Abstract
Four soils from various origins, (tropical and temperate regions) were amended with 14C labelled glucose (1mg C.g-1 soil) and incubated at 15ºC and 35ºC to determine the temperature effect on the carbon turnover and on the microbial biomass. The temperature effect on the biomass increased with the glucose addition. The biomass mineralization rates were higher at 35ºC than at 15ºC and higher for Woburn and Pegwell soils (temperate region) than for Capinopolis and Janauba (tropical region). Specific respiration rate (SRR) of new biomass (from glucose) and old biomass showed different behaviors between soils. At 15ºC, the turnover C was 207, 225, 115 and 141 days for Janauba, Capinopolis, Woburn and Pegwell soil, respectively. At 35ºC, it was 92, 69, 69 and 33 days for the same soils. The residual 14C in the soil was higher at 35ºC. The final total biomasses at 15ºC and 35ºC were correlated with the initial soil carbon content. There was an average of 31 and 8 mg of biomass C.g-1 soil organic carbon, respectively at 15ºC and 35ºC. The initial carbon content was an important factor to explain the mineralization rate at 35ºC.
Highlights
Soil microbial biomass is the living part of soil organic matter, other than living plant material and organisms greater than 500 mm3 in volume
It is well known that soil organic matter is the key to successful and sustainable productivity of soils in the tropics
Henrot & Robertson (1994), measured the biomass-C in two humid tropical soils. Both soils showed a similar pattern in total soil organic matter and biomass carbon decline following vegetation removal; after 3 yr, total C and N were reduced by 20%
Summary
Soil microbial biomass is the living part of soil organic matter, other than living plant material and organisms greater than 500 mm in volume. It is the agent of organic residue breakdown and can be considered as the. Soil organic matter affects positively structure, aggregation, cation exchange capacity, microbial activity and the water retention capacity. Henrot & Robertson (1994), measured the biomass-C in two humid tropical soils. Both soils showed a similar pattern in total soil organic matter and biomass carbon decline following vegetation removal; after 3 yr, total C and N were reduced by 20%. Our main aim in this work was to study the effects of incubation at different temperatures on the turnover time of the microbial biomass in four soils, two from temperate (i.e. United Kingdom) and two from tropical (i.e. Brazilian) climate
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