CANOPY TYPE, FOREST FLOOR, PREDATION, AND COMPETITION INFLUENCE CONIFER SEEDLING EMERGENCE AND EARLY SURVIVAL IN 2 MINNESOTA CONIFER-DECIDUOUS FORESTS

There is concern that the conifer component of mixed conifer-deciduous forests in the Great Lakes region is on the decline, possibly the res ult of insufficient conifer regeneration. Limitations on conifer regen eration that occur during the first 18 months of seedling emergence an d establishment were examined for Abies balsamea (L.) Mill. and Pinus strobus L. in two mixed conifer-deciduous forest types in northeastern Minnesota. We hypothesized that the removal of potential barriers to regeneration, including forest floor, seed predation, and competition with understory vegetation, will enhance conifer regeneration. We also hypothesized that the importance of the above regeneration barriers, and early regeneration success of each species, will differ beneath de ciduous and conifer canopy types. The study was conducted under conife r and deciduous canopy types for two sites of each forest type: Abies balsamea - Populus tremuloides Michx, forest and Thuja occidentalis L. - Betula papyrifera Marsh. Germination experiments were conducted wit h seeds of A. balsamea and P. strobus. Experimental treatments include d forest floor removal, caging to exclude seed predators and herbivory , and weeding to study the effects of understory competition. Abies ba lsamea and P, strobus responded differently to experimental treatments at different developmental stages. The best conditions for early rege neration of both A. balsamea and P, strobus included reduction of seed predation (p < 0.0001) and competition with understory vegetation (p less than or equal to 0.001). Abies balsamea additionally benefited fr om a conifer overstory (p < 0.0001) and a reduction in thickness of th e forest floor (p < 0.01).