Grassland ecological restoration based on the relationship between vegetation and its below-ground habitat analysis in steppe coal mine area.

Abstract

Coal mining activities have caused severe disturbances to the regional ecosystem and soil properties. Studying the relationship of vegetation and its below-ground habitat (RVBGH) is of great significance to the coal mine land ecological restoration. To identify the optimal thickness of the soil layer for mine land ecosystem recovery and characterize the changes of the reclaimed soil-vegetation ecosystem, we studied natural and reclaimed grassland at the coal mine of Baorixile, located in Hulunbuir Steppe, Northeastern China. The vegetation and its below-ground habitat (BGH), including "root mass" and soil properties in the soil profile (0-100cm), were surveyed in the natural and different year-reclaimed grassland. The "root mass" is the part of root system that has the most amounts of root hairs, which is the functional zone for plant growth. The RVBGH was identified by the "root mass" and plant water extraction depth, measured through the isotope δD and δ18O method. Firstly, the BGH of natural grassland was identified as a "double layer" vertical structure, with the "root mass" of 37.11±2.57% fine roots at 0-20cm range and 30.44±2.67% at 20-40cm range. The annual and perennial plant "root mass" was found at 0-20cm and 20-40cm depth, respectively. Secondly, an optimal thickness of the soil covering of 30-40cm was proposed for grassland reclamation. Thirdly, along the reclamation chronosequence, the values of the reclaimed vegetation properties (height, density, coverage and diversity) increased and a deep root system was established. The "root mass" increased from one layer to double layer and the amount of total fine roots increased from 1621±231.9 to 4459±456.0. Moreover, the reclaimed soil properties of organic matter, cation exchange capacity, available N and P also increased. The study proposed that vegetation restoration was significantly correlated with its BGH, suggesting that vegetation BGH recovery is crucial in ecological restoration.