Soil organic matter (SOM) in forest ecosystems is not only important to global carbon (C) storage but also to sustainable management of forestland with vegetation types, being a critical factor in controlling the quantity and dynamics of SOM. In this field experiment soil plots with three replicates were selected from three forest vegetation types: broadleaf, Masson pine (Pinus massoniana Lamb.), and Chinese fir (Cunninghamia lanceolata Hook.). Soil total organic C (TOC), two easily oxidizable C levels (EOC1 and EOC2, which were oxidized by 66.7 mmol L-1 K_2Cr_2O_7 at 130-140℃and 333 mmol L-1 KMnO4 at 25℃, respectively), microbial biomass C (MBC), and water-soluble organic C (WSOC) were analyzed for soil samples. Soil under the broadleaf forest stored significantly higher TOC (P (?) 0.05). Because of its significantly larger total soil C storage, the soil under the broadleaf forest usually had significantly higher levels (P (?) 0.05) of the different labile organic carbons, EOC1, EOC2, MBC, and WSOC; but when calculated as a percentage of TOC each labile C fraction of the broadleaf forest was significantly lower (P (?)0.05) than one of the other two forests. Under all the three vegetation types temperature as well as quality and season of litter input generally affected the dynamics of different organic C fractions in soils, with EOC1, EOC2, and MBC increasing closely following increase in temperature, whereas WSOC showed an opposite trend.
The concentrations of N, P, K, Ca and Mg in different organs of Phyllostachys pubescens with in sequence of age and the amount of soil nutrients were analyzed. The results showed that the content of four nutrition elements(N, P, Ca, Mg) in different organs were in the order as: leaf > branch > stem; while for K: leaf >stem >branch. The abundance of different elements in leaf, in branch and in stem respectively ranged as: N>K>Mg>P>Ca, K>N>Mg>P>Ca and K>N>Mg>Ca>P. The nutrition elements in various organs of P. pubescens were interrelated one another at some extent, significant( P <0 05) or great significant correlation ( P <0 01)existed between eleven pairs nutrient elements contents out of total thirty pairs of nutrient elements. The productivity of the woods in on_year was much higher than that in off_year, while the content of N, P and K in leaf was much higher in off_year. The nutrition in bamboo were generally correlated to nutrients of soils, eg, nitrogen content in leaf had a significant relationship with organic matter, total nitrogen, available nitrogen and available potassium in soil, phosphorus content in leaf had a strong relationship with organic matter and available nitrogen in soil, however, only good relationships in stem were found between nitrogen content and organic matter, available potassium in soil. Potassium content in branch were negatively correlated to organic matter, total nitrogen and available nitrogen in soil.
Soil samples for conventional management (CM) and intensive management (IM) practices were taken over a year at 2-month intervals to determine the effect of management practices on soil organic carbon (SOC) and to quantify seasonal dynamics in SOC for bamboo (Phyllostachys pubescens Mazel ex H. de Lehaie) stands. The results with IM compared to CM showed large decreases in total organic carbon (TOC), microbial biomass carbon (MBC), water-soluble organic carbon (WSOC), and the MBC/TOC ratio in the soils. With all IM plots in the 0-20 cm depth across sampling periods, average decreases compared with CM were: TOC, 12.1%; MBC, 26.1%; WSOC, 29.3%; the MBC/TOC ratio, 16.1%; and the WSOC/TOC ratio, 20.0%. Due to seasonal changes of climate, seasonal variations were observed in MBC and WSOC. Soil MBC in the 0-20 cm depth in September compared to May were 122.9% greater for CM and 57.6% greater for IM. However, due primarily to soil temperature, soil MBC was higher during the July to November period, whereas because of soil moisture, WSOC was lower in July and January. This study revealed that intensive management in bamboo plantations depleted the soil C pool; therefore, soil quality with IM should be improved through application of organic manures.
Soils under broad-leaved,masson pine,Chinese fir and bamboo forests in the area of Huzhou,Zhejiang were collected and analyzed in January 2000.Soil total organic carbon(TOC) under broad-leaved and bamboo forests were considerately higher than(P<0.01)those under masson pine and Chinese fir.There was no significant differences in microbial biomass carbon(MBC) in soils among various types of vegetation,however,the bamboo stands constituted a lower(P<0.05) proportion of MBC compared with broad-leaved forest,masson pine and Chinese fir were similar in MBC to TOC,indicating that intensive management in bamboo stand reduced the proportion of soil MBC in TOC.MBC in soils under broad-leaved forest,masson pine forest and Chinese fir forest had strong positive relationships with the corresponding TOCs,the correlation coefficients were respective 0.744 4,0.648 4 and 0.552 1.It was found that soil easily oxidizable carbon(EOC) in bamboo forest was much higher than those in the other 3 forests.The higher percentages of EOC were detected from soils under bamboo forest(52.40%) and Chinese fir forest(50.50%) compared with broad-leaved forest(48.90%) and masson pine forest(45.74%).Soil EOC for all 4 forests were closely correlated(P<0.01)with the correspondent TOCs.
