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Whitebark pine (Pinus albicaulis) is an important component of high‐elevation ecosystems throughout the northern Rocky Mountains; however, the species was recently listed as "threatened" under the Endangered Species Act due to widespread mortality throughout its native range. Land managers tasked with whitebark pine conservation and restoration require information on strategies that can positively influence whitebark pine establishment and promote growth and defense of preexisting trees on the landscape. Our study investigated the response of whitebark pine tree growth and resin duct defenses to thinning and removal of competing shade‐tolerant conifers in the Caribou‐Targhee National Forest, Idaho, USA. In the nine years following thinning treatments, we found that whitebark pine trees (>12.7 cm diameter at breast height [dbh]) responded favorably to thinning and experienced a 60% increase in basal area increment (52% increase in ring width index) while also producing 34% more resin ducts. Additionally, resin ducts were 23% larger with 49% increased area in the nine years post‐thinning compared with trees in the control. Small diameter (<5 cm dbh) whitebark pine in the treatment experienced a dramatic growth release with over 90% increase in basal area increment (74% increase in ring width index). Thinning also created conditions favorable for whitebark pine seedling and sapling establishment. In the treatment, 75% of seedlings and 93% of saplings were whitebark pine, compared with 32% seedlings and 14% saplings in the control. In addition, 93% of overstory trees in the treatment were whitebark pine, compared with 42% in the control. Whitebark pine tree mortality was similar across both the control (26%) and the treatment (25%), indicating that the thinning treatments did not have any adverse impacts on tree mortality. The positive effects of thinning on whitebark pine establishment and tree growth, coupled with the lack of elevated mortality in the treatment, provide strong evidence in support of thinning as a viable silvicultural technique in whitebark pine conservation efforts. [ABSTRACT FROM AUTHOR]

Resin canals produce and transport oleoresins that are important for tree defenses within the Pinaceae family. Rapid measurement techniques are needed to better understand how resin canal characteristics vary due to genetic and environmental effects. Here we describe a semi-automated microscopy imaging system that was built for quantifying longitudinal resin canals. Tree increment cores from 210 loblolly pine (Pinus taeda L.) trees were prepared into radial strips and the transverse surface of the samples polished with 400 and then 600 grit sandpaper. Each sample was imaged along its entire length (pith to bark) with the images collected from a monochrome camera connected to a Plan Fluorite 4× objective lens. The samples were imaged on the transverse surface via transmitted 850 nm near-infrared light directed at the radial surfaces of the samples. A total of 24 153 images were collected and then processed offline in Python using the Open Computer Vision Library (OpenCV) using a series of algorithms including contrast correction, noise removal, thresholding, contour identification, erosion, and dilation. A total of 24 491 resin canals were identified and their size quantified. The resin canals were assigned into annual rings and positioned within the earlywood or latewood of a ring using cross-correlation whereby a pseudo-density value was derived from the images and matched with density values measured by X-ray densitometry. Of the total resin canals identified, 51.5% were in the earlywood and 48.5% in the latewood, with the majority being detected in the earlywood in the first six years and the latewood in years 7 and above. This study represents the most information collected on the resin canals of loblolly pine. The detailed description of the hardware and image analysis methods should serve as a useful guide to others interested in imaging resin canals as well as other anatomical features. [ABSTRACT FROM AUTHOR]

The recent mountain pine beetle outbreaks have caused widespread mortality among lodgepole pine trees in western North America, resulting in a reduced population of surviving trees. While previous studies have focused on the cascading impacts of these outbreaks on the physiology and growth of the surviving trees, there remains a need for a comprehensive study into the interactions among various physiological traits and the growth in post-outbreak stands. Specifically, the relationship between chemical (primarily terpenes) and anatomical (mainly resin ducts) defences, as well as the allocation of non-structural carbohydrates (NSCs) to support these defence modalities, is poorly understood. To address these gaps, we conducted a field survey of surviving lodgepole pine trees in post-mountain pine beetle outbreak stands in western Canada. Our retrospective analysis aimed at determining correlations between the post-outbreak concentrations of monoterpenes, diterpenes, and NSCs in the phloem and the historical resin duct characteristics and growth traits before and after the outbreak. We detected strong correlations between the post-outbreak concentrations of monoterpenes and historical resin duct characteristics, suggesting a possible link between these two defence modalities. Additionally, we found a positive relationship between the NSCs and the total concentrations of monoterpenes and diterpenes, suggesting that NSCs likely influence the production of these terpenes in lodgepole pine. Furthermore, historical tree growth patterns showed strong positive correlations with many individual monoterpenes and diterpenes. Interestingly, while surviving trees had enhanced anatomical defences after the outbreak, their growth patterns did not vary before and after the outbreak conditions. The complexity of these relationships emphasizes the dynamics of post-outbreak stand dynamics and resource allocations in lodgepole pine forests, highlighting the need for further research. These findings contribute to a broader understanding of conifer defences and their coordinated responses to forest insect outbreaks, with implications for forest management and conservation strategies. [ABSTRACT FROM AUTHOR]

Abstract Whitebark pine (Pinus albicaulis) is an important component of high‐elevation ecosystems throughout the northern Rocky Mountains; however, the species was recently listed as “threatened” under the Endangered Species Act due to widespread mortality throughout its native range. Land managers tasked with whitebark pine conservation and restoration require information on strategies that can positively influence whitebark pine establishment and promote growth and defense of preexisting trees on the landscape. Our study investigated the response of whitebark pine tree growth and resin duct defenses to thinning and removal of competing shade‐tolerant conifers in the Caribou‐Targhee National Forest, Idaho, USA. In the nine years following thinning treatments, we found that whitebark pine trees (>12.7 cm diameter at breast height [dbh]) responded favorably to thinning and experienced a 60% increase in basal area increment (52% increase in ring width index) while also producing 34% more resin ducts. Additionally, resin ducts were 23% larger with 49% increased area in the nine years post‐thinning compared with trees in the control. Small diameter (

The recent mountain pine beetle outbreaks have caused widespread mortality among lodgepole pine trees in western North America, resulting in a reduced population of surviving trees. While previous studies have focused on the cascading impacts of these outbreaks on the physiology and growth of the surviving trees, there remains a need for a comprehensive study into the interactions among various physiological traits and the growth in post-outbreak stands. Specifically, the relationship between chemical (primarily terpenes) and anatomical (mainly resin ducts) defences, as well as the allocation of non-structural carbohydrates (NSCs) to support these defence modalities, is poorly understood. To address these gaps, we conducted a field survey of surviving lodgepole pine trees in post-mountain pine beetle outbreak stands in western Canada. Our retrospective analysis aimed at determining correlations between the post-outbreak concentrations of monoterpenes, diterpenes, and NSCs in the phloem and the historical resin duct characteristics and growth traits before and after the outbreak. We detected strong correlations between the post-outbreak concentrations of monoterpenes and historical resin duct characteristics, suggesting a possible link between these two defence modalities. Additionally, we found a positive relationship between the NSCs and the total concentrations of monoterpenes and diterpenes, suggesting that NSCs likely influence the production of these terpenes in lodgepole pine. Furthermore, historical tree growth patterns showed strong positive correlations with many individual monoterpenes and diterpenes. Interestingly, while surviving trees had enhanced anatomical defences after the outbreak, their growth patterns did not vary before and after the outbreak conditions. The complexity of these relationships emphasizes the dynamics of post-outbreak stand dynamics and resource allocations in lodgepole pine forests, highlighting the need for further research. These findings contribute to a broader understanding of conifer defences and their coordinated responses to forest insect outbreaks, with implications for forest management and conservation strategies.

Trees must allocate resources to core functions like growth, defense, and reproduction. These allocation patterns have profound effects on forest health, yet little is known about how core functions trade off over time, and even less is known about how a changing climate will impact tradeoffs. We conducted a 21‐year survey of growth, defense, and reproduction in 80 ponderosa pine individuals spanning eight populations across environmental gradients along the Colorado Front Range, USA. We used linear mixed models to describe tradeoffs among these functions and to characterize variability among and within individuals over time. Growth and defense were lower in years of high cone production, and local drought conditions amplified year‐to‐year tradeoffs between reproduction and growth, where trees located at sites with hotter and drier climates showed stronger tradeoffs between reproduction and growth. Our results support the environmental stress hypothesis of masting, which predicts that greater interannual variation in tree functions will be associated with more marginal environments, such as those that are prone to drought. With warming temperatures and increased exposure to drought stress, trees will be faced with stronger interannual tradeoffs, which could lead to further decreases in growth and defensive efforts, ultimately increasing risks of mortality. [ABSTRACT FROM AUTHOR]

The morphologically diverse and globally distributed tribe Vernonieae (Compositae) has had a long taxonomic history whereby the majority of its taxa ended up being put into its "core" genus, Vernonia Schreb. Recent phylogenetic studies using DNA sequence data are only now beginning to tease apart this complicated "evil tribe" and provide a better understanding of the underlying morphological relationships within. With strong support from a recent molecular phylogenetic study of the Vernonieae across its entire geographical range, 10 Mexican species of Vernonia and Vernonanthura are examined in this paper and placed in a new genus, Vickianthus. [ABSTRACT FROM AUTHOR]

Different studies have emphasized the influence of resin canal traits in the susceptibility of pine trees to the pine wood nematode (PWN) Bursaphelenchus xylophilus. Resin canals can facilitate the PWN migration through the stem and are involved in the accumulation of volatile terpenes in the xylem in response to the pathogen, inducing tracheid embolisms. In this work, we conducted a PWN inoculation experiment under greenhouse conditions to investigate the anatomical traits of constitutive resin canals among seven Pinus species with different degrees of susceptibility to the PWN: P. canariensis, P. halepensis, P. pinea and P. taeda were grouped into a 'low-susceptible group', and P. pinaster, P. radiata, and P. sylvestris were grouped into a 'high-susceptible group'. The high-susceptible group presented higher xylem radial growth, wider constitutive canals in the cortex, lower frequency of constitutive canals in the cortex, and smaller constitutive canals in the xylem than the low-susceptible group. The size of constitutive cortical canals was positively related to the number of seedlings colonized by the PWN, suggesting that wider canals facilitated migration. The inoculation of the PWN increased the frequency and diminished the mean area of canals in the xylem, and the high-susceptible group showed more frequency of induced xylem canals than the low-susceptible group. Additionally, the high-susceptible group presented larger radial growths in the xylem than the low-susceptible group. These results suggest a role of resin canal traits on Pinus spp. susceptibility to the PWN. Nevertheless, the high interspecific variability found in these traits within each susceptibility group evidences the importance of other factors in the susceptibility to the PWN. [ABSTRACT FROM AUTHOR]

Dynamic resource availability leads to trade‐offs among functions in plants. The growth‐differentiation balance hypothesis (GDBH) predicts greater allocation of carbon to defense than growth when resources are scarce, with optimum defense production occurring at a point between the minimum and maximum growth rates. While the GDBH has been widely tested, consideration of phenotypic variation in rates for which defense is traded for growth and what this variation means for plant resistance remains rare. For defense, pines produce and store oleoresin in "resin ducts." Retrospective comparisons of resin ducts in pines have revealed that trees with greater numbers, sizes, or areas of xylem resin ducts are more likely to avoid or survive insect attack. We used tree ring chronologies to quantify phenotypic variation in growth and resin duct defenses in pairs of living and bark beetle‐killed Pinus ponderosa trees in southern New Mexico, USA, and to test the utility of the GDBH for explaining tree mortality. We also assessed the sensitivity of annual growth to climate and competitor density in years preceding mortality in each pair. Survivors had greater growth rates and total cross‐sectional areas of resin ducts than trees killed by bark beetles. We did not observe a difference in climate–growth relationships among the groups; however, trees killed by bark beetles suffered negative effects of competition while survivors did not. Growth‐defense trade‐offs conformed to the GDBH's prediction of a quadratic relationship; however, the two groups significantly differed in the rate at which defense was traded for increasing levels of annual growth. Our results demonstrate that phenotypic variation in the trade‐off between growth and defense could be used to characterize trees that were killed by or survived recent natural enemy epidemics. We hypothesize that the GDBH could be integrated with the characterization of phenotypic variation in growth‐differentiation strategies—along with parsing of gene versus environment influences on phenotypes—at both local and landscape scales to increase our understanding of patterns of natural enemy impacts in plant populations. [ABSTRACT FROM AUTHOR]

Abstract Dynamic resource availability leads to trade‐offs among functions in plants. The growth‐differentiation balance hypothesis (GDBH) predicts greater allocation of carbon to defense than growth when resources are scarce, with optimum defense production occurring at a point between the minimum and maximum growth rates. While the GDBH has been widely tested, consideration of phenotypic variation in rates for which defense is traded for growth and what this variation means for plant resistance remains rare. For defense, pines produce and store oleoresin in “resin ducts.” Retrospective comparisons of resin ducts in pines have revealed that trees with greater numbers, sizes, or areas of xylem resin ducts are more likely to avoid or survive insect attack. We used tree ring chronologies to quantify phenotypic variation in growth and resin duct defenses in pairs of living and bark beetle‐killed Pinus ponderosa trees in southern New Mexico, USA, and to test the utility of the GDBH for explaining tree mortality. We also assessed the sensitivity of annual growth to climate and competitor density in years preceding mortality in each pair. Survivors had greater growth rates and total cross‐sectional areas of resin ducts than trees killed by bark beetles. We did not observe a difference in climate–growth relationships among the groups; however, trees killed by bark beetles suffered negative effects of competition while survivors did not. Growth‐defense trade‐offs conformed to the GDBH's prediction of a quadratic relationship; however, the two groups significantly differed in the rate at which defense was traded for increasing levels of annual growth. Our results demonstrate that phenotypic variation in the trade‐off between growth and defense could be used to characterize trees that were killed by or survived recent natural enemy epidemics. We hypothesize that the GDBH could be integrated with the characterization of phenotypic variation in growth‐differentiation strategies—along with parsing of gene versus environment influences on phenotypes—at both local and landscape scales to increase our understanding of patterns of natural enemy impacts in plant populations.

Background: In La Malinche National Park (LMNP), Pinus species are exploited mainly because they are a non-woody source of products such as ocote (resinous wood chips) and wood. Questions/Objective: Which Pinus species are subjected to wood-stripping (WS) in the LMNP? What are their dendrometric characteristics? Do WS trees present traumatic resin ducts associated with the ocoteo practice? Does the number of trees subjected to WS increase with altitude? Study site and dates: La Malinche National Park; Tlaxcala, México, 2017-2018. Methods: Random stratified sampling was done in a total of 33 plots in three different altitudes to quantify the number of damaged and undamaged trees and the total height and diameter per tree in each plot. Increment borers were obtained to estimate tree age, samples were taken for taxonomic determination, and tissue samples to evaluate mechanical damage. Results: Pine species subjected to wood-stripping (ocoteo) were P. leiophylla, P. montezumae, P. pseudostrobus, and P. teocote, with P. montezumae being the most affected in high and mid altitudes. WS trees were those with the greatest diameter and with the largest number of traumatic resin ducts. The species having the highest number of traumatic resin ducts was P. teocote. Conclusions: WS intensity in the LMNP is greater in the mid and low altitudes and in trees of greater diameter, height, and age. The species most affected by WS is P. montezumae and all WS individuals have a significantly higher number of traumatic resin ducts.

Key message: Large sugar pine mortality was associated with recent growth and defense measures. Many old-growth pine forests across the western United States have encountered widespread and concerning increases in tree mortality attributed to increased competition and reduced vigor associated with prolonged fire exclusion that can make trees more vulnerable to bark beetles. We investigated the importance of growth and resin duct defense on recent mortality of large sugar pine (Pinus lambertiana) in a fire-excluded, mixed-conifer forest of the Sierra Nevada, in California, USA. Growth and defense were measured from tree rings for 33 pairs of live and dead sugar pine. The 10-year trend in basal area increment prior to sampling declined by 1.78 cm2 year− 1 in sugar pine that died and increased by 0.34 cm2 year− 1 in paired live sugar pine. The 10-year trend in resin duct total area showed declines of 0.0154 mm2 year− 1 in trees that died and increases of 0.0068 mm2 year− 1 in trees that survived. The most informative models of large sugar pine mortality included measures of both growth and defense. The top model included the trends of basal area increment and resin duct total area 10 years before mortality, and growth variability 5 years before mortality. In general, trends and variability in growth and defense over shorter time windows (< 10 years) were more informative than average measures or longer time windows. The results from our study suggest treatments that result in neutral to positive trends in allocation to growth and defense may contribute to conditions that reduce probability of mortality in the future. [ABSTRACT FROM AUTHOR]

Conifers possess chemical and anatomical defences against tree‐killing bark beetles that feed in their phloem. Resins accumulating at attack sites can delay and entomb beetles while toxins reach lethal levels. Trees with high concentrations of metabolites active against bark beetle‐microbial complexes, and more extensive resin ducts, achieve greater survival. It is unknown if and how conifers integrate chemical and anatomical components of defence or how these capabilities vary with historical exposure. We compared linkages between phloem chemistry and tree ring anatomy of two mountain pine beetle hosts. Lodgepole pine, a mid‐elevation species, has had extensive, continual contact with this herbivore, whereas high‐elevation whitebark pines have historically had intermittent exposure that is increasing with warming climate. Lodgepole pine had more and larger resin ducts. In both species, anatomical defences were positively related to tree growth and nutrients. Within‐tree constitutive and induced concentrations of compounds bioactive against bark beetles and symbionts were largely unrelated to resin duct abundance and size. Fewer anatomical defences in the semi‐naïve compared with the continually exposed host concurs with directional differences in chemical defences. Partially uncoupling chemical and morphological antiherbivore traits may enable trees to confront beetles with more diverse defence permutations that interact to resist attack. Plants defend against attacks by multiple mechanisms spanning chemical and physical components. We investigated how two pine species with varying historical exposure to the mountain pine beetle integrate anatomical and chemical defences. We found that the pine species that had more frequently encountered mountain pine beetle in recent history had superior anatomical defences than the species now becoming increasingly exposed due to climate change. In both pines, metrics of anatomical defences were largely unrelated to concentrations of important chemical traits, suggesting independent allocation that possibly presents beetles with more diverse permutations of defence. [ABSTRACT FROM AUTHOR]

The aim of this work was to study changes in anatomical structure of phloem tissue in pine (Pinus sylvestris L.) stems influenced by creeping forest fires of various rates. The experiments were carried out in the Lower Angara river region of the Angara provenance, Krasnoyarsk Krai, Central Siberia. The trees with green crowns and different fire damaged butts were chosen as models. Control (undamaged) trees were taken from stands adjacent to experimental plots. The changes of inner bark thickness, number of phloem annual layers between cambium and periderm and number of cells in conductive phloem were found in the stem side opposite to fire scars. The structure fluctuations of phloem tissue were detected: disturbances of sieve cell arrangement, phloem ray enlargements, resin canal overgrowth and formation of great resin ducts. The lignin accumulation was observed in inner bark and a large amount of callusing was detected between conductive and nonconductive phloem. Over the course of time, repairing of tissues occurred and the normal inner bark structure and chemistry (without lignin) were restored. The creeping fire of low intensity caused the maximal changes of phloem quantitative characteristics in trees with bark charring and these tendencies were stored after eight years. After creeping fire of high intensity the tendency for phloem thickening in trees with one fire scar and to thinning in strongly damaged trees were revealed. Also tendencies to decrease of the number of phloem annual layers, number of sieve cells in conductive phloem and ray frequency with increasing of stem injury degree were observed, besides axial parenchyma percentage trended to increase. Eight years after fire these tendencies were often not visible.

Resins are plant exudates of economic importance used by plants as defence. They flow out of resin ducts, open and long tube-like intercellular spaces lined by a layer of specialized parenchyma cells, called the epithelium, which secrete resin into the duct lumen. A model that describes resin flow in conifers is presented to investigate how duct structure, resin loading, crystallisation, and viscosity affect flow and could explain differences between species. Considering resin viscosity, the structure of resin ducts, and a pressure-driven resin loading through the duct wall, the unsteady Stokes equation was applied. There is an increase in flow towards the open end that is favoured by the duct geometry. Both flow and pressure depend on the loading mechanism and on the duct resistance, which depends on the duct geometry, viscosity and duct wall permeability to resin. These results confirm previous measurements and observations made on Pinaceae and seem to be physiologically advantageous for the defence role of resin. Understanding of how these physiological and morphological parameters affect resin flow might be useful for selecting varieties and species having a high resin yielding capacity. The model presented in this paper is also applicable to other external secretory systems in plants. [ABSTRACT FROM AUTHOR]

Occupancy of cold habitats by evergreen species requires structural modification of photosynthetic organs for stress resistance and longevity. Such modifications have been described at interspecific level, while intraspecific variation has been underexplored., To identify structural and anatomical traits that may be adaptive in cold environments, we studied intraspecific variability of needles of Scots pine ( Pinus sylvestris L.), a wide-ranging tree, along a 1,900 km temperate-boreal transect in Europe., Needles from 20 sites representing mean minimum winter temperatures between −4.0 and −19.9°C and mean annual temperatures between 8.3 and −1.7°C were sampled for measurements of leaf mass per area ( LMA, g/m2), leaf density ( LD, g/cm3) and 30 other morpho-anatomical traits., Needles from cold sites lived longer, were shorter, showed higher LMA and LD, had narrower and more collapse-resistant tracheids, thicker epidermal cells with thicker cell walls and wider resin ducts occupying larger fraction of needle volume in comparison to needles from warmer sites., Along the steep climatic gradient, needles presented a coordinated phenotypic spectrum of external and internal traits that are largely interpretable in functional, adaptive terms. This intraspecific pattern of covarying traits provides insight into the adaptive syndrome associated with stress tolerance and extended needle longevity under cold conditions of high latitudes., A is available for this article. [ABSTRACT FROM AUTHOR]

The formation of traumatic resin ducts (TRDs) represents an important induced defense in woody plants that enhances oleoresin production and flow in response to environmental perturbations. In some genera ( Pinus), resin ducts are copious and conspicuous; however, in others ( Picea), resin ducts are relatively rare. The occurrence and strength of resin ducts, in particular TRDs, in annually resolved rings could be used to reconstruct mechanical damage associated with natural disturbances. We analyzed tree-ring data from paired live and dead Engelmann spruce ( Picea engelmannii Parry ex Engelm.) that recently experienced a spruce beetle outbreak. The presence of TRDs, defined as resin ducts aligned tangentially and arranged compactly, indicated mechanical damage associated with epidemic spruce beetle ( Dendroctonus rufipennis (Kirby)) populations. TRD prevalence during the outbreak was significantly higher than over tree lifespans. All other metrics characterizing tree vigor (diameter, age, ring width, and basal area increment) were not significantly different between live and dead trees, suggesting that the inherent capability to produce TRDs that can 'pitch out' attacking spruce beetles could be the primary mechanism by which Engelmann spruce survived the outbreak. Because TRD production in our Engelmann spruce was exceedingly rare, this discovery represents a new line of tree-ring-based evidence that can be used to reconstruct other spruce beetle outbreaks. [ABSTRACT FROM AUTHOR]

• Treatments help multiple species resist drought and bark beetle outbreak. • Thinning and prescribed fire promote tree resistance to multiple disturbances. • Despite unprecedented drought, thinning and prescribed fire mitigate tree mortality. Long-term trends show increased tree mortality over the last several decades, coinciding with above-average temperatures, high climatic water deficits, and bark beetle outbreaks. California's recent unprecedented drought (2012–2016) highlights the need to evaluate whether thinning and prescribed fire can improve individual tree drought resistance and reduce bark beetle-associated mortality. Using a thinning and prescribed fire study on the Stanislaus-Tuolumne Experimental Forest in the central Sierra Nevada implemented prior to the drought (2011–2013), we used dendrochronological methods to estimate metrics of tree vigor (i.e., growth and resin ducts) of sugar pine (Pinus lambertiana Douglas) and white fir (Abies lowiana [Gordon & Glend.] A. Murray bis) among treatments, as well as between trees that died from bark beetle-associated mortality and their paired counterparts that survived. We used tree vigor to estimate drought resistance as the ratio between growth during drought (2012–2016) and pre-drought (2007–2011) for both species. For sugar pine, we also created analogous ratios for multiple resin duct characteristics to evaluate defense during drought. Our findings indicate that lower competition increased growth resistance of white fir, while prescribed fire had negligible impacts on growth. This translated to lower mortality, with live white fir showing higher growth resistance than those that died. While competition did not strongly affect sugar pine growth, greater growth resistance was noted for trees that lived than trees that died. However, reduced competition and prescribed fire increased defense resistance and resin duct density and relative resin duct area were negatively associated with sugar pine mortality. Live sugar pine showed greater defense resistance than dead counterparts particularly under higher levels of competition. These findings suggest thinning can promote or maintain growth during severe drought conditions and prescribed fire can be applied with negligible costs to tree growth while also producing the additional benefit of stimulating defense systems in sugar pine, which may enable them to better survive bark beetle outbreaks. Therefore, susceptibility to bark beetle-associated mortality may be ameliorated through increasing tree vigor with a combination of forest thinning and prescribed fire. [ABSTRACT FROM AUTHOR]

Variability of eight morpho-anatomical traits of two-year-old needles of the Macedonian pine (Pinus peuceGriseb.), collected from natural populations of Montenegro (Zeletin and Sjekirica) and Serbia (Mokra Gora), was investigated. The needles have two resin ducts of the external type (touching epidermis). The average values were as follows: 7.14 cm (needle length), 0.86 mm (needle width), 0.66 mm (needle thickness), 13.32 μm (cuticle+epidermis thickness), 16.24 μm (height of hypodermal cells), 1.45 (number of hypodermis layers), 2 (number of resin ducts) and 52.45 μm (resin duct diameter). The most variable characters were needle width and needle thickness. PCA visualizes overlapping of three populations. Cluster analysis suggests that the Sjekirica population is more similar to the Mokra Gora population than to the geographically nearest population of Zeletin. Given results are discussed in relation to our previous investigations of this species based on terpenes andn-alkanes, where the population from Mt. Zeletin also exhibited differences compared to the population from other Balkan localities. [ABSTRACT FROM PUBLISHER]

External induction of resin secretion, based on the defence system of Pinus trees, has been performed by humans since Classical times through various methods. The socio-economic implication of this practice in Spain and the expansion of the Chinese market justify a new approach to tapping methodology and the effects of this activity on the tree. The resin yield of 561 Pinus pinaster trees in a stand in central Spain, tapped in 2012 using four different methods (mechanised or traditional tool, upwards or downwards), was analysed. An anatomical study was made of 13 trees (8 tapped and 5 controls) in another stand 13 km away with similar climate and soil conditions, tapped in 2011 using the same four methods. From each tapped tree, eight cores were taken at different locations and varying distances from the tapping wound. In each core, an analysis was made of growth ring, earlywood and latewood width, and axial canal frequency, area, mean size and location from one year before tapping to two years after (2010–2013). The highest mean annual resin yield was found for traditional tool upward tapping, which also induced the highest increase in axial canal frequency and area. The lowest yield was found for mechanised tapping, which showed no differences between the upward and downward directions. The strongest induction of systemic induced responses in terms of resin canal frequency and area was detected one year after tapping for upward tapping. This suggests the involvement of signalling processes that spread mainly upwards, and the importance of adaptive processes as a defence to periodic insect attacks for this forest tree. [ABSTRACT FROM AUTHOR]

Variability of eight morpho-anatomical characters of 2-year-old needles of the Bosnian pine (Pinus heldreichiiChrist.), collected from natural populations in Montenegro (Lovćen, Zeletin and Bjelasica) and Serbia (Zlatibor-Pešter) were investigated. The needles have 0–13 resin ducts, predominantly of the medial type (settled in mesophyll tissue). The average values were as follows: 7.86 cm (needle length), 1.44 mm (needle width), 0.85 mm (needle thickness), 20.82 μm (cuticle+epidermis thickness), 21.08 μm (height of hypodermal cells), 3.31 (number of hypodermis layers), 4 (number of resin ducts)57.05 μm (resin duct diameter). Needle width and thickness were the most variable characters. Principal component analysisseparation of the geographically most distant populations Lovćen and Zlatibor-Pešter from themselves and from other populations. Cluster analysis suggests biggest similarities between populations Lovćen and Bjelasica and biggest differences between Lovćen and Zlatibor-Pešter. [ABSTRACT FROM AUTHOR]

In many fire-prone woodlands and forests, fire exclusion has resulted in substantial litter and duff accumulations capable of long-duration smoldering once fire is reintroduced. While previous research has shown that the soil heating from smoldering fires resulted in short-term reductions in coarse root non-structural carbohydrates and latewood growth, information on the long-term effects of smoldering fire is lacking. Our study compared the effects of three smoldering fire treatments (root only, stem only, root and stem) and two control treatments (no fire and surface fire only) on longleaf pine ( Pinus palustris ) growth and defense ten years after treatments. We cored 17–29 similar sized trees per treatment and measured growth as basal area increment and defense as resin duct properties (e.g., resin duct size, % resin duct area). We used generalized linear mixed models to determine the influence of smoldering treatments and climate on basal area increment and resin duct properties. Variation in basal area increment and resin duct size during the previous ten years were positively correlated with the subsequent ten years, r 2 = 0.71 and r 2 = 0.65, respectively. Additionally, temporal variation in growth and defense were related to climatic factors. Growth had the strongest correlation with current August temperatures ( r = −0.50), and defense had the strongest correlation with current December temperatures ( r = −0.64). Basal area increment was best predicted by summer and fall Palmer Drought Severity Index, while resin duct size was best predicted by the interaction of treatment and precipitation during the previous November. During the three driest years following treatment smoldering duration had a negative relationship with basal area increment ( p < 0.0085; r 2 = 0.08) and resin duct size ( p < 0.0003; r 2 = 0.16). While longleaf pine growth was generally resistant to long-duration soil heating following years of fire exclusion, the proceeding growth response was contingent on the post-fire climate. Longleaf pine resin duct size was sensitive to the effects of smoldering fire, and potential negative impacts may be exacerbated by lower precipitation. Restoring fire to long-unburned sites proceeded by warmer and drier climate conditions may result in reduced longleaf pine growth and defense that may contribute to increased probability of mortality during subsequent disturbances. [ABSTRACT FROM AUTHOR]

Conifers have incurred high mortality during recent global-change-type drought(s) in the western USA. Mechanisms of drought-related tree mortality need to be resolved to support predictions of the impacts of future increases in aridity on vegetation. Hydraulic failure, carbon starvation and lethal biotic agents are three potentially interrelated mechanisms of tree mortality during drought. Our study compared a suite of measurements related to these mechanisms between 49 mature piñon pine (Pinus edulis Engelm.) trees that survived severe drought in 2002 (live trees) and 49 trees that died during the drought (dead trees) over three sites in Arizona and New Mexico. Results were consistent over all sites indicating common mortality mechanisms over a wide region rather than site-specific mechanisms. We found evidence for an interactive role of hydraulic failure, carbon starvation and biotic agents in tree death. For the decade prior to the mortality event, dead trees had twofold greater sapwood cavitation based on frequency of aspirated tracheid pits observed with scanning electron microscopy (SEM), smaller inter-tracheid pit diameter measured by SEM, greater diffusional constraints to photosynthesis based on higher wood δ13C, smaller xylem resin ducts, lower radial growth and more bark beetle (Coleoptera: Curculionidae) attacks than live trees. Results suggest that sapwood cavitation, low carbon assimilation and low resin defense predispose piñon pine trees to bark beetle attacks and mortality during severe drought. Our novel approach is an important step forward to yield new insights into how trees die via retrospective analysis. [ABSTRACT FROM AUTHOR]

Comprehensive comparative anatomy of Pinus leaves was carried out. Some anatomical features were found to be quite useful and supported the classification of genus to subgenus and section level. The number of needles per fascicle, number of vascular bundles, position of resin ducts, shape of leaf in cross section, and distribution of stomata on the leaf surface showed remarkable variation between different species and facilitated the classification of Pinus into minor groups: subgenus, section, and subsection. The members of subgenus Pinus had two vascular bundles whereas members of subgenus Strobus had only one vascular bundle. The position of resin ducts was more consistent in subgenus Strobus than in subgenus Pinus. Interestingly, the species of subsection Strobus included in this study lacked stomata on the abaxial surface. The results indicate that the number of needles per fascicle and needle size are inversely related, and more importantly that a greater numbers of needles per fascicle lead to a more angular shape. [ABSTRACT FROM AUTHOR]

In the research on the variability of the morpho-anatomical properties of the Serbian spruce (Picea omorika/PanČ./ Purkyne), we investigated seven characteristics of 2-year-old needles, collected from four natural populations in Serbia. The hypodermis of the Serbian spruce subject to our study is single layered. The needles sport 0–2 resin ducts, predominantly of the external type (touching the epidermis). The average values were as follows: 13.60 mm (needle length), 1.49 mm (needle width), 0.82 mm (needle thickness), 22.83 μm (cuticle+epidermis thickness), 17.51 μm (hypodermis thickness), 0.74 (number of resin ducts), and 51.82 μm (resin duct diameter). Needle width and thickness were the most variable characteristics. Principle component analysis visualizes an overlapping among the populations in the region of Mt. Tara and a partial separation of the population from Mileševka Canyon. Cluster analysis suggests the biggest differentiation between geographically distant populations (Štula and Mileševka Canyon). All the analyzed characteristics were compared with appropriate literature sources. [ABSTRACT FROM AUTHOR]

Bark beetles have recently killed billions of trees, yet conifer defenses are formidable and some trees resist attack. A primary anti-insect defense of pines is oleoresin from a system of resin ducts throughout the tree. Resin defense traits are heritable, and evidence suggests that resin duct characteristics are associated with resistance to insects. However, comparisons of resin ducts in trees killed by bark beetles to trees that resisted attack are unavailable. We compared vertical resin duct characteristics (number, density, and size) and growth rates from trees that were 'resistant' (survived mass attack) versus 'susceptible' (killed by attack) to bark beetles in lodgepole ( Pinus contorta) and limber ( Pinus flexilis) pines. Resistant trees of both species had significantly more resin ducts in recent growth than susceptible trees. Discriminant analysis (DA) correctly categorized 84 % of lodgepole and 92 % of limber pines as susceptible/resistant based on combinations of resin duct and growth characteristics from recent 5- through 20-year growth intervals. DA models using measures from only the most recent 5 years of growth correctly categorized 72 and 81 % of lodgepole and limber pines, respectively. Comparing resistant to susceptible trees independent of species identity led to the correct categorization of 82 % of trees based on factors from 5- to 20-year intervals, and 73 % of trees using only resin duct counts from the most recent 5 years. We conclude that resin duct characteristics can be used to assess tree resistance to bark beetles across pine species, and offer a metric for management to enhance pest resistance. [ABSTRACT FROM AUTHOR]

• Many tree-killing bark beetles attack large old trees for reasons that are unclear. • Phloem and defence traits varied with size of young and old mature lodgepole pine. • Phloem quantity and quality were greater in young stands, increasing with tree size. • Tree defences were greater in young stands and tended to increase with tree size. • Phloem thickness may not be main reason that large old trees are attacked. Tree size often predicts the occurrence of bark beetles that breed in the inner bark (phloem) of trees. A notable example is mountain pine beetle, Dendroctonus ponderosae, which primarily kills large, old trees during outbreaks. The tree mortality pattern is often attributed to increasing phloem thickness with tree size, although tree size-dependent defences may also be important. Age effects may confound interpretations of tree size effects. We examined phloem and anatomical defence traits in single-cohort lodgepole pine, Pinus contorta , stands as a function of tree size and age within and across young mature stands (trees 25–45 years old) and old stands (115–140 years old). Phloem thickness increased linearly with tree size within and across stands, more strongly for trees in young stands that had thicker phloem than same-sized trees in old stands. Phloem nitrogen was greater in young stands and did not vary with tree size. Resin duct investment was generally greater in larger trees within stands, but young trees had more and larger ducts than old trees. These results are consistent with canopy dominance of larger trees within stands that can acquire more carbon for both growth and defence; relationships between tree size and both phloem and defence traits were weaker across stands of different ages. Greater defence in young trees may reflect greater risk and costs of herbivory that might be associated with higher phloem nitrogen in younger stands. Our results suggest that the best phloem resources (quantity and quality) are found in relatively large trees in young stands, which is a poor match for the pattern of attacks by mountain pine beetles that favour large trees in old stands. Lower defences in old stands may also explain the pattern of tree mortality by beetles. Other benefits of large trees merit more attention in understanding the importance of tree size to bark beetles. [ABSTRACT FROM AUTHOR]

Abstract: In order to compare Norway spruce (Picea abies) and silver fir (Abies alba) with respect to susceptibility to wound colonizing fungi, wood stains and rots, experimental cortical lesions were created in situ on mature trees. The study was performed with 40 Norway spruce and 39 silver fir. Two years after the infliction of the lesions the experiment was evaluated with respect to fungal colonization. The most common fungi isolated from xylem beneath the wound area of Norway spruce were Neonectria fuckeliana, Stereum sanguinolentum and Leptodontium beauverioides. Overall, fungal wound infection rate of Norway spruce was 4.6-fold higher compared to silver fir. Only 7% of the Norway spruce stems were sterile in opposite to 67% sterile silver fir trees. Wood decay fungi were isolated from 28% of Norway spruce trees compared to only 8% of silver fir. Accordingly, discolorations in the wood of Norway spruce were clearly larger in their extent. Silver fir mostly displayed only superficial discoloration. On the other hand, the impact on xylem of both tree species was only slightly influenced by the season of wounding (May versus October). Histological examination revealed that in Norway spruce fungal infections occurred through regular resin channels which appeared to be easily colonized by fungi facilitating long distance growth of fungal hyphae. In contrast, traumatic resin ducts formed by both tree species were not found to be infected by fungi. Very obviously, silver fir – being void of primary resin channels – was able to seal injuries by deposition of accessory substances close to the surface of the exposed xylem, thus inhibiting sapwood dehydration and impeding xylem colonization by fungi. For Norway spruce, computer tomography strongly indicated specific sapwood desiccation in the wound region, while in silver fir no such desiccation could be found. [Copyright &y& Elsevier]

Copyright of Botanica Serbica is the property of University of Belgrade, Institute of Botany & Botanical Garden Jevremovac 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.)

Copyright of Botanica Serbica is the property of University of Belgrade, Institute of Botany & Botanical Garden Jevremovac 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 structure, distribution and patterns of resin ducts in processes of its initiation and development were studied with the methods of thin section and ultrathin section. This paper emphasized the ultrastructural changes during canal development by a ring of the live epithelial cells, and the epithelial cells were usually surrounded with one or two layered sheath cells, which were normal parenchyma cells in some primary resin ducts and became dead cells with thick walls in other primary and secondary resin ducts. The resin ducts were found to occur in almost all organs, except in cotyledon. The resin ducts were formed by schizogeny and their development can be divided into three stages (e.g., initial stage, formation stage and mature stage). At the initial stage, the initial cells had many plastids without integral membrane structures, which contain one or two starch grains in them, and there are a few black osmiophilic droplets on the endoplasmic reticulum and membranes. A small number of osmiophilic droplets were present in the plastids. At the formation stage, the number of plastids, mitochondria and Golgi bodies in epithelial cells increased. The plastids were commonly surrounded by endoplasmic reticulum sheath. The larger osmiophilic droplets in cytoplasm and the smaller osmiophilic droplets on the plastids envelope, mitochondrion envelope and Golgi vesicles obviously increased in number during canal developing. At the mature stage, the cytoplasm of epithelial cells became thin with small nucleus. The number of mitochondria and Golgi body decreased, but numerous plastids still existed. Osmiophilic droplets were abundant in epithelial cells as in previous status. Taken together, the structures of plastids in epithelial cells gradually became well developed and the synthesis of resin was remarkably enhanced during resin duct formation and plastids should be the main site for resin synthesis. [ABSTRACT FROM AUTHOR]

Tree voles are dietary specialists, feeding almost exclusively on conifer needles and bark. They reduce their exposure to conifer chemical defenses by physically removing resin ducts from many needles before ingesting the remaining tissue. The portion of needle removed differs among tree species, depending on the location of the resin ducts. To evaluate the amount of resin avoided by this behavior we removed the resin ducts from Douglas-fir,Western Hemlock, and Sitka Spruce needles and used gas chromatography to compare volatile resin concentrations in needles with and without the resin ducts removed. Needle tissues without resin ducts contained no terpenoid resin, demonstrating that tree voles can regulate the nutritional quality of their diet by controlling the amount of resin ingested. We suggest that differences in the physical structure (and possibly chemical composition of terpenes) of the needles make it difficult for voles to easily switch between tree hosts. [ABSTRACT FROM AUTHOR]

Defence in young trees has been much less studied than defence in older ones. In conifers, resin within ducts in bark is an important quantitative defence, but its expression in young trees may be influenced by developmental or physical constraints on the absolute size of the resin ducts as well as by differential allocation of resources to growth and resin synthesis. To examine these relationships, we used nitrogen fertilisation of 1- and 2-year-old pine and spruce to produce trees of different sizes and measured the effect on the number and size of resin ducts and the amount of resin they contained. All of these variables tended to increase with stem diameter, indicating a positive relationship between resin-based defence and growth of 1- and 2-year-old trees. In pine, however, the mass of resin flowing from severed ducts was much lower relative to duct area in 1- than in 2-year-old trees, suggesting that the older trees allocated a higher proportion of the carbon budget to resin synthesis. Resin-based defence in 1-year-old pines appears to be both positively related to growth and resource limited. In spruce, resin production was generally lower, and age-related differences were not observed, suggesting that resin-based defence is less important in this species. Bio-assays of 2-year-old trees with the pine weevil, Hylobius abietis, emphasised the importance of resin as a defence against this bark feeding insect. Nitrogen fertilisation had a limited influence on resistance expression. One-year-old trees remained susceptible because of their small size, low resin production and limited response to fertilisation. The strong growth response of 2-year-old trees to fertilisation increased resin-based defence, but most spruce trees remained susceptible, while most pines were resistant at all levels of fertilisation. [ABSTRACT FROM AUTHOR]

Abstract: Past activity of geomorphic processes can be reconstructed on tree-ring series using the presence of injuries, reaction wood or abrupt changes in the annual increment. The analysis of these features provides valuable data on years with process activity. In contrast, an intra-annual dating has so far normally only been possible through the analysis of injuries. In this technical note, it is shown that, in tree-ring studies realized with conifers, resin ducts may have the potential for providing information on the intra-seasonal timing of past geomorphic processes as well. However, because ducts may occur as a result of influences other than geomorphic, detailed field investigations and the identification of processes present at the study site imperatively need to precede dendrogeomorphological investigations. Data obtained from 1298 cross-sections indicate that the presence of resin ducts in Picea abies (L.) Karst. and Larix decidua Mill. can be considered to be the result of geomorphic activity if they form tangentially oriented rows with a compact and continuous arrangement of traumatic ducts. The presence of resin ducts may also help to improve the quality of reconstructions in studies using Abies alba Mill. as vertical resin ducts occur exclusively at or next to injuries. In contrast, resin ducts apparently cannot be used for dendrogeomorphological analyses of Pinus ssp. [Copyright &y& Elsevier]

Meristematic activity in the bud meristem of Abies nordmanniana was visualized by ubiquitin immunohistochemical localization from before bud break and throughout shoot expansion. Ubiquitin was detected in meristematic cells either in the cytosol or nucleus, or both, depending on tissue type and developmental stage. During winter dormancy, ubiquitin was only observed in the protodermal/hypodermal layers, but at bud break in mid May, the signal expanded to the entire shoot tip. At the end of May, a clear zonation in ubiquitin localization appeared that lasted about one month. Throughout this period, ubiquitin was barely detectable in a central group of cells that might indicate an organizing center with stem cells. At the end of June, coinciding with the transition from scale leaf to needle primordia production, ubiquitin again was more prevalent in the peripheral cell layers. During shoot expansion, a strong ubiquitin signal developed in the axil of all needles. Most of these signals later disappeared, except for those few axils where buds actually developed. A strong ubiquitin signal was also observed in cells lining the young resin ducts. Our data showed that ubiquitin may be used as a marker for metabolic activity associated with seasonal development in the apical meristem. [ABSTRACT FROM AUTHOR]

Pinus leucodermis (=P. heldreichii var. leucodermis) is widespread in the Balkan Peninsula and is present as a post-glacial relict in Southern Italy. The oldest Italian populations of this species are located at high elevation in the National Park of Pollino, where grazing and logging had endangered their survival, especially during the 20th century. In 1993 the National Park was founded and anthropogenic activities were restricted. To understand the response of P. leucodermis at the upper tree-line to climatic and anthropogenic activity variations, we developed a tree-ring width chronology (1464–2003). For the period 1804–2003 separate chronologies for the earlywood and latewood were built, and resin duct density was assessed on total ring, earlywood and latewood. Age structure of saplings was also determined. After 1950 a steep decline in tree-ring width was followed by a recovery since 1981. During the 20th century radial growth response to climate was not strong and not stable. In the period 1953–2000 P. leucodermis radial growth seemed to take advantage of high temperatures and low precipitation. Resin duct density chronologies were not a reliable dendroecological variable, but they documented a metabolic trade-off between growth and differentiation processes. The gap in the age structure between long-lived trees (over 200 years old) and saplings around 40 years old, which mainly grow in protected microsites between rocks, could indicate a negative influence of grazing and related human activities. We suggest that the protection strategies introduced by the National Park could play a positive role in the recruitment of new saplings and in the ring growth recovery of old trees of P. leucodermis. [Copyright &y& Elsevier]

We investigated the cellular responses of stem tissues of mature Scots pine (Pinus sylvestris L.) trees to inoculations with two fungal pathogens. The bark beetle vectored fungus, Leptographium wingfieldii Morelet, induced longer lesions in the bark, stronger swelling of polyphenolic parenchyma cells, more polyphenol accumulation and increased ray parenchyma activity compared with the root rot fungus, Heterobasidion annosum (Fr.) Bref., or mechanical wounding. Axial resin ducts in the xylem are a general feature of the preformed defenses of Scots pine, but there was no clear induction of additional traumatic axial resin ducts in response to wounding or fungal infection. The anatomical responses of Scots pine to pathogen infection were localized to the infection site and were attenuated away from bark lesions. The responses observed in Scots pine were compared with published studies on Norway spruce (Picea abies (L.) Karst.) for which anatomically based defense responses have been well characterized. [ABSTRACT FROM PUBLISHER]

• No evidence of tradeoff between growth/defense among trees in natural forest stands. • Differences in resin chemistry support field observations of bark beetle activity. • Whitebark pines produce more compounds that beetles exploit to enhance attack success. • Lodgepole pines produce more compounds that beetles exploit to recognize hosts. • Engelmann spruce negatively influences constitutive monoterpene concentrations. Recent, widespread tree mortality in the western U.S. resulting from changes in climate, pathogens, insect activity, and forest management practices has led to concerns for many ecologically and culturally important species. Within conifers, resin-based defenses have long been recognized as a primary defense mechanism against a variety of insects and pathogens. Oleoresin produced by trees contain complex mixtures of terpenoids that have numerous insecticidal and fungicidal properties. Research has also identified links between resin duct characteristics and increased probability of survival during bark beetle outbreaks. Whitebark pine (Pinus albicaulis) is a culturally significant high elevation species that provides numerous ecological services within subalpine and alpine ecosystems. Whitebark pine has co-evolved with a suite of biotic and abiotic disturbances. Individual trees allocate resources towards growth and resin-based defenses, making it a good candidate species to evaluate growth and defense relationships and tradeoffs. In this study we compared constitutive resin chemistry, tree growth and resin duct anatomy between similarly aged whitebark and lodgepole pine (P. contorta var latifolia) growing in proximity within a disturbance-prone, mixed-conifer forest in northwestern Montana. These two host species have varying degrees of historical exposure to mountain pine beetle. Our research yields four important findings. First, we did not find evidence of a tradeoff between tree growth and tree defenses (resin duct morphology and resin chemistry). This suggests that trees growing under favorable field conditions can experience high growth rates and still allocate ample resources towards defense. Second, we found that resin ducts and constitutive mono- and sesqui- terpenes were not correlated in lodgepole pine while duct production and area were positively related to constitutive monoterpenes, and duct size and area were positively related to constitutive sesquiterpenes, in whitebark pine. The lack of distinct, consistent relationships between these defensive features suggests that both whitebark and lodgepole pine trees present beetles with numerous, complex combinations of resin-based defenses. Third, based on constitutive terpene profiles, bark beetles are more likely to enter lodgepole pine but more likely to successfully elicit mass attacks in whitebark pine, which agrees with beetle attack and success patterns observed in the field. Fourth, overstory competition, particularly by Engelmann spruce (Picea engelmannii), can influence tree defenses, specifically by reducing constitutive terpene concentrations in lodgepole and whitebark pine. Competitive tree interactions could lead to altered bark beetle-conifer interactions as host and nonhost species migrate in response to changing climate. Our results suggest that strategies designed to support whitebark pine populations can benefit from better understanding interactions among growth, competition and physical and chemical defenses in response to multiple disturbance. [ABSTRACT FROM AUTHOR]

1. Young plants of a northern (Alaska) and southern (Oregon) provenance of Sitka Spruce, Picea sitchensis, were subject to high and low light and high and low nitrogen treatments in a polyhouse experiment. The effect of treatments on growth, needle and resin duct size, water content and concentration of quantitative defences (resin and polyphenols), sugars and nitrogen in needles, stems and roots was determined. 2. Concentrations of resin, polyphenols and carbohydrates were higher in low nitrogen treatments as predicted by resource-availability models of defence and the changes were similar in all parts of the trees including roots and in tissues formed prior to experimental treatments. Variation in the relative concentration of resin and polyphenols between tissues may indicate a defensive trade-off. The size of needle resin ducts was positively correlated with tree growth but no evidence for ‘structural’ limitation of resin concentration in needles was found. 3. Changes in concentration of quantitative defences did not appear to be the result of a direct trade-off with growth but reflected treatment-induced variation in the root/shoot ratio. Production of quantitative secondary chemicals may therefore be part of an integrated response of the trees to environmental stress. 4. Bioassays with Elatobium abietinum, Gilpinia hercyniae and the fungus Phacidium coniferarum showed that changes in needle size, the nutritional and water content of tissues and the balance between nutrients and secondary chemicals influenced performance of one or more of the organisms. Changes in the concentration of carbon-based secondary chemicals alone were, therefore, of only limited value in predicting susceptibility of Spruce to insects and fungi. [ABSTRACT FROM AUTHOR]

Digital imaging using high-resolution X-ray micro-computed tomography has become a methodology with increasing importance for assessing wood tissues. This chapter aims to describe the use of this nondestructive, noninvasive, and reproducible technique to new researchers interested in analyzing the three-dimensional properties of the resin duct systems in pine stem wood samples., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

• High resin yield slash pine trees need to be identified for breeding purpose. • Resin flow rate measuring technology allowed identification of high yield trees. • Higher beta-pinene and lower alpha-pinene were detected in high yield trees. • Seasonal variations for relative contents of most resin components were small. • High resin yield trees are characterized by larger duct sizes and total areas. In pine species, resin ducts are the specialized secretory structures to synthesize and store resin. Resin terpenes finds broad applications in pharmaceutical, chemical, biofuel, and food fields. Previous slash pine (Pinus elliottii Engelm.) breeding programs mainly focused on improvements in growth and wood properties in China. The incorporation of resin production into selective slash pine tree breeding occurred rarely, as standard tapping method to identify high-resin yield (RY) individuals is time-consuming, laborious, and expensive. The objective of this study was to identify high-RY slash pine trees with the method of resin flow rate (RFR) in a short timeframe in three plantations of southern China. The comparison of chemical profile between high- and low-yield individuals was also conducted. Moreover, the structural basis referred to resin secretion was studied by investigating the relationship between resin duct characteristics and RY. The phenotypic and genetic correlation coefficients between RY and RFR at all three sites were 0.44−0.85 and 0.58−0.71 respectively, which indicated that RFR measuring technology was reliable for tree breeders to select slash pine trees with high RY for breeding purpose. Resin component analysis revealed that the relative contents of β-pinene were higher in more productive trees; however, for α-pinene, the relative contents were significantly lower. Seasonal variation was low for most resin components and highly consistent across resin yielding classes and test sites. There were strong relations between RY and resin duct size and area at all three sites. High-yield individuals were always characterized by larger duct sizes and larger total areas when compared with low-yield trees. The RFR, certain resin components such as β-pinene, and most resin duct characteristics could be useful criteria for evaluating resin production in slash pine and could be applied to improve tapping management and breeding programs. [ABSTRACT FROM AUTHOR]

Tree mortality associated with drought and concurrent bark beetle outbreaks is expected to increase with further climate change. When these two types of disturbance occur in concert it complicates our ability to accurately predict future forest mortality. The recent extreme California USA drought and bark beetle outbreaks resulted in extensive tree mortality and provides a unique opportunity to examine questions of why some trees die while others survive these co-occurring disturbances. We use plot-level data combined with a three-proxy tree-level approach using radial growth, carbon isotopes, and resin duct metrics to evaluate 1) whether variability in stand structure, tree growth or size, carbon isotope discrimination, or defenses precede mortality, 2) how relationships between these proxies differ for surviving and now-dead trees, and 3) whether generalizable risk factors for tree mortality exist across pinyon pine (Pinus monophylla), ponderosa pine (P. ponderosa), white fir (Abies concolor), and incense cedar (Calocedrus decurrens) affected by the combination of drought and beetle outbreaks. We find that risk factors associated with mortality differ between species, and that few generalizable patterns exist when bark beetle outbreaks occur in concert with a particularly long, hot drought. We see evidence that both long-term differences in physiology and shorter-term beetle-related selection and variability in defenses influence mortality susceptibility for ponderosa pine, whereas beetle dynamics may play a more prominent role in mortality patterns for white fir and pinyon pine. In contrast, incense cedar mortality appears to be attributable to long-term effects of growth suppression. Risk factors that predispose some trees to drought and beetle-related mortality likely reflect species-specific strategies for dealing with these particular disturbance types. The combined influence of beetles and drought necessitates the consideration of multiple, species-specific risk factors to more accurately model forest mortality in the face of similar extreme events more likely under future climates. Identified within-species risk factors for tree-level mortality due to the combination of severe drought and concurrent bark beetle outbreaks associated with the 2012–2016 California, USA drought. Risk factors are categorized by species and category of metric measured. While we do not attempt to disentangle the effects of drought and bark beetles, host-specific beetles were identified as contributing to mortality for ponderosa pine, pinyon pine, and white fir, while incense cedar showed no clear evidence of bark beetle attacks. BAI refers to basal area increment (i.e. radial tree growth), Δ13C refers to discrimination of the heavier (13C) carbon isotope measured from tree rings, and PDSI refers to the Palmer Drought Severity Index. Unlabelled Image • Recent drought and bark beetles caused extensive tree mortality in California, USA. • A three-proxy approach is used to elucidate risk factors for tree-level mortality. • Living and dead trees exhibit some differences in growth, isotopes (Δ13C) and defenses. • Differences between living and dead trees are not consistent across species. • Effects of drought with beetles mask generalizable risk factors of mortality. [ABSTRACT FROM AUTHOR]