Transitions of pre-settlement mixed white pine-hemlock/hardwood forests in relation to environment and post-settlement land-use

Background/Question/Methods

Over the past 150 years, eastern white pine (Pinus strobus) has been lost from much of the mesic hemlock-hardwood forest of the Great Lakes region. Active restoration may be necessary to bring about the return of this species due to loss of seed source, changes in disturbance regimes, and pressure from browsing, pathogens, and hardwood competition. We surveyed 201 US public land survey (PLS) section and quarter-section corners in two districts of the Chequamegon-Nicolet National Forest (CNNF) at which white pine was present in pre-settlement forests. Specific objectives were: 1) to investigate site characteristics and present-day forest composition at locations in which white pine was present in the pre-settlement forest and 2) to relate transitions in forest composition and structure to landscape factors, pre-settlement forest composition, and post-settlement land-use. We replicated surveyor witness tree sampling methods at each location and also installed nested circular plots to inventory tree species up to a radius of 100m.

Results/Conclusions

In the Medford district, we found that white pine was retained on only 7.2% of locations that had white pine present in the pre-settlement forest. In the Eagle River/Florence (ERF) district, white pine was retained on 15.3% of locations. At these pre-settlement pine locations, the relative importance rank of white pine declined from 1^st to 6^th in the ERF landscape, and even more drastically, from 1^st to 15^th, in the Medford landscape. At Medford, the primary shifts in forest composition at areas that once supported white pine were toward domination by aspens (Populus sp.; unranked in presettlement to 3^rd in present-day) and both red maple (Acer rubrum; 9^th to 1^st) and sugar maple (Acer saccharum; 10^th to 2^nd). In the ERF landscape, a similar pattern was seen as both red maple (unranked to 4^th) and aspen (11^th to 3^rd) increased strongly in their rankings and sugar maple (2^nd to 1^st) became highly dominant. While these results are consistent with overall patterns seen in large-scale investigations of forest change in this region, we highlight specific changes associated with a forest type that is of interest to many land-managers. Additional results illustrate shifts in forest composition and structure in relation to environmental characteristics of the landscape and post-settlement land-use patterns.