| Soil carbon cycle under different land use types has recently received considerableconcern. Changes in soil labile carbon can be an indicator of soil organic carbon dynamics.Soil aggregates stability which could be influenced by soil environment, soil managementpractices and land use type can be used as an indicator of soil structural quality.Thisresearch which was based on the field investigation, sampling and laboratory analysismethod was carried out to study the imPacts of land use patterns and cultivating ages onsoil labile carbon and soil water-stable aggregates in Naban river watershed. The resultsdemonstrated that:1. Contents of Soil Total Organic Carbon (TOC), Soil Microbial Biomass Carbon（SMBC）, Dissolved Organic Carbon (DOC), Readily Oxidized Carbon (ROC) andParticulate Organic Carbon (POC) reduced significantly (P<0.05) with conversion fromnatural forest into cornfields, rice-Paddy fields and rubber Plantation in latosols conditionand latosolic red soil area.2. Content of TOC reduced significantly by29.05%,24.78%,20.08%,20.08%and34.18%resPectively, content of SMBC reduced significantly by53.44%,43.17%,66.68%,23.84%and27.25%respectively and that of DOC reduced significantly by47.24%,27.91%,71.35%and21.77%under rubber plantation which had been converted fromnatural forest for one, fiver, ten, fifteen and twenty-five years respectively, content of ROCdropped significantly by22.81%and14.35%respectively under rubber plantationreclaimed from natural forest for one and five years respectively, content of POC droppedsignificantly by29.39%,38.54%,2.20%and23.71%respectively under rubber plantationconverted from natural forest for one, five, fifteen and twenty-five years respectively inlaterite area. As compared with that of natural forest, concentration of TOC decreasedsignificantly by8.48%,7.39%and27.17%respectively and that of POC dropped significantly by14.12%,15.58%and21.08%respectively converted from natural forest forten, twenty and thirty years respectively, concentration of SMBC decreased significantlyby44.87%,46.01%,40.01%and7.98%respectively and that of DOC reducedsignificantly by31.29%,28.15%,34.07%and12.07%respectively converted from naturalforest for five, ten, twenty and thirty years respectively, concentration of ROC decreasedsignificantly by29.68%converted from natural forest for thirty years in latosols area.3. Changes in land use patterns had significant influence on the distribution of>5mm,5-2mm and2-1mm soil water-stable aggregate and water stability of soil aggregatesdecreased significantly under corn fields in latosols area. Distribution of>5mm,5-2mm,2-1mm,1-0.5mm and0.5-0.25mm of soil water-stable aggregates were affected by landuse type and water stability of soil aggregates decreased significantly under corn fields inlatosolic red soil area. Distributions of>5mm and5-2mm soil water stable aggregates weresignificantly influenced by rubber planting ages and water stability of soil aggregatesincreased with increase in rubber cultivating ages. Distributions of>5mm,2-1mm and0.5-0.25mm of soil water-stable aggregate distribution were effected by tea planting agesand soil aggregate water stability increased with increase in tea cultivating ages4. Correlation analysis showed that TOC, SMBC, ROC and POC were significantlypositively (P <0.05) related with content of5-2mm of soil water stable aggregates; TOC,SMBC and POC were significantly negatively related with content of0.5-0.25mm of soilwater stable aggregates. Contents of SMBC and DOC were extremely significantly andnegatively related to pH. The contents of TOC, ROC and POC were extremelysignificantly and negatively related to the5cm toPsoil temperature. Contents of>0.25mmsoil water stable aggregates, MWD and GMD were extremely significantly (P<0.01) andpositively related to the contents of>5mm and5~2mm soil water-stable aggregates. |
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