Analysis on tablets dissolution rate and carbon sink under different vegetation in north China karst area: A case study of Fenyang, Shanxi Province
The study area,the Mapao spring,is located in southwest of the Jinzhong basin,Shangxi Province.The Mapao spring catchment has an area of 212.06 km2.Annual air temperature and precipitation in the study area average in 11.11 ℃ and 444.44 mm and the elevation ranges from 1 100 m to 1 900 m,decreasing from west to east and from north to south.The strata exposed in the study area are primarily carbonate rocks (limestone and dolomite) of the Cambrian-Ordovician system.By means of comparison dissolution experiment under different vegetation conditions,testing analysis on the contents of soil organic carbon and soil inorganic carbon,and field measurement for the concentration of soil CO2 and moisture content,the features of the dissolution rate and its impact factors in semiarid conditions in north China are revealed as follows.(1) The tablets dissolution rate,obvious different under different vegetation conditions,is the largest in forest land with the value of 0.551 1 mg/(cm2 · a),which is 2.13 times,2.16 times higher than that under shrub conditions and meadow land respectively.This result indicates that carbonate dissolution rate has an increas ing tendency along with the positive succession of vegetation.(2) The tablets dissolution rate is mainly affected by soil organic carbon,soil inorganic carbon,soil moisture,but slightly affected by the soil CO2 concentration.The soil organic carbon content and soil moisture is positive related with the tablets dissolution rate,the soil inorganic carbon content is negatively related with the tablets dissolution rate.So,high levels of inorganic carbon can lead to the weight of some tablets increase instead of decrease after a year's corro sion,which results in the tablets dissolution rate becomes slower.(3) The karst carbon sink intensity,i.e.1.815 tCO2/(km2 · a),calculated in light of the average dissolution rate in forest land and shrub land as well as grassland is smaller in comparison with the former figure,i.e.8.69 tCO2/(km2 · a),calculated in accordance with hydrochemistry-runoff method.This means that the amount of karst carbon sink being calculated by means of dissolution method is likely to be smaller than the actuality.
dissolution ratecarbon sinksoil organic carbonsoil inorganic carbonsoil CO2karst area with semiarid environment
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