Search

Higher productivities for loblolly pine (Pinus taeda L.) growing at exotic locations (e.g., Hawaii, Brazil) indicate that the full growth potential of this southern pine species has yet to be reached in plantations across the southeastern United States (US). The higher productivity of Hawaii-grown loblolly pine has been attributed to more favorable climate conditions. To date, physical, anatomical, and chemical property data for loblolly pine wood from exotic locations are scarce. Mid-infrared spectroscopy coupled with multivariate analysis was used to screen for chemical differences between wood samples from Hawaii (HI), North Carolina (NC), and Mississippi (MS). The principal component analysis scores plot showed that the MS samples formed a distinct cluster apart from overlapping clusters for the other two sites. Using standard wet chemistry procedures, we found that the mean lignin content for the MS site (30.1%) was significantly lower than that determined for the NC (34.5%) and HI (33.9%) sites; said lower lignin value was offset by significantly higher glucose and mannose contents. Results on the US mainland were seemingly consistent with the greater formation of latewood at sites with longer growing seasons, and the lower lignin content of latewood relative to earlywood shown for pines. Given the low percent latewood for the HI site (37.2%) relative to both mainland sites (MS, 54.8%; NC, 53.1%), yet similar lignin contents between the NC and HI sites, it appears that the relative lignin value for these exotically-grown loblolly pine trees cannot be solely attributed to the proportion of latewood. [ABSTRACT FROM AUTHOR]

Key message: Longleaf pine demonstrated general resistance to reduced soil moisture and increased VPD, but results highlight the soil and atmospheric conditions that could trigger declines in longleaf pine function and productivity. Low soil moisture and high atmospheric vapor pressure deficit (VPD) independently limit tree function and forest productivity. However, questions remain about how large, established trees respond to dry soil and high VPD over longer time periods. We carried out a 3-year throughfall reduction experiment in a young (12–14-year-old) longleaf pine plantation in west Georgia (USA). We hypothesized that throughfall reduction would reduce soil moisture, leaf-scale stomatal conductance (gs), and net photosynthesis (Pnet), but increase intrinsic water-use efficiency (iWUE). We also hypothesized that throughfall reduction would reduce canopy conductance (Gs) at a reference VPD of 1 kPa and Gs sensitivity to VPD. In addition, we used Gs data collected across both treatments to identify breakpoints in the relative control of soil moisture and VPD on Gs. Throughfall reduction decreased soil moisture and caused small reductions in gs (– 21%) and Pnet (– 13%), but no change in iWUE. As expected, reduced throughfall decreased Gs and Gs sensitivity to VPD by 20 and 8%, respectively. Despite this, throughfall reduction had very little effect on tree growth or forest productivity. Importantly, Gs sensitivity to VPD was similar at intermediate soil moisture, but highest and lowest at soil moistures above field capacity and below the permanent wilting point, respectively. Consequently, we could identify thresholds in the relative control of soil moisture and VPD over Gs. These results demonstrate the general resistance of longleaf pine plantations to reduced soil moisture and increased VPD but highlight the soil and atmospheric conditions that could trigger declines in longleaf pine function and productivity. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Studies linking wood properties of the southern pines to climate parameters and/or irrigation treatments have generally used seedlings or mid-rotation age trees, the latter comprised primarily of juvenile wood. To investigate possible drought-induced effects on mature wood physical properties, densitometry data from 50-year-old slash (Pinus elliottii Engelm.), longleaf (Pinus palustris Mill.), and loblolly (taeda L.) pine trees were matched with annual soil moisture values. Each of two growth ring groupings per increment core had a two-year period of ample moisture followed by a two-year period of drought; these were centered at ages of 20 and 38 years. For slash pine, the latewood width was 30% lower (p = 0.011) for the drought period at age 20. Seemingly similar results were obtained for longleaf pine, but the probability (p = 0.051) just exceeded the threshold for significance (α = 0.05). No differences were observed for either earlywood or total ring widths. Ring specific gravity (SG) values that were 11% lower for slash pine and 7% lower for longleaf pine can be attributed to drought-related reductions in latewood formation. Unlike other studies with younger trees, both percent latewood and ring SG values for mature loblolly pine were unaffected by drought. [ABSTRACT FROM AUTHOR]

Lignin contents of mature wood growth rings formed under soil moisture extremes were determined to investigate the possibility of drought-caused reductions in lignin deposition for the southern pines. A well-defined set of slash (Pinus elliottii Engelm.), longleaf (Pinus palustris Mill.) and loblolly pine (Pinus taeda L.) increment cores were processed to excise growth rings formed during multiyear periods of above- (wet) or below-normal (drought) soil moisture. The average acid-insoluble (Klason) lignin content of the resultant drought-formed slash pine wood samples was significantly lower (31.4% vs. 34.1%; P = 0.0005) than that for the corresponding wood samples from growth rings formed under conditions of ample soil moisture; respectively higher glucan (40.6% vs. 36.9%; P = 0.0010) and mannan (11.7 vs. 10.4%; P = 0.0010) values were also observed. Small, but significant differences for other hemicellulose derived sugars (xylan, arabinan) were determined for the longleaf and loblolly pine wood samples. Altogether, these data represent the first wet chemical results showing differences in lignin and polysaccharide sugar contents for mature wood formed in pine trees during annual droughts. Among the southern pines evaluated here, slash pine is the least drought tolerant; the lower lignin content observed for the slash pine drought-formed wood is particularly intriguing since it occurred with the species most susceptible to water stress. [ABSTRACT FROM AUTHOR]

In recent decades, conservation objectives have driven changes to the management of some pine forests in the southeastern United States. Forest thinning and frequent burning of old-field and plantation pine forests have resulted in an open loblolly-shortleaf pine forest community which resembles the original longleaf pine forest. It is, however, unclear how the structure, composition, and function of the loblolly-shortleaf forest compare to natural longleaf pine forest, and whether it represents an alternative stable state, or simply a transitional state. Understanding the stability of open loblolly-shortleaf pine forest is critical, particularly because several threatened and endangered species are now reliant on it for habitat. The structure and composition of loblolly-shortleaf forest and natural longleaf pine forest were compared using data from permanent forest plots at Fort Benning, Georgia, USA. To assess the stability of the loblolly-shortleaf pine forest and determine whether it is an alternative stable or transitional state, the LANDIS-II forest landscape simulation model was used to simulate changes in forest type cover under no disturbance, and a frequent-fire regime at Fort Benning. Under both management scenarios, nearly all loblolly-shortleaf pine forest converted to mixed hardwood forest over the course of the simulation, with most conversion occurring within 60 yr. In contrast, longleaf pine forest cover increased under frequent fire. Several important structural and compositional differences may have contributed to the instability of loblolly-shortleaf pine forest compared to longleaf pine forest. These include, among other factors, higher densities of resprouting hardwood trees and shrubs in loblolly-shortleaf pine forest, including sweetgum, a resilient broadleaf species capable of transforming ecosystem structure. These results highlight the instability of the open loblolly-shortleaf pine forest community and confirm that is a transitional state, destined for mixed hardwood forest in the coming decades under either no disturbance or frequent fire alone. Future forest planning should consider an active transition from the loblolly-shortleaf pine forest in the coming decades if open pine forest is to be conserved for wildlife and conservation objectives. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forests can partially offset greenhouse gas emissions and contribute to climate change mitigation, mainly through increases in live biomass. We quantified carbon (C) density in 20 managed longleaf pine ( Pinus palustris Mill.) forests ranging in age from 5 to 118 years located across the southeastern United States and estimated above- and belowground C trajectories. Ecosystem C stock (all pools including soil C) and aboveground live tree C increased nonlinearly with stand age and the modeled asymptotic maxima were 168 Mg C/ha and 80 Mg C/ha, respectively. Accumulation of ecosystem C with stand age was driven mainly by increases in aboveground live tree C, which ranged from <1 Mg C/ha to 74 Mg C/ha and comprised <1% to 39% of ecosystem C. Live root C (sum of below-stump C, ground penetrating radar measurement of lateral root C, and live fine root C) increased with stand age and represented 4-22% of ecosystem C. Soil C was related to site index, but not to stand age, and made up 39-92% of ecosystem C. Live understory C, forest floor C, downed dead wood C, and standing dead wood C were small fractions of ecosystem C in these frequently burned stands. Stand age and site index accounted for 76% of the variation in ecosystem C among stands. The mean root-to-shoot ratio calculated as the average across all stands (excluding the grass-stage stand) was 0.54 (standard deviation of 0.19) and higher than reports for other conifers. Long-term accumulation of live tree C, combined with the larger role of belowground accumulation of lateral root C than in other forest types, indicates a role of longleaf pine forests in providing disturbance-resistant C storage that can balance the more rapid C accumulation and C removal associated with more intensively managed forests. Although other managed southern pine systems sequester more C over the short-term, we suggest that longleaf pine forests can play a meaningful role in regional forest C management. [ABSTRACT FROM AUTHOR]

Rapid and accurate estimations of the heterotrophic and autotrophic components of total soil respiration (Rs) are important for calculating forest carbon budgets and for understanding carbon dynamics associated with natural and management-related disturbances. The objective of this study was to use deep (60 cm) root exclusion tubes and paired control (i.e., no root exclusion) collars to estimate heterotrophic respiration (Rh) and Rs, respectively, in three 26-year-old longleaf pine (Pinus palustris Mill.) stands in western Georgia. Root biomass was measured in root exclusion tubes and control collars after 102-104 days of incubation and fine root biomass loss from root exclusion was used to quantify root decay. Mean Rs from control collars was 3.3 micromol·CO2·m-2·s-1. Root exclusion tubes decreased Rs, providing an estimate of Rh. Mean Rh was 2.7 micromol·CO2·m-2·s-1 when uncorrected by pretreatment variation, root decay, or soil moisture compared to 2.1 micromol-·CO2·m-2·s-1 when Rh was corrected for root decay. The corresponding ratio of Rh to Rs ranged from 66% to 82%, depending on the estimation method. This study provides an estimate of Rh in longleaf pine forests, and demonstrates the potential for deep root exclusion tubes to provide relatively rapid assessments (i.e., ~40 days post-treatment) of Rh in similar forests. The range in Rh to Rs is comparable to other reports for similar temperate coniferous ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Currently, little information is available to estimate individual tree attributes for longleaf pine (Pinus palustris Mill.), an important tree species of the southeastern United States, the majority of available models are local, relying on stem diameter outside bark at breast height (dbh, cm) and not including stand-level parameters. We developed a set of individual tree equations to predict tree height (H, m), stem diameter inside bark at 1.37 m height (dbhIB, cm), stem volume outside bark (VOB, m3), and stem volume inside bark (VIB m3), as well as functions to determine merchantable stem volume ratio (both outside and inside bark) from the stump to any top diameter. Local and general models are presented for each tree attribute. General models included stand-level parameters such as age, site index, dominant height, basal area, and tree density. The user should decide which model type to use, depending on data availability and level of accuracy desired. To our knowledge, this is the first comprehensive individual tree-level set of equations reported for longleaf pine trees, including local and general models, which can be applied to longleaf pine trees over a large geographical area and across a wide range of ages and stand characteristics. The system presented here provides important new tools for supporting future longleaf pine management decisions [ABSTRACT FROM AUTHOR]

Longleaf pine (Pinus palustris Mill.) is an important tree species of the southeast U.S. Currently there is no comprehensive stand-level growth and yield model for the species. The model system described here estimates site index (SI) if dominant height (Hdom) and stand age are known (inversely, the model can project Hdom at any given age if SI is known). The survival (N) equation was dependent on stand age and Hdom, predicting greater mortality on stands with larger Hdom. The function that predicts stand basal area (BA) for unthinned stands was dependent on N and Hdom. For thinned stands BA was predicted with a competition index that was dependent on stand age. The function that best predicted stand stem volume (outside or inside bark) was dependent on BA and Hdom. All functions performed well for a wide range of stand ages and productivity, with coefficients of determination ranging between 0.946 (BA) and 0.998 (N). We also developed equations to estimate merchantable volume yield consisting of different combinations of threshold diameter at breast height and top diameter for longleaf pine stands. The equations presented in this study performed similarly or slightly better than other reported models to estimate future N, Hdom and BA. The system presented here provides important new tools for supporting future longleaf pine management and research. [ABSTRACT FROM AUTHOR]

Interest in restoration of longleaf pine (Pinus palustris Mill.) in the southern United States offers opportunities for carbon (C) sequestration. To better understand C fluxes in longleaf pine, soil CO2 efflux (SR) and forest C pools were measured in 50-year-old stands varying in basal area from 7 to 36 m² ha-1. Soil CO2 efflux measured monthly ranged from 1.6 to 6.4 μmol CO2 m-2 s-1 and was strongly related to soil temperature and only weakly related to basal area and forest characteristics associated with varying basal area. The annual sum of SR ranged from 11.0 to 17.9 Mg C ha-1 year-1. Litter mass explained the majority (38%) of the variation in annual SR among plots varying in basal area. Standing C stocks, which included longleaf pine aboveground and below-stump biomass, litter, soil C, live and dead fine and coarse roots (all species), down deadwood and buried coarse woody debris, ranged from 63.8 to 176.8 Mg C ha-1 Similar SR but low longleaf pine net primary productivity in low basal area stands suggests that those stands were carbon sources; however, more information on the contribution of the herbaceous layer to ecosystem net primary productivity and SR is needed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Mountain Longleaf National Wildlife Refuge (MLNWR), located in northeastern Alabama, is unique in that it holds significant acreages of young and old-growth montane longleaf pine forest (Pinus palustris Mill.). We conducted a study to aid in the management and restoration of longleaf pine communities on the MLNWR. Our objectives were to: (I) establish permanent forest monitoring plots; (2) document herbaceous and woody vegetation; and (3) measure forest diversity, structure, and fuel loads in montane longleaf pine communities with varying fire and management histories. We established 48 plots, 0.04 ha in area, in winter 2008 and measured all plots in summer 2008. The MLNWR has recently incorporated prescribed burning in their management plans and each plot was categorized by the year it was burned (2008, 2006, 2004, no-burn) and whether hardwood control treatments were applied. We identified 18, 19, and 22 different woody plant species in the overstory, mid-story, and understory, respectively, across plots. Longleaf pine basal area ranged from 5 to 10 m² ha-1 and represented as much as 80% of basal area across plots. Mid-story basal area and woody plant species diversity were lower in plots receiving fire or hardwood control. Longleaf pine regeneration was found in only 17 plots and was highest in burned plots or plots receiving hardwood control. Burning also increased grass and herbaceous ground cover. Fuel loads were high with an average humus layer accumulation of 35 Mg ha-1. Regular fire intervals are needed to reduce fuels and mid-story density and aid in the regeneration of longleaf pine. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Long-term hydraulic acclimation to resource availability was explored in 3-year-old Populus deltoides Bartr. ex Marsh. clones by examining transpiration, leaf-specific hydraulic conductance (GL), canopy stomatal conductance (GS) and leaf to sapwood area ratio (AL:AS) in response to irrigation (13 and 551 mm year-1 in addition to ambient precipitation) and fertilization (0 and 120 kg N ha-1 year-1). Sap flow was measured continuously over one growing season with thermal dissipation probes. Fertilization had a greater effect on growth and hydraulic properties than irrigation, and fertilization effects were independent of irrigation treatment. Transpiration on a ground area basis (E) ranged between 0.3 and 1.8 mm day-1, and increased 66% and 90% in response to irrigation and fertilization, respectively. Increases in GL, GS at a reference vapor pressure deficit of 1 kPa, and transpiration per unit leaf area in response to increases in resource availability were associated with reductions in AL:AS and consequently a minimal change in the water potential gradient from soil to leaf. Irrigation and fertilization increased leaf area index similarly, from an average 1.16 in control stands to 1.45, but sapwood area was increased from 4.0 to 6.3 m² ha-1 by irrigation and from 3.7 to 6.7 m² ha-1 by fertilization. The balance between leaf area and sapwood area was important in understanding long-term hydraulic acclimation to resource availability and mechanisms controlling maximum productivity in Populus deltoides. [ABSTRACT FROM AUTHOR]

Tropospheric ozone can affect crop yield and has been reported to cause reductions in growth and biomass of forest tree species in laboratory and glasshouse studies. However, linkages between growth and ambient ozone concentrations in the field are not well established for forest trees. Ambient ozone concentrations have been shown to cause foliar injury on a number of tree species throughout much of the eastern USA. Symptom expression is influenced by endogenous and exogenous factors and, therefore, ozone-exposure/tree-response relationships have been difficult to confirm. Clearly defined, cause-effect relationships between visible injury and growth losses due to ozone have not been validated. Generalizations of sensitivity of forest trees to ozone are complicated by tree development stage, microclimate, leaf phenology, compensatory processes, within-species variation and other interacting stresses. In general, decreases in above-ground growth at ambient ozone levels in the eastern USA appear to be in the range of 0-10% per year. However, these conclusions are based on a small number of tree species, with the vast majority of studies involving individual tree seedlings in a non-competitive environment. Comparative studies of small and large trees indicate that seedlings are not suitable surrogates for predicting responses of mature trees to ozone. Process-level modelling is a promising methodology that has been recently utilized to assess ozone effects on a stand to regional scale, indicating that ozone is affecting forest growth in the eastern USA. The extent and magnitude of the response is variable and depends on many edaphic and climatic factors. It is imperative when conducting assessment exercises, however, that forest biologists constantly keep in mind the tremendous variability that exists within natural systems. Scaling of single site/physiological response phenomena from an individual tree to an ecosystem and/or region necessitates further research. [ABSTRACT FROM AUTHOR]

There is an increasing interest in estimating biomass for longleaf pine (Pinus palustris Mill.), an important tree species in the southeastern U.S. Most of the individual-tree allometric models available for the species are local, relying on stem diameter outside bark at breast height (DBH) and total tree height (HT), but seldom include stand-level variables such as stand age, basal area or stand density. Using the biomass dataset of 296 longleaf pine trees sampled in the southeastern U.S. by different forestry research institutions, we developed a set of local and general systems of tree biomass equations to predict total tree total above-stump biomass, bole biomass outside bark, live branch biomass and live foliage biomass. The local systems were based on DBH or DBH and HT, and the general systems included in addition to DBH and HT, stand-level variables such as age, basal area and stand density. This paper reports the first set of general allometric equations reported for longleaf pine trees. These systems of biomass equations provide tools to support managers in making management decisions for the species in a variety of ecological, silvicultural and economics applications. The systems can be applied to trees growing over a large geographical area and having a wide range of ages and stand characteristics. [ABSTRACT FROM AUTHOR]