Study on root distribution and mechanical properties of pinus tabulaeformis in dumps of an opencast coal mine, Shanxi, China

The study area was the dumps of maximum opencast coal mine in Shanxi, the three reclamation substrates of thin loess, thick loess and soil-rock mixture were chosen as sample plots, the root distributions of pinus tabulaeformis growing in which were surveyed by profile excavation method and local specimens method. The mechanical properties of roots and water-holding capacity of litter of pinus tabulaeformis were tested. The results showed that:(1) In the thin loess, the root diameter of pinus tabulaeformis was 0-6.5 mm, the root weight density and root length density distributed evenly and were wavy with the increasing diameter in each soil layer. In the thick loess, the root diameter was between 0-3.5 mm, the root weight density and root length density were the biggest in deep soil layers. In the soil-rock mixture, the range of root diameter and root weight density and root length density were all the smallest, and roots tended to develop in surface soil. (2) The root diameters tested successfully ranged from 1.49 to 3.31 mm, the tensile force increased with increasing diameter according to a power function, the tensile strength decreased with increasing diameter at the level of a power function. The root stress-strain curve showed the single-peak curve with the characteristics of elastic-plastic. (3) The water-holding rate of litter increased with socking time at a power function, and there was a significant difference in three reclamation substrates (P < 0.05). The reclamation substrate has a great influence on the root distribution and soil reinforcement.