Trees最新文献

Key message

A climate-sensitive height to crown base (HCB) model developed by combining a nonlinear mixed-effects model and dummy variable approach led to higher prediction accuracy of HCB than those without climatic variables for moso bamboo.

Height to crown base (HCB) is one of the important variables used in forest growth and yield models, as it is crucial for assessing vitality, competition, growth and development stage, stability, and production efficiency of the individuals. As climate impact is substantial on HCB, its inclusion of any forest model is crucial to make the model climate sensitive. However, existing HCB models do not consider climate impact on Phyllostachys pubescens (moso bamboo) HCB. With data collected from 26 moso bamboo sample plots in Jiangsu and Fujian provinces in China, we used five common HCB functions to develop climate sensitive HCB models. Modeling showed the significant effects of two individual variables (height—H, diameter at breast height—DBH), two stand-level variables (quadratic mean DBH—QMD, canopy density—CD), and two climate variables (extreme maximum temperature—EXT and Hargreaves’ climatic moisture deficit—CMD) on HCB. Compared with the basic model, the introduction of covariates (QMD, CD, EXT and CMD), dummy variable (regions), and random effects (block- and sample plot-level random effects) resulted in increased R² by 5.01%, 7.13%, 7.14%, and 13.34%, respectively. The logistic model provided better fit statistics than other models we evaluated. Two-level nonlinear mixed-effects (NLME) models significantly improved fit statistics. Response calibration (model localization) with two medium-sized bamboos per sample plot provided the optimal prediction accuracy. This strategy can be considered as a reasonable compromise between the measurement costs and errors for HCB prediction.

Key message

Inventory and seasonal variation of terpene emissions from tropical trees in French Guiana: implications for environmental and ecological roles.

Abstract

A limited understanding of foliar terpene emissions from different tree species is prominent in diverse tropical forests. We conducted a study in French Guiana, screening BVOC emissions from 36 tropical woody species. We focused on 32 species in the dry season and 33 in the wet season, documenting terpene emissions for the first time in some of these tree species. Our findings show that 93.8% emitted terpenes in the dry season, while only 33.3% did so in the wet season. Terpene emissions ranged from 0.01 to 80.9 μg g⁻¹ h⁻¹ in the dry season and 0 to 11.7 μg g⁻¹ h⁻¹ in the wet season, consistent with previous reports. We identified and quantified 23 terpene compounds, including 19 monoterpenes and 4 sesquiterpenes. Additionally, 2 non-terpenoid compounds were detected: 2,2,4,6,6-pentamethylheptane (with no detected emissions in the dry season) and toluene. Among the monoterpenes, the most abundant were α-terpinolene, limonene, α-pinene, β-ocimene, and sabinene. As for sesquiterpenes, β-caryophyllene, α-caryophyllene, and α-copaene were observed during the dry season, while during the wet season, α-terpinolene predominated, followed by limonene, α-pinene, sabinene, β-caryophyllene, and α-copaene. Isoprene was detected in most of the species studied in both seasons. Sesquiterpene emissions displayed a notable phylogenetic pattern, whereas total terpenes and monoterpenes did not; however, total terpenes and monoterpenes exhibited a significant seasonal influence. Our study demonstrates that seasonality strongly influences BVOC production in tropical trees, with higher emissions in the dry season. These findings imply that various factors and conditions influence tree emissions in this tropical forest, affecting their ecological, environmental, and climatic roles, as well as the implementation of atmospheric chemistry models.

Key message

Models of bark thickness and trunk cavity occurrence improve allometry assessments and provide good indicators of the probability of tree decay or vitality—knowledge useful for old-growth tree conservation and management.

Abstract

This study aimed to model the attributes of Araucaria angustifolia that influence allometry assessments and its biomechanics. We used samples collected during dendrochronological studies to measure bark thickness and data from old-growth attribute surveys to assess the occurrence of trunk cavities (or hollows) associated with heartwood decay. First, nonlinear mixed-effects models were calibrated to predict bark thickness. Then the probability of hollow occurrence was evaluated with binomial regression using generalized linear models. Bark thickness increased with tree size, attaining an asymptote of 11.9 cm. This finding suggests that thickness above the asymptote may not offer additional protection to trees. Because bark has an influence on allometry assessments, we provide an accurate model to improve wood volume estimates. Hollows are associated with tree size and affect mechanical stability, and due to their empty space, it can cause bias in allometry assessment of biomass and wood volume. Suitable predictors of the probability of tree decay or vitality are provided. The predictors evaluated can also be used as a tree-level indicator of quality in selection systems. Our results highlight the importance of accounting for bark thickness and trunk hollows in carbon, conservation, and management surveys of Araucaria forests.

Key message

The studied populations of Persian oak (Quercus brantii Lindl.) showed high phenotypic variation that is very necessary for the planning, design, and implementation of genetic protection programs for oaks.

Abstract

Persian oak (Quercus brantii Lindl.) the most important tree species in the Zagros region includes more than 50% of the forests in this region. In the present study, 53 morphological traits were used to evaluate phenotypic variation among 100 trees belonging to Q. brantii collected from 10 areas of Kohgiluyeh-va-Boyerahmad province, Iran. Considerable variability was exhibited among the trees collected based on the traits measured (ANOVA, P < 0.01). The coefficient of variation (CV) ranged from 12.73 (in nut diameter) to 76.06% (in the transparency of leaf upper color). Leaf margin was highly variable, including doubly serrate, serrate, broadly spiny, spiny, and narrowly spiny. Leaf blade length ranged from 59.41 to 122.53 mm, nut weight ranged from 1.39 to 17.24 g, and kernel weight varied from 0.63 to 13.09 g. Principal component analysis (PCA) showed 15 main components, which contributed 76.60% of the total variance. Cluster analysis based on Ward’s method showed two different major clusters among all the trees studied. Besides, the studied 10 populations were placed into four groups in the bi-plot generated with PCA of population analysis. The studied populations of Q. brantii showed high phenotypic variation that is very necessary for the planning, design, and implementation of genetic protection programs for oaks.

Management of food resources is considered fundamental for supporting insect pollinators, whose abundance shows a downward trend on the global scale. Here, the nectar and pollen production (per flower, per 1 m² of tree crown), the composition of nectar carbohydrates and the levels of pollen proteins was evaluated in eight Tilia species (Malvaceae) growing in SE Poland. In the warm-summer continental climate, Tilia species can improve nectar and pollen resources mainly in June/July. Although the flowering period of each species is short (8.0–14.7 days), appropriate selection of species can extend the availability of food for more than a month. However, the considerable variations in the flowering onset (11.2–20.1 days) may cause significant inter-seasonal shifts in food accessibility.

The nectar with its highly changeable sugar concentration (29.5–77.4%) was composed of sucrose, glucose, and fructose; protein content in pollen was 7.2–16.8%. The mean sugar yield was in the range of 0.95–19.1 g per 1 m² (T. amuriensis – T. platyphyllos, respectively), whereas the mean pollen yield was 1.37–4.1 g per 1 m² of tree crown (T. amuriensis – T. × euchlora, respectively). Significant year-to-year fluctuations of sugar and pollen yield in linden trees have to be taken into account in conservation schemes, and the introduction of other flowering plants with more stable sugar and pollen production should be considered in an area with a high density of linden trees. Linden flowers mainly support honey bees; nevertheless, wild pollinators (bumble bees, solitary bees, and dipterans) can also benefit from linden floral resources.

Plant grafting involves naturally or intentionally merging distinct plant parts to form a single organism. Although it is a common horticultural practice used to improve the yield, quality, and resistance of horticultural crops and study the long-distance transport of molecules, the underlying mechanism of graft union formation (GUF) remains poorly understood. In this study, we optimized the in situ analysis method for plant hormones and explored the spatial and temporal distribution of endogenous hormones (IAA, ABA, and ZR) during walnut GUF. The results demonstrated that changes in endogenous IAA and ZR levels in the graft union were consistent, with an increase during the rapid proliferation phase of callus tissue and enrichment in the cambium and cells of the grafting interface. As callus tissue entered the differentiation stage, endogenous IAA and ZR levels rapidly decreased and were mainly distributed in the callus tissue. Conversely, the level and distribution of endogenous ABA showed no significant changes during the rapid proliferation phase of callus tissue. However, they increased rapidly after entering the differentiation stage, mainly in the scion cambium and callus tissue. We also observed "S"-shaped, “M”-shaped, and “N”-shaped trends in the dynamic changes of IAA/ABA, IAA/ZR, and ZR/ABA ratios, respectively. Based on these results, we propose a spatial and temporal distribution model of endogenous hormones during walnut GUF. This provides a foundation for further investigation into the molecular mechanisms of hormone-mediated GUF in walnut and other woody plants.

Tamarix taklamakanensis is an endangered shrub endemic to northwestern China. Single-nucleotide polymorphism (SNP) loci obtained by Genotype-by-sequencing (GBS) method were used to estimate the genetic diversity and population structure of the species for developing conservation strategies. A moderate level of genetic diversity was (mean H_E = 0.16) detected for the species, and sampled sites were grouped into two genetically distinct clusters by Bayesian assignment, principal coordinates analyses, and maximum-likelihood (ML) tree. The moderate level of genetic diversity is likely due to its reproductive characteristics and long-lived life-history traits, and the strong genetic differentiation between the two clusters suggests a positive response to habitat fragmentation. Based on the results, we provide useful conservation strategies for this species.

Key message

We identified seven OfNCEDs and analyzed the potential function of OfNCED4, which is involved in the biosynthesis of carotenoids and abscisic acid in Osmanthus fragrans.

Abstract

In plants, 9-cis-epoxycarotenoid dioxygenases (NCEDs) can cleave carotenoids and are rate-limiting enzymes for the biosynthesis of abscisic acid (ABA). Sweet osmanthus (Osmanthus fragrans Lour.), an important ornamental and fragrant tree, contains abundant carotenoids in its flowers. To examine the function of the 9-cis-epoxycarotenoid dioxygenases (NCEDs) involved in ABA biosynthesis and floral coloration in O. fragrans, the sequences of seven OfNCEDs were isolated from the genomic DNA and cDNA of O. fragrans. A bioinformatics analysis showed that these OfNCEDs encode 422 ~ 591 amino acids, and they all contain the RPE65 domain. These OfNCEDs showed different patterns of expression, and that of OfNCED4 was most consistent to the patterns of ABA accumulation during the flowering process. Moreover, the levels of expression of seven OfNCEDs in the O. fragrans flowers were significantly induced by exogenous ABA. ABA-responsive elements were found in the promoters of OfNCEDs. The overexpression of OfNCED4 resulted in increased contents of chlorophylls, carotenoids and ABA, and up-regulation of NtCRTISO, NtLCYE, NtLCYB, and NtNXS, and down-regulation of NtCCD1 and NtCCD4 in tobacco leaves. It suggests that OfNCED4 probably mediates the biosynthesis of ABA. Taken together, this study systematically identified the bioinformatics, pattern of expression of OfNCED genes and the potential function of OfNCED4, which could provide molecular evidence for further research on the regulation of carotenoid biosynthesis and floral color of O. fragrans.