Influence of logging, fire, and forest type on biodiversity and productivity in southern boreal forests

The effects of logging on ecosystem sustainability are controversial. Surpr isingly, existing data are inadequate to allow a comprehensive evaluation o f logging effects on biodiversity, composition, and productivity since appr opriate comparisons of stands of similar ages and differing disturbance his tories are rare. We addressed this issue using a study of 2000 plots in 80 southern boreal forest stands in northern Minnesota, USA, wherein we contra sted naturally regenerated aspen (Populus tremuloides), jack pine (Pinus ba nksiana), and black spruce (Picea mariana) stands established following log ging or the dominant natural disturbance, wildfire, for stands of two age c lasses (25-40 and 70-100 yr old). For young stands, those established postl ogging had higher vascular plant diversity than those postwildfire. Otherwi se, we found no evidence of differing species diversity (including canopy t ree, shrub, herbaceous, and bryophyte species), composition, productivity, or nitrogen cycling, in forest stands of comparable age and forest type tha t originated after logging compared to after wildfire. These variables, how ever, differed significantly among forest types, with aboveground net prima ry productivity and plant species diversity generally higher in aspen than jack pine stands, even when growing on comparable soils, and lowest in blac k spruce. Although there is evidence that logging has increased the proport ional landscape dominance by aspen, a forest type with higher diversity, nu trient cycling, and productivity than other types, our evidence refutes the idea that disturbance by logging has diminished stand-scale productivity o r plant diversity in comparison to the common natural disturbance, wildfire .