Stand age structures of single and mixed-species of fire-origin boreal stands in central Canada

Keywords : biodiversity, bimodal, boreal forest, cover type, developmental stage, old-growth, reverse-J, stand age structure, time since fire, wildlife habital, [disturbances, spruce budworm, wind, harvesting, logging].Stand age structure has been linked to wildlife habitat and can affect biodiversity. Further, certain stand age structures (such as those associated with old-growth) are valuable from an aesthetic and fiber supply perspective. A review and synthesis of literature indicated that boreal forest stand age structure is influenced by time since stand replacing fire, stand composition, and disturbances such as spruce budworm (Choristoneura fumiferana) and wind. Silvicultural options and implications for managing age structure at the stand and landscape level are discussed. My objectives were to examine how stand age structure changes among stand developmental stages and stand cover types. I sampled living trees in 32 stands representing typical conifer, mixedwood, and hardwood stand types in the central boreal forest region o f North America representing the stem exclusion/canopy transition, canopy transition, canopy transition/gap dynamic, and gap dynamic stages o f stand development. Using a 400 m2 plot in each stand as the sampling unit, the diameter at breast height (DBH) o f all canopy trees (DBH >10 cm) was measured. Five canopy trees in each diameter class ((1) 10-14.9 cm, (2) 15-19.9 cm, (3) 20-24.9 cm, (4) 25-29.9 cm, and (5) > 30 cm) for each species were randomly selected, and the height o f each tree was measured and an increment core was taken and aged. Three circular 25 m subplots were then randomly established within each 400m plot and the diameter at root collar and height of all seedlings and saplings (DBH