Abstract:

Different fractions of soil C were detected in Phyllostachys praecox stands. It was found that the total soil organic C (C_T) was almost the same as that of Pinus massoniana natural stands, but higher than that of Castnea mollissima stands which is adjacent to Phyllostachys praecox stands. Soil microbial biomass C (C_MB) decreased by 23.12% (compared to Pinus massoniana) and 12.63% (compared to Castnea mollissima).C_MB and C_MB/C_T declined more apparently in continuous chemical fertilizer application stands.C_MB and C_MB/C_T decreased by 61.54% and 58.82% respectively in 3-year chemical fertilizer application stand compared to the stands with mixed application of chemical and organic fertilizer. Continuous mulching with organic material in winter, however, was detected an increase in C_MB and C_MB/C_T. Soil active C (C_A) measured by 333 mmol·L^-1 KMnO₄ and C_A/C_T sustained the same level with Pinus massoniana.C_A and C_A/C_T were respective 1.39 and 1.23 times over in 3-year combining application of chemical and organic fertilizer relative to monotonous chemical fertilizer application and C_A was increasing with the mulching years. Mulching material in winter was also observed to result a growing in water-soluble C (C_WS), one times of increase in C_WS was measured from 1-year to 5-year mulching stands and corresponding C_WS/C_T increased 0.75 folds, but unactive C (C_UA) was observed no increase. Significant relationships (P<0.01) were detected between C_T and C_A,C_WS, between C_A and C_WS, between C_T,C_A,C_WS and total N(N_T), hydrolyzable N(N_H), available-P(P_A), available-K(K_A). There was no good relationship between C_MB and C_T,C_A,C_WS,N_T, N_H, P_A, K_A.

Key words: Phyllostachys praecox, Soil total organic C, Soil microbial biomass C, Soil active C, Water-soluble C, Unactive C