Availability and Structure of Coarse Woody Debris in Hemiboreal Mature to Old-Growth Aspen Stands and Its Implications for Forest Carbon Pool

European aspen deadwood is extensively studied as a habitat for saproxylic species, while less is known of its dynamics and role in carbon sequestration. We studied unmanaged mature (41-60 years), moderately overmature (61-80 years), overmature (81-100 years), and old-growth (101-140 years) and managed mature and moderately overmature aspen stands on fertile mineral soils. In unmanaged stands, marginal mean CWD volume was from 67.3 +/- 12.1 m(3) ha(-1) in moderately overmature to 92.4 +/- 5.1 m(3) ha(-1) in old-growth stands, with corresponding marginal mean CWD carbon pool 8.2 +/- 1.6 t ha(-1) and 12.5 +/- 0.7 t ha(-1) (all p > 0.05), respectively. High CWD volume was present in most stands, by at least two-thirds of plots comprising more than 20 m(3) ha(-1), and about half of CWD was larger than 30 cm in diameter. Changes in CWD species composition toward a higher proportion of deciduous deadwood in old-growth stands, together with a high volume of recently dead trees, suggest early senescence of the dominant aspen cohort.