts from 0-60 cm soil layers, respectively. SRL did not decrease much with soil depth, and even appeared reverse in the 80-140 cm soil layers. The relationship between the SRL and the soil depth could be described by a cubic polynomial. 2) With increasing horizontal distance from the tree trunk, the fine root biomass, RLD and the root area index decreased gradually. The SRL increased in the range of 40-80 cm and 120-160 cm respectively. 3) The environmental factors strongly influenced the root distribution, and the influence degree was in an order: Soil temperature>soil moisture content>soil bulk density. A multivariate linear regression model was established between root parameters and environmental factors and the model achieved 95% significant level.

Key words: Robinia pseudoacacia, spatial distribution pattern, root parameters, soil physical factors