Elucidating the mechanisms of warming-induced stability for soil organic C is one of the keys for evaluating the tendency of soil C sources/sinks in projected global warming models. Organic C densities in soil,and soil physical and biochemical fractions,under different warming scenarios in the Karst Plateau were investigated following a 4-yr continuous warming using infrared radiators,via density fractionation and acid hydrolysis. Six treatments were arranged: no warming( ambient temp,CK); symmetric warming...