Coarse woody debris in late-successional Picea abies forests in northern Europe: Variability in quantities and models of decay class dynamics

Abstract

Coarse woody debris pools and their decay class dynamics were studied in three areas of unmanaged boreal forest in northern Finland, and in the Murmansk and Arkhangelsk provinces in northwestern Russia. The study areas had varying climatic and edaphic conditions, and disturbance histories. Living and dead trees (diameter at 1.3 m height ≥10 cm) were measured in five late-successional Picea abies-dominated stands in each of the three areas. Wood density and time since death were determined from randomly sampled dead P. abies, and their decay class dynamics were modeled using stage-based matrix models. Volumes and decay class distributions of coarse woody debris reflected each site's productivity and disturbance history. Volumes ranged from 41 to 170 m 3 ha −1, and as a proportion of total wood volume varied from 28% in an area with constant tree mortality, to 38% and 53% in areas with past episodic disturbances. Expected residence times (or half-lives) of snags varied from 12 to 27 years, and for down woody debris from 20 to 40 years, so that the residence times for both decreased from north to south. The results imply naturally variable quantities and residence times of coarse woody debris in late-successional European boreal forests. These data also indicate the role of a site's disturbance history as a determining factor for quantity and decay class distributions. The developed models for decay class dynamics are applicable for both assessing the habitat availability for deadwood-dependent organisms, and carbon dynamics.