The ecology of testate amoebae (Protozoa:Rhizopoda) in oceanic peatlands in Newfoundland, Canada: Modelling hydrological relationships for palaeoenvironmental reconstruction

Abstract

:The improvement of soil conditions by water table lowering through drainage is indicative of the potential for tree growth response to this treatment. We measured water table level, peat water content and temperature, and rates of decomposition of Sphagnum peat, cellulose and wood sticks in a black spruce (Picea mariana [Mill.] BSP.) peatland of eastern Québec, on a control site and a drained site. In general, the water table was lowered within 15 m of the ditches, resulting in a marked difference between spacings of 20-30 m and 40-50-60 m. In the middle of the 40-m spacing, the frequencies of lowering below the root zone (20 cm) and the 30-cm depth were respectively increased by 33% and 40%. Peat water content at 10-cm depth decreased by 20% to 29% following drainage and the effect appeared related to ditch closeness. At 20- and 30-cm depths, decreases of the same order were observed only at 5 m from the ditch. At distances of 10 m and more, the average water content remained within 10% of saturation at 20 cm and within 5% at 30 cm. After drainage, the seasonal maximum temperature at the 10-cm depth increased by 3.5°C at 5 m from the ditch and by 1.5°C at greater distances, com-pared to the control where the mean seasonal maximum was 13.5°C. At all distances, the autumnal cooling of the substrate was accelerated and winter temperature was 1 to 2°C less than the control site. Temperature at 30-cm depth was not modified by drainage. Rates of decomposition were accelerated, mainly at the 30-cm depth and within the first 10 m from the ditch. At 10-cm depth, decomposition was weakly related to drainage and it is possible that relatively low water contents countered the effect of temperature increase.