Abstract: The vertical distribution, seasonal dynamic of soil total organic carbon (SOC), micro-biomass carbon (MBC), hot water-extraction organic matter (HWC), water-soluble organic carbon (WSOC), easily oxidized organic carbon (ROC) and the soil environmental factors were studied in pure Phyllostachy edulis plantations, P. edulis and Cunninghamia lanceolata mixed forests in the hilly region, central Hunan Province. The result showed that: The content of SOC, MBC,HWC,WSOC, and ROC decreased with the increase of soil depth, and in the soil layer of 0-60 cm, SOC and WSOC had the highest average contents in January, while MBC in July and ROC in October. However, HWC in P. edulis plantations had the highest content in July, while that in P. edulis and C. lanceolata mixed forests had the highest content in January. P. edulis and Cunninghamia lanceolata mixed forests had higher the contents and the ratios of different types of organic matters, but with lower stability than the pure P. edulis plantations. Temperature and moisture were very significantly negatively correlated with WSOC (P < 0.01), but very significantly positively correlated with MBC (P < 0.01). Decrease in soil density and increase in soil ventilation and water-holding capacity were conductive to increasing soil organic matter; soil organic matter was very significantly positively correlated with SOC, MBC, and HWC (P<0.01), while significantly positively correlated with ROC (P<0.05). Moreover, there existed very significantly positively relationships between the contents of total N and available P with SOC, and between total N content with MBC (P<0.01),and there were significantly positively relationships between available N, total P and total K with SOC and MBC, available K with SOC, and between available P with MBC. Increasing quality of bacteria and actinomycetes was beneficial to SOC accumulation, however, increase in fungi was not beneficial for stability of SOC; catalase was more closely correlated with SOC compared with the other enzymes and significantly positively correlated with SOC and ROC.

Key words: Phyllostachy edulis, soil organic carbon, vertical distribution, seasonal dynamics, central Hunan Province