Trees最新文献

Understanding species-specific adaptations to climate change, which exacerbates drought stress and heat waves, is crucial for sustainable forests. This knowledge can help in selecting potential alternatives for species such as Norway spruce (PIAB), which faces significant dieback in Central European forests. In this study, we focused on the adaptive capacity under novel climate of native silver fir (ABAL) and alien Douglas-fir (PSME) as potential alternatives for the most threatened old spruce stands in the Sudetes (Poland). We applied dendrochronological approach to track tree growth dynamics over the last 70 years and quantified how species resisted and recovered from the extreme drought events of 2003 and 2015. Our results revealed the highest potential to adapt to climate change manifested by ABAL. It displayed not only lower sensitivity to precipitation shortages but it also showed greater resilience and resistance to extreme drought compared to the remaining species. In addition, both ABAL and PSME could benefit from extended growing seasons. On the other hand, the non-native PSME outperformed both native species in terms of growth rate. However, it was similarly sensitive to summer precipitation as PIAB and showed low drought tolerance. Our findings supports a better understanding of species-specific differences in their adaptive potential and can help forest managers make informed decisions about species selection for climate change-adapted future forest.

Key message

Hydraulic architecture and conductivity of current-year shoots of Japanese beech trees are closely related to the leaf area soon after full leaf expansion.

Abstract

To assess the impact of artificially reducing leaf area at two time points after full leaf expansion on the stem xylem hydraulic architecture and conductivity of current-year shoots in Fagus crenata, we manipulated leaf area by partially cutting the leaves in various proportions of potted beech trees at different times. The reduction in leaf area soon after full leaf expansion resulted in a decrease in the mean vessel diameter, number of vessels, and sapwood area of current-year shoots. Simultaneously, it increased vessel density, leading to a proportional decrease in hydraulic conductivity (K_h) and xylem-specific hydraulic conductivity (K_S). However, the leaf-specific hydraulic conductivity (K_L) of current-year shoots remained unchanged, irrespective of the reduction in leaf area. In contrast, the artificial reduction of leaf area one month after full leaf expansion increased K_L but did not significantly affect the mean vessel diameter, number of vessels, vessel density, sapwood area, K_h, and K_S. These results suggest that the stem xylem hydraulic architecture and conductivity of current-year shoots in Japanese beech are closely related to leaf area soon after full leaf expansion.

Branch growth is an important aspect of the tree growth process. Studying the branch growth pattern is important for understanding the growth of trees and optimizing forest management decisions. A total of 48 planted Korean pine sample trees from northeast China were selected, and a total of 327 sample branches were measured for branch diameter growth model development and 323 sample branches for branch length. Based on the aforementioned research objectives and the obtained data, the impact of individual tree variables, branch variables, and forest stand competition variables on branch growth were initially investigated in this study. Finally, we constructed nonlinear mixed-effects models at the individual tree level. The results show that the Mitscherlich growth equation had the best fitting accuracy and was selected as the base model for developing the Korean pine branch growth model. Forest stand competition of the ratio of the basal area of the subject tree to the mean basal area of the stand (CI₂) and branch variables of the branch length and branch diameter had the most significant contributions and were selected and introduced into the branch growth models. The branch growth became larger with increasing CI₂, branch length and branch diameter, but the effects of the branch height and diameter at the breast height on branch growth should be considered in combination with their parameters and other variables together. In addition, the introduction of random effects effectively improves the fitting accuracy of the branch growth model. Overall, the Korean pine branch growth models developed in this study have good fitting performance and have important theoretical and practical value.

Blackberry (Rubus spp.) fruit has high nutritional value and antioxidant effects. The role of miR172 and its target gene APETALA2 (AP2) in regulating plant growth and development and secondary metabolism has been studied. However, the regulatory effects of miR172 and AP2 on blackberry fruit ripening are unclear. Here, based on the transcriptome data from blackberry fruits at different developmental stages, candidate blackberry AP2 members were identified, and their physical and chemical properties, protein structure, and phylogeny were analyzed. Digital gene expression profiles revealed that the transcripts per million of miR172 in unripe and ripe blackberry fruits were different, and the expression levels of the potential target genes AP2-1 and AP2-6 of miR172 were relatively high in unripe blackberry fruits. RT‒qPCR showed similar results. The sequencing results of the degradation group showed that miR172-z could target RuAP2-1 and miR172-y could regulate RuAP2-6. The cleavage sites were 2503 and 2329. The sequences of RuAP2-1 and RuAP2-6 were cloned, and the complementary sequence of miR172 was found. Overall, the miR172–AP2 interaction may be important in regulating the ripening process of blackberry fruit. This study provides information for future research on the posttranscriptional regulation of blackberry AP2 family members.

Wood color is a crucial factor influencing the overall quality of wood products. In this study, we investigated color differences between sapwood (SW) and heartwood (HW) in 4 Chinese fir clones of the same age, using the CIE L*a*b* system. Our results revealed distinct color variations between SW and HW within the same clone, with notable discrepancies observed among different clones. Interestingly, these variation in wood color correlated with wood density, consistent with previous research. Metabolite analysis using an untargeted metabolomics approach was conducted, employing ultra-performance liquid chromatography in conjunction with a quadrupole time-of-flight tandem mass spectrometer (UPLC/Q-TOF–MS/MS), identifying a total of 938 metabolites spanning 12 superclasses. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) revealed distinct metabolic differences between SW and HW in various Chinese fir clones, with significant variations in abundance patterns and species-specific differences observed in the HW group. Further analysis, through Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA), pinpointed specific metabolites responsible for these distinctions. Among these metabolites, flavonoids, recognized for their role in color formation, stood out prominently. Metabolomic pathway enrichment analysis (MPEA) indicated the involvement of these differential metabolites in various pathways, including flavonoid biosynthesis. The study underscores the intricate relationship between metabolites and wood color variation in Chinese fir clones, accentuating potential applications in enhancing wood quality and decay to resistance.

Key message

Repeated defoliation soon after full leaf expansion reduces xylem hydraulic transport safety in beech trees.

Abstract

Japanese beech trees undergo branch dieback and eventual mortality following years of repeated leaf loss due to leaf-feeding insects attacking immediately after full leaf expansion. To study the impact of recurrent defoliation on beech debilitation and mortality, we investigated xylem hydraulic transport safety and observed the xylem vessel architecture in field-grown medium-sized Japanese beech trees that had been artificially defoliated repeatedly for 4 years immediately after full leaf expansion. Multiple years of defoliation immediately after full leaf expansion increased the susceptibility to xylem cavitation (P50 value; − 4.46 ± 0.38 MPa (mean ± SD) for non-defoliated control beeches, and − 2.32 ± 0.20 MPa for defoliated beeches), despite a decrease in their vessel diameter and an increase in their vessel density. In defoliated beech, many irregularly shaped, axially wrinkled and partially cracked vessels, mountain-folded intervessel pits, and fibers with thin and less-lignified cell walls were observed. The intervessel double-wall thickness of the defoliated beech was thinner than that of the control beech. Furthermore, the size and shape of intervessel pits did not change in defoliated beech, but the density of intervessel pits and the total number and total area of intervessel pits per 1 mm of vessel length increased. We conclude that the increased susceptibility to xylem cavitation caused by repeated defoliation immediately after full leaf expansion may be due to an increased total area of intervessel pits with thin pit membranes per unit vessel wall area, in addition to cell wall alteration and vessel deformation and damage.

Key message

Silver birch growing on extremely nutrient-poor stands of inland dunes was characterized by low contents of these nutrients in its biomass. The nutrient accumulation also depended on its age.

Abstract

Silver birch (B. pendula) often colonizes inland dunes, as geomorphologically sensitive and unstable environments. Considering its importance in the protection of ecosystems associated with such landforms, we aimed to evaluate the nutrient distribution and bioaccumulation in the organs of that tree. The study covered three stands, aged 12, 20, and 34 years. Ten average trees were sampled from each stand, including fine and coarse roots, stemwood, bark, coarse and fine branches, and leaves along with soil samples at depths of 0–10, 10–20, 20–40, and 40–80 cm. The contents of macro- and micronutrients were analyzed in collected soil and biomass samples. The soils were strongly acidic and very poor in the studied elements. The nutrient distribution in the birch biomass was highly variable. For most of the elements, the highest contents were recorded in leaves. The highest amounts of Fe were found in fine roots, while Mn and Zn were the most abundant in the bark. Wide variability was also apparent in the bioaccumulation factors. These were usually the highest in the leaves or bark and the lowest in the stemwood. Among the studied elements, N was the most bioaccumulated, followed by S, Zn, Cu, Mn, and P. Nutrient distribution in the birch biomass was typical for tree species. Nutrient levels were generally low, however, significantly higher than their concentrations in the soil, indicating a strong bioaccumulation. The relationship between nutrient accumulation and stand age was observed.

Key message

Covering young ‘Hass’ trees with Silver 60% shading nets during cold winters mitigates frost damage and improves tree performance, apparently through a mechanism other than increasing nighttime air temperature.

Abstract

Avocado is a commercially important subtropical evergreen fruit tree. Severe frost may damage foliage, floral buds, flowers and fruit, thereby reducing avocado crop yield and restricting its geographical distribution and expansion. Shading nets are frequently used to protect agricultural crops from climate-related damage. To determine their ability to mitigate frost damage, Silver 60% shading nets were deployed over young ‘Hass’ trees during two consecutive winters and uncovered trees served as controls. Freezing and chilling temperatures occurred in the experimental orchard during the winter of each year, from December to March, reaching − 2.49 ℃ in January 2022. In the control, 93% of the examined floral buds were severely damaged compared to 4% in the Silver 60% trees. Damage to young vegetative shoots was assessed at 4.35 out of 5 in the control compared to 0.5 out of 5 in the Silver 60% trees. In both years, minimum air temperatures under the Silver 60% shading nets were similar to those of the control. Leaf-level photosynthetic photon flux density was ~ 60% lower under the shading nets. In most measurements, CO₂-assimilation rate, stomatal conductance, ratio of variable to maximum fluorescence (Fv/Fm) and chlorophyll concentration in the leaves of the Silver 60% trees were higher than, or similar to the controls. Trunk diameter and flowering intensity of the Silver 60% trees were higher than for the control. These results indicate that covering young ‘Hass’ trees with Silver 60% shading nets during cold winters can mitigate frost damage and improve tree performance.

Indian Mahogany (Toona ciliata, Family: Meliaceae) is a fast-growing and multi-purpose timber species. The species is well adapted to sub-tropical climates and generally grows in moisture-prone areas. It is frequently naturalized throughout the western sub-Himalayan tract, valleys of the outer Himalayas, and Eastern and Western Ghats and also cultivated on a fairly large scale in the plains of India, but no information about SSR-based genetic diversity and population structuring of T. ciliata in the Indian context has been available till now. Notably, population genetic analysis of T. ciliata is important for its long-term conservation, management, and genetic improvement programs. Thus, the present study was conducted to characterize natural populations of T. ciliata using simple sequence repeat (SSR) markers. In total, 444 individuals collected from 15 distant geographical locations in the western Himalayas were analyzed with 10 SSR loci. A total of 71 alleles were generated, with a mean of seven alleles, which ranged from 4 to 12 alleles for individual marker loci. Overall, a low level of genetic diversity (mean He = 0.315, range = 0.251–0.366) and high genetic differentiation (F_ST = 0.338) were recorded for the analyzed populations. Genetic clustering and STRUCTURE analysis revealed a strong genetic structure where most analyzed populations were grouped into two major clusters, indicating the existence of two gene pools. Further, the partitioning of genetic variance was significant (p ≤ 0.001) which revealed 34% of genetic variance among the populations. The Mantel test was used to estimate the genetic distance in relation to horizontal and altitudinal geographical distance, but a non-significant correlation was obtained. The results indicated that genetic distance between populations is not influenced by horizontal and altitudinal geographical distance. Overall, the study on population genetic analysis of T. ciliata will be of paramount importance to the researchers, foresters, and policymakers for guiding future conservation decisions.