Temperature-dependent changes in the soil bacterial community in limed and unlimed soil

A humus soil with a pH(H2O) of 4.9 was limed to a pH of 7.5 and was incubated together with samples from unlimed and field limed (pH 6.1) soils at 5, 20 and 30degreesC for up to 80 days. The changes in the phospholipid fatty acid (PLFA) pattern were most rapid for the bacterial community of the soil incubated at 30degreesC, while no changes were found in the soil incubated at 5degreesC. The response of the community activity to temperature was measured using the thymidine incorporation method on bacteria extracted from the soil. The bacterial community in soil incubated at 30degreesC became more adapted to high temperature than that in soil samples incubated at 5degreesC. When soil samples incubated at 30degreesC and 20degreesC were returned to 5degreesC for 35 days, only small changes in the PLFA pattern were found. No significant shift in community temperature adaptation was found. Thus, higher temperatures (with higher turnover) led to higher rates of change in both the PLFA pattern and the activity response to temperature, compared with lower temperatures. No effect of liming as a way of increasing substrate availability and turnover on the rate of change was observed. Changes in the PLFA pattern appeared sooner than changes in the activity response to temperature, indicating that changes in the PLFA pattern were mainly due to phenotypic acclimation and not to species replacement