2007 Summaries of Wildlife Research Findings - Minnesota State ...

Of particular importance as a source of forest disturbance are insects, whose geographic
ranges are largely determined by temperature. Short generation times and high reproductive
rates result in rapid responses by insects to changing conditions, more rapid than those of their
slow-growing tree hosts (Logan et al. 2003). Thus, insects will likely expand into forest
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communities that have previously been outside their range. This may disrupt the synchrony and
associations between forest plant communities and forest pests that have formed over long
periods of time, which may cause infestations to become persistent rather than episodic (USGAO
2007). Adverse effects of insects or other forest pests can appear suddenly, occurring when a
temperature limit or other climatic threshold is passed and can include changes out of proportion
to the relatively small climatic change that induced the effect.
3.2.1.1.1. Coniferous forests
Coniferous forests in Minnesota occur almost exclusively in the Laurentian Mixed Forest
Province. Dominant conifer species in the province include white, jack, and red pines in
uplands, where fire was the main historical disturbance, and black spruce, tamarack, and white
cedar in lowlands, where small-scale blowdown was the main historical disturbance (MNDNR
2006).
Changes in plant species abundance and distribution will depend on species dispersal
ability and moisture regimes, which are determined not only by precipitation but also by
temperature, topography, evapotranspiration, and soils. Fire dependent forest systems (many
pine types) will be particularly sensitive to a change in moisture regimes that result in wetter
conditions and less frequent or less intense fires. If this scenario is realized, fire dependent forest
systems will become less abundant in the Laurentian Mixed Forest Province. Mesic hardwood
systems (e.g., red oak-sugar maple types) would likely experience a range expansion. Generally,
a shift northward for spruce-fir forests is predicted (Hansen et al. 2003, Iverson and Prasad
2001). Tree species associated with lowland coniferous forests are predicted to decline in
abundance and may convert to lowland hardwood forests (Hogg and Hurdle 1995). New
combinations of plant and animal communities should be anticipated as species’ ranges
(described here primarily as tree species) shift. It is likely that global warming will cause the
southern boundary of the near-boreal forest to migrate northward out of Minnesota.