The survival and growth of shortleaf pine systems in the Missouri Ozarks : effects of competition, genetics, and site preparation
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Establishing shortleaf pine (Pinus echinata) across portions of its historical range has proven challenging due to shade intolerance, slow early growth, and poor competitive ability. The objectives of this study were to determine the expected survival and growth rates of planted shortleaf pine relative to artificial and natural hardwoods, identify barriers to regeneration success, and develop tools for individual tree assessment. Data from three long-term studies in southeastern Missouri were used to examine the survival and growth of over 5500, 1-0 seedlings as a function of understory competition, overstory density, genetic selection, and site preparation in artificially and naturally regenerated stands. Growth of planted 1-0 shortleaf pine exceeded that of planted 1-0 white oak (Quercus alba) and northern red oak (Q. rubra) when grown in the open during a 22-year monitoring period. However, during the first 10 years, planted shortleaf pine had lower survival and height growth where competing with natural oaks and other hardwood regeneration originating from advance reproduction rather than planted seedlings. Regression analysis indicated that height and diameter growth in natural stands was further reduced by retaining a hardwood overstory, while survival was not. Planted shortleaf pine grows faster than planted oaks in open stands with few other hardwood competitors. However, most regeneration occurs in mixed hardwood stands where large advance reproduction outcompetes planted shortleaf pine after harvesting. Due to the variation encountered in shortleaf pine growth, height-growth percentiles present an opportunity to assess and classify individual trees, while allowing for predictions to be made about future growth potential.