资源环境科技发展态势分析平台

Old-growth stands are considered as key components of boreal forest diversity and their preservation is largely integrated into management plans. However, while the differences between old-growth and young forests have largely been studied, little is known about the diversity of boreal old-growth forests. In managed landscapes, the efficacy of old-growth conservation plans may be reduced depending on how these old-growth forests are considered: as a single, homogeneous and steady-state forest type or as multiple, diverse and dynamic forest types. To fulfil this gap, our objectives were: (1) to create a typology of old-growth boreal structures; (2) to observe how these structures are influenced by environmental and temporal parameters; and (3) to elaborate a succession model of old-growth structural dynamics along temporal and environmental gradients. Seventy-one mature and overmature stands were sampled within a 2200 km(2) territory situated in Eastern Canada. Cluster analysis divided the sampled stands into two even-aged types, three transition old-growth types and six true old growth types. Slope, minimum time since last fire and organic horizon depth were the three environmental and temporal parameters influencing the old-growth structures. Paludification-related productivity decline was present in only one old-growth forest type, while the other sites remained productive. These results allowed the creation of three succession models of the dynamics of old-growth stands in the boreal forest of eastern Canada. Boreal stands can undergo numerous structural changes once the old-growth succession process is initiated. An increase in structural diversity when the true old-growth stage is reached, coupled with a variety of secondary disturbance characteristics, favours multiple pathways of structural evolution of these ecosystems over time. Therefore, forest management planning should incorporate this complexity to improve the preservation of old growth forests in managed territories.