Loblolly Pine Stands Research Articles

Responses of Arthropods to Large-Scale Manipulations of Dead Wood in Loblolly Pine Stands of the Southeastern United States

Large-scale experimental manipulations of dead wood are needed to better understand its importance to animal communities in managed forests. In this experiment, we compared the abundance, species richness, diversity, and composition of arthropods in 9.3-ha plots in which either (1) all coarse woody debris was removed, (2) a large number of logs were added, (3) a large number of snags were added, or (4) no coarse woody debris was added or removed. The target taxa were ground-dwelling arthropods, sampled by pitfall traps, and saproxylic beetles (i.e., dependent on dead wood), sampled by flight intercept traps and emergence traps. There were no differences in total ground-dwelling arthropod abundance, richness, diversity, or composition among treatments. Only the results for ground beetles (Carabidae), which were more species rich and diverse in log input plots, supported our prediction that ground-dwelling arthropods would benefit from additions of dead wood. There were also no differences in saproxylic beetle abundance, richness, diversity, or composition among treatments. The findings from this study are encouraging in that arthropods seem less sensitive than expected to manipulations of dead wood in managed pine forests of the southeastern United States. Based on our results, we cannot recommend inputting large amounts of dead wood for conservation purposes, given the expense of such measures. However, the persistence of saproxylic beetles requires that an adequate amount of dead wood is available in the landscape, and we recommend that dead wood be retained whenever possible in managed pine forests.

Environmental and genetic effects on crown shape in young loblolly pine plantations

Tree crown shape is an important trait affecting the light environment in forest canopies. We examined genetic and environmental effects on outer crown shape of young single-family stands of loblolly pine ( Pinus taeda L.). Crown diameter profiles were measured after canopy closure at four experimental sites in the southeastern US. The two examined families of contrasting aboveground productivity differed in crown length but not in their outer crown shapes or crown shape ratios, defined as the ratio of crown diameter to crown length. Within each site, intensive silvicultural treatment, consisting of fertilization and control of competing vegetation, had little effect upon crown shape. A strongly significant effect of site on crown shape parameters was found in the family grown at all four experimental sites; however, density differences among the experimental series likely accounted for a part of the across-sites variation in crown shape. In contrast to other studies on crown shape in trees, and to findings at age 2 years in the same stands, we conclude that family effects on the outer crown shape were small compared with the environmental effects in these 5-year-old pine plantations, following canopy closure.

Competition dynamics in pure- versus mixed-family stands of loblolly and slash pine in the southeastern United States

Few studies within the native range of loblolly ( Pinus taeda L.) and slash pine ( Pinus elliottii Engelm. var. elliottii) have compared yield and stand dynamics in pure-family block versus mixed-family block plantings under a range of silvicultural treatments. Understanding intergenotypic competitive interactions is important for predicting phenotypic performance, defining growth strategies and ideotypes, and deploying the correct mix of families that possess complementary characteristics for enhanced yield and pest resistance. In 2000, replicated experimental trials were installed in the southeastern United States, controlling for genotype (pure- and mixed-family plantings; consisting of seven full-sibling loblolly and six full-sibling slash pine families), planting density (1334 vs. 2990 trees/ha), and levels of silvicultural treatment intensity (operational vs. intensive). We measured four installations of these trials. There were numerous examples of differential family performance in mixed versus pure plots manifested as significant deployment × family interactions for diameter at breast height, height, basal area, volume, survival, disease, and damage traits. Significant and consistent interactions of several families with mixed versus pure deployment led to the identification of putative crop and competition ideotypes in both loblolly and slash pine. Tree-level crown architectural traits and an index of growth efficiency for the identified families were consistent with the hypothesized ideotypes.

Resin flow responses to fertilization, wounding and fungal inoculation in loblolly pine (Pinus taeda) in North Carolina

Resin flow is the primary means of natural defense against southern pine beetle (Dendroctonus frontalis Zimm.), the most important insect pest of Pinus spp. in the southern United States. As a result, factors affecting resin flow are of interest to researchers and forest managers. We examined the influence of fertilization, artificial wounding and fungal inoculation on resin flow in 6- and 12-year-old stands of loblolly pine (Pinus taeda L.) and determined the extent of that influence within and above the wounded stem area and through time. Fertilization increased constitutive resin flow, but only the younger trees sustained increased resin flow after wounding and inoculation treatments. An induced resin flow response occurred between 1 and 30 days after wounding and inoculation treatments. Wounding with inoculation resulted in greater resin flow than wounding alone, but increasing amounts of inoculum did not increase resin flow. Increased resin flow (relative to controls) lasted for at least 90 days after wounding and inoculation. This increase appeared to be limited to the area of treatment, at least in younger trees. The long-lasting effects of fungal inoculation on resin flow, as well as the response to fertilization, suggest that acquired resistance through induced resin flow aids in decreasing susceptibility of loblolly pine to southern pine beetle.

Tree-Soil Interactions Affect Production of Loblolly and Slash Pine

Abstract Species-related differences in needle litter nutrient concentrations and subsequent N mineralization were examined in 17-year-old stands of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) at a common site. Results of this common-garden study indicate that a feedback may exist between foliar litter nutrient concentration and soil N mineralization. Net N mineralization (to 30 cm) was significantly greater in loblolly pine than in slash pine stands, which was attributed to greater litter nutrient concentrations in loblolly pine. Stand volume production was also greater in loblolly pine than in slash pine and was positively correlated with N mineralization. Although lower litter nutrient concentrations may have reduced productivity of slash pine relative to loblolly pine in this study, they may serve as a mechanism to increase the relative fitness of the species by lowering the soil nutrient availability below the optimum of loblolly pine.

Stand Assessment through Lidar-Based Forest Visualization Using Immersive Virtual Environment Technology

Abstract This study examined the utility of light detection and ranging (lidar) remote sensing combined with immersive virtual environment technology for timber stand assessment. Lidar data were used to identify locations and extract dimensional information of trees in immature and mature loblolly pine (Pinas taeda, L) stands in northeast Mississippi. Computer visualized stands were built on the basis of lidar measurements and were projected with an interactive room-size stereoscopic display. Representational quality of lidar-based virtual forests was assessed through stand descriptions made by human subjects recruited from the Department of Forestry at Mississippi State University. Subjects examined either field-recorded videos or computer visualizations of immature and mature stands and estimated stocking, tree size class, height class, rotation stage, stand structure, and hardwood competition of each stand. Estimated stand characteristics by the two groups were compared. Significant viewer group differences were found in height class and rotation stage but not in other characteristics. Discussion includes how the immersive virtual environment technologies are potentially useful in natural resources management. Further study of economic aspects and interface development would be required to promote these technologies to an operational system.

Scaling Taper Relationships from Miniature-Scale to Operational-Scale Stands of Loblolly Pine

Abstract Taper relationships for trees grown in miniature- and operational-scale stands of loblolly pine were established using stem analysis data from 106 and 173 trees, respectively. Tree taper was modeled using segmented polynomial and dimensionally compatible taper equations. The relationship was then scaled from miniature to operational scale using the profiles obtained from these taper equations. Stump diameter was used in the taper equations instead of dbh in scaling the relationship. A simple linear regression equation described well the taper relationship between trees grown at miniature and operational scales. The fit statistics for both the segmented polynomial and dimensionally compatible taper equations were comparable at both scales. In terms of predictive accuracy, however, the segmented polynomial taper equation was superior to the dimensionally compatible taper equation in scaling the taper relationship for trees from miniature- to operational-scale plots.

Estimating biomass of individual pine trees using airborne lidar

Airborne lidar (Light Detection And Ranging) is a proven technology that can be used to accurately assess aboveground forest biomass and bio-energy feedstocks. The overall goal of this study was to develop a method for assessing aboveground biomass and component biomass for individual trees using airborne lidar data in forest settings typical for loblolly pine stands (Pinus taeda L.) in the southeastern United States. More specific objectives included: (1) assessing the accuracy of estimating diameter at breast height (dbh) for individual pine trees using lidar-derived individual tree measurements, such as tree height and crown diameter, and (2) investigating the use of lidar-derived individual tree measurements with linear and nonlinear regression to estimate per tree aboveground biomass. In addition, the study presents a method for estimating the biomass of individual tree components, such as foliage, coarse roots, stem bark, and stem wood, as derived quantities from the aboveground biomass prediction. A lidar software application, TreeVaW, was used to extract forest inventory parameters at individual tree level from a lidar-derived canopy height model. Lidar-measured parameters at individual tree level, such as height and crown diameter, were used with regression models to estimate dbh, aboveground tree biomass, and tree-component biomass. Field measurements were collected for 45 loblolly pine trees over 0.1- and 0.01-acre plots. Linear regression models were able to explain 93% of the variability associated with individual tree biomass, 90% for dbh, and 79–80% for components biomass.

A weighted relative density model applied to loblolly pine (Pinus taeda L.) stands

We present a weighted, individual-tree relative density approach whose reference conditions have the same distribution of crown areas and species as a subject stand. An initial evaluation of the method’s efficacy was performed within an even-aged loblolly pine (Pinus taeda L.) plantation. Species-specific reference density equations were developed using plot data and existing crown width equations. Diameter growth prediction was evaluated using data from a thinned 20-year-old plantation. Regression analysis was used to related annual diameter increment and the approach’s density indices. The predictive ability of the presented method was compared to existing approaches such as Stand Density Index (SDI) and Crown Competition Factor (CCF). Results suggest the weighted, individual-tree approach predicts diameter increment as well as traditional indices. These findings suggest an individual tree approach may not be necessary within an even-aged loblolly pine plantation with a narrow diameter range. Key words: relative density, size-density, Pinus taeda L., loblolly pine.

Comparing forest assessment based on computer visualization versus videography

This study examined the representational validity of computer-visualized forests by comparing them with field-recorded walkthrough videos (field videos) from a timber stand management perspective. Computer-visualized replicas of field conditions at selected locations in loblolly pine ( Pinus taeda, L.) stands were generated using measured data. Human subjects examined either field videos or computer visualizations and assessed characteristics of five distinct stands which consist of three well managed spacing stands (1.5 m, 2.4 m, and 3.0 m) and two minimally managed stands (immature and mature stands). Subjects viewing computer visualizations tended to estimate lower stem density and higher mean diameter of the well managed stands. Assessed stand structure of the well managed stands through the field videos and computer visualizations were in relatively high level of agreement. In minimally managed stands, significant differences were not found in density assessments including mean spacing, stem density, and mean diameter; however, horizontal crown cover in the immature stand was estimated lower using computer visualizations. Field video and computer visualization groups perceived different stand structure in the mature stand in which hardwoods were present in the mid-canopy.

Differential impacts of the southern pine beetle, Dendroctonus frontalis, on Pinus palustris and Pinus taeda

Patterns of host use by herbivore pests can have serious consequences for natural and managed ecosystems but are often poorly understood. Here, we provide the first quantification of large differential impacts of the southern pine beetle, Dendroctonus frontalis Zimmermann, on loblolly pine, Pinus taeda L., and longleaf pine, Pinus palustris P. Mill., and evaluate putative mechanisms for the disparity. Spatially extensive survey data from recent epidemics indicate that, per square kilometre, stands of loblolly versus longleaf pine in four forests (380–1273 km2) sustained 3–18 times more local infestations and 3–116 times more tree mortality. Differences were not attributable to size or age structure of pine stands. Using pheromone-baited traps, we found no differences in the abundance of dispersing D. frontalis or its predator Thanasimus dubius Fabricius between loblolly and longleaf stands. Trapping triggered numerous attacks on trees, but the pine species did not differ in the probability of attack initiation or in the surface area of bark attacked by growing aggregations. We found no evidence for postaggregation mechanisms of discrimination or differential success on the two hosts, suggesting that early colonizers discriminate between host species before a pheromone plume is present.

Silvicultural Thinning Intensity Effects on Increasing the Growth of Planted Loblolly Pine (Pinus taeda L.) Stands in Northern Iran

Loblolly pine (Pinus taeda L.) is 1 of the main exotic species in commercial plantations in northern Iran. These plantations are situated in the Caspian forests of Iran, which border the southern coast of the Caspian Sea and cover an area of 1.9×10^6 ha. For the present experiment, unthinned, and lightly and moderately thinned stands were selected as 3 populations. Data were collected from a total of 180 trees among the different stand densities. For basal area analysis, 93 plots were measured. Variables such as diameter at breast height (dbh), total height, tree volume, bark thickness, basal area per hectare, crown length, and crown diameter were measured. The growth rate ratios of dbh in the lightly and moderately thinned stands were 1.09 and 1.18, while the mean annual increments of basal area growth rates in the 2 thinned populations were 1.186 and 1.20, respectively. Moderate thinning increased the volume of stands by about 20.60% of the stand volume. This analysis indicated that moderate thinning drastically affected the basal area and the growth rate of volume. After thinning, dimensions of live crowns increased and more branches were evident. Percentages of live crown ratios in the 3 study populations were calculated to be 41.23, 43.87, and 44.52%. Growth rate interpretations were supported by statistical multivariate analysis of variance using Wilk's (Λ) and Hotelling's T(superscript 2 subscript 2) tests. Wilk's test was carried out on a mean vector of 6 variables in the 3 study populations. The null-hypothesis (F(subscript c)=14.435＞F(subscript t)=4.37) was rejected at the 0.01 level of significance. Thus, the results indicated that moderate thinning significantly influenced increased growth rates of planted loblolly pine stands.

Using multispectral satellite imagery to estimate leaf area and response to silvicultural treatments in loblolly pine stands

The relationship between leaf area index (LAI) of loblolly pine plantations and the broadband simple ratio (SR) vegetation index calculated from Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data was examined. An equation was derived to estimate LAI from readily available Landsat 7 ETM+ data. The equation developed to predict LAI with Landsat 7 ETM+ data was tested with ground LAI measurements taken in 12 plots. The root mean square error of prediction was 0.29, an error of approximately 14% in prediction. The ability of Landsat 7 ETM+ data to consistently estimate SR over time was tested using two scenes acquired on different dates during the winter (December to early March). Comparison between the two images on a pixel-by-pixel basis showed that approximately 96% of the pixels had a difference of <0.5 units of SR (approximately 0.3 units of LAI). When the comparison was made on a stand-by-stand basis (average stand SR), a maximum difference of 0.2 units of SR (approximately 0.12 units of LAI) was found. These results suggest that stand LAI of loblolly pine plantations can be accurately estimated from readily available remote sensing data and provide an opportunity to apply the findings from ecophysiological studies in field plots to forest management decisions at an operational scale.

Poultry Litter Application to Loblolly Pine Forests

Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8-yr-old stands at 0, 4.6, and 18.6 dry Mg ha-1, supplying 0, 200, and 800 kg N ha-1 and 0, 92, and 370 kg P ha-1, respectively. Levels of nitrate in soil water, monitored at a 50-cm depth with porous cup tension lysimeters, exceeded 10 mg N L-1 during the first two years after application in the 18.6 Mg ha-1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha-1 rate. Mehlich III-extractable phosphate peaked in excess of 100 microg P g-1 soil during the third year of the study for the 18.6 Mg ha-1 rate. The 4.6 Mg ha-1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross-sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha-1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha-1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.

Repeatability estimates for oleoresin yield measurements in three species of the southern pines

Repeatability was estimated for constitutive oleoresin yield measurements in 10 stands of three species of pines native to southeastern United States. Trees of these species that discharge large quantities of oleoresin upon wounding are considered to be most resistant to attack by southern pine beetle ( Dendroctonus frontalis Zimmermann). Oleoresin yield is usually measured from one or more small surface wounds cut into the bole at breast height. Because multiple measurements per tree are possible, phenotypic variation in oleoresin yield includes among- and within-tree components. Thus it is of interest to determine the repeatability or relative contribution of variation among trees to phenotypic variation in oleoresin yield observed in populations. In the sample of stands studied, repeatability estimates were moderate to moderately high ( r = 0.43–0.77), with no stands displaying low repeatability. For most stands estimates were greater than 0.5, implying that variation among trees is greater than variability within trees. These results suggest that for most purposes, two measurements per tree are adequate for estimating tree resin yields at breast height. Because initial attacks of D. frontalis are believed to most frequently occur at bole heights of 3–5 m, measurements taken on trees in two loblolly pine stands were used to develop equations for predicting oleoresin yields at a height of 4.5 m from assessments made at 1.5 m. To obtain reasonably good predictions it was necessary to develop a unique equation for each site. In addition, a new expression for approximating the standard error of repeatability estimates is introduced.

Factors Influencing Acadian Flycatcher Nesting Success in an Intensively Managed Forest Landscape

We examined factors affecting the nesting success of a migratory songbird, the Acadian flycatcher (Empidonax virescens), in loblolly pine plantations in the coastal plain of South Carolina, USA. From 1997–2000, we located and monitored 163 Acadian flycatcher nests in loblolly pine stands and corridors that were 18–27 years old. We used Mayfield logistic regression (Aebischer 1999, Hazler 2004) to model the effects of edge and stand-level vegetation structure on nest daily survival rate. There was no evidence of an effect of edge on nest survival, but nest survival was positively related to the height of the deciduous subcanopy and to the density of shrub cover. Although Acadian flycatchers are generally regarded as habitat specialists requiring mature hardwood forests, our data suggest that pine plantations can support breeding populations, provided that a substantial hardwood component is present. We believe that maintaining multiple vegetation strata and increasing the length of harvest rotations would improve the habitat value of pine plantations for Acadian flycatchers and presumably other species more typically associated with deciduous forests. Maintenance of a corridor network, as practiced by some industrial forest managers, is one means of providing more mature forest habitat, thereby fostering higher nesting success. Concern that these corridors might act as ecological traps seems to be unwarranted in our study area. Corridors thus appear to be a valuable management tool for promoting wildlife values within the context of an industrial forest landscape.

Fertilization effects on forest carbon storage and exchange, and net primary production: A new hybrid process model for stand management

A critical ecological question in plantation management is whether fertilization, which generally increases yield, results in enhanced C sequestration over short rotations. We present a rotation-length hybrid process model (SECRETS-3PG) that was calibrated (using control treatments; CW) and verified (using fertilized treatments; FW) using daily estimates of H 2O and CO 2 fluxes, canopy leaf area index ( L), and annual estimates of tree growth and dimension. Herein, we focus on two decades of loblolly pine ( Pinus taeda L.) growth and establishment for stands growing on a nutrient poor, droughty soil (SETRES; Southeast Tree Research and Education Site) in North Carolina, USA, on a site previously occupied by a ∼30-year-old natural long-leaf pine ( P. palustris Mill.) stand. The SECRETS-3PG model combines: (1) a detailed canopy process model with hourly and daily resolution, (2) a biometrically accurate tree and stand growth module for monthly allocation, 3-PG, and (3) empirical models of soil CO 2 efflux ( R S). Simulated L, quadratic mean tree diameter, and total standing biomass all tracked field measurements over a 10-year period. Simulated maintenance respiration, canopy transpiration, and R S mirrored, with minor exceptions, short-term independently acquired data. Model correspondence with the independent measurements provided a basis for making short-term estimates of net ecosystem productivity (NEP) and longer-term estimates of net primary production (NPP) over the 20-year period from planting. Simulations suggest that optimum fertilization amendments; (1) increased NEP by more than 10-fold over control – FW (952 g C m −2 a −1) and CW (71 g C m −2 a −1) – at maximum NPP and (2) increased NPP two-fold (1334 and 669 g C m −2 a −1 for FW and CW, respectively) at maximum L. Seasonal patterns in NEP suggest that autumn and winter may be critical periods for C uptake in nutrient-limited loblolly pine stands. We conclude that increased L in response to improved nutrition may enable loblolly pine to achieve positive annual NEP earlier in rotation.

Small Mammal Distributions Relative to Corridor Edges Within Intensively Managed Southern Pine Plantations

Abstract We characterized small mammal communities in three loblolly pine (Pinus taeda) stands in the Lower Coastal Plain of South Carolina during June 1998–Aug. 2000 to investigate influence of corridor edges on small mammal distribution. We live-trapped small mammals in three regenerating stands following clearcutting. Harvested stands were bisected by 100-m-wide, 20–23-year-old pine corridors. During 47,040 trap nights, we recorded 907 captures of 661 individual small mammals. Species captured included southern short-tailed shrews (Blarina carolinensis), cotton mice (Peromyscus gossypinus), cotton rats (Sigmodon hispidus), eastern harvest mice (Reithrodontomys humulis), marsh rice rats (Oryzomys palustris), and golden mice (Ochrotomys nuttalli). We did not observe an edge effect (i.e., preference or avoidance) in small mammal captures at the corridor edge. Rodent captures were greatest in harvested stands, declined near the edge of mature pine corridors, and were lowest within corridors. Shrew captures were generally greatest in mature pine corridors and least in the interior of harvested stands. Retention of mature pine corridors of only 100 m may maintain some small mammals (i.e., shrews) that would not occur if stands were completely harvested. South. J. Appl. For. 29(3):148–151.

Juvenile diameter distributions of loblolly pine characterized by the two-parameter Weibull function

Diameter distributions of juvenile loblolly pine (Pinus taeda L.) were characterized utilizing a two-parameter Weibull distribution to aid in forecasting and simulation of young stands. Juvenile diameter distributions were studied to gain insight into the effects of various stand-level factors. Results show that diameter distributions in juvenile loblolly pine stands can be successfully characterized with the two-parameter Weibull function. Repeated measures analysis detected significant planting density, age, and age by planting density interaction effects for the scale and shape parameter estimates from the two-parameter Weibull distribution. Using parameter recovery techniques, estimated diameter distributions were derived from easily attainable stand-level characteristics (i.e. basal area per hectare, planting density, age, and quadratic mean diameter). A thorough understanding of juvenile diameter distributions should prove especially useful for operational planning of stands on short rotations that require estimates of productivity at early ages.

Diet of Southern Toads (Bufo terrestris) in Loblolly Pine (Pinus taeda) Stands Subject to Coarse Woody Debris Manipulations

In the southeastern United States, coarse woody debris (CWD) typically harbors high densities of invertebrates. However, its importance as a foraging substrate for southeastern amphibians is relatively unknown. We examined effects of CWD manipulations on diet composition of southern toads (Bufo terrestris) in upland loblolly pine (Pinus taeda) stands in the Coastal Plain of South Carolina. Twelve 9.3-ha plots were assigned one of the following treatments: removal- all CWD ≥10 cm in diameter and ≥60 cm long removed; downed- five-fold increase in volume of down CWD; and unmanipulated control stands. We collected southern toads ≥4 cm snout-vent length (SVL) during 14 d sampling periods in June and October 2002, June 2003 and during a 28 d sampling period in April 2003. We collected 80, 36 and 35 southern toads in control, downed and removal treatments, respectively. We found no difference in relative abundance or frequency of invertebrate groups consumed among treatments (P > 0.05). Average body weight (g), SVL (cm) and stomach content weight (g wet) of individuals also were similar among treatments (P > 0.05). The role of CWD as a foraging substrate for southern toads in loblolly pine stands of the southeastern Coastal Plain may be negligible, at least in the early stages of decay.