Growth and root morphology of planted and naturally-regenerated Douglas fir and Lodgepole pine

Abstract

Summary — Root system morphology and growth of Douglas fir (Pseudotsuga menziesii var glauca (Beissn) Franco) and Lodgepole pine (Pinus contorta var latifolia Engelm) saplings transplanted from containers to the field in 1979 were compared with naturally-regenerated saplings of the same species and age. Naturally-regenerated saplings of both species were significantly taller than planted trees, had greater leader growth in the previous year and height/diameter ratios, and smaller taproot diameters 10 cm below groundline. Naturally-regenerated saplings also had up to 2.3-fold the number of lateral roots compared with planted saplings. Seventy to 79% of all primary lateral roots of naturally-regenerated saplings occurred within the top 10 cm of the soil surface, compared with 3042% for the planted trees. The depth of the first structural lateral root associated with naturallyregenerated saplings was also significantly less than that of planted saplings. The shape of the container in which seedlings were raised in the nursery was clearly evident when root system architecture of planted saplings was examined. Many container-initiated seedling root systems exhibited conical shaping with little lateral root egress. A variety of root deformities which included constriction, coiling and kinkiness were detected in planted, but not naturally-regenerated saplings. These results are discussed in relation to potential difficulties arising from artificial forest regeneration with pine and Douglas fir.