DISTINCTION OF SOIL THERMAL REGIMES UNDER VARIOUS EXPERIMENTAL VEGETATION COVERS

Five vegetation treatments were established in 1.2 m x 1.2 m plots in 1990: (1) bare mineral soil, (2) Epilobium angustifolium, (3) Rubus spectabilis, (4) Alnus rubra and (5) a mixture of all three species. Soil temperatures were measured at 10-cm depths in three replicates of each treatment during the early summer of 1991. Mean, maximum and minimum temperatures always exhibited the same rank order of treatments - bare > Epilobium > Rubus > mixture > Alnus - but the latter four treatments were not readily distinguishable. A data-adjustment procedure based on Fourier analysis was conducted and its utility discussed for use in the separation of treatment effects where observations exhibit a detectable diurnal cycle. Using this method, the soil therm regime of the Epilobium treatment was demonstrated to be statistically distinct from that of the bare plots and from those of the other vegetation treatments.