Abstract
We examined reassembly of winning and losing tree species, species traits including shade and fire tolerance, and associated disturbance filters and forest ecosystem types due to rapid forest change in the Great Lakes region since 1850. We identified winning and losing species by changes in composition, distribution, and site factors between historical and current surveys in Minnesota’s mixed and broadleaf forests. In the Laurentian Mixed Forest, shade-intolerant aspen replaced shade-intolerant tamarack as the most dominant tree species. Fire-tolerant white pine and jack pine decreased, whereas shade-tolerant ashes, maples, and white cedar increased. In the Eastern Broadleaf Forest, fire-tolerant white oaks and red oaks decreased, while shade-tolerant ashes, American basswood, and maples increased. Tamarack, pines, and oaks have become restricted to sites with either wetter or sandier and drier soils due to increases in aspen and shade-tolerant, fire-sensitive species on mesic sites. The proportion of shade-tolerant species increased in both regions, but selective harvest reduced the applicability of functional groups alone to specify winners and losers. Harvest and existing forestry practices supported aspen dominance in mixed forests, although without aspen forestry and with fire suppression, mixed forests will transition to a greater composition of shade-tolerant species, converging to forests similar to broadleaf forests. A functional group framework provided a perspective of winning and losing species and traits, selective filters, and forest ecosystems that can be generalized to other regions, regardless of species identity.
Highlights
McKinney and Lockwood [1] proposed that anthropogenic disturbance and introduction of exotic species will lead to expansion in abundance and range by winning species and reduction in abundance and range by losing species
Changes in disturbance regimes create the potential for reassembly from an ecosystem type dominated by species that share a set of functional traits to a different ecosystem type dominated by species of another functional group
Compositional Change In the Laurentian Mixed Forest, tamarack decreased from the most abundant trees species to a minor component, while aspens increased to the most dominant tree species group
Summary
McKinney and Lockwood [1] proposed that anthropogenic disturbance and introduction of exotic species will lead to expansion in abundance and range by winning species and reduction in abundance and range by losing species They suggested that replacement of a diversity of losing species by a few generalist winning species will be amplified if losers share functional traits, often clustered to a common taxonomy. Just as the functional group of the most dominant species may determine function of the ecosystem type [3], attributes of the most dominant species may determine the ecosystem type. Changes in disturbance regimes create the potential for reassembly from an ecosystem type dominated by species that share a set of functional traits to a different ecosystem type dominated by species of another functional group
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