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Background and aimsFine roots can be functionally classified into an absorptive fine root pool (AFR) and a transport fine root pool (TFR). Different methods give significantly different fine root production, mortality and decomposition estimates. However, how methodological difference affects fine root estimates has not been assessed by functional type, impeding accurate construction of fine root C budgets.MethodsWe used dynamic-flow model, a model based on measurements of litterbags and soil cores, and balanced-hybrid model, a model based on measurements of minirhizotrons and soil cores, to quantify AFT and TFR estimates in a planted loblolly pine forest.ResultsAnnual production, mortality, and decomposition were comparable between AFRs and TFRs when measured using the dynamic-flow model (P > 0.1) but significantly higher for AFRs than for TFRs when measured using the balanced-hybrid model (P < 0.05). Annual production, mortality and decomposition estimates using the balanced-hybrid model were 75%, 71% and 69% higher than those using the dynamic-flow model, respectively, for AFRs, but 12%, 6% and 5% higher than those using the dynamic-flow model, respectively, for TFRs. The balanced-hybrid model yielded more reliable AFR and TFR estimates than the dynamic-flow model by directly measuring fine root production and mortality dynamics.ConclusionThe balanced-hybrid model has greater estimation accuracy than the dynamics-flow model. The methodological difference has greater effects on AFR than TFR estimates. The choice of method is critical for quantifying AFR and TFR contributions to fine root C budget.

This study aims to optimize strong acid hydrolysis-based production of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) from pre-extracted and fully bleached kraft pulp of loblolly pinewood, the most abundant and commercially significant softwood species in southeastern United States. The effect of four parameters, including acid concentration, temperature, duration and pulp particle size, on the yield and properties of CNCs was investigated using the central composite design (CCD) of response surface methodology (RSM) for process optimization. While CNC yield was significantly affected by acid concentration and hydrolysis temperature and was adequately explained by an empirical model, none of the characteristic properties of CNCs, including crystallinity index, surface charge and particle size, displayed any strong correlation to the process parameters within the experimental ranges tested. At different hydrolysis severities, we not only analyzed the waste streams to determine the extent of holocellulose degradation, but also evaluated the properties of leftover partially hydrolyzed pulp, called cellulosic solid residues (CSR), to gauge its potential for CNF production via mechanical fibrillation. Conditions that maximized CNC yields (60% w/w) were 60% acid concentration, 58 °C, 60 min and 40 mesh particle size. Twenty percent (w/w) of the pulp was degraded under these conditions. On the other hand, conditions that maximized CSR yields (60% w/w) were 54% acid, 45 °C, 90 min and 20 mesh particle size, which also produced 15% CNCs, caused minimal pulp degradation (< 5%) and imparted sufficient surface charge such that CSR was easily microfluidized into CNFs. Therefore, the strong acid hydrolysis process could be tuned to maximize the production of cellulose nanocrystals and nanofibers and obtain two products with different properties and applications through the process optimization.

Compression wood (CW) negatively affects the industrial quality of Pinus taeda by causing distortion in sawn boards and is visually characterized by a darker reddish colour. Thinning is considered a key factor influencing its formation, but the reported effects have been inconsistent. This study evaluated CW incidence at final rotation under five thinning regimes: 500-200, 500-325, 800-600-400, 700-450, and 1000-650 trees.ha−1. The defect was assessed on log ends, basal discs, and sawn boards. Although overall CW severity was low, regimes differed significantly. The 500-325 trees.ha−1 regime showed the highest stain and board defects, while the 500-200 trees.ha−1 regime of similar intensity had lower values, indicating that intensity alone does not explain the occurrence of defects. After thinning, CW in growth rings increased and was positively associated with ring width and negatively with stand density index, indicating that reduced competition and accelerated radial growth are linked to higher formation levels. Visible CW staining on log ends was moderately correlated with board defects, indicating its potential as a practical, low-cost indicator of log quality. Thinning affects compression wood through its impact on growth and stand structure. In addition to intensity, timing and the effect of the wind must also be considered. Moderately intensive regimes help minimize defects, although their practical adoption may be limited by commercial priorities.

Tree crown width relates directly to wood quality and tree growth. The traditional method used to measure crown width is labor-intensive and time-consuming. Pairing imagery taken by an unmanned aerial vehicle (UAV) with a deep learning algorithm such as a faster region-based convolutional neural network (Faster-RCNN) has the potential to be an alternative to the traditional method. In this study, Faster-RCNN outperformed single-shot multibox detector (SSD) for crown detection in a young loblolly pine stand but performed poorly in a dense, mature loblolly pine stand. This paper proposes a novel Faster-RCNN algorithm for tree crown identification and crown width extraction in a forest stand environment with high-density loblolly pine forests. The new algorithm uses Residual Network 101 (ResNet101) and a feature pyramid network (FPN) to build an FPN_ResNet101 structure, improving the capability to model shallow location feature extraction. The algorithm was applied to images from a mature loblolly pine plot in eastern Texas, USA. The results show that the accuracy of crown recognition and crown width measurement using the FPN_ResNet101 structure as the backbone network in Faster-RCNN (FPN_Faster-RCNN_ResNet101) was high, being 95.26% and 0.95, respectively, which was 4.90% and 0.27 higher than when using Faster-RCNN with ResNet101 as the backbone network (Faster-RCNN_ResNet101). The results fully confirm the effectiveness of the proposed algorithm.

We present a method for recording cool-season (mid-October–May) weather events near Nags Head, North Carolina. Standardized traumatic resin duct frequency (TRDsf) formations in loblolly pine (Pinus taeda L.) were determined from earlywood radial growth samples using the number of traumatic resin ducts that occur in response to stressful weather events. Based on a sample of 39 cores collected at Nags Head Woods Ecological Preserve during summer 2020, we tested if the occurrence of traumatic resin ducts in the earlywood was caused by late-season tropical cyclones, mid-latitude windstorms, and snow/ice storms and served as a proxy for extreme weather frequency during 1950–2019. TRDsf was significantly related to years that had at least one documented cool-season weather event. The average TRDsf in a non-storm year was 1.95 while the average for a storm year was 2.99. Further, TRDsf was correlated with the number of cool-season weather events and there was no tree age-related bias to storm-event detection. These results support using TRD frequency to reconstruct cool-season storm history beyond current climate records at locations where older (150+ years) stands of loblolly pine forests exist along coastal North Carolina.

Loblolly pine plantations in the western portion of the species’ range are sometimes planted with genotypes from the eastern portion of its range to improve plantation productivity. Advances in loblolly pine breeding have led to the development of clonally propagated genotypes with higher potential growth rates and better form than more commonly planted half-sib genotypes. At a site in the western portion of the loblolly pine range, four genotypes from the eastern portion of the loblolly pine range were established. Two genotypes (HS756 and HS8103) were half-sib, and two genotypes (V9 and V93) were varieties. The V93 genotype was propagated from the HS756 genotype. The objective of this study was to determine the effects of genotype on seasonal trends in gas exchange parameters at the leaf and crown levels, growth, and biomass allocation patterns. During the two-year study, one year had precipitation and temperature trends similar to the long-term average and one year had extreme drought, with record heat. The HS756, V9, and V93 genotypes had the highest height growth throughout the study. The V93 genotype was sensitive to the drought; its leaf- and crown-level Asat and gs, declined during the drought more markedly than those of the other genotypes. Although its Asat and gs were affected by drought, height growth productivity of V93 may have been sustained during the drought by its biomass partitioning pattern of allocating higher proportions of its root biomass to small and fine roots and its aboveground biomass to foliage. These results suggest that a variety such as V93 could be more susceptible to changes in C fixation and water uptake with recurrent drought.

Root feeding bark beetles in the family Curculionidae and the ophiostomatoid fungi they vector contribute to root disorders of Pinus species around the world. In the southeastern United States root feeding beetles in the genus Hylastes (Coleoptera: Curculionidae), including Hylastes salebrosus and Hylastes tenuis, are associated with stands of Pinus taeda experiencing premature mortality. Despite this, direct evidence of Hylastes species breeding, with their associated ophiostomatoid fungi, in Pinus taeda has not been observed until this point. In one P. taeda stand experiencing increased mortality in Alabama, roots were excavated and dissected from pines exhibiting a range of crown conditions in order to determine if Hylastes breeding and feeding damage could be detected and to investigate the relationship between beetles, ophiostomatoid fungi, and tree crown condition. Hylastes salebrosus and H. tenuis represented the majority of beetles collected (94%) and were found nearly exclusively in root of trees with dying crowns. Adult beetles and beetle galleries were associated with a host of ophiostomatoid fungi, including Leptographium terebranis, Grosmannia huntii, L. procerum, and L. serpens. These observations suggest roots of dying trees represent a valuable host substrate for expanding H. salebrosus and H. tenuis populations. A more comprehensive study is required to confirm these findings. Key Words: galleries, Hylastes, loblolly pine decline, ophiostomatoid fungi, root disorders Los escarabajos de la corteza en la familia Curculionidae que se alimentan de raices y los hongos ophiostomatoides que ellos transmitan contribuyen a los trastornos de las raices de especies de Pinus por todo el mundo. En el sudeste de los Estados Unidos, los escarabajos que alimentan de las raices que pertenecen al genero Hylastes (Coleoptera: Curculionidae), incluyendo Hylastes salebrosus y Hylastes tenuis, son asociados con los lotes de Pinus taeda que estan experimentando la mortalidad prematura. A pesar de esto, evidencia directa de que Hylastes se este reproduciendo junto con los hongos ophiostomatoides en Pinus taeda no se ha observado hasta este momento. En un lote de P. taeda en Alabama que esta experimentando una mayor mortalidad, las raices fueron excavadss y disectadas de pinos que muestran una serie de condiciones de la corona para determinar si la reproduccion y el dano causado por la alimentacion de Hylastes se peude ser detectado e investigado entre la relacion de los escarabajos, hongos ophiostomatoides y el estado de la copa de de los arboles. Hylastes salebrosus y H. tenuis representaba a la mayoria de los escarabajos recolectados (94%) y fueron encontrados casi exclusivamente en las raices de los arboles con coronas que estan muriendo. Los escarabajos adultos y las galerias de los escarabajos fueron asociados con una gran cantidad de hongos de ophiostomatoides, incluyendo Grosmannia huntii, Leptographium terebranis, L. procerum y L. serpens. Estas observaciones sugieren que las raices de los arboles que estan muriendo representan un substrato valioso para la expansion de poblaciones de H. salebrosus y H. tenuis. Un estudio mas amplio es necesario para confirmar estos hallazgos. Palabras Clave: galerias, Hylastes, disminucion de pino loblolly, hongos ophiostomatoides, trastornos de raices

Novel lignin is formed in a mutant loblolly pine (Pinus taeda L.) severely depleted in cinnamyl alcohol dehydrogenase (E.C. 1.1.1.195), which converts coniferaldehyde to coniferyl alcohol, the primary lignin precursor in pines. Dihydroconiferyl alcohol, a monomer not normally associated with the lignin biosynthetic pathway, is the major component of the mutant's lignin, accounting for ∼30 percent (versus ∼3 percent in normal pine) of the units. The level of aldehydes, including new 2-methoxybenzaldehydes, is also increased. The mutant pines grew normally indicating that, even within a species, extensive variations in lignin composition need not disrupt the essential functions of lignin.

Bark beetle infestations have historically been primary drivers of stand thinning in Mexican pine forests. However, bark beetle impacts have become increasingly extensive and intense, apparently associated with climate change. Our objective was to describe the possible association between abundance of bark beetle flying populations and the occurrence of given value intervals of temperature, precipitation and their balance, in order to have a better comprehension of the climatic space that might trigger larger insect abundances, an issue relevant in the context of the ongoing climatic change. Here, we monitored the abundance of two of the most important bark beetle species in Mexico, Dendroctonus frontalis and D. mexicanus. We sampled 147 sites using pheromone-baited funnel traps along 24 altitudinal transects in 11 Mexican states, from northwestern Chihuahua to southeastern Chiapas, from 2015 to 2017. Through mixed model analysis, we found that the optimum Mean Annual Temperatures were 17°C-20°C for D. frontalis in low-elevation pine-oak forest, while D. mexicanus had two optimal intervals: 11-13°C and 15-18°C. Higher atmospheric Vapor Pressure Deficit ([greater than or equal to] 1.0) was correlated with higher D. frontalis abundances, indicating that warming-amplified drought stress intensifies trees' vulnerability to beetle attack. As temperatures and drought stress increase further with projected future climatic changes, it is likely that these Dendroctonus species will increase tree damage at higher elevations. Pine forests in Mexico are an important source of livelihood for communities inhabiting those areas, so providing tools to tackle obstacles to forest growth and health posed by changing climate is imperative.

The course of the bark beetle-vectored fungus, Leptographium terebrantis S. J. Barras and T. J. Perry, in stemwood growth loss of declining pines in the southeastern United States was assessed in a 13-year-old loblolly pine (Pinus taeda L.) plantation near Eufaula, Alabama, U.S.A. Using stem inoculation as a surrogate for root infection, we hypothesized that L. terebrantis infection impairs sapwood function and thus limits the tree leaf area (A[sub.L] ), new root production, and stemwood growth. Sterile toothpicks colonized by L. terebrantis at varying inoculum densities was used to elicit host growth responses. In the third year after inoculation, the root pathogen reduced the foliage moisture content, whole-tree leaf area (A[sub.L] ), the ratio of A[sub.L] to tree sapwood area (A[sub.S] ), and stemwood growth in trees receiving the high inoculation treatment relative to those receiving the low or medium inoculation treatments, or the wound or control treatments after seven months of water deficit. The absence of a similar response to water deficit among trees that were noninoculated, wounded, or inoculated at the low or medium densities suggests that, in the loblolly pine-L. terebrantis pathosystem at our study site, the physiological stress caused by water deficit and the high inoculum density was required for the pathogen to elicit a stemwood growth loss. Thus, in loblolly pine forests of the southeastern United States, where climate and soil conditions yield prolonged periods of physiological stress, the presence of L. terebrantis has the potential to reduce stand volume and widen the gap between the predicted and actual stemwood production.