Abstract: Alkane and alkene, two major types of volatile organic compounds (VOCs), play critical roles in atmospheric chemistry and have great effect on global carbon cycle. Continuing elevated nitrogen deposition will change forest soil ecological processes, which will then influence VOCs fluxes from the forest floor. Static chambers and preconcentratorGC-MS technique were used to investigate the responses of alkane and alkene fluxes to the simulated nitrogen deposition from the floor of two typical forest ecosystems, namely masson pine forest (PF) and monsoon evergreen broadleaf forest (BF) in Dinghushan. The results showed that for the natural nitrogen deposition, PF floor acted as a sink for alkane and a source for alkene, with the maximum uptake rate of -117.616±73.048 pmol·m^-2·s^-1 for undcane and the maximum emission rate of 220.301±159.543 pmol·m^-2·s^-1 for α-pinene. BF floor acted as a source of both alkane and alkene. Simulated nitrogen deposition promoted the emission of alkane, changed the function of PF forest floor from alkane “sink” to “source”, and the effect became more significant with the elevating nitrogen level. On the contrary, the emission of alkene was restrained in PF, or even PF floor changed from alkene “source” to “sink”, and the low level of nitrogen input had a significant influence. Simulated nitrogen deposition changed the BF floor from “source” to “sink” for both alkane and alkene. Additionally, alkane flux differed significantly between the two forests, and the alkene flux differed among compounds in the same forest.

Key words: albic soil, physical and chemical properties, evolution characteristics., rice growing