Trees最新文献

Key message

Species interactions should be considered during the design of restoration plans for tropical dry forests.

Abstract

Legume trees dominate old-growth and regenerating tropical dry forests with some pioneers becoming temporarily monodominant during secondary succession. Yet, the mechanisms promoting legume coexistence in this ecosystem are poorly understood but essential to develop restoration strategies for degraded forests. We studied plant–plant interactions in the regeneration niche of an early and a late successional legume tree species, increasingly co-occurring in northwestern Mexico due to persistent climatic and anthropogenic disturbance that is altering forest dynamics. Our experiment comprised two species (Acacia cochliacantha, typical early successional and monodominant, and Lysiloma watsonii, typical late successional) × two habitats (direct light and shade) × three plant interaction treatments (control, intraspecific and interspecific). Each of the 12 experimental units contained 20 pots, totaling 240 replicates. We examined germination, seedling survival, and growth dynamics and determined seedling dry mass (total and root: shoot) at the end of the experiment. Our results suggest that legume monodominance in regenerating tropical dry forests starts early during germination and may be temporarily maintained through the interplay between interspecific facilitation and intraspecific competition. In contrast, late successional species may avoid negative heterospecific interactions by recruiting later (benefiting from neighbors’ shade) and maintaining neutral associations with conspecifics since early ontogenetic stages. Therefore, a cautious selection of early and late successional species and their spatial arrangement should be considered during the planning stage of restoration programs for tropical dry forests. Advancing our understanding of plant interactions in tropical dry forests should lead us to develop better tools for restoring this highly degraded ecosystem.

Key message

The growth rates of current-year shoots, fruits and trunks in apple trees peak sequentially during the growing season. The period of most intense growth coincided with the lowest NSC reserves.

Abstract

Vegetative and reproductive growth and storage are major carbon sinks in fruit trees; however, little is known about their mutual seasonal coordination. In this study, we monitored growth dynamics of trunks, fruits and current-year shoots together with the concentration of non-structural carbohydrates (NSC) in trees subjected to defoliation, early season flower thinning, mid-season fruit thinning and their respective combinations across the season. We found that defoliation had a negative effect on both trunk radial growth and annual fruit yield. Flower and fruit thinning caused lower fruit number per tree, but the individual fruits were larger resulting in a similar annual fruit yield among the treatments. Shoot extension growth was not significantly affected by the defoliation and flower and fruit thinning treatments. The concentration of non-structural carbohydrates was also similar across treatments. Modelled daily growth rates of shoots, fruits and trunks peaked sequentially one after another throughout the growing season with a delay of 15 and 18 days, respectively. The period of most intense growth of tree’s organs corresponded well with the lowest NSC reserves and a temporary depletion of starch in 1-year-old branches. Taken together, our study illustrates a tight temporal coordination of major carbon sinks and improves our understanding of sink/source relations of commercially important apple trees.

Key message

The 164 DAA maturation stage is superior in terms of germination and seedling formation, with gains of 4.2 months in relation to the last stage, and X-ray densitometry is a new and efficient technique to analyze Euterpe edulis seeds.

AbstractEuterpe edulis Martius is an endangered palm species that grows in the Atlantic Forest and the Cerrado of South America. Economic exploitation of its antioxidant-rich fruits could ensure the sustainable management of this species. However, this relies on the rapid selection of high-quality seeds from which to derive seedlings. Image analysis and X-ray densitometry can be quick, practical, and best of all, non-destructive techniques for selecting seeds, ensuring the sustainability of the species. The objective of this study was to investigate the maturation of E. edulis seeds using image analysis and X-ray densitometry. Fruits were harvested from ten matrices at different stages of maturation, from 94 days after anthesis (DAA) to 290 DAA. Seed dry mass, water content, germination, vigor, and density were quantified at each stage. At the same time, seeds were analyzed by GroundEye^® imaging, radiography, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The design was completely randomized and consisted of 29 treatments (maturation stages) and four replications with 10 seeds each. The highest dry mass was detected 255 DAA (0.83 g), in vitro germination began 115 DAA and achieved 100% from 150 DAA, and maximum vigor was observed 164 DAA, whereby 100% of seedlings appeared normal. X-ray imaging revealed dehydrated seeds and small mechanical damage, such as cracking of the pericarp. X-ray densitometry revealed that seed density increased considerably 185 DAA. SEM/EDS detected changes between maturation stages, such as the accumulation of K and Si, in the mesocarp and endocarp. Overall, E. edulis seeds presented maximum in vitro germination, vigor, percentage of normal seedlings, and physicochemical qualities 164 DAA (green epicarp), which corresponds to 126 days earlier compared with the fruits harvested 290 DAA (black epicarp) for ex vitro germination. The analyses proposed in this study, together with the analysis of seed germination and vigor throughout maturation, were promising for increasing the speed, classification accuracy, and selection of E. edulis seeds. Such analyses have a high potential since they are practical and many are non-destructive, adding cost-benefit with accurate results.

In Ecuador, between the foothills of the Andes and the well-drained terra firme forests of the Amazon, there are two useful palm species, Oenocarpus bataua and O. mapora, which differ mainly in size. Both species are negatively affected by deforestation and land conversion for agriculture and cattle ranching, altering the structure and functioning of ecosystems. Management and restoration plans are therefore needed. To contribute with local knowledge of the species, we studied the diversity of flower visitors of both species in 9 sites in Napo Province during the flowering seasons of 2021 and 2022. We collected 16 inflorescences and measured the length, number of rachillae and flowers of each and correlated them with the richness and abundance of their floral visitors. Finally, we calculated a similarity index between species and developed an interaction network to observe associations between their inflorescences and flower visitors. We found 89 morphospecies of flower visitors, 77 in O. bataua and 51 in O. mapora, and 19 morphospecies are potential pollinators because they are active during the staminate and pistillate phases. This is the first report of flower visitors of O. mapora in western Amazonia, and it shared 40% of flower visitors with O. bataua, which is a higher percentage than previously reported between O. bataua and other species of the genus. The most common morphotypes in the staminate phase were Discocoris drakei, Notesia sp.2, Andrathobius sp.1, Mystrops vasquezi, and in the pistillate phase: D. drakei, A. bicarinatus and Phylotrox sp.1. These insect species should be taken into consideration when monitoring the status of the palm species and for conservation plans.

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.