Pine straw, the uppermost forest floor layer of undecayed, reddish-brown pine needles, is raked, baled, and sold as a landscaping mulch throughout the southeastern United States. Loblolly (Pinus taeda, L.), longleaf (P. palustris, Mill.), and slash (P. elliottii Engelm. var. elliottii) pine are the three southern pine species commonly raked for pine straw. The value of pine straw as a forest product is large. Private landowner pine straw revenues have steadily increased throughout the southeastern United States over the past two decades and now total more than USD 200 million. Information is limited on the short- or long-term effects of pine straw removal on foliage production or stand growth in southern pine stands. Results from most published studies suggest that annual pine straw raking without fertilization on non-old-field sites reduces straw yields compared to no raking. Old-field sites often do not benefit from fertilization with increased pine straw or wood volume yields. Though fertilization may be beneficial for pine straw production on some sites, understory vegetation presence and disease prevalence may increase following fertilization. This review addresses pine straw removal effects on pine straw production and stand growth parameters based on recent studies and provides fertilization recommendations to maintain or improve pine straw production and stand growth and yield.

Shortleaf pine (Pinus echinata)–hardwood mixtures were once a common forest type on upland sites throughout the southeastern United States. These forest types have declined throughout much of shortleaf pine’s native range. Information on restoring shortleaf pine–hardwood types when a shortleaf pine seed source is not present is lacking. The objectives of this study were to investigate the effects of four site-preparation and release treatments (control, burn, herbicide, and herbicide and burn) on the development of even-aged mixtures of planted shortleaf pine and natural hardwoods located on the Highland Rim physiographic province of Tennessee, USA. Three years after study establishment, statistical differences among treatments occurred for shortleaf pine survival and basal diameter. Survival was greatest in the herbicide-only treatment. Height and basal diameter growth were greatest in the herbicide and burn treatment. Stem densities were greater in treatments that did not include a herbicide release than those where herbicide was used alone or combined with prescribed burning. The herbicide and burn treatment had the greatest potential after 3 years for developing into a balanced, mixed shortleaf pine–hardwood stand, whereas most treatments had an influx of exotic, invasive species such as Chinese privet (Ligustrum sinense) and callery pear (Pyrus calleryana).

Cluster planting of shortleaf pine, along with various site preparation and release treatments, were tested to restore mixed shortleaf pine (Pinus echinata Mill.)–hardwood stands in areas where the shortleaf pine has diminished in recent years. Shortleaf pine–hardwood mixtures were once a common forest type throughout the Cumberland Mountains and Plateau physiographic regions of the southeastern United States. Knowledge of how to restore shortleaf pine–hardwood mixtures is limited throughout shortleaf pine’s large native range. The objectives of this study were to compare planted shortleaf pine and natural hardwood regeneration survival, growth, and composition following various site preparation and early release treatments. Cluster planting and partial timber harvesting were used to reintroduce shortleaf pine and create two-aged stands in the Cumberland Mountains of Tennessee, USA. Results indicated that shortleaf pine survival, basal diameter, and height growth did not differ following four growing seasons among treatments. Natural regeneration stem densities and heights within shortleaf pine clusters did not differ significantly by treatment. Natural regeneration stem densities differed by species group and height class across the site, while the treatment × species interaction term was also significant. At this early stage of stand development, the brown-and-burn treatment appears poised for greater shortleaf pine growth rates than the other treatments. The herbicide treatment had the fewest regenerating hardwoods per hectare and the most desirable hardwood species composition.

Longleaf pine (Pinus palustris Mill.) is frequently planted on former agricultural fields throughout the southeastern United States. Limited information is available on the long-term growth and yield as well as stem quality of longleaf pine growing on these sites with and without midrotation fertilization. The objectives of this study were (1) to determine the growth rates, wood yields, and stem quality of old-field longleaf pine and (2) to quantify growth improvements provided by midrotation fertilization. Study sites were established on former agricultural fields in Screven and Tift County, Georgia in unthinned longleaf pine stands planted during December 1986. Three treatments including a control, single full dose, and split dose of nitrogen, phosphorus, and potassium were applied prior to thinning. Assessments of diameter at breast height, height growth, volume, green weight, and basal area at both sites were conducted at ages 21, 23, 27, 30, and 32. After 32 years, results indicated no statistically significant improvements of any growth parameters compared to the control in relation to midrotation fertilization treatments, and stem defects occurred in approximately 29–35 percent of trees. The fast growth rate and low nutrient demand of longleaf pine on these sites obviate the need for midrotation fertilization.

Midrotation management, including vegetation control and fertilization, can improve growth and yield of southern pine stands. This study investigated the 12-year response of slash pine ( Pinus elliottii), thinned at midrotation to additional treatments of herbicide, fertilization, liming (one site), and combinations of these treatments in the Coastal Plain region of Georgia, USA. There was a significant treatment × stand age interaction observed at the Ware County site for height ( p < 0.001), diameter at breast height (dbh) ( p < 0.001), and individual tree green weight ( p < 0.001). The herbicide + NPK and herbicide treatments resulted in the most consistent growth improvements 0 to 4 years post-treatment compared to the untreated control. The lime + NPK and herbicide treatment resulted in the longest lived (4–12 years) significantly improved growth response. Results revealed no tested treatments improved growth during the 12-year study duration at the Wayne County site. Results from this study suggest that thinned slash pine stands with diagnostics indicating midrotation fertilization or vegetation control may be beneficial do not always respond as expected to inputs. When stands are responsive, single application midrotation treatments can offer long-term growth improvements, yet growth response can differ depending on time since application.

The effects of midrotation competition control and fertilization were studied in two loblolly pine stands in the Coastal Plain of Georgia. The use of fertilizer or herbicide alone did not enhance wood yields above the control, which negates the cost spent to conduct these practices. The combined treatment of fertilization and herbicide promoted higher average pine annual increment and greater proportion of sawtimber. Site limiting factors, most likely both competing woody vegetation and low nutrient status, largely determined the effectiveness and priority of midrotation treatments. The economic returns of the combined treatment varied considerably depending on stumpage prices, treatment costs, and magnitude and duration of the growth response. Sawtimber prices (absolute value and relative to pulpwood and chip-n-saw) play a critical role in the marginal returns of midrotation treatments. Continued depressed sawtimber prices will discourage private landowners from investing in midrotation vegetation control and fertilization.