Mature Pine Plantations as Potential Sites for Oak Regeneration in Parks and Natural Areas of Southern Michigan

Poor regeneration of oak species (genus Quercus) is a widespread problem throughout the east- ern United States. Recent research on forests managed for timber in northern Michigan has indicated that Civilian Conservation Corps (CCC) era pine (genus Pinus) plantations may provide better sites for oak regeneration than forests currently dominated by an oak overstory. Although not widely recognized, pine plantations were also established in southern Michigan during the same period and tend to reside on state and county parks managed primarily for conservation and recreation. We set out to determine the extent of pine plantations on three large public recreation areas in southern Michigan and to assess their potential as sites for oak regeneration. First, we analyzed aerial imagery to assess the proportion of upland areas occupied by planted conifer stands (including those dominated by pines). Next, we visited a sample of pine stands and adjacent upland oak forests to ground- truth our cover type classification and to assess the status of oak regeneration. We estimated there to be 147 ha of planted conifers in Waterloo State Recreation Area (3.2% of total upland forest area), 97 ha of planted conifers in Island Lake State Recreation Area (9.5% of total upland forest area), and 14 ha of planted conifers in Lake Lansing Park North (15.7% of total upland forest area). The plantations encountered varied in composition, but in general were dominated by either white pine (Pinus strobus L.) or red pine (Pinus resinosa Ait.). Other conifer species such as jack pine (Pinus banksiana Lamb.), scotch pine (Pinus sylvestris L.), and Douglas-fir (Pseudotsuga menzesii (Mirb.) Franco) were occasionally present. One large stand of Norway spruce (Picea abies (L.) H. Karst.) was also encountered. Oak seedling and sapling densities were similar and did not statistically differ between pine plantations and adjacent oak forest. Additionally, oak seedlings were significantly taller under planted pine than under oak forest, suggesting that these plantations provide better conditions for growth and recruitment into larger size classes. Together our results suggest that mature pine plantations in southern Michigan could be a focal point for managers seeking to promote oak regeneration.