Abstract: Determining the effects of atmospheric sulfur (S) deposition on soil organic carbon (SOC) dynamics can provide useful information for understanding the process of carbon cycling of forest ecosystem and its response to global change. Therefore, a simulated S deposition experiment was conducted in a 34-year-oldLarix principis rupprechtii plantation at the Taiyue Mountain of Shanxi Province in 2015. Sulfur deposition treatments included control (CK, 0 kg S·hm^-2·a^-1), low S (LS, 50 kg S·hm^-2·a^-1), medium S (MS, 100 kg S·hm^-2·a^-1) and high S (HS, 150 kg S·hm^-2·a^-1) with three replicates. The experiment was initiated in April 2015. In this study, SOC and its fractions including coarse particulate organic carbon (CPOC, >250  μm), fine particulate organic carbon (FPOC, 53-250  μm) and mineral associated organic carbon (MOC, <53  μm) as well as POC/MOC ratios in surface layer (0-10 cm) and subsurface layer (10-20 cm) were determined in June, August and October of 2015, respectively. Soil temperature, humidity, pH were also measured, and the relationships between three fractions of SOC and soil environmental factors were studied through path analysis. The results showed that the contents of POC, MOC, and the ratios of POC/MOC in the surface layer were higher than those in the subsurface layer. The POC and MOC in August were significantly lower than those in June and October. In the control, the value of POC/MOC in June was lower than that in August and October in the surface soil; however, there was an opposite pattern in the subsurface soil. Sulfur deposition significantly changed the MOC but not the POC. In the surface layer, the MOC was significantly lower in the low and medium S treatments than that in the control (P<0.01). However, in the subsurface soil, the MOC was significantly greater in the high S treatment than that in the control (P<0.01). The CPOC, FPOC and MOC had a significant negative correlation with soil temperature, humidity and pH. In addition, by analyzing the responses of soil organic carbon to environment, we found that soil temperature had strong direct effects on these soil organic fractions. However, soil humidity was not the main factor affecting the POC. These results indicated that the shortterm S deposition depressed the stability of SOC in theL. principisrupprechtii plantation. More attention should be paid on the effect of temperature on SOC dynamics in longe-term study.

Key words: soil water content, maize yield., straw returning, soil physical property, subsoiling