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Understory Restoration in Longleaf Pine Plantations: Overstory Effects of Competition and Needlefall

Informally Refereed

Abstract

Overstory and midstory vegetation layers strongly limit abundance and species richness of understory herbaceous plants in longleaf pine (Pinus palustris Mill.) plantations. However, the separate effects of overstory competition and needlefall remain unknown and are the subject of this study. Four levels of overstory thinning were applied to 0.10-hectare plots in each of three 13- to 15-year-old plantations at the Savannah River Site, resulting in 0, 25, 50 and 100 percent pine stockings. Four split plots were established within each main plot: trenching (presence or absence) to eliminate pine root competition and needlefall (presence or absence). Containerized seedlings of selected herbs were grown in a greenhouse, planted within each treatment, and their abundance and size were monitored during 1999-2000. Soil surface temperature and availabilities of light, soil water, and soil and foliar nutrients also were measured periodically. Light availability and temperature each decreased with pine stocking, while in specific months, availabilities of soil water and nitrogen were greater in the presence versus absence of trenching. Reductions of seedling performance with increasing pine stocking were less in the presence versus absence of trenching. Certain species demonstrated shade tolerance, while others had optimal growth at 0 percent pine stocking. For several species, cover increased (1999) and then decreased (2000) in response to accumulation of needlefall. Results indicate that plant responses to light availability were strongly regulated by soil water availability and needlefall.

Citation

Dagley, Christa M.; Harrington, Timothy B.; Edwards, M. Boyd. 2002. Understory Restoration in Longleaf Pine Plantations: Overstory Effects of Competition and Needlefall. In: Gen. Tech. Rep. SRS–48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. pg. 487-489
https://www.fs.usda.gov/research/treesearch/4777