Successional Trends of Six Mature Shortleaf Pine Forests in Missouri

—Many of Missouri’s mature oak-shortleaf pine (Quercus-Pinus echinata) forests are in a mid-transition stage characterized by partial pine overstory, limited pine recruitment, and minimal pine regeneration. Restoration of shortleaf pine communities at a large scale necessitates the understanding and management of natural regeneration. To understand late-successional conditions of shortleaf pine forests, we conducted a complete survey of woody vegetation and canopy openings at six uncut and old second-growth oak-pine stands in southeastern Missouri. A total of 121 canopy gaps were mapped and measured in terms of their size, age, and vegetation structure. Shortleaf pine was a common canopy replacement tree along with black oak (Quercus velutina), white oak (Quercus alba), and hickories (Carya spp.). The abundance of shortleaf pine appears to be diminishing, however, owing to the absence of shortleaf in understory and regeneration layers. The resulting forest probably will consist almost exclusively of hardwoods. Shortleaf pine regeneration in canopy openings was limited by aspect, seed source, and litter depth. In addition to their current conditions, information from these forests provides insight into the future development and management needs of younger oak-pine communities. In forests where regeneration and recruitment of shortleaf pine are lacking, restoration efforts require timely action because the overstory seed source is crucial to preserving the shortleaf pine component. These fi ndings contribute to an understanding of shortleaf pine forests, and can ultimately determine restoration and management guidelines for shortleaf pine forests in the Missouri Ozarks. 1Senior Research Specialist (MCS), Department of Forestry, University of Missouri-Columbia, Columbia, MO 65211; and Associate Professor (R-MM), Department of Forestry, University of Missouri-Columbia, Columbia, MO 65211. MCS is corresponding author: to contact, call (573)882-8841 or email at stambaughm@ missouri.edu INTRODUCTION Although historic evidence suggests that oak-shortleaf pine (Quercus-Pinus echinata Mill.) forests of the Ozark region were strongly infl uenced, if not perpetuated, by recurring fi res for at least 300 years prior to the 16th century (Masters and others 1995, Guyette and others 2002, Guyette and others 2006), contemporary policies and logistics often reduce the occurrence of burning. This situation is an important issue to the conservation of many fi re adapted species, including shortleaf pine. In general, the disturbance regime of shortleaf pine forests has changed from one that included fi re to one that primarily excludes fi re and is represented by small-scale events (Stambaugh and others 2002) that result in canopy gap openings. In an attempt to understand the effects of these changes on species composition and forest succession, we examined canopy gap disturbances and forest stand dynamics of six representative uncut and old second-growth oak-shortleaf pine forests. Our objectives were to: 1) describe the current overstory composition, 2) characterize and quantify the frequency of canopy gap disturbances, and 3) identify trends in vegetation development within canopy gaps, specifi cally addressing the potential for shortleaf pine regeneration and recruitment to the overstory.