Conifer Species Research Articles

Biogeographic, climatic, morphological, cytological and molecular data reveal a new diploid species from China in the genus Xanthocyparis (Cupressaceae)

AbstractThe genus Xanthocyparis was described in 2002 for a new conifer species X. vietnamensis from northern Vietnam, which became well‐known for its rarity. Recently, natural diploid populations were found in a small area of northern Guangxi, China, whereas material from Vietnam plus newly discovered populations from southern Guangxi were determined to be tetraploids. We integrated evidence from multiple data sources to perform a taxonomic evaluation of the two ploidy levels present in Xanthocyparis. Morphometric analyses detected statistically significant differences in cone and leaf characters, whereas microsatellite and transcriptome analyses revealed clear genetic divergence between diploid and tetraploid material. Furthermore, analysis of bioclimatic variables confirmed divergence in ecological niches. Gene trees from homologous sequences indicate that tetraploid material might have arisen via allopolyploidy from the extant diploid material and a third, possibly extinct lineage. Therefore, we recognize and describe a new diploid species from northern Guangxi China: Xanthocyparis guangxiensis.

Tree Rings Mercury Controlled by Atmospheric Gaseous Elemental Mercury and Tree Physiology.

Tree rings are an emerging atmospheric mercury (Hg) archive. Questions have arisen, though, regarding their mechanistic controls and reliability. Here, we report contrasting tree-ring Hg records in three collocated conifer species: Norway spruce (Picea abies), Scots pine (Pinus sylvestris), and European larch (Larix decidua), which are from a remote boreal forest. Centennial atmospheric Hg trends at the site, derived from varved lake sediments, peats, and atmospheric monitoring, indicated a steady rise from the 1800s, peaking in the 1970s, and then declining. Prior to ca. 2005, larch and spruce tree rings reproduced the peak in the atmospheric Hg trend, while pine tree rings peaked in the 1930s, likely due to the prolonged sapwood period and ambiguity in the heartwood-sapwood boundary of pine. Since ca. 2005, tree rings from all species showed increasing Hg concentrations in the physiologically active outer rings despite declining atmospheric Hg concentrations. The good agreement between Hg and nitrogen concentrations in active tree-ring cells indicates a similar transport mechanism and cautions against their applicability as atmospheric Hg archives. Our results suggest that tree-ring Hg records are controlled by atmospheric Hg and tree physiology. We provide recommendations for using tree-ring Hg archives that take tree physiology into account.

Contrasting survival strategies for seedlings of two northern conifer species to extreme droughts and floods.

Lowland northern white-cedar (Thuja occidentalis) forests are increasingly exposed to extreme droughts and floods that cause tree mortality. However, it is not clear the extent to which these events may differentially affect regeneration of cedar and its increasingly common associate, balsam fir (Abies balsamea). To test this, we measured how seedlings of cedar and fir were able to avoid, resist, and recover from experimental drought and flood treatments of different lengths (8-66days). Overall, we found that cedar exhibited a strategy of stress resistance and growth recovery (resilience) from moderate drought and flood stress. Fir, on the other hand, appears to be adapted to avoid drought and flood stress and exhibited overall lower growth resilience. In drought treatments, we found evidence of different stomatal behaviors. Cedar used available water quickly and therefore experienced more drought stress than fir but cedar was able to survive at water potentials > 3MPa below key hydraulic thresholds. On the other hand, fir employed a more conservative water use strategy and therefore avoided extremely low water potential. In response to flood treatments, cedar survival was higher and only reached 50% if exposed to 23.1days of flooding in contrast to only 7.4days to reach 50% mortality for fir. In both droughts and floods, many stressed cedar were able to maintain partially brown canopies and often survived the stress, albeit with reduced growth, suggesting a strategy of resistance and resilience. In contrast, fir that experienced drought or flood stress had a threshold-type responses and they either had full live canopies with little effect on growth or they died suggesting reliance on a strategy of drought avoidance. Combined with increasingly variable precipitation regimes, seasonal flooding, and complex microtopography that can provide safe sites in these forests, these results inform conservation and management of lowland cedar stands.

Lignocellulose hydrothermal artificial humic acid production: Reaction parameters screening and investigation of model/real feedstock

Utilizing relatively mild hydrothermal conversion technique (under optimized conditions, 200 °C, 4 h, 1:10 solid-liquid ratio, 0.5 M NaOH), lignocellulosic biomass can be efficiently transformed into humic acids, thereby significantly enhancing its utilization. Additionally, this approach provides a means for precise manipulation of the composition and properties of the resulting humic acids. In this comprehensive study, lignocellulosic biomass, comprising various attributes like coniferous, broadleaf, and grassy species, as well as model components like cellulose, hemicellulose, and lignin, underwent hydrothermal reactions to produce humic acids. Firstly, a systematic evaluation was conducted to determine the influence of operational parameters on the formation of humic acids. Subsequently, the characteristics of humic acids derived from diverse lignocellulosic biomass sources were analyzed and benchmarked against commercial humic acids. Based on the empirical findings, a mechanistic pathway for the generation of humic acids was figured out. The results indicate that the primary stages in the hydrothermal conversion of lignocellulosic biomass to humic acids involve initial hydrolysis into smaller molecular components, followed by further reactions leading to the formation of humic acids. Notably, the interplay between cellulose, hemicellulose, lignin, and other minor components, such as tannins and pectins, plays a pivotal role in the synthesis of humic acids. The characterization of the derived humic acids revealed several noteworthy distinctions from commercial products. In the infrared spectroscopy (FTIR) and elemental analysis (EA) characterization, the synthetic humic acid has more oxygen functional groups, alkane groups and aromatic structures. In the X-ray photoelectron spectroscopy (XPS), the synthetic humic acid has more diverse forms and proportions of elements. In thermogravimetric analysis (TGA), the synthesized humic acid has higher thermal stability. The synthetic humic acid has a rougher surface microstructure. The synthetic humic acid has higher fluorescence intensity in three-dimensional fluorescence spectrum (3D EEM). Lignocellulose biomass raw materials with high wood quality content can obtain higher humic acid yield, but the interaction of cellulose, hemicellulose, lignin and other group components (such as tannins, pectin, etc.) in the hydrothermal process plays an important role in the generation of humic acid. This research offers valuable insights into the chemically driven production of humic acids and the strategic control of their properties, based on the structural and compositional nuances of the raw materials.

Chemometric analysis of monoterpenes and sesquiterpenes of conifers.

Volatile organic compounds (VOCs) and essential oils of conifers are widely used in the pharmaceutical industry. This work aimed to analyze the VOCs of 30 conifer species representing the Pinaceae and Cupressaceae families. Samples were collected from arboreta in Hungary, and their chemical composition was determined by gas chromatography (SPME-GC/MS); then, chemometric analyses were performed using multivariate methods to identify characteristic VOCs of conifers. Here, we present results for monoterpene and sesquiterpene profiles of the examined conifer samples. The most abundant compounds detected were α-pinene, bornyl acetate, limonene, β-pinene, β-caryophyllene, β-myrcene, δ-3-carene, and β-phellandrene. The results showed that the following volatiles were characteristic of the conifer groups: sabinene (RRT=6.0) for the cupressoid group (which includes the Cupressaceae species), longifolene (RRT=15.0) and β-pinene (RRT=6.1) were characteristic of the pinoid group (including Picea, Pinus, and Pseudotsuga species), and camphene (RRT=5.5) and bornyl acetate (RRT=12.6) were characteristic of the abietoid group (including Abies, Cedrus, and Tsuga species). Our results on VOCs in the Pinaceae and Cupressaceae families contribute to the elucidation of biodiversity patterns of conifer species and, in addition, may support the industrial application of terpenes.

Coniferous Biomass for Energy Valorization: A Thermo-Chemical Properties Analysis

Forest biomass energy, when utilized responsibly, presents a carbon-neutral and viable alternative to fossil fuels for energy storage. This research investigates the energy potential of various coniferous species, focusing on their complex chemical compositions and suitability for energy production. Key characteristics such as moisture content, volatile matter, ash content, and fixed carbon were analyzed, along with elemental composition (including nitrogen, carbon, oxygen, and hydrogen) and both gross and net heating values across different species. The proximate analysis revealed significant interspecies variations. For example, Pseudotsuga menziesii and Chamaecyparis lawsoniana exhibited the lowest moisture contents. Elemental analyses showed a broad range of values, with Larix decidua having the lowest nitrogen content and Sequoiadendron giganteum the highest carbon content. Gross and net heating values also varied considerably, with Podocarpus macrophyllus showing the lowest values and Pinus strobus the highest. Principal component analysis (PCA) was employed to identify underlying patterns, revealing correlations between the analyzed variables and the energy potential of the species. Additionally, PCA combined with cluster analysis allowed for the identification of coherent groups of species with similar characteristics. Overall, these findings highlight the diverse energy valorization potential inherent in coniferous species, underscoring the importance of considering specific chemical compositions for efficient energy production. The insights provided here are valuable for selecting coniferous species for energy valorization, emphasizing the need to consider both chemical composition and calorific potential.

Spatially heterogeneous selection and inter-varietal differentiation maintain population structure and local adaptation in a widespread conifer

BackgroundDouglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plays a critical role in the ecology and economy of Western North America. This conifer species comprises two distinct varieties: the coastal variety (var. menziesii) along the Pacific coast, and the interior variety (var. glauca) spanning the Rocky Mountains into Mexico, with instances of inter-varietal hybridization in Washington and British Columbia. Recent investigations have focused on assessing environmental pressures shaping Douglas-fir’s genomic variation for a better understanding of its evolutionary and adaptive responses. Here, we characterize range-wide population structure, estimate inter-varietal hybridization levels, identify candidate loci for climate adaptation, and forecast shifts in species and variety distribution under future climates.ResultsUsing a custom SNP-array, we genotyped 540 trees revealing four distinct clusters with asymmetric admixture patterns in the hybridization zone. Higher genetic diversity observed in coastal and hybrid populations contrasts with lower diversity in inland populations of the southern Rockies and Mexico, exhibiting a significant isolation by distance pattern, with less marked but still significant isolation by environment. For both varieties, we identified candidate loci associated with local adaptation, with hundreds of genes linked to processes such as stimulus response, reactions to chemical compounds, and metabolic functions. Ecological niche modeling revealed contrasting potential distribution shifts among the varieties in the coming decades, with interior populations projected to lose habitat and become more vulnerable, while coastal populations are expected to gain suitable areas.ConclusionsOverall, our findings provide crucial insights into the population structure and adaptive potential of Douglas-fir, with the coastal variety being the most likely to preserve its evolutionary path throughout the present century, which carry implications for the conservation and management of this species across their range.

Post-Pyrogenic Successions in Oak-Korean Pine Forests with Schisandra chinensis and Corylus mandshurica in Sikhote-Alin

This article discusses the results of long-term stationary studies of the formation and development of oak-cedar pine forests with magnolia berry and hazel growing in the Southern and Middle Sikhote-Alin. Considered here are the peculiarities of stands decline, seed-based reforestation, as well as the tree species growth and development courses during the process of reforestation successions in areas with different intensity of fire exposure. Following persistent ground fires, the stands decline is most intensive in the first 5 years, with decay rates and the number of surviving trees varying in different types of burnt areas. The most active seed-based reforestation occurs on post-fire sites mainly during the first 2 years, with birch, aspen and other early stage species predominating. The rate of annual growth of the young generation of trees is the most intensive on plots significantly damaged by fire, in serial species (birch, aspen, Maak’s bird cherry, etc.) they are an order of magnitude higher than in climax broadleaved and coniferous species. Determination of dominance indices, equally dependent on the numbers of undergrowth, thin and large trees, showed that during reforestation successions after both rapid and persistent lowland fires, the phytocenotic importance dynamics in Korean pine, Mongolian oak and other forest forming species has its own peculiarities.

Effect of bedrock, tree size and time on growth and climate sensitivity of Norway spruce in the High Tatras

AbstractTree growth is a multifaceted process influenced by various factors at different spatial and temporal scales, including intrinsic tree traits and environmental conditions. Climate factors have a significant impact on tree growth dynamics, while geological controls can also play a crucial role. However, our understanding of the interplay between these factors concerning tree growth is currently limited. This study focuses on Norway spruce (Picea abies [L.] Karst.), one of the economically most important coniferous tree species in Europe, to investigate the interplay of growth, climate, and environment at the forest and corresponding treeline sites in the High Tatra Mountains of Slovakia. Specifically, we developed chronologies of tree-ring width (TRW) and late-wood density (MXD) for different tree size classes across two limestone and granitic sites. Growth rates of Norway spruce trees have been increasing in forests since the 1930s and from the 1950s at treelines. Growth rates were consistently higher on limestone bedrock compared to granitic bedrock conditions. Variability of radial growth is primarily driven by climate at both geological settings with trees on granitic bedrock displaying more pronounced responses to climatic variables. We observed weakening (non-stationarity) in climate signals over time and across all size classes in both geological settings. The magnitude of these effects is small, but varies across size classes, with larger trees generally displaying stronger climate sensitivities compared to smaller ones. Therefore, our findings accentuate the potential implications of geological settings, climate, and environmental factors on the absolute growth and growth dynamics of Norway spruce, highlighting the need for further research to fully understand and manage forest ecosystems in mountainous regions.

Plant peptide hormone phytosulfokine promotes embryo development of mass in Pinus massoniana

Pinus massoniana is a critical afforestation and ecological tree species in China. However, the continued existence of this pine is severely threatened by pine wilt disease. Somatic embryogenesis serves as a highly efficient clonal propagation approach. Although significant progress has been made in somatic embryogensis research on P. massoniana, resulting in the successful regeneration of plants, the limited embryogenic potential of improved cell lines and loss of embryogenic properties resulting from prolonged proliferation have posed obstacles to the industrialization of SE production. In this study, we investigated the effect of phytosulfokine on embryo development of cell lines from P. massoniana which lead to a cascade of physicochemical changes. Eight embryogenic cell lines of P. massoniana were used to observe phenotype and cytological changes. Physiological factors and the contents of nutrients and endogenous hormones were measured before and after phytosulfokine addition. We found that PSK promoted a change in the embryogenic mass of P. massoniana, leading to their development from pro-embryogenic mass (PEM)I to PEMII or PEMIII stages of pro-embryos. In addition, PSK accumulated soluble sugar, protein, and starch, and maintained redox homeostasis during cell line proliferation by reducing H2O2 levels. Our findings increase our understanding of how PSK affects somatic embryogensis in P. massoniana, thereby providing a valuable tool for establishing efficient somatic embryogensis systems in conifer species.

The influence of forest types including native and non‐native tree species on soil macrofauna depends on site conditions

AbstractThe ongoing climate change calls for managing forest ecosystems in temperate regions toward more drought‐resistant and climate‐resilient stands. Yet ecological consequences of management options such as planting non‐native tree species and mixing coniferous and deciduous tree species have been little studied, especially on soil animal communities, key in litter decomposition and pest control. Here, we investigated the taxonomic and trophic structure of soil macrofauna communities in five forest types including native European beech (Fagus sylvatica), range‐expanding Norway spruce (Picea abies) and non‐native Douglas fir (Pseudotsuga menziesii) as well as conifer‐beech mixtures across loamy and sandy sites in northern Germany. Abundance of primary decomposers (feeding predominantly on litter) was high in Douglas fir and beech forests, benefiting from less acidic soil and more favorable litter resources compared to spruce forests, while secondary decomposers (feeding predominantly on microorganisms and microbial residues) reached highest densities in spruce forests. Differences in abundance and species richness among forest types generally varied between regions and were most pronounced in Douglas fir of the sandy region. However, trophic guilds differed more between regions than between forest types, indicating that environmental factors outweigh the importance of forest type on soil macrofauna communities. The analysis of stable isotopes (δ15N and δ13C values) supported the general robustness in trophic position of macrofauna trophic guilds against variations in forest types and regions, but indicated reduced detrital shifts and food‐chain lengths in coniferous compared to European beech forests with mixtures mitigating these effects. Overall, for evaluating consequences of future forest management practices on the structure and functioning of soil animal communities, regional factors need to be considered, but in particular at loamy sites the taxonomic and trophic structure of soil macrofauna communities are resistant against changes in forest types.

Spruce and pine utilization of phosphorus in soil amended with 33P‐labelled hydroxylapatite

AbstractMined rock phosphate is expected to become a scarce resource within the next few decades as global phosphorus (P) deposits are declining. As a result, mineral P fertilizer will be less available and more expensive. Therefore, improved knowledge is needed on other P resources, for example, apatite fertilizers derived from the by‐products of iron mining. Forestry is a potential future consumer of apatite‐rich products with the aim of obtaining more wood per hectare. The actual P availability in apatite to plants has so far been barely quantified. We therefore examined tree P uptake using 33P apatite under chamber‐grown and outdoor conditions. We examined the P uptake for the two main conifer species spruce (Picea abies) and pine (Pinus sylvestris) used in Fenno‐Scandinavian forestry. We synthesized 33P‐enriched apatite and applied it to mesocosms with growing seedlings of spruce and pine. The P uptake from 33P‐labelled hydroxylapatite was subsequently traced by (bio)imaging of radioactivity in the plants and by liquid scintillation counting (LSC) upon destructive harvest in all plant fractions (leaves, stem and roots) and rhizosphere soil. Two climatic conditions were compared, one at natural outdoor conditions and one set as 5°C warmer than the climate record from the previous years. Plant P uptake from 33P‐labelled hydroxylapatite was enhanced in chamber‐grown compared with outdoor seedlings for both tree species. This uptake was manifested in the clear radioactive images obtained over ca. 1 month after soil apatite application. Furthermore, all aboveground plant fractions of both spruce and pine seedlings showed a higher P uptake in warmer than colder daytime environments. The observed quantities and rates of P uptake from 33P‐labelled hydroxylapatite by spruce (18 Bq g−1 hour−1) and pine (83 Bq g−1 hour−1; averages in chamber condition) are as to our knowledge unique observations. Natural forest soils in Sweden are often P‐poor. Our research suggests that apatite‐based P fertilization of spruce and pine forests can increase wood production by overcoming any existing P limitation.

Pinus mugo Turra and its Therapeutic Potential: A Narrative Review

Pinus mugo Turra is a coniferous species of shrub or small tree typical of central and south-eastern Europe. It is commonly called mugo pine, mountain pine, or dwarf mountain pine referring to its habit and small size. Indeed, this plant lives at higher altitude above 1400 m above the see level where it deals with harsh conditions typical of high mountain. From an ethnotraditional point of view, P. mugo is mainly used for respiratory disorders and wound healing. In particular, its essential oils have been shown to possess interesting antimicrobial and antioxidant activities, which can substantiate its potential therapeutic effect in pulmonary and urinary tract diseases, as well as antinflammatory and antitumor effects. This review also offers a summary on the chemical constituents of P. mugo that contribute to its therapeutic potential.

Ellipse or superellipse for tree-ring geometries? evidence from six conifer species

Ellipse or superellipse for tree-ring geometries? evidence from six conifer species

Composition of Paleocene forests from Antarctica based on fossil wood

A new assemblage of fossil wood of Paleocene age from Seymour Island, Antarctic Peninsula, is described. Conifer species have been identified, belonging to the fossil genera Agathoxylon, Phyllocladoxylon, Protophyllocladoxylon, and Podocarpoxylon. Angiosperm fossil wood species are assigned to Nothofagoxylon, Caldcluvioxylon, and Myrceugenellites. New wood types have been described with possible affinity to Atherospermataceae and Asteraceae (daisy family). A newly identified fossil angiosperm species, Aextoxicoxylon jacksius, has been recorded from Antarctica for the first time. It shares traits with modern Aextoxicon punctatum and other Aextoxicoxylon wood from South America but is considered a separate species due to significant differences in vessel density, ray height, and frequency. This study indicates, in accordance with previous studies that conifers were the most common elements in the Paleocene Antarctic vegetation. In particular, Agathoxylon being the most dominant wood type. Nothofagoxylon was the most common angiosperm wood type. Overall the composition of the Antarctic Paleocene vegetation deduced from the presence of fossil wood resembles that of the modern warm to cool temperate forests of Tasmania, New Zealand and southern South America. Possible upland and lowland forest types have been identified, with the lowland forests likely most similar to the modern mixed cool temperate forests on South Island, New Zealand, and Tasmania. The upland forests were similar to the modern open canopy Araucaria-Nothofagus forests on the high Andes today.

Unveiling the aromatic secrets: analysis of odor-active components in Cupressus torulosa needles essential oil using GC-O and aroma extract dilution analysis

ABSTRACT The essential oils derived from various coniferous species, including Cupressus torulosa, have been historically valued for their aromatic properties. In the present study, essential oil from C. torulosa needles (CTEO) was analyzed using Gas Chromatography (GC), Gas Chromatography-Mass Spectrometry (GC-MS), and Gas Chromatography-Olfactometry (GC-O) with Aroma Extract Dilution Analysis (AEDA). A total of 36 compounds were identified, with δ-3-carene (0.1824 ± 0.0084 mg/g), sabinene (0.1125 ± 0.036 mg/g), and terpinen-4-ol (0.0891 ± 0.0034 mg/g) as major constituents. Of these, 24 were odor-active. The aroma profile of CTEO featured top notes of green, fresh leafy, cool, fruity, and citrus scents, middle notes of dry woody tones, and base notes of spicy and dry characteristics. Predictive models including FD factor, Odor Activity Values, and Relative Flavor Activity highlighted α-pinene, α-terpinene, linalool, bornyl acetate, β-pinene, camphor, limonene, and terpinen-4-ol as key aroma contributors. This study provides valuable insights into the aromatic profile of CTEO, with potential applications in the aroma industry.

Different patterns of fine-root exudation rates along soil depth of Pinus densiflora, Chamaecyparis obtusa, and Cryptomeria japonica in coniferous forests

Tree fine-root exudation and organic carbon compounds in the soil affect physiological functions through degradation by microorganisms around the roots and the enhancement of allelopathic effects on invasion attempts by other plant species. However, the underlying mechanism of fine-root action in vertically heterogeneous resource-distribution patterns along the soil profile is little known. Here, we quantified root exudation and its morphological and chemical traits in the soil layers down to 100-cm depth for three conifer species, Pinus densiflora (ectomycorrhiza), Chamaecyparis obtusa, and Cryptomeria japonica (arbuscular mycorrhiza), in a cool temperate Japanese forest. By using glass filter-trap method, root exudation rates in all three species varied with soil depth in a species dependent pattern. Specifically, the root exudation rate of P. densiflora was significantly higher in the middle soil layer, and lower in the topsoil layer, whereas the exudation rates significantly decreased in C. japonica and did not vary in C. obtusa along soil depth. Exudation strongly correlated with variation in root traits in C. obtusa and C. japonica but not in P. densiflora. These findings suggest that differences in exudation patterns among tree species are likely compensated for by structural modifications in fine roots in response to soil depth. In addition, the traits with mycorrhizal types might be related to adequate root exudation and enhanced soil-nutrient acquisition. Distinct differences among species in exudation, associated with vertical root distribution, will increase our understanding of root survival strategies for nutrient acquisition and carbon sequestration in forest tree species.

Identification and analysis of gibberellin 2-oxidase (GA2ox) members in Cunninghamia lanceolate and the negative regulatory character of ClGA2ox12 in tree stature and xylem lignin deposits

Cunninghamia lanceolata (Lamb.) Hook (C. lanceolate) is a fast-growing evergreen coniferous tree species with high wood yield and fantabulous timber quality. To date, numerous studies have revealed that gibberellins (GAs) regulate the formation of plant wood (secondary xylem). Moreover, GA 2-oxidases (GA2oxs) are known as the major enzymes that deactivate GAs. However, a small or no number of the GA2oxs involved in xylem development and lignin biosynthesis mediated by the GA pathway in woody plants have been identified previously. In this study, 5 GA2oxs members were identified in C. lanceolate, including 4 ClGA2ox12s and one ClGA2ox8-like. Exogenous gibberellin not only promoted lignin deposition in the stem of C. lanceolate but also up-regulated the expression of the lignin biosynthesis gene ClCAD1 by 2–3 folds and one of ClGA2ox12s (designated ClGA2ox12) by 4 folds, suggesting that ClGA2ox12 may be involved in the modulation of lignin deposition by the gibberellin signaling pathway in C. lanceolate. Furthermore, transgenic Populus tomentosa overexpressing ClGA2ox12 exhibited growth retardation and a typical dwarfing phenotype, with a reduction of approximately 40 % in the number of xylem cell layers and a decrease of approximately 16.7 %-26.9 % in lignin content relative to wild-type plants. At the same time, the expression level of lignin biosynthetic genes and lignin content were down-regulated in transgenic plants. Together, these results suggested that ClGA2ox12 functioned as a GA 2oxs catabolic enzyme that plays pivotal roles in plant growth processes, xylem development, and lignin biosynthesis, which gives insights into producing dwarf and low-lignin varieties of C. lanceolate.

Differential response by seedlings of three sub-boreal conifer species to high- and low-carbon wood ash amendment

In Canada, there is a need to implement value-added uses for wood ash (hereafter ash) generated from bioenergy facilities as most ash is landfilled. Ash application to forests can provide benefit via nutrient supply, amelioration of soil acidity and, sometimes, increased tree growth. However, information is limited on the response of conifer species to different wood ash types applied to fine-textured soil typical of north-central B.C. We conducted a 16-month seedling pot trial that examined the response of Douglas-fir ( Pseudotsuga menziesii), lodgepole pine ( Pinus contorta var. latifolia), and hybrid white spruce ( Picea glauca × engelmannii) to high- (HCA) and low-carbon ashes (LCA) applied (up to 10 Mg mineral matter ha−1 equiv.), with and without fertilizer N (200 kg N ha−1 equiv.), to fine-textured forest soil. Pine and spruce exhibited a 1.6- and 1.4-fold increase in shoot biomass at the high rate of HCA with fertilizer N. At study end, the high rate of LCA had the greatest soil pH, EC and total K in the upper forest floor, but the HCA had greater total B, P and Zn. LCA elicited increased foliar B in pine, but HCA increased foliar Ca in spruce when co-applied with fertilizer N. In general, Douglas-fir growth did not respond to ash treatments, and seedling mortality was observed in some LCA treatments. Ash treatments helped offset some nutrient deficiencies induced by N fertilization. Ash type influenced soil chemical as well as seedling growth and nutrition responses.

Effects of Low-Temperature Stress on Physiological Characteristics and Microstructure of Stems and Leaves of Pinus massoniana L.

Pinus massoniana L. is one of the most important conifer species in southern China and is the mainstay of the forest ecosystem and timber production, yet low temperatures limit its growth and geographical distribution. This study used 30-day-old seedlings from families of varying cold-tolerance to examine the morphological traits of needles and stems, chlorophyll fluorescence characteristics, protective enzymes, and changes in starch and lignin under different low-temperature stresses in an artificial climate chamber. The results showed that the seedlings of Pinus massoniana exhibited changes in phenotypic morphology and tissue structure under low-temperature stress. Physiological and biochemical indexes such as protective enzymes, osmoregulatory substances, starch, and lignin responded to low-temperature stress. The cold-tolerant family increased soluble sugars, starch grain, and lignin content as well as peroxidase activity, and decreased malondialdehyde content by increasing the levels of actual photochemical efficiency (ΦPSII), electron transport rate (ETR), and photochemical quenching (qP) to improve the cold tolerance ability. This study provides a reference for the selection and breeding of cold-tolerant genetic resources of Pinus massoniana and the mechanism of cold-tolerance, as well as the analysis of the mechanism of adaptation of Pinus massoniana in different climatic regions of China.