Forest Floor Volume and Litter Decomposition Dynamics in Mid-Boreal Spruce Stands on Albic Stagnosols

The study was carried out in the Kivach Nature Reserve (62°17′ N, 33°58′ E) from September 2019 to October 2022 in the mature middle-taiga spruce forests on Albic Stagnosols developed from varved clays. The dynamics of litter decomposition was estimated by the litterbags method. The samples of ten different litter fractions were studied: needles, leaves, bark of the dominant tree species ( Picea abies , Populus tremula , Betula pendula ), and leaves of a subshrub ( Vaccinium myrtillus ). The sample mass loss and changes in chemical composition of the plant material were analyzed over 9, 14, 28, and 38 months of the experiment. The impact of different factors on the litter decay rate was studied, taking into account its volume, diversity, and quality. We estimated the rates of litter input and decay, as well as the forest floor turnover rate in relation to the parcella (unit of the biogeocenosis horizontal structure) heterogeneity. Forest floor volumes varied among zones of the tree phytogenic field from 26 to 108 t/ha. The forest floor turnover period was between 13–14 and 34 years in the spruce forest studied.