Decomposition of pure and mixed foliage litter in a young lodgepole pine – Sitka alder stand in the central interior of British Columbia

Abstract

A 7-year litterbag experiment examined mass loss dynamics of Sitka alder ( Alnus viridis (Chaix) DC. subsp. sinuata (Regel) A. Löve & D. Löve) and lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm. ex S. Watson) foliage litter in a young stand dominated by these species in the Sub-Boreal Spruce biogeoclimatic zone of central British Columbia. Although mass loss was initially faster for alder litter, the amounts of mass remaining for alder, pine, and mixed pine–alder (50:50 by mass) litter began to converge after 2 years. Mass loss by the mixed litter differed significantly from that predicted from the behaviour of its pure components, but the mechanisms responsible could not be determined from this experiment. Limit values for the projected maximum extent of mass loss ranged from 63.5% (alder) to 76.9% (pine), with the latter value considerably below estimates reported for lodgepole pine in Scandinavia. Despite these differing limit values, forest floor mass measurements prior to the experiment did not show significantly higher organic matter accumulations under long-established alder clumps on this site.