Evaluation of planting sites common to a southeast Alaska clear-cut. III. Effects of microsite type and ectomycorrhizal inoculation on growth and survival of Sitka spruce seedlings

Abstract

Hebelomacrustuliniforme (Bull. ex St. Amans) Quel., Laccarialaccata (Scoop. ex Fr.) Berk and Br., and Cenococcumgeophilum (L. ex Fr.) Pers. ex Hooker were established as ectomycorrhizae on container-grown Sitka spruce seedlings. These seedlings and noninoculated controls were planted in rotten wood, exposed mineral soil, undisturbed duff, and undisturbed duff on the north side of large stumps on one clear-cut site in southeast Alaska. At planting, seedling heights differed significantly among fungal treatments: the tallest were those inoculated with C. geophilum, the shortest with H. crustuliniforme. Some height differences persisted after planting, but 3-year height and diameter increments did not differ significantly among fungal treatments and controls. As a percentage of their initial height, seedlings inoculated with L. laccata increased the least in size after 3 years (70%), significantly less than for seedlings with H. crustuliniforme (126%). All test fungi survived for 2 years, but most seedlings were further colonized by one or more on-site ectomycorrhizal fungi, frequently C. geophilum. Regardless of fungal treatment, seedlings in rotten wood had the least percentage increase in height after 3 years (69%), significantly less than the 121% increase for seedlings in undisturbed duff on the north side of stumps. Seedling survival after 3 years was over 92% and did not differ by microsite or fungal treatment. At another clear-cut site, survival of noninoculated seedlings after 3 years was 86% in exposed mineral soil, significantly less than the 98% on all other microsites. Frost heave was the primary cause of mortality. These data suggest that prior colonization by these ectomycorrhizal fungi provides little survival or growth benefit after out planting Sitka spruce seedlings on various microsites in southeast Alaskan clear-cuts. Some improvement in early height growth and survival may be obtained, however, by planting in undisturbed duff, particularly near stumps, and by avoiding exposed mineral soil.