| Soil labile organic carbon(LOC) refers to the fractions of organic carbons that are easy to move and to be oxidized and mineralized, and they are quite available to plant and soil microorganisms. Soil water-soluble organic carbon(WSOC), microbial biomass carbon(MBC), and easily oxidisable organic carbon (EOC) are considered to be the useful indicators of LOC. Soil labile organic carbon is involved in all biological and biochemical processes in soil, the minor change of LOC can be detected before the content of total organic carbon(TOC) in soil has changed, although it accounts for small fraction of TOC. The types of vegetation influence the size and quality of soil organic matterr. The spatia-temporal of soil LOC pool under various types of vegetation as affected by human practice is necessary for assessing the alteration of soil quality. In this paper, 4 types of vegetation(broad-leaved , masson pine, Chinese fir and phyllostachy pubescens), which are widely distributed in subtropical area of southern China, were selected to investigate cotent and spatia-temporal, characteristic of WSOC. Two kinds of bamboo {phyllostachy pubescens and Phyllostachys Praecox) were used to test the effects of intensive management on soil LOC. The results were summaried as follows1. Field investigation showed that TOC in soils under broad-leaved and phyllostachy pubescens stand was considerately higher than under masson pine and Chinese fir(P<0.01). The content of soil WSOC follow as the order of phyllostachy pubescens >broad-leaved> Chinese fir > masson pine stand. There were great significant differences between phyllostachy pubescens and masson pine stand, (P<0.01) the significant differences were observed between broad-leaved and masson pine stand(P<0.05), between phyllostachy pubescens and Chinese fir stand, and between Chinese fir and masson pine stand. The soils under broad-leaved stands contained a larger proportion of WSOC to organic carbon (OC), but the soils under masson pine stands contained the lowest proportion of WSOC. A significantly positive correlation was found between TOC and WSOC extraction at 100℃ in masson pine stands (0.5106*), between TOC and WSOC extraction at 25℃ in Chinese fir stand (0.4739*) and between TOC and WSOC extraction at 25℃ in phyllostachy pubescens stand(0.4752*). The order of soil MBC was broad-leaved > masson pine> phyllostachy pubescens > Chinese fir stand. Soils under phyllostachy pubescens stand had a lower (P<0.05) proportion of MBC than under broad-leaved, masson pine and Chinese fir. Soil MBC was possitively related to TOC under different types of vegetation, the correlation coefficients were 0.7444**, 0.6484** and 0.5521* under broad-leaved stand, masson pine stand and Chinese fir stand respectively. The easily oxidisable carbon (EOCl)by permanganate in phyllostachy pubescens stand was much higher than that in the other three tands. The higher percentages of EOC exisited in soils under phyllostachy pubescens stand and Chinese fir stand than under broad-leaved stand and masson pine stand. Soil EOC under all four stands were also closely correlated (P<0.01)with TOC, the correlation coefficients were 0.8658** for broad-leaved stand,0.8525** for masson pine, 0.8767** for Chinese fir and 0.8604** phyllostachy pubescens stand.2. Soil EOC1 under broad-leaved stand increased gradually with temperature and reached the maximun in July and September. A more flat curve of soil EOC1 was observed in masson pine stand with a peak in July. The peak of soil EOC1 for Chinese fir occurred in May, the much higher percentage of EOC 1 to TOC wereobserved in March and July,. There was a similar dynamic pattern of WSOC for all three stands , in which higher WSOC was found in cold season and lower in warmer season. The MBC was obseved higher in warmer season, the peak under broad-leaved stand occurred in July, under masson pine stand in March and under Chinese fir stand in May respectively. Soil EOC1 was negatively correlated to WSOC under broad-leaved stand (r=-0.8663*)and positively...
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