Effects of longleaf pine planting density and other factors on stand structure and associated wildlife habitat

Abstract

The primary objective of many longleaf pine (Pinus palustris) restoration programs is to enhance or restore habitat for wildlife dependent on herbaceous plant communities. Because herbaceous cover is inversely related to canopy cover, restoration programs often place restrictions on longleaf pine planting density. However, the influence of planting density on understory plant communities has been inadequately evaluated. Therefore, we initiated a study to examine the relative influences of planting density and other factors on overall understory composition and forage availability for white-tailed deer (Odocoileus virginianus) and northern bobwhite (Colinus virginianus) in nine longleaf pine stands throughout the Coastal Plain of Alabama during 2017-2018. We found that coverage of herbaceous plants decreased 3.5%, coverage of woody plants decreased 2.4%, and coverage of northern bobwhite forage plants decreased 1.9% for each 1 m 2 /ha increase in longleaf pine basal area. However, planting density was not a significant predictor of current basal area, nor coverage of any functional group of plants we examined, likely because current longleaf pine density averaged only 46% (range = 30-64%) of seedling planting density. We did not detect an effect of prescribed fire on stand condition or understory plant communities, likely due to variability in fire timing and frequency. Our findings related to planting density were likely a function of low longleaf pine survival, which is not uncommon. Because of this and the inherent variability in growth rates for young longleaf pine stands, restoration programs should consider placing greater emphasis on post-planting monitoring and management than planting density. Implications for Practice• Restoration of longleaf pine ecosystems may be accomplished via plantation forestry, but variability in seedling survival makes it difficult to predict the relationship between planting density and understory plant community composition and structure. • It is important to monitor longleaf pine plantings post-establishment to determine whether stands are currently meeting wildlife habitat or other ecological objectives because inherent and management-driven differences among sites will determine stand conditions over time.• Longleaf pine restoration programs should focus more on post-establishment monitoring than pre-establishment prescriptions when longleaf pine ecosystem restoration is the goal.