Patterns of initial versus delayed regeneration of white spruce in boreal mixedwood succession

The timing of white spruce regeneration in aspen (Populus tremuloides Michx.) – white spruce (Picea glauca (Moench) Voss) boreal mixedwood stands is an important factor in stand development. We examined boreal mixedwood stands representing a 59-year period of time since fire and determined (1) whether and when a delayed regeneration period of white spruce occurred, (2) whether the relative abundance of initial (<20 years) versus delayed (≥20 years postfire) regeneration is related to seed availability at the time of the fire, and (3) what are the important regeneration substrates for initial versus delayed regeneration. Initial regeneration occurred primarily on mineral soil or humus, while delayed regeneration established primarily on logs and peaked 38–44 years after fire. Of the 20 stands investigated, seven were dominated by initial regeneration, six were dominated by delayed regeneration, and seven were even mixtures of both. The dominance of a site by initial or delayed regeneration could not be simply explained by burn timing relative to mast years or distance to seed source; our results suggested that fire severity and the competitive influence of initial regeneration on delayed regeneration were important at fine scales. Based on our results we describe several possible postfire successional pathways for boreal mixedwood forests.

Mapping conifer understory within boreal mixedwoods from Landsat TM satellite imagery and forest inventory information

Information about conifer understory within deciduous-dominated mixed-wood stands would increase the possible range of management options for these complex communities, yet cost-effective and accurate inventory methods remain elusive. Maps of conifer understory produced from field-checked photo interpretation were compared with classified images created from Landsat Thematic Mapper data and two image classifiers. The highest accuracy achieved was 71% using an evidential reasoning classifier that integrated satellite remote sensing observations with stand inventory information. The image map did provide an advantage by capturing some of the spatial variability of conifer understory that is not captured by photo interpretation methods. Predicting the presence and spatial distribution of conifer understory is difficult because its establishment is influenced by many factors such as ecosite, available substrate, distance to seed source and mechanisms of recruitment that are not typically available in spatial formats. The image maps are considered estimates that may be suitable for broad strategic planning, and may serve as validation information for national satellite land cover mapping initiatives. Keywords: boreal mixedwood, conifer understory, image classification, Landsat TM, reflectance, forest inventory, vegetation index