Young Longleaf Pine Research Articles

Experimental throughfall reduction has little effect on shoot and needle developmental patterns or leaf area dynamics in a young longleaf pine (Pinus palustris Mill.) plantation

Reduced precipitation and, consequently, low soil moisture are known to limit tree growth and function by affecting shoot and foliage development, as well as canopy-scale leaf area dynamics and litterfall. Longleaf pine (Pinus palustris Mill.) is considered one of the most drought-resistant forest species in the southeastern U.S. and could serve as a pathway to increase drought resistance of forests in the region. Still, reduced precipitation and low soil moisture impacts on longleaf canopy phenology and growth are not well understood. Over three years (2017–2019), we determined the effects of a 40% throughfall reduction (TR40) (relative to ambient throughfall treatment, TR0) on shoot and foliage phenology and growth in a young (12–14 yr. old) longleaf pine plantation. Each year, we repeatedly measured shoot and needle lengths on primary and secondary branch axes of multiple trees in each treatment plot. We fit growth curves for each tree and branch axis to estimate shoot and needle growth rate, growth start and cessation dates, growth duration (growth start - growth cessation), and final shoot and needle lengths. At the plot level, we documented temporal patterns of leaf area index (LAI) and litterfall to determine whether branch-scale phenological and growth responses to reduced water availability corresponded with temporal changes in LAI and litterfall. We observed significant and consistent differences in shoot and needle elongation patterns between primary and secondary branches. Timing of needle development varied among years and was generally later each successive year. However, shoot elongation patterns were relatively consistent across years. Although soil moisture was lower under throughfall reduction, shoot and needle growth patterns were not affected. LAI and litterfall patterns were also not affected by throughfall reduction. Our results indicate that reductions in rainfall amount (without changes in rainfall frequency or timing) may have little impact on shoot and needle phenology, canopy development, and litter production in established longleaf plantations.

Physiological Mechanisms of Foliage Recovery after Spring or Fall Crown Scorch in Young Longleaf Pine (Pinus palustris Mill.)

We hypothesized that physiological and morphological responses to prescribed fire support the post-scorch foliage recovery and growth of young longleaf pine. Two studies conducted in central Louisiana identified three means of foliage regrowth after fire that included an increase in the gas exchange rate of surviving foliage for 3 to 4 months after fire. Saplings also exhibited crown developmental responses to repeated fire that reduced the risk of future crown scorch. Starch reserves were a source of carbon for post-scorch foliage regrowth when fire was applied in the early growing season. However, the annual dynamics of starch accumulation and mobilization restricted its effectiveness for foliage regrowth when fire was applied late in the growing season. As such, post-scorch foliage regrowth became increasingly dependent on photosynthesis as the growing season progressed. Additionally, the loss of foliage by fire late in the growing season interrupted annual starch dynamics and created a starch void between the time of late growing season fire and mid-summer of the next year. The occurrence of drought during both studies revealed barriers to foliage reestablishment and normal stem growth among large saplings. In study 1, spring water deficit at the time of May fire was associated with high crown scorch and poor foliage and stem growth among large saplings. We attribute this lag in stem growth to three factors: little surviving foliage mass, low fascicle gas exchange rates, and poor post-scorch foliage recovery. In study 2, May fire during a short window of favorable burning conditions in the tenth month of a 20-month drought also reduced stem growth among large saplings but this growth loss was not due to poor post-scorch foliage recovery. Application of this information to prescribed fire guidelines will benefit young longleaf pine responses to fire and advance efforts to restore longleaf pine ecosystems.

Effects of longleaf pine planting density and other factors on stand structure and associated wildlife habitat

The primary objective of many longleaf pine (Pinus palustris) restoration programs is to enhance or restore habitat for wildlife dependent on herbaceous plant communities. Because herbaceous cover is inversely related to canopy cover, restoration programs often place restrictions on longleaf pine planting density. However, the influence of planting density on understory plant communities has been inadequately evaluated. Therefore, we initiated a study to examine the relative influences of planting density and other factors on overall understory composition and forage availability for white‐tailed deer (Odocoileus virginianus) and northern bobwhite (Colinus virginianus) in nine longleaf pine stands throughout the Coastal Plain of Alabama during 2017–2018. We found that coverage of herbaceous plants decreased 3.5%, coverage of woody plants decreased 2.4%, and coverage of northern bobwhite forage plants decreased 1.9% for each 1 m2/ha increase in longleaf pine basal area. However, planting density was not a significant predictor of current basal area, nor coverage of any functional group of plants we examined, likely because current longleaf pine density averaged only 46% (range = 30–64%) of seedling planting density. We did not detect an effect of prescribed fire on stand condition or understory plant communities, likely due to variability in fire timing and frequency. Our findings related to planting density were likely a function of low longleaf pine survival, which is not uncommon. Because of this and the inherent variability in growth rates for young longleaf pine stands, restoration programs should consider placing greater emphasis on post‐planting monitoring and management than planting density.

Restoring Longleaf Pine: Effects of Seasonal Prescribed Fire and Overstory Density on Vegetation Structure of a Young Longleaf Pine Plantation

Young longleaf pine (Pinus palustris Mill.) plantations provide an important starting point for restoration of longleaf pine ecosystems in the southeastern United States, with management goals often emphasizing restoration of vegetation composition and structure, as well as reestablishment of important ecological processes such as fire. We evaluated the influence of seasonal prescribed fire and overstory density on vegetation structure across overstory, midstory, and understory vegetation strata of a 23-year-old longleaf pine plantation in west-central Georgia. After three prescribed fire cycles through 8 years, we found significantly fewer broad-leaved woody stems in the midstory on both winter- and summer-burned plots compared to unburned plots, as well as fourfold greater herbaceous vegetation cover on burned plots compared to unburned plots. While we predicted that summer burning may be more important in controlling woody plants on low-density overstory plots compared to high-density plots, we found no meaningful interactions between fire seasonality and overstory density. Reductions in litter cover via prescribed fire appeared to be an important mechanism regulating herbaceous vegetation, suggesting that restoration should emphasize management of the forest floor to reduce litter cover and enhance opportunities for herbaceous plant establishment.

Longleaf and loblolly pine seedlings respond differently to soil compaction, water content, and fertilization

Aims Longleaf pine (Pinus palustris Mill.) is being restored across the U.S. South for a multitude of ecological and economic reasons, but our understanding of longleaf pine’s response to soil physical conditions is poor. On the contrary, our understanding of loblolly pine (Pinus taeda L.) root and shoot growth response to soil conditions is well established. Methods We performed a comparative greenhouse study which modeled root length density, total seedling biomass, and the ratio of aboveground:belowground mass as functions of volumetric water content, bulk density and soil fertility (fertilized or not). Results Root length density was about 35 % greater in longleaf pine seedlings compared to loblolly pine seedlings, and was reasonably well modeled (R 2 =0.54) for longleaf pine by bulk density (linear), volumetric water content (quadratic), soil fertility, and the interactions of bulk density, volumetric water content, species, and soil fertility. The aboveground:belowground mass ratio (ABR) increased at both extremes of water content. Conclusions This research indicates that young longleaf pine seedling root systems respond more negatively to extremes of soil physical conditions than loblolly pine,

Plant-community characteristics of bahiagrass pasture during conversion to longleaf-pine silvopasture

Silvopasture is considered a sustainable agroforestry practice as a result of benefits the system offers for biodiversity, economic returns, and environmental quality. However, little is known about temporal and spatial dynamics of forage species composition of pastures being converted to silvopasture. Research objectives were to determine (1) the response of forage species composition to a young longleaf pine (Pinus palustris Mill.)-bahiagrass (Paspalum notatum Flugge) silvopasture versus open bahiagrass pasture, and (2) the impact that alley position relative to trees has on forage species composition in a young longleaf pine-bahiagrass silvopasture. The research was conducted in a randomized complete block design with three replications from 2003 to 2007 at Americus, Georgia, USA in a longleaf-pine silvopasture established in 2000 in an existing bahiagrass pasture and an adjoining bahiagrass open-pasture. Silvopasture forage-species composition was measured within alleys. Plant community diversity was greater in the silvopasture versus open-pasture early in the growing season, but open-pasture had greater diversity during the later growing season. Alley position in silvopasture also had a significant effect on understory forage species composition. This study indicated that conversion of bahiagrass pasture to longleaf-pine silvopasture in the Southern Coastal Plain can influence plant-community characteristics by the time trees are six to seven years old.

Leaf Physiological and Morphological Responses to Shade in Grass-Stage Seedlings and Young Trees of Longleaf Pine

Longleaf pine has been classified as very shade intolerant but leaf physiological plasticity to light is not well understood, especially given longleaf pine’s persistent seedling grass stage. We examined leaf morphological and physiological responses to light in one-year-old grass-stage seedlings and young trees ranging in height from 4.6 m to 6.3 m to test the hypothesis that young longleaf pine would demonstrate leaf phenotypic plasticity to light environment. Seedlings were grown in a greenhouse under ambient levels of photosynthetically active radiation (PAR) or a 50% reduction in ambient PAR and whole branches of trees were shaded to provide a 50% reduction in ambient PAR. In seedlings, shading reduced leaf mass per unit area (LMA), the light compensation point, and leaf dark respiration (RD), and increased the ratio of light-saturated photosynthesis to RD and chlorophyll b and total chlorophyll expressed per unit leaf dry weight. In trees, shading reduced LMA, increased chlorophyll a, chlorophyll b and total chlorophyll on a leaf dry weight basis, and increased allocation of total foliar nitrogen to chlorophyll nitrogen. Changes in leaf morphological and physiological traits indicate a degree of shade tolerance that may have implications for even and uneven-aged management of longleaf pine.

Effects of AtmosphericCO2Enrichment on SoilCO2Efflux in a Young Longleaf Pine System

The southeastern landscape is composed of agricultural and forest systems that can store carbon (C) in standing biomass and soil. Research is needed to quantify the effects of elevated atmospheric carbon dioxide (CO2) on terrestrial C dynamics including CO2release back to the atmosphere and soil sequestration. Longleaf pine savannahs are an ecologically and economically important, yet understudied, component of the southeastern landscape. We investigated the effects of ambient and elevated CO2on soil CO2efflux in a young longleaf pine system using a continuous monitoring system. A significant increase (26.5%) in soil CO2efflux across 90 days was observed under elevated CO2; this occurred for all weekly and daily averages except for two days when soil temperature was the lowest. Soil CO2efflux was positively correlated with soil temperature with a trend towards increased efflux response to temperature under elevated CO2. Efflux was negatively correlated with soil moisture and was best represented using a quadratic relationship. Soil CO2efflux was not correlated with root biomass. Our data indicate that, while elevated CO2will increase feedback of CO2to the atmosphere via soil efflux, terrestrial ecosystems will remain potential sinks for atmospheric CO2due to greater biomass production and increased soil C sequestration.

The pathogenicity and virulence of four Ophiostomatoid fungi on young Longleaf pine trees

In southeastern USA, insect vectors transfer pathogenic ophiostomatoid fungi that cause disease in southern pines. During 2007 and 2008, potted longleaf pines (P. palustris Mill.), of similar ages ranging in height from 58 to 198 cm, were inoculated with the following fungi to assess their pathogenicity (and virulence): Grosmannia huntii, Leptographium procerum, L. serpens and L. terebrantis. Seventeen weeks after inoculation, L. terebrantis, L. serpens and G. huntii were found to cause significantly larger lesions and more sapwood discolouration than wounded uninoculated controls. Leptographium terebrantis caused significantly more sapwood discolouration than all other fungi. Despite significant sapwood occlusion after fungal inoculation, no reductions in needle water potentials were observed between treatments. All fungal species were successfully re-isolated from longleaf pine trees.

Partitioning of applied 15N fertilizer in a longleaf pine and native woody ornamental intercropping system

The cultivation of ornamentals to produce woody floral products—the fresh or dried stems that are used for decorative purposes—may be an attractive option for southeastern landowners looking to generate income from small landholdings. Since many shrubs native to the understory of the longleaf pine (Pinus palustris Mill.) ecosystem have market potential, one possibility is the intercropping of select species in the between-row spacing of young longleaf pine plantations. The objective of this study was to evaluate how interspecific competition affects the fate of 15N fertilizer when American beautyberry (Callicarpa americana L.), wax myrtle (Morella cerifera (L.) Small) and inkberry (Ilex glabra (L.) A.Gray) are intercropped with longleaf pine. Nitrogen derived from fertilizer (NDF), utilization of fertilizer N (UFN) and recovery of fertilizer N (RFNsoil) were compared between agroforestry and monoculture (treeless) treatments to assess the effects of competition. Results varied by species, with NDF being higher for C. americana foliage and lower for all M. cerifera tissues in the agroforestry treatment. No effect was observed for I. glabra. UFN was lower for all species in the agroforestry treatment. RFNsoil was higher in the agroforestry treatment for I. glabra, but no treatment effects were observed for C. americana or M. cerifera. Overall, while it is clear that interspecific competition was present in the agroforestry treatment, the inefficiency of fertilizer use suggests that nitrogen was not the most limiting resource. Management interventions, particularly those that address competition for water, will likely be critical to the success of this system.

Production physiology of three native shrubs intercropped in a young longleaf pine plantation

The objective of this study was to evaluate how competition would affect the physiology, and thus productivity of American beautyberry (Callicar- pa americana L.), wax myrtle (Morella cerifera (L.) Small) and inkberry (Ilex glabra (L.) A. Gray) when intercropped in a longleaf pine (Pinus palustris Mill.) plantation in the southeastern United States. The effect of competition was assessed via comparisons of mortality, biomass, light transmittance, gas exchange and soil moisture between intercropping and mono- culture (treeless) treatments. Overall, shrubs in the intercropping treatment performed worse than those in the monoculture, with higher mortality, and reductions in biomass of 75.5, 50.6, and 68.7% for C. americana, M. cerifera and I. glabra, respectively. Root-shoot ratios for all species were significantly higher and soil moisture during dry periods was significantly lower in the intercropping treatment. Light transmittance below the pine canopy was high (57.7%) and I. glabra was the only species that exhibited reduced Amax when belowground resources were not limiting. These results suggest that the effect of shading is minimal and belowground competition is likely the most important determinant of productivity in this system.

Predicting Diameter Distributions for Young Longleaf Pine Plantations in Southwest Georgia

Abstract Parameter prediction equations for the Weibull distribution function were developed based on four percentile functions and a parameter recovery method for longleaf pine (Pinus palustris Mill.) in Southwest Georgia. Four percentiles were expressed as functions of stand-level characteristics based on stepwise regression and seemingly unrelated regression. Using a percentile-based parameter recovery method (PCT), estimated diameter distributions were obtained from available stand-level variables. The PCT method was also compared with a cumulative distribution function (CDF) regression method. The PCT method produced consistently better goodness-of-fit statistics than the CDF method. The results indicate that diameter distribution in longleaf pine stands can be successfully characterized with the Weibull function.

Nitrogen source influences on forage and soil in young southern-pine silvopasture

Southern-pine silvopasture can be established by thinning an existing forest plantation then adding or improving a forage component, or by adding low densities of trees to existing pasture. Studies in mature loblolly ( Pinus taeda L.) pine silvopasture (26 years) developed from a thinned plantation on the Western Coastal Plain of Louisiana, USA estimated higher forage biomass production for open-pasture versus silvopasture. However, little is known about temporal and spatial dynamics of forage productivity and soil quality in permanent pastures being converted to silvopasture on the Southern Coastal Plain of the Southeastern USA. The objectives of this research were to determine the impact of nitrogen (N) source (legume-N versus fertilizer-N), pasture type (silvopasture versus open-pasture), and alley position relative to trees in young Southern Coastal Plain silvopasture on (1) forage productivity and quality; (2) soil aggregate stability, density of fungal hyphae, and soil penetration resistance. This research was conducted in a randomized complete block design with three replications from 2005 to 2007 at Americus, Georgia, USA in a young longleaf pine ( Pinus palustris Mill.)-bahiagrass ( Paspalum notatum Flugge) silvopasture and adjoining bahiagrass pasture without trees (open-pasture). Treatments included either fertilizer-N or overseeded crimson clover ( Trifolium incarnatum L. ‘Dixie’). Silvopasture forage parameters were monitored at two (2005: 1.0 and 6.1 m) or three (2006–2007: 1.0, 3.5, and 6.1 m) alley positions relative to the tree base; soil parameters were monitored at two alley positions (1.0 and 6.1 m). Cool-season (April or May) forage biomass was 40% higher and forage N concentration 27% higher for the legume-N versus fertilizer-N treatment. When compared to the 3.5- or 6.1-m alley positions, forage productivity at the 1.0-m alley position decreased when the pines were 6 years old. Lower N and higher acid detergent fiber (ADF) levels were found in forage from silvopasture versus open-pasture in August 2006, and July and September 2007, the result of pine straw accumulation in the forage alleys. Water stable aggregates were 5% lower in silvopasture versus open-pasture. Soil penetration resistance was lower in silvopasture versus open-pasture at 10–15- and 15–20-cm in 2005, and at 15–20-cm in 2007. This research found that forage productivity and forage and soil quality can be improved, and N fertilizer additions replaced by introduction and maintenance of crimson clover into young longleaf pine-bahiagrass silvopasture during the hay-production period of pasture to silvopasture conversion on Southern Coastal Plain soil in the Southeastern USA.

Compatible Stem Taper, Volume, and Weight Equations for Young Longleaf Pine Plantations in Southwest Georgia

Abstract Outside and inside bark diameter measurements were recorded from tree disks obtained at 0-, 0.5-, 2.0-, 4.5-, 6.0-, 16.6-, and at 4-ft-height intervals above 6 ft to a 2-in. diameter outside bark top diameter on 42 longleaf pine trees selected from intensively managed longleaf pine (Pinus palustris Mill.) plantations in Dougherty and Worth Counties in southwest Georgia. Trees were sampled from unthinned, cutover stands in their 11th and 14th growing season, which are currently part of an existing growth and yield study. Sample trees ranged from 2 to 7 in. in diameter and from 18 to 40 ft in total height. Parameters for a segmented polynomial taper and compatible cubic foot volume and weight equation were simultaneously estimated using a seemingly unrelated nonlinear fitting procedure to volumes based on a generalized Newton formula and an overlapping bolt methodology. Average error was approximately 0.25 in., 0.04 ft3, and 2.5 lb for taper, volume, and weight estimation, respectively.

Fruit Abundance and Local Distribution of Wintering Hermit Thrushes (Catharus Guttatus) and Yellow-Rumped Warblers (Dendroica Coronata) in South Carolina

Abstract We conducted winter censuses of two short-distance migrants, Hermit Thrushes (Catharus guttatus) and Yellow-rumped Warblers (Dendroica coronata), over seven years in five different habitats to determine whether their local abundances could be predicted by fruit pulp biomass. Sampled habitats were stands of upland and bottomland hardwood, loblolly pine (Pinus taeda), longleaf pine (P. palustris), and young (<10 years) longleaf pine. Hermit Thrush abundance, which was highest in bottomland hardwood habitats, was positively related to total dry mass of fruit pulp. Those results are consistent with the hypothesis that resource availability affects the local distribution of migrant passerines on their wintering grounds. Our results also indicate that bottomland hardwood habitats in the southeastern United States may be especially important to wintering Hermit Thrushes. Yellow-rumped Warbler abundance was correlated with ripe-fruit pulp dry mass of Myrica cerifera, a major source of winter food for that species. However, because M. cerifera pulp dry mass was confounded with habitat type, we could not distinguish the relative importance of fruit resources and habitat for Yellowrumped Warblers. Our results underscore the importance of fruit to wintering birds. However, the overall percentage of variation in winter bird abundance explained by differences in ripefruit biomass was modest, indicating that other factors are also important.

FRUIT ABUNDANCE AND LOCAL DISTRIBUTION OF WINTERING HERMIT THRUSHES (CATHARUS GUTTATUS) AND YELLOW-RUMPED WARBLERS (DENDROICA CORONATA) IN SOUTH CAROLINA

Abstract We conducted winter censuses of two short-distance migrants, Hermit Thrushes (Catharus guttatus) and Yellow-rumped Warblers (Dendroica coronata), over seven years in five different habitats to determine whether their local abundances could be predicted by fruit pulp biomass. Sampled habitats were stands of upland and bottomland hardwood, loblolly pine (Pinus taeda), longleaf pine (P. palustris), and young (<10 years) longleaf pine. Hermit Thrush abundance, which was highest in bottomland hardwood habitats, was positively related to total dry mass of fruit pulp. Those results are consistent with the hypothesis that resource availability affects the local distribution of migrant passerines on their wintering grounds. Our results also indicate that bottomland hardwood habitats in the southeastern United States may be especially important to wintering Hermit Thrushes. Yellow-rumped Warbler abundance was correlated with ripe-fruit pulp dry mass of Myrica cerifera, a major source of winter food for tha...

Effect of burning and brush treatments on nutrient and soil physical properties in young longleaf pine stands

Over a period of 16 years, unburned longleaf pine ( Pinus palustris Mill.) pole stands grew an average of 27% more volume than similar stands regularly burned. Treatments included biennial burns in winter, spring, and summer plus an unburned check, each of which was combined with three supplemental treatments, namely, initial herbicide injection of all hardwoods, repeated handclearing of all woody stems, and no treatment. All unburned and winter-burned plots were paired to study this growth reduction relative to treatments. The status of nitrogen, phosphorus, available moisture holding capacity, bulk density, and macropore space was determined in both surface and subsurface soils. Foliage from pines on sampled plots was analyzed for N, P, K, Ca, Mg, Mn, Cu, Fe, and Zn. Burning did not significantly affect either soil N and P or foliar nutrients. However, burning reduced available moisture holding capacity and macropore space and increased the bulk density of surface soils, and also reduced the moisture-holding capacity of subsurface soils. The results from this and other studies suggest that growth losses are due, at least in part, to increased moisture stress associated with changes in soil physical properties.

Variations in height-over-age curves for young longleaf pine plantations

Variations in height-over-age curves for young longleaf pine plantations