[Soil organic carbon storage changes with land reclamation under vegetation reconstruction on opencast coal mine...

Vegetation reconstruction was an effective solution to reclaim the opencast coal mine dump which was formed in the process of mining. To understand the impact of the vegetation reconstruction patterns' on the mine soil organic carbon (SOC) storage was essential for selecting the methods of vegetation restoration and also important for accurately estimating the potential of the soil carbon sequestration. The study area was on the Heidaigou opencast coal mine, which was 15 years reclaimed coal mine dump in Zhungeer, Inner Mongolia autonomous region, we selected 5 vegetation reconstruction patterns (natural recovery land, grassland, bush land, mixed woodland of arbor and bush, arbor land), and 16 vegetation types, 408 soil samples (0-100 m), to study the effect of the vegetation reconstruction patterns on the SOC storage. The results were showed as follows: (1) on the reclaimed coal mine dump, the vegetation reconstruction patterns significantly affected the SOC content and its distribution in the soil profile (P < 0.05). The surface 0-10 cm SOC content was grassland > shrub land > arbor forest > mixed forest of arbor and shrub > natural recovery land, in which the grassland, shrub land and arbor forest were about 2.2, 1.3, and 1.3 times of natural recovery land (2.14 g · kg(-1)) respectively. The total nitrogen (TN) showed the similar trends. (2) Among the vegetation types, Medicago sativa had the highest surface SOC content (5.71 g · kg(-1)) and TN content (0.49 g · kg(-1)), that were 171.3% and 166.7% higher than the natural recovery land, and two times of Hippophae rhamnoides, Amorpha fruticosa + Pinus tabulaeformis and Robinia pseudoacacia. (3) The effect of vegetation types on SOC mainly concentrated in the 0-20 cm depth, and the effect on TN accounted for 40 cm. (4) For the SOC storage, the order was original landform area > reclaimed dump > new dump and grassland > woodland (including arbor and shrub land). After 15 years revegetation, the soil carbon storage of the grassland, shrub land and arbor land were increased by 15.47 t · hm(-2), 6.93 t · hm(-2) and 6.95 t · hm(-2) respectively in the 100 cm depth, which were equivalent to 2/3, 1/2 and 1/2 of the original landform levels. The results showed a great ability of carbon sequestration.