Trees最新文献

Forest plant productivity, as a key factor affecting plant carbon sequestration, is often used to reflect the tree growth and the magnitude of ecosystem functions, which can be affected by various factors, including individual competition, tree social status and biodiversity. To explore the impact of these factors on plant productivity, we randomly selected six forest types in Hunan province, including Cunninghamia lanceolata pure forest (CPF), C. lanceolata coniferous broad-leaved mixed forest (LMF), Pinus massoniana pure forest (MPF), P. massoniana coniferous broad-leaved mixed forest (MMF), P. elliottii pure forest (EPF) and P. elliottii coniferous broad-leaved mixed forest (EMF), where the pure forests were representative examples of plantations, while the mixed forests exemplified the main forest types of close-to-nature forest management. The results showed (1) there were significant differences in stand structure among different forest types, and the complexity of forest structure in mixed forest was generally higher than that in pure forest. (2) The competition distance varied depending on variations in stand structure. (3) The competition intensity was influenced by the composition of tree species and tree size, with larger trees demonstrating higher competitiveness. (4) The interaction between tree size and competition plays a crucial role in determining forest productivity, with tree size serving as a more powerful explanatory factor. In both mixed and pure forest, dominance and tree height were significant positively correlated with tree growth (p < 0.001). The findings enhance our comprehension of the influence of stand structure and competition on productivity, and has a great significance for improving forest structure to improve forest quality and carbon sequestration capacity.

Key message

The developmental stage of cotyledonary explants influences morphogenesis in Delonix regia, with immature and seedling-derived explants being more responsive to in vitro regeneration.

Abstract

The developmental stage of the explants plays a crucial role in the expression of morphogenesis. This study aimed to evaluate the morphophysiological behavior of cotyledonary explants at different developmental stages during somatic embryogenesis induction of Delonix regia (Bojer ex Hook.) Raf. cotyledons from seedlings (SC), immature (IC), and mature (MC) zygotic embryos were inoculated in MS culture medium with 1.0 mg L^− 1 of dichlorophenoxyacetic acid (2,4-D) and 0.125 mg L^− 1 of 6-benzyladenine (BA). The experiment was conducted in a growth room at 25 ± 1 °C, in the dark, for 30 days. The IC and SC presented calluses on their surface and gained fresh mass. These calluses showed cell clusters with meristematic-like cytological features, confirming the morphogenetic potential of the calluses. In contrast, MC did not present morphogenetic response or cytological changes. Unlike the IC and SC storage contents, the MC protein, lipid, and carbohydrate contents did not change significantly throughout the in vitro culture. Interestingly, explants that showed morphogenetic responses (IC and SC) had significantly higher indole-3-acetic acid, proline, and putrescine content than MC. The results obtained demonstrate the influence of the development stage of cotyledonary explants for the induction of morphogenetic pathways and contribute to a better understanding of the in vitro behavior of cotyledonary explants for the establishment of regeneration systems of D. regia and other woody species.

Key message

Low-altitude trees allocate a greater proportion of assimilated carbon to growth, whereas treeline trees preferentially allocate carbon to storage to cope with environmental constraints.

Abstract

Stomatal conductance contributes decisively to regulate water and carbon fluxes and constitutes a fundamental mechanism to guarantee water conservation and leaf survival in water-limited environments. There is controversy with respect to the role of stomatal traits in the determination of stomatal conductance values and their variations through time. We analyzed the stomatal traits, leaf phenology, leaf water potentials and the maximum (g_max) and minimum (g_min) stomatal conductance in two Mediterranean Quercus species (Quercus faginea Lam. and Q. pyrenaica Willd.) and their hybrids, as well as their changes across a climatic gradient. Our purpose was to study whether the stomatal traits determine the possible differences in conductance between genetic groups and between sites. Q. faginea exhibited more drought-adapted traits (larger stomatal density, but lower stomatal index and g_max) than Q. pyrenaica. Hybrids possessed intermediate stomatal traits between the two parent species but maintained g_max values similar to those of Q. pyrenaica. Mean leaf longevity was shorter for Q. pyrenaica and the hybrids with respect to Q. faginea, mainly because of delayed leaf emergence. This suggests that the higher g_max of Q. pyrenaica and hybrids may be due to the need to increase CO₂ assimilation during the shorter time available to compensate investments in leaf production. Within a single genetic group, there were no changes in stomatal traits across the climatic gradient. However, g_max was significantly larger and g_min lower for all groups at the warmest site, which indicates that operational stomatal conductance would vary independently of stomatal traits.

In temperate forests, tree growth and vitality are significantly influenced by drought, often reflected by low stem diameter growth. Additionally, masting, the cyclic production of seeds, can also affect growth, particularly through its interactions with environmental factors like drought. Despite extensive research on the individual impacts of drought and masting, their combined effects on growth allocation remain underexplored, especially for a broader variety of species. This study aims to bridge this gap by investigating how drought and/or masting influence growth patterns in the coniferous species Abies alba and Picea abies, as well as the deciduous broadleaved species Fagus sylvatica and Quercus petraea. Utilising tree-ring data collected over several decades, we analysed how basal area increment (BAI) at 1.3 m stem height as well as along the stem axis responds to various scenarios of drought and masting. Our results showed that drought consistently reduced BAI in all species. F. sylvatica and P. abies experienced significantly lower BAI during mast years that coincided with drought, suggesting a potential trade-off between vegetative and reproductive growth under resource limitation. In contrast, Q. petraea exhibited higher BAI during mast years, indicating a distinct carbon allocation strategy. Furthermore, our study revealed that differences in BAI between mast and non-mast years were most prominent in the upper stem in the deciduous species, particularly during drought periods. These findings highlight the complex interactions between environmental stress, stem diameter growth and seed production, emphasising the need for further research into whole-tree carbon allocation processes.

Key message

Ensemble modeling predicts Picea orientalis habitat shifts in Türkiye, with contraction near the Black Sea and inland expansion, highlighting the need for drought-resistant provenances and adaptive forest management strategies.

Abstract

Picea orientalis is an ecologically and economically important tree species (accounting for about 2.3% of the total forest area) and naturally occurs between 550 and 2400 m a.s.l. in Northeastern Anatolia and Caucasus. However, P. orientalis is negatively affected by climate change due to decreasing precipitation and increasing temperature, which are the adverse effects of global climate change. In this research, based on 38 spatially refined out of 82 occurrence records of P. orientalis and 23 environmental parameters, the potential distribution areas (PDAs) for P. orientalis under two different climate change scenarios (SSP5-8.5 and SSP2-4.5) were investigated with the help of an ensemble model (EM). According to the findings, the mean area under the receiver operating characteristic (ROC) curve (AUC) and the true skill statistic (TSS) value of EM were 0.99 and 0.97, respectively. P. orientalis PDAs in Türkiye are severely affected by Precipitation Seasonality (Coefficient of Variation) (Bio15), Annual Precipitation (Bio12) and Temperature Seasonality (Bio4). In conclusion, according to the SSP2-4.5 scenario, PDAs of P. orientalis are expected to decrease near the Black Sea coast and to expand inland regions. According to the SSP5-8.5 scenario, an initial decrease in PDAs is projected, followed by a significant expansion until 2100. This study emphasizes prioritizing drought-resistant provenances for afforestation and reforestation, ensuring forest health and functionality, and calls for integrated management strategies addressing key tree species’ physiological and ecological responses to environmental changes.

Dioecious plants exhibit significant sexual dimorphism in responses to environmental stressors under global climate change. Heat and drought stress are major factors adversely impacting plant development, particularly in the fluctuating water-level zones of the Three Gorges Reservoir area (TGR) where dioecious plants play a crucial role in ecological restoration. We conducted a comparative analysis of female and male Salix variegata plants subjected to drought (DS), heat (HTS), and combined heat-drought stress (HTDS). Both sexes showed significant declines in plant height, photosynthetic rate, chlorophyll content, root non-structural carbohydrates (NSC), and leaf relative water content under all stresses, with the most severe inhibition under HTDS. Notably, females exhibited superior adaptability through higher photosynthetic efficiency, enhanced chlorophyll retention, and greater NSC allocation to aboveground organs, which supported sustained growth and water status maintenance under combined stress. Specifically, females had higher plant height, aboveground biomass, chlorophyll levels, malondialdehyde, and leaf NSC than males under HTDS. These findings demonstrate that female S. variegata employs more effective physiological strategies to mitigate stress damage, suggesting their greater resilience in future warming-drying climates. This sexual divergence in adaptation is critical for maintaining population stability and ecosystem function in vulnerable riparian habitats of the TGR.

Key message

The mangrove genus Avicennia dominates extensive intertidal habitats through specialised wood anatomical adaptations, regulated by a trade-off between conductive efficiency, embolism resistance, and mechanical strength, making it a key contributor to sedimentary blue carbon.

Abstract

Globally, the dominant mangrove genus Avicennia exhibits unique wood anatomical specialisations that ensure its survival across varying salinity levels within and between mangrove habitats. The anomaly in its wood anatomy is attributed to successive cambia, a rare feature in woody plants and not reported in other mangrove trees (except Aegialitis). The activity of successive cambia is patchy in nature, forming a complex three-dimensional network of cambium derivatives across the wood. This activity intensifies under low-salinity conditions during the monsoon and diminishes in the dry season. The vessel diameter in Avicennia exhibits plasticity, adjusting to environmental salinity by narrowing to reduce embolism. Additionally, phloem patches and parenchyma interspersed between rigid vessels and thick-walled fibres provide mechanical flexibility. These living tissues also contribute to embolism resistance. The adaptations of Avicennia can be explained through a trade-off mechanism comprising conductive efficiency, embolism resistance, and mechanical strength—collectively termed the trade-off triangle. As a dominant genus in coastal mangrove habitats, Avicennia has evolved to allocate resources towards enhancing mechanical strength. Consequently, its wood has a high lignin composition, though not always superior to that of all mangrove species. However, the high weight-average molecular weight (M_w) and number-average molecular weight (M_n) of its lignin indicate greater recalcitrance compared to other species, making Avicennia a significant contributor to sedimentary blue carbon storage. Thus, species of Avicennia can be recognised as ‘Key Blue Carbon Species’ within the ‘Blue Carbon Ecosystem’.

Magnolia calimaensis is an endemic tree from the central Chocó region in Colombia. It is classified as Critically Endangered, with fewer than 100 individuals remaining in an estimated distribution area of less than 50 km². This research aimed to evaluate the population structure and reproductive biology of the species, through the census and the observation of the individuals recorded. Three locations within its proposed distribution range in the departments of Chocó and Valle del Cauca were surveyed, where dasometric variables were measured, and the presence of reproductive structures was recorded to describe the floral opening process and insect-plant interactions. Thirty-eight individuals were localised in a gregarious dispersal pattern in two geographic populations. Their dimensions oscillate between 6 up to 20 m height and 3 up to 50 cm diameter at breast height. The species blooms between November and March in a evening-night model and a protogynous cycle of 2 days, where it is presumed that beetles of the Nitidulidae family carry out the pollination. The distribution range of M. calimaensis exclusively includes the Bajo Calima and Bahía Málaga localities in Valle del Cauca department; in the latter, 23% of the individuals were recorded near Urámba Bahía Málaga National Natural Park and La Sierpe Regional Natural Park. Basic information about the autoecology of M. calimaensis is provided, encouraging the scientific community and competent entities to take measures for the management and conservation of the species.

Key Message

Elevated CO₂ boosts the growth of açaí plants mainly through increased carbon assimilation and starch accumulation, however, there are signs of acclimation by sugar sensing mechanisms.

Abstract

Açaí (Euterpe oleracea) is an important sustainable crop in the Amazon region, used as a food supplement and widely consumed locally and exported globally. This study aimed to investigate the physiological and metabolic responses of açaí to elevated atmospheric CO₂, focusing on non-structural carbohydrate dynamics. Juvenile plants grew in open-top chambers under ambient (~ 380 ppm) and elevated (~ 760 ppm) CO₂ levels for 90 days, carbon assimilation, stomatal conductance, transpiration, growth, dry mass, and non-structural carbohydrate content (starch, sucrose, glucose, fructose, raffinose, and myo-inositol) were measured. Elevated CO₂ significantly increased carbon assimilation, particularly in the second leaf, while reducing stomatal conductance and transpiration. Starch accumulation in leaves increased by 180%, and overall dry mass was higher, although the area of the first leaf decreased. Non-structural carbohydrate levels varied among organs, with roots showing the lowest levels. These findings suggest that elevated CO₂ can promote growth in juvenile açaí plant due to high carbohydrate (starch) accumulation. However, signs of acclimation were observed over development, with declines in photosynthesis and relative growth rate. The pattern of carbohydrate metabolism, especially starch accumulation and slight raffinose transient decay, indicates that acclimation may involve sugar-sensing mechanisms.