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Highlights • Oak sprouts were most successful in pine stands with 25% canopy cover. • As implemented, the two prescribed fires did not benefit oak regeneration. • Browsing, frosts, and red maple competition synergistically limited oak success. Abstract Overstory and understory treatments were established in natural oak stands and red pine plantations in Michigan in 1991 to test the hypotheses that (1) oak seedling survival and growth would be greater in pine than oak stands and (2) removal of competitors would enhance oak seedling performance. Late spring prescribed fires were implemented in 2002 and 2008 to investigate their effectiveness in controlling understory red maple. Performance of planted northern red oaks has been monitored since 1991 and the abundance of naturally regenerating oak and red maple seedlings and sprouts in different size classes has been documented since 2001. A subset of oaks has been protected against deer browsing since planting. Results suggest partial competitor removal enhances oak seedling and sprout performance, whereas complete removal increases mortality from browsing and frost. Increases in red maple abundance and decreases in oak abundance were documented after the prescribed fires in 2015. Greater growth and survival of planted oaks was observed in the pine stands, provided they were protected from browsing. Based on these results, the most viable management scenario for maximizing survival and growth of oak seedlings and sprouts in the study region would include protecting oak seedlings from deer in 25% canopy cover shelterwoods in pine plantations. Opportunities exist for developing systems involving alternating rotations and mixtures of oak and pine. [ABSTRACT FROM AUTHOR]

Abstract: Red pine (Pinus resinosa Ait.) was the most abundant species in the overstory on intermediate-quality sites in north central Lower Michigan prior to the lumbering era of the late 1800s. Northern red oak (Quercus rubra L.) stands that replaced portions of the presettlement pinery are maturing. However, these sites are not returning to the former species composition due to greater abundance of red maple (Acer rubrum L.) and white pine (Pinus strobus L.) and a lack of oak and red pine regeneration. Our primary objective was to compare the effects of pine and oak cover types on natural oak and red maple regeneration. We measured oak and red maple regeneration in 2001, 10 years after initial application of canopy cover and understory treatments in natural oak stands and red pine plantations on comparable sites. Oak shelterwoods harvested to 25% canopy cover contained significantly more oak seedlings (∼60cm height) than all other treatments, a majority of which were located in understory treatment plots, where red maple regeneration was mechanically removed. In agreement with other research in oak-dominated stands, these results suggest that light shelterwoods with understory control may be the most viable means of recruiting oaks. Lack of oak regeneration that was progressing toward the canopy in the oak stands compared to the pine stands suggested that, even with understory control after shelterwood cutting, oak may not compete as well in the understory of oak as in pine stands. In contrast, red maple dominated the understory of oak stands, but exhibited poor development and was significantly less abundant in the pine stands. Oak regeneration was also less dense in the pine stands, but free to grow. Factors in the red pine plantations studied, such as increased litter depth, few seed sources, and decreased availability of soil moisture and nitrogen are likely to have reduced the germination and competitive ability of understory red maple stems, thereby benefiting the growth of oak seedlings having lesser shade tolerance. The differential success of oak and red maple regeneration observed in the red pine stands on intermediate-quality sites has led us to suggest that restoration of beneficial oak and pine interactions and a shift in focus from regenerating oak beneath oak to regenerating oak beneath pine may be warranted. [Copyright &y& Elsevier]