Classification of meteorological conditions to assess the potential for concrete frost formation in boreal forest floors

Abstract

During spring 1990, 76% of the Lac Laflamme watershed (47∞N, 71∞W), Canada, was covered with substantial amounts of concrete frost in the boreal forest floors (litter, organic layer). Spatial distribution of concrete frost on the watershed was associated with forest floor composition. The objective of this note is to assess the potential for concrete frost formation in the forest floor by classification of different meteorological conditions and to verify if the type of meteorological combination encountered during 1989n1990 was exceptional. Meteorological records at the Montmorency Forest station for air temperature and precipitation from 1965 to 1990 were analyzed and classified to detect events potentially favourable for the development of concrete frost. Each year was divided into two seasons: snow accumulation and spring snowmelt. When we considered together the accumulation and the snowmelt seasons, 21 years showed one or more events susceptible to initiate concrete ice formation. Four of 25 years had meteorological conditions harsher than the accumulation season of 1989n1990. If the meteorological conditions permitting the formation of concrete frost in the forest floor are not exceptional, then we can hypothesize that the formation of concrete frost is not exceptional as well. Resume : Durant le printemps 1990, 76% du bassin du lac Laflamme (47∞N, 71∞W), Canada, Otait recouvert de quantitOs importantes de glace compacte dans ses litires forestires. La distribution spatiale de cette glace Otait associOe ‡ la