Wood chemical composition as related to properties of handsheets made from loblolly pine refiner groundwood

Summary Burst and tear strengths of handsheets made from 48 pulps disk-refined from chips of varying chemical composition decreased with increasing extractive content after the independent effects of fiber morphology were specified. This result was attributed to lessened bond strength caused by reduced surface tension forces and blocking of reactive sites on the fiber surfaces.

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Zusammenfassung Berstzahl und Reißfestigkeit der Blätter von 48 verschiedenen Zellstoffen aus scheibengemahlenen Spänen mit unterschiedlichen chemischen Bestandteilen verringerten sich mit ansteigendem Extraktstoffgehalt; die davon unabhängigen Einflüsse des Faseraufbaues sind dabei berücksichtigt. Diese Tatsache wird der verminderten Bindungskraft zugeschrieben, verursacht durch die herabgesetzte Oberflächenspannung und die Blockierung von Bindungsstellen an den Faseroberflächen.

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The author appreciatively acknowledges the assistance of the Roy O. Martin Lumber Co., Alexandria, La.; R. A. Leask and J. Adams of Bauer Bros. Co., Springfield, Ohio; and D. Bower, mathematical statistician at the Southern Forest Experiment Station, New Orleans, La.     

Water use in thinned loblolly pine plantations

Soil moisture and throughfall were monitored for two growing seasons under three thinning intensities: basal areas of 7.8 m²ha⁻¹, 12.6 m²ha⁻¹ and 26.6 m²ha⁻¹ (unthinned control) in an 11- to 12-year-old loblolly pine (Pinus taeda L.) plantation. The first year after thinning soil water decreased at a rate of 0.8 mm day⁻¹, 1.0 mm day⁻¹ and 1.4 mm day⁻¹, respectively, in the 7.8 m²ha⁻¹, 12.6 m²ha⁻¹, and 26.6 m²ha⁻¹ basal area plots between May and late August. The more rapid development of soil moisture deficits in the unthinned stand was owing to both greater soil moisture use and reduced throughfall. For the same time period in the second year, with below-normal rainfall, soil moisture deficits developed at a rate of 1.5, 1.5 and 1.7 mm day⁻¹ for the two heavily thinned and the unthinned treatments. Estimated growing season soil water use rates were 4.4 mm day⁻¹, 4.2 mm day⁻¹, and 4.0 mm day⁻¹, respectively for the 7.8 m²ha⁻¹, 12.6 m²ha⁻¹ and 26.6 m²ha⁻¹ basal area levels in Year 1. The second year after thinning water use rates for the same period were 2.7 mm day⁻¹, 2.6 mm day⁻¹, and 2.5 mm day⁻¹, respectively. The results of this study suggest that the capacity to manage available water in loblolly pine stands by thinning is more a function of reduced interception loss and increased throughfall than reduced water use and is also weather dependent. Growing seasons with low rainfall or only one or two large rainfall events will not permit much opportunity to manage soil moisture.     

Availability of residual phosphorus fertilizer for loblolly pine

Fertilizing pine plantations with phosphorus has been a common practice on the Coastal Plain since the 1960s. A decision to fertilize a second or subsequent rotation must take into consideration the availability of residual phosphorus fertilizer. We tested the efficacy of phosphorus applied in a first rotation loblolly pine stand to support the growth of the subsequent second rotation stand. Phosphorus rates applied in 1967 at the time of planting of the first rotation were 0, 28 and 56 kg/ha. Retreatments included the application of 45 kg/ha P at midrotation in 1978, and the application of 45 kg/ha P at the beginning of the second rotation in 1991. The field trial had a split-block design with the three initial P rates crossed by five retreatments, and replicated four times. The first rotation 28 kg/ha P treatment had 91% and the 56 kg/ha P treatment 101% of the volume at age 5 of all the treatments fertilized with P in the second rotation. Foliar P levels, in the second rotation, were elevated at age 2 relative to ages 3 and 5, presumably due to effective competition control. Twenty-nine percent, 40% and 75% of the trees fertilized with 28 kg/ha P in 1967, 56 kg/ha P in 1967, and 45 kg/ha P in 1991, respectively, had foliar P concentrations of 0.10% or above at age 3. Based on foliar analyses, we recommend refertilizing stands fertilized with 45 kg/ha P in the first rotation by age 3 in the second rotation.     

火炬松人工林间伐效应的研究

在8、12、16年生火炬松人工林中设置了不同间伐强度试验林，通过对林分树因子和间伐作业经济效益的分析表明，间伐对火炬松林分保留木个体生长具有一定的促进作用，对幼龄林的促进作用明显大于中大龄林分，随着间伐强度增大，较大径阶立木株数比例增大，但期末总收获量减少。火炬松人工林第1次间伐宜在12年生之前进行，保留1000－1100株／hm^2。在造纸材有销路的地区，初植密度较大的林分第1次间伐可在8年生时进行，保留1100－1300株／hm^2；第2次间伐的间隔期为6年，以培育大中径材为目标的大龄林分，应以弱度至中度调整为主，保留1000株／hm^2。另外，间伐有利于提高保留木材性的均质性。     

Growth of young loblolly pine trees following pruning

Pruning loblolly pine trees is sometimes practiced to improve wood quality even though reduced growth following treatment may occur. Two experiments were established in February 2000 in the Piedmont region of Virginia, USA, to examine the impact of timing and intensity of pruning on subsequent growth of young loblolly pine trees. Results of one study indicated that there is a window of opportunity during the early portion of stand development where up to 50% of the live crown length can be removed without a significant loss of long-term height or diameter growth. Within a year following pruning at ages 3, 6 and 9 (all pruning treatments occurred prior to crown closure), crown mass had been restored and growth comparable to an unpruned control resumed. By age 11 there were no significant differences in cumulative height or dbh of any of the one-lift pruning treatments and the control. Findings from a second study planted at closer spacings where pruning treatments occurred at crown closure (age 6) showed that pruning some of the trees in a loblolly pine plantation does not result in a loss of long-term height or diameter growth or crown dominance for the pruned trees as compared to their unpruned neighbors. For both studies, growth reductions following pruning were small and transitory.     

Aluminum sensitivity of loblolly pine and slash pine seedlings grown in solution culture

To probe variation in Al sensitivity of two co-occurring pine species, seedlings from six full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were grown in solution culture containing 4.4 mM (high-Al) or 0.01 mM (low-Al) AlCl(3) at pH 4 for 58 days. On average, both pine species had 41% less total dry weight in the high-Al treatment than in the low-Al treatment. Stem volume growth of slash pine was more sensitive to the high-Al treatment than that of loblolly pine. In both species, the high-Al treatment inhibited root dry weight more than shoot dry weight. Within-species variation in Al sensitivity among families was greater in loblolly pine (24 to 52% inhibition of seedling dry weight) than in slash pine (35 to 47% inhibition of seedling dry weight). Foliar Al concentration was positively correlated with Al sensitivity in slash pine but not in loblolly pine; however, in both species, the concentration of Al in roots was 20-fold greater than in foliage.     

Post-fertilization physiology and growth performance of loblolly pine clones

The physiological processes leading to enhanced growth of loblolly pine (Pinus taeda L.) following fertilization are not clearly understood. Part of the debate revolves around the temporal response of net photosynthetic rate (A(n)) to fertilization and whether the A(n) response is always positive. We measured light-saturated photosynthetic rate (A(sat)), dark respiration rate, growth and crown silhouette area in eight clones of loblolly pine before and after nitrogen (N) fertilization (112 kg ha(-1)) to track the initial physiological changes prior to any changes in growth. Overall, there were positive photosynthetic and growth responses to fertilization; however, there were pronounced physiological and growth differences among clones, even among clones with the same parents. Clones 4, 6 and 7 showed large volume growth and A(sat) responses to fertilization. Clone 1 and Clone 8 (a full-sibling of Clone 7) mainly showed a volume growth response, whereas Clone 2 (full-sibling of Clone 1) showed an A(sat) response only. Clone 5 (full-sibling of Clone 6) showed little response to fertilization, whereas Clone 3 (full-sibling of Clone 4) showed a negative A(sat) response. Thus, within-family variation warrants further study to ensure that relatively expensive clonal material is used efficiently.     

Modeling survival in juvenile and mature loblolly pine plantations

Data from a large, region-wide set of permanent plots were used to develop equations for predicting stand-level survival in thinned and unthinned loblolly pine plantations growing in the southeastern United States. A pre-competitive model predicts survival at young ages based on age and total number of trees surviving. A post-crown closure model predicts survival after the onset of intraspecific competition based on age, site index, thinning intensity, percent hardwood basal area and number of trees surviving. Analyses of the pre-competitive data indicated that survival trends differed by drainage class and site preparation method. Thus, separate sets of coefficients were estimated for two drainage class/site preparation groups. Analyses of the post-competitive data indicated that survival trends differed for thinned and unthinned stands and were affected by the amount of hardwood competition. Therefore, the post-crown closure model was developed and parameterized to reflect the changes in survival as a result of hardwood competition and thinning from below.     

表达耐盐基因的转基因火炬松的再生

盐害是限制作物和树木分布和生产的重要因素。盐分过多导致细胞内水分缺失并影响许多重要的细胞代谢活动。本文利用火炬松作为模式植物建立了一套提高植物耐盐性的新技术。这一技术以火炬松合子胚为材料,利用农杆菌介导的转化方法将山犁醇脱氢酶和甘露醇脱氢酶基因转入火炬松。然后再生转化的愈伤组织和转基因植株。经DNA杂交证实的转基因植株被用于耐盐性试验,结果表明这些转基因的植株的耐盐性有明显的提高。这一技术对针叶树的遗传工程育种有重要的参考价值。图3表2参26。     

Effects of uneven-aged silviculture on the stand structure,species composition,and economic returns of loblolly pine stands

Uneven-aged silviculture in loblolly pine (Pinus taeda L.) stands has many economic and ecological benefits. Here, the consequences of various uneven-aged management regimes are predicted with the SouthPro simulator. Results indicate that target distributions for pines with residual merchantable basal areas of ≈12.5 m² ha⁻¹, maximum diameters of ca. 40 cm, and q-ratios of 1.2–1.25 for 2.5 cm DBH classes are likely to provide high economic returns on good sites when combined with hardwood control. Increasing this maximum diameter would enhance tree-size diversity, but reduce sawtimber production and profits. Retaining a hardwood component with 1.15–2.3 m² ha⁻¹ of basal area could enhance tree-species diversity, but this too would result in moderate reductions in income. Insisting on maximizing tree-size diversity or tree-species diversity among softwoods, soft hardwood, and hard hardwoods would be quite costly in terms of lost income and production. Results also illustrate how short-term economic incentives can lead to high-grading practices, despite substantial reductions in stand productivity and net returns in the long term.     

Determining nitrogen status of young loblolly pine by leaf reflectance

Five-year-old lobloliy pine (Pinus taeda L.) seedlings were grown in sand culture in a completely randomized experimental design with eight nitrogen concentrations and three replications. Nitrogen concentration in the nutrient solution varied from 2 to 400 ppm. After a full growing season under treatment, percent reflectance of sunlight by new foliage was determined. Foliar samples were analyzed for nitrogen and chlorophyll. There was a strong positive correlation between nitrogen content and chlorophyll content (r = 0.895). The natural logarithm of percent reflectance was negatively correlated with both percent nitrogen content (r = -0.845) and chlorophyll content (r = -0.838). From these results, prediction equations for estimating nitrogen and chlorophyll content, as a function of reflectance, were formulated by regression analysis.     

Water relations of loblolly pine seedlings from diverse geographic origins

Leaf conductance at three absolute humidity deficits (AHDs) (7, 14 and 21 g m(-3)), hydraulic conductance and components of tissue water potential were measured in one-year-old loblolly pine seedlings from six origins representing the geographic range of the species. Measurements were made on seedlings grown (a) with ample water (moist regime) and (b) with recurring severe drought (dry regime). However, all seedlings were well-watered prior to and during measurements. Seedlings grown in the moist regime had greater mean leaf conductances (0.30 versus 0.13 cm s(-1)) and greater responses to AHD than seedlings grown in the dry regime. They also exhibited greater hydraulic conductances (0.53 versus 0.35 microg cm(-2) s(-1) MPa(-1), less negative osmotic potentials (-1.45 versus -1.57 MPa) and higher relative water contents at turgor loss (0.72 versus 0.65). Seed source differences in water relations characteristics were detected only in seedlings grown in the moist regime. In these, trees from the three interior origins had greater mean leaf conductances than those from the three coastal sources (0.32 versus 0.28 cm s(-1)), but no differences in response to changing AHD were observed. Seedlings from North Carolina had lower osmotic potentials at turgor loss than those from Florida, Georgia or Texas. These differences in water relations characteristics are not clearly related to the observed greater survival ability of trees from interior origins compared with those from coastal origins.     

Measuring loblolly pine crowns with drone imagery through deep learningOA

In modeling forest stand growth and yield, crown width, a measure for stand density, is among the parameters that allows for estimating stand timber volumes. However,accurately measuring tree crown size in the field, in particular for mature trees, is challenging. This study demonstrated a novel method of applying machine learning algorithms to aerial imagery acquired by an unmanned aerial vehicle(UAV) to identify tree crowns and their widths in two loblolly pine plantations in eastern Texas, US...     

The effects of sulfometuron on the root growth of loblolly pine

The effect of sulfometuron (Oust) on the root growth of loblolly pine (Pinus taeda L.) seedlings was studied in the field and in two soil types in the greenhouse. In the greenhouse study sulfometuron was applied to the foliage only, the soil only, and to both foliage and soil at the rates of 0.10, 0.21, and 0.42 kg ai/ha. Twenty-eight days after application root growth significantly decreased for all methods of application and with increasing rates e.g., 0.10, 0.21, and 0.42 kg ai/ha sulfometuron reduced new root length by 42%, 53%, and 64%, respectively. Application in the field at the rate of 0.30 kg ai/ha resulted in a 68% reduction in root growth. However, by the end of the growing season treated seedling root and shoot biomass were 115% and 64% greater, respectively. To ensure earlier season survival the rate of sulfometuron applied should be kept at a minimum level that will allow both weed control and adequate root growth. Low rates would be particularly important during a dry planting season.     

Seasonal changes in intensity of bud dormancy in loblolly pine seedlings

The terminal buds of six-month-old loblolly pine (Pinus taeda L.) seedlings remained closed for approximately six months, although bud dormancy, as measured by rate of bud break in a standard greenhouse environment, was only exhibited for about one month. The peak of bud dormancy was in December for seedlings grown near Auburn, Alabama. However, the timing and intensity varied with seed source and may have been affected by the warm fall temperatures. Seedlings from the more northern provenances entered dormancy first and reached a deeper state of dormancy than seedlings from southern provenances. The rate of shoot elongation was not consistently related to the rate of bud break.     

Preliminary studies on establishment of genetic transformation system in loblolly pine

A transformation system was established for loblolly pine (Pinus taeda L.) mature zygotic embryos usingAgrobacterium tumefaciens. The gene coding for the β-glucuronidase (GUS) gene was introduced into loblolly pine tissues and its transient expression was detected with histochemical staining. The influences of different genotypes.Agrobacterum concentrations. and cocultivation time on GUS expression and kanamycin resistant callus and shoot regeneration were investigated. The results showed that the highest GUS expression frequency (16.3%) and shoot regeneration frequency (78%) were obtained from genotype 9–1003 withAgrobacterium concentration decreased 9 times and cocultivation time of 56 hours respectively. GUS expression was obtained in all genotypes tested. The successful expression of the GUS gene in different genotypes suggested that it will be a useful transformation system for loblolly pine. (Responsible Editor: Chai Ruihai)     

Aluminum fractions in root tips of slash pine and loblolly pine families differing in Al resistance

Aluminum (Al) distribution among several cellular fractions was investigated in root tips of seedlings of one Al-resistant and one Al-sensitive family of slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) grown in nutrient solution containing 100 microM AlCl3 (pH 4) for 167 h. Aluminum present in 5-mm-long root tips was fractionated into cell-wall-labile (desorbed in 0.5 mM citric acid), cell-wall-bound (retained after filtering disrupted cells through 20-microm mesh) and symplasmic (filtrate following cell disruption) fractions. When averaged across both species, 12% of Al absorbed by root tips appeared in the symplasmic fraction and 88% in the apoplasmic fraction (55% as cell-wall-labile, and 33% as cell-wall-bound). On a fresh mass basis, total Al in root tips was lower in loblolly pine than in slash pine, lower in the Al-resistant slash pine family than in the Al-sensitive slash pine family, and lower in the Al-resistant families than in the Al-sensitive families across species. Although the data support the hypothesis that Al-resistant plants limit Al uptake to root apices, they do not exclude other mechanisms of Al resistance. Differential Al resistance between the species and between slash pine families may also be associated with the size of the total non-labile and cell-wall-labile Al fractions, respectively. We were unable to identify the basis for differential Al resistance in loblolly pine.     

Restoring longleaf pine (Pinus palustris Mill.) in loblolly pine (Pinus taeda L.) stands: Effects of restoration treatments on natural loblolly pine regeneration

Historical land use and management practices in the southeastern United States have resulted in the dominance of loblolly pine (Pinus taeda L.) on many upland sites that historically were occupied by longleaf pine (Pinus palustris Mill.). There is currently much interest in restoring high quality longleaf pine habitats to such areas, but managers may also desire the retention of some existing canopy trees to meet current conservation objectives. However, fast-growing natural loblolly pine regeneration may threaten the success of artificially regenerated longleaf pine seedlings. We evaluated the establishment and growth of natural loblolly pine regeneration following different levels of timber harvest using single-tree selection (Control (uncut, residual basal area ∼16 m²/ha), MedBA (residual basal area of ∼9 m²/ha), LowBA (residual basal area of ∼6 m²/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m²) created by patch cutting at two ecologically distinct sites within the longleaf pine range: Fort Benning, GA in the Middle Coastal Plain and Camp Lejeune, NC in the Lower Coastal Plain. The density of loblolly pine seedlings was much higher at Camp Lejeune than at Fort Benning at the end of the first growing season after harvesting. Following two growing seasons, there were no significant effects of canopy density or gap position on the density of loblolly pine seedlings at either site, but loblolly pine seedlings were taller on treatments with greater canopy removal. Prescribed fires applied following the second growing season killed 70.6% of loblolly pine seedlings at Fort Benning and 64.3% of seedlings at Camp Lejeune. Loblolly pine seedlings were generally less than 2 m tall, and completeness of the prescribed burns appeared more important for determining seedling survival than seedling size. Silvicultural treatments that include canopy removal, such as patch cutting or clearcuts, will increase loblolly pine seedling growth and shorten the window of opportunity for control with prescribed fire. Therefore, application of prescribed fire every 2-3 years will be critical for control of loblolly pine regeneration during restoration of longleaf pine in existing loblolly pine stands.     

Predicted leaf area growth and foliage efficiency of loblolly pine plantations

Foliage dynamics research is helpful for better understanding the process of forest production and improving silvicultural practice. However, the difficulty of measuring foliage amount has slowed down the research progress. Since leaf area of an individual tree can be reliably predicted from its diameter, growth and yield models that provide detailed information for each diameter class can be used to benefit foliage dynamics research. Simulation results from a growth and yield system for unthinned loblolly pine plantations indicated that foliage area increased with stand age, peaked between ages 36 and 51, and decreased after that. Volume growth increased with leaf area for young stands and decreased for older stands, whereas foliage efficiency consistently decreased with age. Better sites supported higher levels of leaf area index, volume growth, and foliage efficiency. Higher planting densities led to higher maximum leaf area indices and shorter time to reach that level. Initial density had no effect on foliage efficiency through time.     

Specific gravity responses of slash and loblolly pine following mid-rotation fertilization

Wood quality attributes were examined in six stands of slash pine (Pinus elliottii Engelm. var. elliottii) and loblolly pine (P. taeda L.) in the lower Coastal Plain of Georgia and Florida. Several plots comprised each stand, and each plot was divided so that it received three fertilizer treatments: a control treatment with herbaceous weed control at planting and brush control at mid-rotation only (control); 45 kg ha⁻¹ N + 56 kg ha⁻¹ P + herbaceous weed control at planting and 224 kg ha⁻¹ N + 45 kg ha⁻¹ P + brush control at mid-rotation (fertilizer with N at planting); and 56 kg ha⁻¹ P + herbaceous weed control at planting and 224 kg ha⁻¹ N + 45 kg ha⁻¹ P + brush control at mid-rotation (fertilizer without N at planting). Ring width, ring earlywood specific gravity (SG), ring latewood SG, whole ring SG, and ring percent latewood were measured on each of seven trees. Of these measurements, this study focused mainly on the properties related to SG. Examination of the rings showed that latewood SG was significantly lower in trees treated with fertilizers with and without N at planting in the two to three years following fertilization, but that latewood SG gradually returned to a level similar to the control. Fertilizer without N at planting may also have had a brief negative effect on earlywood SG following mid-rotation fertilization, but it was not as clear or lasting as the effect on latewood SG. Additionally, although slash and loblolly pine appear to differ in the developmental patterns of these SG properties, there were no significant differences in how these patterns interacted with treatment. This study demonstrated that fertilization treatments have similar short-term effects on the SG of slash and loblolly pines, particularly in latewood, but the trees will return to a SG pattern consistent with unfertilized trees within two or three years.