Carbon dioxide production and oxygen consumption during the early decomposition of different litter types over a range of temperatures in soil-inoculated quartz sand

Abstract

Oat straw, hay, and alfalfa litter, differing in microbial colonization and recalcitrance, were added to organic matter-free quartz sand (5 mg C [g material]-1) and incubated in the laboratory at 5°C, 10°C, 15°C, 20°C, and 25°C. Different incubation periods were chosen so that theoretically the same amounts of CO2 would be produced and the same amounts of O2 would be consumed for each litter type. It was investigated whether Q10 values (change in respiration rate between two temperatures) increase with decreasing temperature and how much these Q10 values and also the respiratory quotient (RQ: mol CO2/mol O2) depend on the litter type. The sums of CO2- C evolved and O2 consumed, but also the contents of microbial biomass C and microbial biomass N showed a nearly 7-fold increase in the order oat straw < hay < alfalfa litter. In contrast, the ratio of the fungal cell-membrane component ergosterol to microbial biomass C was highest in the oat straw (4.1‰) and lowest in the alfalfa litter (0.2‰). This ratio reached a similar level between 5°C and 15°C (1.9‰), significantly higher (p = 0.01) than the level at 20°C (0.9‰). Respiration was similar between 20°C and 25°C, with a mean Q10 value of 1.9. The use of temperature rate-modifying factors suggested by the carbon-turnover model ROTHC revealed that the incubation period for similar respiration rates was underestimated at 5°C and overestimated at 25°C. The lignin-poor and protein-rich alfalfa litter showed the highest Q10 values of the three litter types in the medium temperature range of 10°C to 20°C. In contrast, the lignin-rich and protein-poor oat straw showed significantly highest Q10 values at 5°C and 25°C in comparison with the other two litter types. The RQ was significantly highest in the hay litter (1.05) and in comparison with alfalfa litter (0.97) and oat straw (0.92). Strong temperature-dependent variations in Q10 values and respiratory quotients suggest interactions between litter quality, microbial colonization of litter, and temperature, which warrants further investigation. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.