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Some factors affecting the survival of planted Douglas-fir seedlings in the coastal forests of British Columbia Addison, John Walker

Abstract

A comprehensive literature review of the factors affecting the survival of planted Douglas-fir seedlings is presented. Original data from operational planting trials was analyzed to determine the effect of some seedling, planting and environmental factors on survival. The use of 2+1 stock was found to result in increased survival of fall-planted seedlings, but not of spring planted seedlings. 1+0 stock showed comparatively good survival when spring-planted on sites with little brush and/or slash competition. The size of planting stock, and a subjective assessment of grade were not found to be related to survival after one growing season. Fall lifting dates from October 15 to December 2 were analyzed in relation to survival using regression analysis. Early-lifted stock was found to result in lower survival than the later-lifted stock. Lifting date had no significant effect on the survival of spring-planted seedlings. Planting dates from February 10 to June 10 in the spring and from October 14 to December 2 in the fall were analyzed in relation to survival using regression analysis. Survival was found to be significantly improved with later fall planting dates and early spring planting dates. Length of storage had no detectable influence on survival. The nursery origin of the seedlings was found to be significantly related to survival. Where ground cover competition was severe, slash-burning resulted in increased survival; where ground cover competition was light or non-existent, slashburning resulted in reduced survival. Heavy ground cover competition reduced the survival of both spring and fall-planted seedlings, except on north to east aspects. Elevation and aspect of the planting site were both found to be significantly related to survival. Planting in thick duff reduced the survival of spring and fall-planted seedlings. The survival of fall-planted seedlings was also reduced by planting in rolling topography, and on steep south to west aspects. Planting during sunny weather resulted in reduced survival. Planting during snowy weather reduced the survival of fall-planted seedlings only. Some genetic factors, such as origin of the seed, seed classification, and aspect and elevation of the seed collection areas compared to that of the plantation were analyzed in relation to survival with inconclusive results. The author concludes that no one factor is of overriding importance in all situations, but that all factors act and interact to varying degrees. Therefore in most cases it is very difficult to assign a specific reason for mortality. It is important that the relative importance of each factor under different sets of conditions be known. The key to better survival, therefore, is planning and forethought, to ensure that as few factors as possible are limiting to survival at any one time. Based on the data analyzed, some specific recommendations for improving the survival of planted Douglas-fir seedlings are presented.

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