Soil Total Carbon Transport In Weathered Granite Hilly Slope Land Under Simulated Extreme Rainstorm Conditions

Soil and water loss refers to the phenomenon of simultaneous loss of water and soil due to natural or man-made factors.Soil erosion destroys the physical protection of carbon in soil aggregates and accelerates the decomposition of organic carbon,affecting the storage of organic carbon in soil and making the soil barren.It also changes the CO₂ flux exchanged with the atmosphere,which is an important factor causing the greenhouse effect.The soil developed on the parent material of the weathered granite has a large proportion.In addition,this soil is always distributed in the hilly areas of the subtropical regions.The surface is undulating,with high temperature and abundant rainfall,which is prone to soil erosion.Until now,only few studies on the characteristics of soil erosion and carbon loss in this kind of sloping land.based on it,this study use the soil developed on the parent material of weathered granite as the subjects,and as the main research contents are the processes of soil and water loss and carbon loss in different intensities.The carbon loss characteristics of weathered granite parent material developed soil were comprehensively studied through 27 effective artificial rainfall simulation experiments.The runoff process and the lateral transport of soil total carbon in exposed sand layer slopes,exposed latertite layer slopes and surface layer slopes of decomposed granite soil in South China under different rainfall intensity?90,120,150 mm/h?and slope gradients?8,15,25 degrees?were studied by artificial rainfall simulation.The effects of rainfall intensity and slope gradients on TC loss were also analyzed.The main results are as follows:?1?Under the super heavy rainfall conditions,the overland flow had the fastest runoff time on exposed sand layer slopes,and the fastest reached 0.33s when the rain intensity was 150mm/h.The TC mass concentration curves in the overland flow of exposed sand layer slopes showed a process of gradually decreasing to a stable after high initial mass concentration,and the trend of the TC mass concentrations in exposed latertite layer slopes and surface layer slopes were not obvious.Under different rainfall intensity and slope gradient conditions,TC loss rates in overland flow of the exposed sandy layer slopes,exposed laterite layer slopes and surface layer slopes did not change significantly with the runoff duration,and all fluctuated within a certain range.?2?There was no interflow in surface layer slopes,and the TC mass concentration in exposed sand layer slopes and exposed latertite layer slopes were single-peak curves,but the TC mass concentration in exposed latertite layer slopes reached the peak in a very short time.The interflow curves of exposed sand layer slopes and exposed latertite layer slopes were similar to the TC mass concentration process curves.Under different rainfall intensity and slope gradient conditions,TC loss rates in the exposed sandy layer slopes and the exposed laterite layer slopes showed the trend that increased and then decreased with the increase of runoff duration,and the peak duration of the TC loss rates in the exposed sandy layer slopes was far greater than that of the exposed laterite layer slopes.?3?TC loss gross amount from exposed sandy and laterite layer slopes was much greater than that from surface layer slopes.Sediment was the main carrier of TC loss in exposed sand layer slopes.The TC loss gross amount with sediment in per rainfall test is more than 50%.The runoff of laterite layer and surface layer slopes was the main carrier of TC,and the TC loss gross amount with runoff in surface layer slopes was more than 60%.?4?Regression analysis showed that rainfall intensity was the most important factor affecting runoff and TC loss under extreme rainfall intensity.At the same time,it can be found that although the mechanism of the impact of heavy rainfall intensity on runoff and TC loss was not clear,it can be found that the average volume of runoff in the three soil slopes is always the largest at 8°.?5?Correlation analysis showed that there was a extremely significant correlation or significant correlation between the rainfall intensity and the TC loss gross amount on the three slopes,the TC loss with sediments and the TC loss with runoff.