不同植被恢复模式下煤矸石山复垦土壤性质及煤矸石风化物的变化特征

为了探讨植被恢复模式对煤矸石山复垦土壤和矸石风化物的影响,对煤矸石山6种主要植被类型(刺槐林、刺槐-柠条混交林、榆树-紫穗槐混交林、侧柏-刺槐混交林、荆条林、紫花苜蓿草丛)下土壤和煤矸石风化物的理化性状及重金属进行了比较研究。结果表明:(1)煤矸石山上种植植被可使土壤容重、土壤持水量和孔隙度明显改善。乔木模式更明显。矸石山植被恢复后,可明显增加土壤养分含量。不同植被模式下,土壤养分增加存在显著差异。侧柏-刺槐和榆树-紫穗槐混交模式效果较好。(2)植被对煤矸石风化物容重和机械组成改善作用依次为针阔混交林>乔灌林>乔木纯林>灌木林>草本。植被促进有机质与全氮积累依次为:侧柏-刺槐>刺槐>刺槐-柠条>榆树-紫穗槐>荆条>紫花苜蓿。荆条林下煤矸石风化物全P含量最大。荆条林与侧柏-刺槐混交林利于速效P积累。对速效K积累有利的是荆条林与榆树-紫穗槐混交林。(3)植被种植可以减少煤矸石风化物中重金属含量。榆树-紫穗槐混交模式对减低超标重金属Cd的效果好,其次是针阔混交林(侧柏-刺槐)。对于超标重金属As而言,侧柏-刺槐模式优于其它植被模式,基本达到重金属As不超标。

Reclaimed soil properties and weathered gangue change characteristics under various vegetation types on gangue pile

The main obstacles to restoration of the vegetation and ecological reconstruction of abandoned mines are from the special and poor physical and chemical properties of the land, particularly to gangue piles. Vegetation is based on soil and also affects soil formation, nutrient cycling and development. Study of nutrient change in soil is important to understand soil fertility and mechanism of nutrient cycling. The study of re-vegetation for coal gangue piles has mainly focused on growth of young forest, soil matrix improvement, vegetation restoration patterns, vegetation dynamics and vegetation restoration techniques and mechanisms, etc. However, there are no many studies on eco-environmental effects of vegetation on gangue piles. Study of the relationship between environment and vegetation on gangue piles is helpful to reveal the stability and dynamic development of existing ecosystem, and to build up the foundation for vegetation regulation on gangue piles. In this study, different reclaimed lands from 280 gangue piles of No.3 coal mine of Yangquan Coal Industry Group in Shanxi Province were included. The effect of different vegetation restoration patterns were analyzed on reclaimed soil and weathered coal gangue. The soil, physical and chemical properties of weathered coal gangue and heavy metals under 6 different vegetation types (platation of Robinia pseudoacacia L., mixed plantation of Robinia pseudoacacia L. and Caragana intermedia, mixed plantation of Ulmus pumila L. and Amorpha fruticosa L., mixed plantation of Platycladus orientalis (L.)Franco and Robinia pseudoacacia L., Vitex negundo var. heterophylla and grass vegetation of Medicago sativa L.) on coal gangue piles were compared. The results showed: (1) The vegetation, particularly the tree plantation on coal gangue piles significantly influenced the soil bulk density, soil water holding capacity and porosity. As the vegetation was recovered, the nutrient content in the soil significantly increased. Soil nutrient content varied with the difference between vegetation restoration types. The mixed plantation of R. pseudoacacia and C. intermedia was much better than other vegetation types. The order of different vegetation types according to their positive effects on soil bulk density and mechanical components of coal gangue were: coniferous> mixed shrub and tree forest> broad-leaf tree pure forest> shrub> grass; (2) The vegetation order according to the accumulation of organic matter and total nitrogen were: mixed plantation of P. orientalis and R. pseudoacacia > R. pseudoacacia plantation > mixed plantation of R. pseudoacacia and C. intermedia > mixed plantation of U. pumila and A. fruticosa > V. negundo var. heterophylla plantation > Grass of M. sativa. Total P content under V. negundo var. heterophylla plantation on weathered gangue piles was the highest. V. negundo var. heterophylla plantation and mixed plantation of P. orientalis and R. pseudoacacia were good for quick P accumulation, and mixed plantation of U. pumila and A. fruticosa for quick K accumulation; (3) Planting of vegetation could reduce the heavy metal content in weathered gangue. Mixed plantation of U. pumila and A. fruticosa was better in reducing excessive heavy metal Cd, and followed by mixed coniferous forest (mixed plantation of P. orientalis and R. pseudoacacia). In reduction of excessive heavy metal As, the mixed plantation of P. orientalis and R. pseudoacacia was better than the other vegetation types, and could control the As level lower than the national standard.