Loblolly Pine Plantations Research Articles

Growth and Competition Response in Intensively Established Loblolly Pine Plantations at Crown Closure

Growth and Competition Response in Intensively Established Loblolly Pine Plantations at Crown Closure

Modulus of elasticity declines with decreasing planting density for loblolly pine (Pinus taeda) plantations

Loblolly pine is often grown in intensively managed plantations for wood production. In order to fully evaluate the effects of management practices on wood quality and ultimately value, it is necessary to relate mechanical properties to management practices. The aim of this study was to evaluate the effect of planting density on mechanical properties of lumber recovered from loblolly pine trees from a 27-year-old spacing trial and develop prediction equations for modulus of elasticity and modulus of rupture from stand, tree, and board characteristics. Regression methods were applied to sample trees from three planting densities (2,989, 1,682, and 746 trees ha−1) and used to relate mechanical properties of lumber extracted from the trees to stand, tree, and board characteristics. Initial planting density was found to be correlated with modulus of elasticity and, to a lesser extent, with modulus of rupture. Including board characteristics and utilizing the visual grade and board position as regressors produced improved prediction equations. The mean modulus of elasticity declines with decreasing planting density while the variability increases, suggesting that planting density is a surrogate for frequency and size of knots. Thus, lower planting densities, while producing more lumber, may produce proportionally fewer boards of greater modulus of elasticity than higher planting densities.

Foliage and Litter Chemistry, Decomposition, and Nutrient Release in Pinus taeda

Following fertilization of forest plantations, high accumulations of nutrients in the forest floor creates the need to assess rates of forest floor decomposition and nutrient release. The study site was a 25-year old experimental loblolly pine plantation in the North Carolina Sandhills Region. Soluble and insoluble N, P, carbohydrate and phenol-tannin fractions were determined in foliage and litter by extraction with trichloroacetic acid. The long-term forest floor decomposition rate and decomposition and nutrient release in an experiment simulating removal of the overstory canopy were also determined. In litter, insoluble protein-N comprised 80%–90% of total-N concentration while soluble inorganic- and organic-P comprised 50%–75% of total-P concentration explaining forest floor N accumulations. Fertilization did not increase soluble carbohydrates in litter and forest floor decomposition rates. Loblolly pine forest floor decomposing in environmental conditions simulating removal of the overstory canopy was greatly accelerated and indicated 75% mass loss and release of 80% of the N pool within one year. This could result in a loss of substantial quantities of N at harvest due to low N uptake by seedlings in the newly planted next rotation suggesting management of the forest floor at harvest is essential to conserve site N capital in these N limited systems.

A Simple Stand Growth Model Based on Canopy Dynamics and Biomechanics

A new approach to simulating net forest growth is presented. The model is based on density effects on mean crown dimensions and the stem geometry required to counteract the bending moment generated from wind action on the crown. Stem geometry is based on the constant-stress principle of stem formation. Various structural and growth properties of hypothetical loblolly pine stands growing on a range of site indexes and with a range of initial tree densities are calculated with the model and compared with published values and well-known patterns. Size-density relations calculated with the model are consistent with converging, curvilinear lines reported for slash pine and loblolly pine plotted on log-transformed axes. Linear relationships between mean crown length and mean spacing agree with observations from various coniferous species, and culmination of current annual increment corresponds with the rapid changes in canopy structure reported with Sitka spruce. Overestimations of mean annual increment appear to result from differences in canopy dynamics in the loblolly pine plots used to fit the model's regression equations and the canopy dynamics in the loblolly pine plantations used for comparisons. The model has the potential to create an alternative approach for accessing environmental changes on forest growth and yield to complement extant carbon-balance models. FOR .S CI. 59(3):335-344.

Relating Quantity, Quality, and Value of Lumber to Planting Density for Loblolly Pine Plantations

Relating Quantity, Quality, and Value of Lumber to Planting Density for Loblolly Pine Plantations

Initial effects of woody biomass removal and intercropping of switchgrass (Panicum virgatum) on herpetofauna in eastern north Carolina

Forests are potential sources for a wide range of alternative fuels, which could reduce dependency on fossil fuels and carbon emissions, but sustainability of producing biofuels from forests has not been well-studied. Therefore, we investigated effects of woody biomass harvest, intercropping perennial grasses, and combinations of these treatments on herpetofauna in loblolly pine (Pinus taeda) plantations in a randomized and replicated field experiment in eastern North Carolina, USA. We sampled amphibians and small reptiles with drift fence arrays from April to July during 1 and 2 years after treatment establishment. We had 425 captures of 15 species of herpetofauna across the 2 sampling seasons, but did not observe large general effects of biomass removal or planting of switchgrass (Panicum virgatum) in pine plantations on detection, diversity, or relative abundance. However, planned contrasts indicated Simpson's index of diversity was greater in plots managed for switchgrass only compared with pine plantations during year 2, and that captures of southern toads (Anaxyrus terrestris) were less common in switchgrass plots than in pine plantations intercropped with switchgrass. Neither intercropping switchgrass with pine nor removal of harvest residuals caused herpetofauna diversity or abundance of common species to differ from traditional plantation management during the first 2 years following treatment establishment. With the exception of switchgrass-only plots, which had lower herpetofauna species evenness, the potential practices we considered for biofuels production are unlikely to have short-term effects on herpetofauna relative to traditional pine management. Future research should monitor herpetofauna through succession and consider landscape-scale effects and other potential feedstock sources. © 2013 The Wildlife Society.

Site preparation for switchgrass intercropping in loblolly pine plantations reduces retained trees and snags, but maintains downed woody debris

Within young pine (Pinus spp.) plantations, coarse woody debris (CWD) and green trees are important habitat structures that may be impacted by the production of biofuel feedstock. Therefore, we compared site preparation procedures associated with switchgrass (Panicum virgatum L.) intercropping to determine effects on CWD and green trees in stands (n ¼24) site-prepared for intercropping, with switchgrass only, or pine plantation in Mississippi, USA. Following site preparation, CWD dispersal or volume did not differ between intercropped and control stands. Intercropped stands had significantly fewer retained trees and snags. Switchgrass monocultures had no retained trees or piles and significantly fewer pieces and less volume of CWD than the other treatments. Our results suggest switchgrass intercropping may provide similar habitat quality to traditional pine plantations for wildlife species using these areas in the year following disturbance, but may provide a less suitable habitat for species that require snags. However, the relationship between snag reduction and wildlife population response in an intercropped setting is not clear and should be further investigated. Regardless, if retaining snags is a desired outcome, site preparation for switchgrass should be restricted to the interbed area where it will be cultivated as opposed to extensive debris removal from the entire site.

Streamside Management Zones Affect Movement of Silvicultural Nitrogen and Phosphorus Fertilizers to Piedmont Streams

Forestry best management practices (BMP) recommendations for streamside management zones (SMZs) are based on limited data regarding SMZ width, partial harvests, and nutrient movements after forest fertilization. Agricultural fertilization is commonly linked to increased stream nutrients. However, less is known about effectiveness of SMZ options for controlling nutrient movements after silvicultural fertilization. Diammonium phosphate and urea were applied to 12 subwatersheds in 3-year-old loblolly pine (Pinus taeda L.) plantations in the Virginia Piedmont. Three replicates of four SMZ treatments were superimposed on 12 subwatersheds in a previous SMZ harvest sediment study (7.6-m SMZ, 15.2-m SMZ thin, 15.2-m SMZ, and 30.5-m SMZ). Surface, near-surface, subsurface, and stream water samples were collected monthly for 1 year and analyzed for nitrate (NO3 ), ammonium (NH4 ), and orthophosphate (ortho-P). Transected measurements from streamside to fertilized plantations allowed interpretations of spatial nutrient measurements across SMZs. When compared with wider SMZs, 7.6-m SMZs had 3–10 surface water NO3 ,3 – 6 near-surface water NO3 , and 1–2 more stream water NO3 . No significant differences were detected for NH 4 for any SMZ treatment. The 15.2-m SMZ thin had small but significant increases (2– 8) in surface runoff for ortho-P relative to other SMZ treatments, perhaps because of increased surface water movement along thinning corridors. Across all SMZ treatments, comparisons of stream edges with fertilized stands indicated NO3 reductions of 33–98%, NH4 reductions of 68 –97%, and ortho-P reductions of 70 –98%. A 39% rainfall deficit during the study influenced results, but conventional SMZs 15.2 m protected streams from fertilization nutrient increases.

Long-Term Effects of Pine Tip Moth (Lepidoptera: Tortricidae) Control, Vegetation Control, and Fertilization on Growth and Yield of Loblolly Pine, Pinus taeda L.

Studies were conducted in Georgia and North Carolina to determine the long-term growth impact of pine tip moth, Rhyacionia spp., attacks on loblolly pines which had been treated with different combinations of insecticides for tip moth control, herbicides for control of competing vegetation, and fertilizer. Height, diameter, and volume responses were significantly greater for tip moth and weed control at age 5, both in Georgia and North Carolina. There was no evidence of a positive response to fertilizer. The largest responses were due to tip moth control, which was the only treatment that retained a significant response through the termination of the study at age 15 in Georgia and age 20 in North Carolina. Stand volumes continued to increase on the tip moth control plots throughout the study with average gains of 3.1 m3/ha/yr (43.8 ft3/acre/yr) at the Georgia site at age 15 and 3.2 m3/ha/yr (45.8 ft3/acre/yr) at age 20 at the North Carolina site. Trees receiving tip moth control also had significantly better form than untreated trees when evaluated at age 5, which may be reflected in higher quality and more valuable forest products at harvest. Treatment responses observed in this study clearly show that tip moth control can provide benefits equal to or greater than other commonly used cultural treatments, and may be necessary to realize anticipated gains from intensive management of loblolly pine plantations when tip moth damage is heavy.

Fixed physiological parameters in the 3-PG model produced accurate estimates of loblolly pine growth on sites in different geographic regions

The goal of this project was to determine if 3-PG could accurately predict growth of loblolly pine (Pinus taeda) plantations across a range of sites in the Piedmont and Coastal Plain provinces of Georgia using a fixed physiological parameter set. The model was slightly modified to improve predictions of volume, mortality and initial biomass growth. We hypothesized that because: (a) many physiological attributes of loblolly pine including rates of net photosynthesis, dark respiration, stomatal conductance and specific leaf area tend to be very similar across sites, and (b) leaf area is highly responsive to fertility but less so to water and other environmental factors, a single physiological parameter set would be suitable for predicting growth across a range of loblolly pine plantations which differed in soil type, climate, and silvicultural treatments. The parameter set was obtained from a combination of published values in the literature and model calibrations developed from a single highly productive stand in the Coastal Plain province in Georgia. Differences in potential productivity among sites were accounted for by only changing the value of the fertility rating and the soil type. The calibrated model was evaluated using observed growth data obtained from a slower growing stand at the same Coastal Plain site as the calibration stand, and three other sites, two in the Piedmont province and one in the Coastal Plain. At each of the four locations the model was evaluated using growth data from two plantations, one that received minimal silvicultural inputs and another that received a highly intensive silvicultural treatment, including complete and sustained competition control and annual fertilization.The model performed well on all stands and treatments, and accurately estimated stem biomass and diameter growth. The percent average deviation between predicted and observed values was less than 20% on most sites. The model did not accurately predict stand density in some cases and tended to overestimate volume on sites with low intensity silviculture. The inaccuracy in predicting volume was attributed to parameterization on a highly fertilized site and an inability to account for fertilization effects on wood density. Despite the discrepancies in measured and modeled stem density and volume it is our conclusion that, overall, the 3-PG model provided an accurate description of loblolly pine plantation growth and productivity and was a particularly good predictor of stand biomass in both the Piedmont and Coastal Plain provinces of the Southeastern US using a single set of physiological parameters.

Responses of white‐tailed deer and northern bobwhite food plants to a gradient of stand‐establishment intensities in pocosin pine plantations

AbstractLoblolly pine (Pinus taeda) plantations are established using various treatments to manage competing vegetation and increase pine production. Although young pine plantations historically supported early successional vegetation communities that contained abundant wildlife forage, increasing intensity of stand‐establishment treatments, particularly herbicides, has caused concern regarding potential effects on composition, availability, and quality of wildlife forage within young pine plantations. Few long‐term studies have described relationships between intensity of site preparation and effects on important forage plants for 2 economically and ecologically important game species: white‐tailed deer (Odocoileus virginianus) and northern bobwhite (Colinus virginianus). Therefore, we examined effects of 6 treatments of increasing stand‐establishment intensity via combinations of mechanical and chemical site preparation with herbaceous weed‐control on deer and bobwhite food plants from 1 year to 8 years after site preparation in loblolly pine plantations (n = 6) within pocosins in the Lower Coastal Plain of North Carolina, USA, during summers of 2002–2005, 2007–2009. Although woody and vine forage plants for deer and quail were common on all treatments, chemical site preparation resulted in long‐term decreases (approx. 50% for 8 yr) in coverage of these plants. Type of mechanical site preparation–spacing and herbaceous weed‐control had few effects on woody and herbaceous deer and quail food plants. Dissimilar from research in other regions, reduction in woody cover did not provide a concurrent increase in herbaceous food plants. Because of relatively poor forage quality in pocosin habitats, vegetation management practices may reduce deer and quail food quantity without increasing quality. However, because abundance of low‐quality forage is high in pocosin habitats, localized forage reductions due to site‐preparation techniques may not affect overall carrying capacity in these areas. © 2012 The Wildlife Society.

A Comparison of Three Methods to Estimate Evapotranspiration in Two Contrasting Loblolly Pine Plantations: Age-Related Changes in Water Use and Drought Sensitivity of Evapotranspiration Components

Increasing variability of rainfall patterns requires detailed understanding of the pathways of water loss from ecosystems to optimize carbon uptake and management choices. In the current study we characterized the usability of three alternative methods of different rigor for quantifying stand-level evapotranspiration (ET), partitioned ET into tree transpiration (T), understory transpiration, interception, and soil evaporation (E S) and determined their sensitivity to drought, and evaluated the reliability of soil moisture measurements by taking into account deep soil moisture dynamic. The analyses were conducted in an early- and in a mid-rotation stand of loblolly pine, the predominant species of southern US forest plantations. The three alternative methods for estimating ET were the eddy covariance measurements of water vapor fluxes (ET EC), the water table fluctuation (ET WT), and the soil moisture fluctuation (ETSM). On annual and monthly scales, the three methods agreed to within 10-20%, whereas on a daily scale, the values of ET SM and ETEC differed by up to 50% and ETSM and ET WT differed by up to 100%. The differences between the methods were attributed to root water extraction below measurement depth and to the sampling at different spatial scales. Regardless of the method used, ET at the early-rotation site was 15-30% lower than that at the mid-rotation site. The dry years did not affect ET at the mid-rotation site but reduced significantly ET at the early-rotation site. Soil moisture trends revealed the importance of measuring water content at several depths throughout the rooting zone because less than 20% of the water is stored in the top 30 cm of soil. Annually, E S represented approximately 9 and 14% of ETEC at the mid-rotation site and the early-rotation site, respectively. At the mid-rotation site, T accounted for approximately 70% of ET EC. Canopy interception was estimated to be 5-10% of annual precipitation and 6-13% of total ETEC. At the early-rotation site, T accounted for only 35% of ET EC. At this site, transpiration from subdominant trees and shrubs represented 40-45% of ET EC, indicating that understory was a significant part of the water budget. We concluded that the eddy covariance method is best for estimating ET at the fine temporal scale (i.e., daily), but other soil moisture and water table-based methods were equally reliable and cost-effective for quantifying seasonal ET dynamics. FOR .S CI. 58(5):497-512.

Effects of considering greenhouse gas consequences on fertilizer use in loblolly pine plantations

Fertilizer use, widely practiced in forest plantation management to stimulate tree growth, contributes to greenhouse gas (GHG) emissions. We explore how accounting for GHG consequences affects optimal fertilizer application rates of commercial forest plantations. A generic model that maximizes the equivalent annual net benefit of timber production and GHG balance is developed and applied to loblolly pine (Pinus taeda L.) plantations in the southern United States. We find that fertilizer use still is a viable practice for managing loblolly pine plantations in the region although fertilizer application rate should be reduced when GHG consequences are valued. A greater reduction in fertilizer application rate is recommended where wood is used for paper production because life cycle GHG emissions of paper products are much higher than those of solid wood or bioenergy products. A higher fertilizer rate should be applied when forest residues are used for the production of bioenergy that offsets GHG emissions from consuming fossil fuels.

Soil Accumulation of Nitrogen and Phosphorus Following Annual Fertilization of Loblolly Pine and Sweetgum on Sandy Sites

A key question that arises following fertilization of forest plantations in the southeastern United States is whether fertilization has a long‐term effect on nutrient availability and long‐term site quality. Site quality could improve if mineral soil N and P pools are increased but is less likely if only forest floor pools are increased. Rapid forest floor decomposition and nutrient release following harvest likely lead to only rotation‐length increases in nutrient availability. To examine the impact of repeated applications of N and P, forest floor and mineral soil N and P pools were measured at a 24‐yr‐old loblolly pine (Pinus taedaL.) plantation in North Carolina (Southeast Tree Research and Education Site [SETRES]) and 13‐yr‐old loblolly pine and sweetgum (Liquidambar styracifluaL.) plantations in Georgia (Mt. Pleasant) receiving annual incremental fertilizer applications totaling >1000 kg N ha−1and >160 kg P ha−1. Mineral soil N pools varied only slightly. In contrast, fertilization increased forest floor N pools by 300 kg N ha−1at SETRES. Long‐term impacts on site N availability and site quality following these large N applications are unlikely. The forest floor P pool at SETRES was increased by 19.8 kg P ha−1. Fertilization also increased the mineral soil extractable P pool at SETRES to a depth of 1.5 m by 56 kg P ha−1but not at Mt. Pleasant where P fertilization during the previous rotation may have already increased this pool. Observed increases in mineral soil P from fertilization indicated a potential for increased long‐term site quality in terms of higher P availability for future rotations.

Modeling the Effects of Stand Development, Site Quality, and Silviculture on Leaf Area Index, Litterfall, and Forest Floor Accumulations in Loblolly and Slash Pine Plantations

Leaf area index (LAI), needlefall (NF), and forest floor (FF) dynamics are tightly linked with stand productivity, nutrient cycling, and carbon, water, and energy exchange. We analyzed a long-term data set to quantify the impacts of stand development, site quality, and silviculture on LAI and litterfall (LF) in loblolly and slash pine plantations. LAI was significantly correlated with stand density index (SDI) for each stand studied (P 0.001), and the parameters of the fitted sigmoidal function were correlated with site index independently for each species. The maximum LAI that a loblolly or slash pine stand attained was linearly correlated with site index (P 0.001), and the slope of that relationship was different for each species (P 0.003). Soil resource availability affected the relationship between SDI and LAI. When weed control or fertilizer treatments were applied, the maximum attainable mean yearly LAI and the value of SDI that corresponded with the attainment of 50% of the maximum LAI (inflection point) were increased (P 0.05). NF production was linearly related to the previous year's LAI (P 0.001), and this relationship was independent of resources availability (P 0.086); however, the relationship was different for both species (P 0.001). Comparison of simulations of NF, LF, and FF with diverse data sets from the literature, encompassing the natural ranges of both species, indicated that these relationships captured the primary drivers of variation, and therefore the models provide a robust synthesis and prediction system for these important variables. FOR .S CI. 58(5):457-471.

Carbon Sequestration from 40 Years of Planting Genetically Improved Loblolly Pine across the Southeast United States

Highly productive, widely deployed genetically improved loblolly pine (Pinus taeda L.) may play an important role in mitigating rising atmospheric CO2 via carbon (C) sequestration. To understand the role of loblolly pine genetic improvement in future C sequestration strategies, we examined the historical (1968–2007) impact of operationally deploying improved families of loblolly pine on productivity and C sequestration across the southeast United States. Since 1977, nearly 100% of loblolly pine plantations in the southeast United States have been established with genetically improved loblolly pine. In recent years, more than 400,000 ha of genetically improved loblolly pine are planted annually. Between 1968 and 2007, we estimate that genetically improved loblolly pine plantations have produced a total of 25.6 billion m3 of stemwood volume and have sequestered 9,865 Tg C in live and dead biomass. Our estimates also indicate that genetic improvement has resulted in an additional 3.7 billion m3 (17% increase) and 1,100 Tg C (13%) of volume production and C sequestration, respectively, relative to volume production and C sequestration with no genetic improvement. We expect that loblolly pine plantation C sequestration will increase as more productive families and clones are deployed and as currently deployed genetic material continues to mature. Together, genetic improvement, intensive silvicultural, and longer rotations aimed at producing long-lived wood products will be important tools for maximizing C sequestration in loblolly pine plantations.

Effect of Harvest Residue Management on Tree Productivity and Carbon Pools during Early Stand Development in a Loblolly Pine Plantation

Soil incorporation of postharvest forest floor or logging residues during site preparation increased mineral soil carbon (C) and nitrogen (N) concentration and had a differential effect on early stand growth in a clonal loblolly pine (Pinus taeda L.) plantation. Incorporating 25 Mg ha 1 of forest floor (FF) (C/N ratio 112:1) or 25 (1LR) or 50 (2LR) Mg ha 1 masticated logging residues (C/N ratio 856:1) increased soil C concentration by 2449% in the top 60 cm of soil compared with that for a nontreated control or a raked (R) treatment where the forest floor (25 Mg ha 1 ) was removed. Although the long-term treatment effects on soil C are unknown, increased macro-organic matter C (150-2,000 m) in the recalcitrant heavy fraction coupled with an estimated 20- to 35-year turnover rate for the incorporated residues suggests that soil C will be elevated in the FF, 1LR, and 2LR treatments through the current rotation. There was a treatment age interaction on stand volume growth (P 0.03) caused by a differential response to FF and LR treatments. Relative to the control, the FF treatment increased stem volume growth and stand homogeneity, resulting in 18% more stand volume at age 6. In contrast, the LR treatments initially suppressed volume growth; however, at age 6 there were no significant differences in stem volume among control and LR treatments. Six-year stand volume was 116.6, 112.6, 135.1, 116.0, and 112.3 (SE 3.6) m 3 ha 1 in the control, R, FF, 1LR, and 2LR treatments, respectively. Whereas the efficacy of organic matter management will be site-dependent, our results suggest that soil incorporation of forest residues during site preparation can have positive benefits for productivity and building soil C on sites with relatively high inherent soil C stocks. FOR .S CI. 58(5):430-445.

The role of harvest residue in rotation cycle carbon balance in loblolly pine plantations. Respiration partitioning approach.

Timber harvests remove a significant portion of ecosystem carbon. While some of the wood products moved off-site may last past the harvest cycle of the particular forest crop, the effect of the episodic disturbances on long-term on-site carbon sequestration is unclear. The current study presents a 25year carbon budget estimate for a typical commercial loblolly pine plantation in North Carolina, USA, spanning the entire rotation cycle. We use a chronosequence approach, based on 5years of data from two adjacent loblolly pine plantations. We found that while the ecosystem is very productive (GEP up to 2900gm-2 yr-1 , NEE at maturity about 900g Cm-2 yr-1 ), the production of detritus does not offset the loss of soil C through heterotrophic respiration (RH ) on an annual basis. The input of dead roots at harvest may offset the losses, but there remain significant uncertainties about both the size and decomposition dynamics of this pool. The pulse of detritus produced at harvest resulted in a more than 60% increase in RH . Contrary to expectations, the peak of RH in relation to soil respiration (SR) did not occur immediately after the harvest disturbance, but in years3 and 4, suggesting that a pool of roots may have remained alive for the first few years. On the other hand, the pulse of aboveground RH from coarse woody debris lasted only 2years. The postharvest increase in RH was offset by a decrease in autotrophic respiration such that the total ecosystem respiration changed little. The observed flux rates show that even though the soil C pool may not necessarily decrease in the long-term, old soil C is definitely an active component in the site C cycle, contributing about 25-30% of the RH over the rotation cycle.

Development of Planting Density‐Specific Density Management Diagrams for Loblolly Pine

For density management diagrams (DMDs), it is usually assumed the relative value between Reineke’s stand density index (SDI) where self-thinning is expected to begin and a maximum size-density relationship species boundary line is constant regardless of planting density. Using estimated size-density trajectories of loblolly pine plantations in the southeastern United States, the quadratic mean diameter at which the onset of self-thinning occurs was determined. An equation was then fitted to estimate the quadratic mean diameter at which self-thinning is expected to begin relative to planting density. DMDs that accounted for planting density showed that self-thinning began at 40 –72% of the species maximum SDI for planting densities ranging from 605 to 2,722 seedlings per acre.

Silvicultural treatments for converting loblolly pine to longleaf pine dominance: Effects on resource availability and their relationships with planted longleaf pine seedlings

Throughout the southeastern United States, land managers are currently interested in converting loblolly pine (Pinus taeda L.) plantations to species rich longleaf pine (Pinus palustris Mill.) ecosystems. In a 3-year study on moderately well- to well-drained soils of the Lower Coastal Plain in North Carolina, we examined the effects of four canopy and three cultural treatments on plant resources and quantified relationships between plant resources and longleaf pine seedling survival and growth. Canopy treatments consisted of four levels of timber harvest applied to loblolly pine stands: Control (uncut, mean basal area of 16.2m2/ha), MedBA (single-tree selection to a mean residual basal area of 9.0m2/ha), LowBA (single-tree selection to a mean residual basal area of 6.4m2/ha), and Clearcut (complete canopy removal). Within each canopy treatment, we applied three cultural treatments designed to benefit the early growth of planted seedlings: no treatment (NT), herbicide (H), and herbicide plus fertilization (H+F). Gap light index (GLI) significantly differed among canopy treatments and nonlinearly increased with decreasing basal area. The H treatment resulted in higher temperatures at 10cm in the soil. Canopy thinning increased foliar calcium (Ca) concentration. The annual root collar diameter (RCD) increment of planted longleaf pine seedlings was positively correlated with GLI, and foliar phosphorus (P) and Ca concentrations but was negatively correlated with soil moisture. Our results confirm that light is an important factor controlling the growth of longleaf pine seedlings.