Effects Of Vegetation Restoration Of Different Tree Species On Soil Carbon In A Post–mining Land

Post–mining lands in coal mine areas tend to be a huge carbon source.Previous studies suggested that vegetation restoration may be an effective way to reverse a carbon source to a carbon sink.The studies on the effects of vegetation restoration on soil carbon fractions are of great significance to enhance soil carbon,to curb regional carbon emissions,and to mitigate greenhouse effects.In this paper,by field survey and lab measurement,soil physical and chemical properties,soil carbon and its fractions of different restoration methods by using different tree species were analyzed in a post-mining land in Xishan coal mine in Taiyuan city,Shanxi province.Moreover,main factors influencing soil organic carbon and its fractions were analyzed.We intended to provide some references for the restoration of carbon sequestration function in post–mining lands,accurate evaluation for its carbon sequestration potential,and for effective management of carbon pools in post-mining lands.The results showed that:Through three restoration models,including artificial restoration by planting Rhus Typhina,Quercus wutaishansea and Pinus tabuliformis,soil properties were improved significantly.Soil pH decreased and soil water content,electrical conductivity and total nitrogen content increased,which were beneficial to improve microbial activity and facilitate vegetation growth.Vertically,pH value,soil water content and electrical conductivity gradually increased with the increase of soil depth while total nitrogen content gradually decreased with the increase of soil depth.Through vegetation restoration,soil organic carbon increased significantly,and there were significant differences among the three restoration models.Mean soil organic carbon was in the order of Quercus wutaishansea>Rhus Typhina>Pinus tabuliformis.This could be explained by the differences of growth characteristics among three tree species,and the the quantity and quality of soil C input were significantly different.Vertically,the soil organic carbon gradually reduced with the increase of soil depth,which may be attributed to the distribution of forest floor litter,fine foot and soil microorganism,most of which were concentrated in the topsoil.Correlation analysis showed that soil organic carbon was positively correlated with total nitrogen and total carbon,while was negatively correlated with pH value.The effect of vegetation restoration on soil inorganic carbon has not yet been clearly explained.The results showed that the restoration type had no significant influence on soil inorganic carbon,which may be mainly controlled by the soil?s parent material.Vertically,the soil inorganic carbon gradually increased with the increase of soil depth.This might result from the migration and deposition of carbonate into the deep soil layer with the precipitation leaching.Soil dissolved organic carbon increased significantly by vegetation restoration and followed the order of Quercus wutaishansea>Pinus tabuliformis>Rhus Typhina.Moreover,restoration type had significant influence on soil dissolved organic carbon.Vertically,the soil organic carbon gradually reduced with the increase of soil depth.Correlation analysis showed that soil dissolved organic carbon was positively correlated with total nitrogen,total carbon and soil organic carbon,while was negatively correlated with pH value and electrical conductivity.There were significant differences of soil microbial biomass carbon among the three restoration models,and soil microbial biomass carbon was in the order of Quercus wutaishansea>Rhus Typhina>Pinus tabuliformis.Vertically,the soil microbial biomass carbon gradually reduced with the increase of soil depth.Correlation analysis showed that soil microbial biomass carbon was positively correlated with total nitrogen,total carbon and soil organic carbon and soil dissolved organic carbon,while was negatively correlated with pH value and electrical conductivity.In sum,due to the significant improvement in soil cabon and soil properties,the results suggested that Quercus wutaishansea would be suitable to be recommended as the preferred species for ecological restoration in post–mining lands.This may be due to the fact that litter biomass and decomposition rate of broad–leaved trees,such as Quercus wutaishansea,was distinctly higher than coniferous evergreen trees,such as Pinus tabulaeformis.