Evaluation of Long-Term Shortleaf Pine Progeny Tests in the Ouachita and Ozark National Forests, USA

Abstract

Between the late 1970s and the early 1990s, the USDA Forest Service installed 155 shortleaf pine (Pinus echinata Mill.) progeny tests in national forests across the Southern Region of the United States. Using control-pollinated crosses from the Mount Ida Seed Orchard, 84 of these progeny tests were established in the Ouachita and Ozark-St. Francis National Forests in Arkansas and Oklahoma. Each of these 84 test locations had, on average, 33 full-sibling families representing three local geographic seed sources (East Ouachita, West Ouachita, and Ozark). Though largely abandoned years ago, the progeny tests that remain provided an opportunity to determine if significant genetic and genetic × environment variance exists for performance traits (d.b.h., tree height, and survival) decades after installation. In 2018 and 2019, we remeasured d.b.h. and height and determined survival in 15 fully stocked progeny tests. Family variances were significant (p < 0.01) for both d.b.h. and height but not for survival (p > 0.05). Seed sources differed significantly (p < 0.05) for d.b.h., with more pronounced latitudinal differences. Additionally, we determined that individual tree and full-sibling family mean heritabilities were moderate (0.15 and 0.72, respectively, for d.b.h and 0.09 and 0.41, for height), suggesting relatively high genetic to environmental variation and good potential for genetic improvement. We also found that shortleaf pine families were broadly adapted in this region since family-by-test variances were non-significant (p > 0.05).

Growth of Two Loblolly Pine Clones Planted in Agroforestry and Plantation Settings: Nine-year Results

“…The two pine clones we used were developed by selecting improved genotypes; therefore, genetics signi cantly affected their performance. However, several exogenous factors can also affect southern pines' growth and survival rates (Hossain et al, 2021;Sharma et al, 2013). These include natural disturbances such as diseases, insects, res, storms (ice and wind), and droughts.…”

“…However, given that our plantings were just eight years old, it is unlikely that they have yet reached canopy closure, which initiates the onset of competition (Adams et al, 2007). We speculate that the full extent of the competition effect cannot be evaluated until these stands become mature (> 15 years of age), and self-thinning would start as a result of more intense intraspeci c competition (Sharma et al, 2013;Hossain et al, 2021). Based on a longer-term study conducted in central Mississippi, Adams et al (2007) reported that the survival of loblolly pine at 17 years was signi cantly affected by spacing, with widely-spaced plantings showing higher survival rates than those with closer spacings, which corroborates with our assumption.…”