The characterization and estimation of soil temperatures in Manitoba

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Krpan, John Daniel Brian.
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Soil temperatures at the 2.5, 5, 10, 20, 50, 100, and 150 cm soil depths have been recorded for up to ten years throughout Manitoba. A best fitting sine wave (as a function of the time of year) was utilized to represent the data for each depth and each soil site. In general the coorelation between observed data and the best fitting curve was very good < R2 > 0.80 in most cases) and correlation coefficients improved with depth. Based on the best fitting sine waves, mean annual and mean summer soil temperature, frost free days, days above 5 and 15C, and degree days above 5 and 15C were calculated. This data was graphically illustrated with the aid of a computer mapping program (Symap) which plotted isolines connecting points of equal value. The symaps provided a good summary of the distribution of soil temperatures across the province and the change in soil temperature with elevation, latitude, drainage and genetic soil type. Warmest soil temperatures at all depths occur in fine and coarse textured Chernozemic Black soils in south central Manitoba. Cooler soils at the same latitude (50 degrees north) are associated with Luvisolic and Organic soils in eastern Manitoba, and in elevated regions west of the Manitoba Escarpment. In general, soil temperatures decrease with soil depth and poorly drained soils are cooler throughout the year...