Leaching of Dissolved Organic Carbon and Cations and the Buffering Capacity of Litters from Forest Stands in Southwestern China

Abstract

Forest soil can buffer acidification and neutralize acidic airborne pollutants, but for acid rainwater, it makes contact with forest litter in the forest ecosystem first before reaching the soil. However, leachate chemistry of forest litter treated with different acid load rates is rarely studied. A leaching experiment was performed on forest litter from mixed conifer-broadleaf (MCB) and evergreen broadleaf (EB) forests in Jinyun Mountain, Three Gorges area, Southwestern China with simulated acid rain (SAR) of pH=2.7, 3.5 and 4.5. Dissolved organic carbon (DOC) and cations were exported from MCB and EB when treated with various acid load rates. The rainwater deacidification of forest litter was enhanced by considerable leachate concentrations of DOC, Ca2+and Mg2+. The acid buffering capacity of EB was stronger than MCB with different composition of forest litter. Leaching of cations increased with decreasing pH of SAR. Although more easily decomposed, EB released greater Al3+ than MCB, leachate Ca/Al ratios of EB did not reach the critical value of 1.0. Thus, in the study area, EB forest may be a better choice for afforestation and reforestation with better forest litter, showing good buffering capacity, keeping soil from acidification and being a greater nutrient pool for soil under it.