Soil CO2 exchange in seven pristine Amazonian rain forest sites in relation to soil temperature

•Soil CO2 efflux measured in seven pristine Amazon rain forest sites.•Mean soil respiration depends on soil type, texture and moisture.•The respiration-temperature time-lags differ between the sites.•Time-lags are often minimal if surface temperature is used.•The longest time-lags occur for the slowest-growing vegetation. We analysed soil respiration measurements made in seven distinctly different pristine rain forests in Central Amazon, ranging from stunted heath forest (Campina) to tall terra-firme rain forest. The differences in soil respiration fluxes between sites and their causes were investigated, as well as diurnal patterns and their dependency on temperature. Ensemble averages of hourly fluxes were calculated for both wet and dry seasons (as far as these were sampled). These values were processed using an analytical model estimating soil surface temperature from the temperature measured at two depths. The soil CO2 efflux can be viewed as a proxy for forest productivity. The low productive Campina stunted heath forest site (on leached sandy soils and covered by scleromorphic vegetation) has the lowest respiration (