Trees最新文献

Repeat elements contribute significantly to genome expansions, gene regulation, and expression of functional traits at the increased cost of genome maintenance, especially in polyploids. Morus serrata Roxb. (Moraceae) is a wild tree species having polyploid genome of Himalayan origin. Upon phenotypic analysis, M. serrata exhibited distinct polyploid-associated traits within the Morus species complex, which are impacted by cell size, cell division rate, and stoichiometry balance. Genomic analysis suggests that genome-wide repeated DNA landscape (repeatome), especially DNA transposons played a substantial role in the genome expansions of M. serrata. Furthermore, M. serrata transcriptome yielded overrepresented genes associated with the transposition of transposable elements (TEs) and nucleic acid metabolism. Overall phenome, repeatome, and transcriptome study reveals that M. serrata devotes a significant portion of its transcriptional budget to maintaining a large genome expended by TEs and loses growth superiority compared to studied species of the genus Morus L. The study provided new insights into the structural and functional aspects of natural polyploidization and loss of growth superiority.

Key Messages

Radial growth of alpine willow shrubs showed contrasting sensitivity to climate warming depending on local soil moisture availability, being enhanced in wet sites.

Abstract

Secondary growth of alpine shrubs such as willow species (Salix spp.) may be enhanced by climate warming, but there could be also negative impacts due to warming-related drought stress. Willow shrubs appear from alpine treelines to mountain glaciers on the southeast Tibetan Plateau, thus proving an ideal setting to test whether their growth is improved by climate warming along wide elevational gradients. We tested this idea by sampling seven willow shrub (Salix gyamdaensis) sites spanning 4400–4800 m in southeast Tibet. A total of 171 ring-width samples were collected and measured. Detrended basal area increment (BAI) series were built for each site. The resulting BAI indices were correlated with NDVI and monthly climate variables. Shrub growth indices were positively associated with summer NDVI, suggesting the regional greening is associated with increased shrub growth. Willow growth also showed positive responses to summer temperatures at five out of the seven study sites. However, shrub growth in the other two sites showed either a positive response to the minimum temperature of the previous December or a negative response to August temperature. In the last site, climate warming may reduce willow growth because of a decrease in soil moisture availability. Climate warming favors the growth of alpine shrubs and subsequent regional greening in sites where soil moisture availability is not limiting, but this growth enhancement is contingent on site aridity.

Tree mortality is a crucial ecological process that is strongly linked to dynamic changes in vegetation and ecosystem function. Given that global climate change increases the risk of mortality, understanding the specific causes that lead to tree mortality at the local level is crucial. However, the contributions of factors explaining tree mortality patterns of Dahurian larch (Larix gmelinii) and White birch (Betula platyphylla) need exploration. Based on comprehensive tree census data (2010–2015) from a fully mapped 0.06-hectare permanent forest dynamics plot in the Da Xing’an Mountains, Northeast China, encompassing 32,565 individual trees, we classified forest stands into three distinct forest types according to species composition: mixed birch and larch forest, pure larch forest, and pure birch forest. A generalized linear mixed model was used to analyze the effects of the factors influencing the mortality of birch and larch in mixed and pure forests. Our research indicates that (1) competition is typically the primary cause of tree mortality. For the two main tree species, birch mortality shows greater sensitivity to increased conspecific competition, whereas larch mortality is more affected by higher hetero-specific competition. (2) For different stand types, species diversity had a more negative effect on the mortality of the two tree species in the mixed forest than in the pure forest. (3) Larch and birch mortality with varying tree diameter classes are found in different stands, and the significance of the factors influencing tree mortality patterns varies significantly. Our research demonstrated significant differences in the relative importance of variables driving tree mortality between pure and mixed forests and emphasized the role of both conspecific and hetero-specific competition in tree mortality. These results offer crucial insights for future studies on forest management in this area and improve our comprehension of the factors leading to individual tree mortality in natural secondary forests in cold temperate zones.

Key message

The application of PKPF mitigates stress from excess solar radiation in the species studied during the planting phase by reducing photochemical damage and increasing photosynthetic assimilation.

Abstract

Global warming represents a significant threat to biodiversity, with rising global temperatures severely impacting ecosystems, including forests. The Atlantic Forest, one of the most diverse and threatened biomes in the world, faces critical challenges in restoring its degraded areas, especially due to high solar radiation that compromises the initial establishment of seedlings. This study explores the use of processed-kaolin particle film (PKPF) technology as a solution to mitigate the harmful effects of excessive solar radiation, promoting seedling development and offering an innovative and promising strategy for Atlantic Forest restoration. PKPF was applied to the leaf surfaces of two native species, Cordia superba and Citharexylum myrianthum, during the intense summer of 2022. Through eco-physiological and anatomical assessments, the study found that PKPF significantly improved plant performance by increasing photosynthetic efficiency and net CO₂ assimilation, reducing stress during radiation peaks, and preserving the mesophyll structure via a protective layer that reflects excess solar radiation. These results highlight PKPF as a viable and innovative tool to support the restoration of Atlantic Forest ecosystems amid increasing pressures from climate change, making it a crucial step to address the early stage challenges of environmental restoration projects.

Key message

Rainfall-related variables control tree radial growth of Detarium microcarpum and Tamarindus indica in West Africa's semi-arid savannas.

Abstract

West Africa constitutes a hotspot region for both land use change and climate change. Land use change, and high climate variability in this region negatively affect tree growth dynamics, ecosystem functioning and services. In the present study, we assessed the impacts of climate variability on tree growth of Detarium microcarpum Guill. & Perr. and Tamarindus indica L., two Fabaceae woody species with high socio-economic significance in West Africa. In total, we collected 18 stem discs from dead trees of the two species in the South-Sudanian phytogeographic zone in Burkina Faso. The studied species showed well-defined growth ring-boundaries demarcated by marginal parenchyma bands. Cross-dating was successful within disc and within species, and enabled the construction of statistically robust tree-ring index chronologies. The chronologies spanned 45 years (1974 − 2019) and 30 years (1990 − 2019) for D. microcarpum and T. indica, respectively. We found a significant variation in tree growth rates (p-value < 0.05) between D. microcarpum (1.711 ± 0.491 mm year⁻¹) and T. indica (2.613 ± 0.473 mm year⁻¹). Pearson correlation analyses showed that the standard ring-width index for both species positively correlated with total annual precipitation amounts (p-value < 0.05) and major seasonal precipitation (p-value = 0.05). However, no significant correlation was found between ring-width index and temperature related variables. These findings support that precipitation controls tree growth of D. microcarpum and T. indica in the semi-arid savannas of West Africa. Consequently, a decrease in mean annual rainfall in West African region may negatively affect tree growth rate and stand dynamics of the studied species.

Key message

Phenological studies are essential for understanding the structure and dynamics of forests, as well as the influence of climate on plants. The phenology of Vouacapoua americana revealed a clear distinction between reproductive and vegetative phases.

Abstract

Understanding the phenological patterns of endangered species is essential for managing and conserving tropical forests, particularly in the biodiversity-rich Amazon. This study examined the phenological behavior of Vouacapoua americana Aubl. (Acapu), an endangered hardwood species with economic potential, over a period of 7 years (2016–2022). We used canopy observation to monitor 35 individuals for reproductive phenophases (floral bud, anthesis, immature and mature fruits, and dispersal) and vegetative phenophases (leaf abscission and sprouting). Analyses were conducted using Principal Component Analysis (PCA), circular analysis, and the Rayleigh test in R software. Results indicated that reproductive phenophases correlated positively with rainfall and relative humidity, peaking from January to April, the period with the highest precipitation. In contrast, leaf phenophases were most intense in the dry season and showed a positive correlation with solar radiation and temperature. Vouacapoua americana displayed clear seasonal and annual behavior, reflecting its adaptation to local climatic variations. These findings are critical for developing conservation strategies, both ex situ and in situ, and for supporting the sustainable use of this species.

Key message

Sown species dominate aboveground carbon stocks in restored forests, exhibiting traits associated with an acquisitive strategy (higher SLA and lower WD), distinct from those of primary forests.

Abstract

Tropical forest restoration is crucial for enhancing carbon sequestration and mitigating climate change. To optimize large-scale restoration, it is essential to develop methods, such as direct seeding. Despite its ecological and socio-economic benefits, as well as its cost-effectiveness, direct seeding remains underutilized in Amazonian restoration initiatives. Thus, we evaluate the functional and taxonomic aspects of carbon recovery in 23 riparian forest permanent plots restored by direct seeding in southern Amazonia, approximately 12 years after restoration. We assessed aboveground carbon (AGC) stocks and four functional traits—specific leaf area (SLA), wood density (WD), seed size, and plant height—to analyse the effects of trait variation and species abundance on AGC stocks. We compared these parameters at the plot level between restored and primary forests, and at the species level between sown and naturally regenerating species. We found that restored forests after 12 years have AGC stocks 79% lower than regional primary forests. Five species account for up to 50% of the AGC, with sown species accumulating up to seven times more AGC than regenerated species. Restored forests showed a more acquisitive strategy, with higher SLA and lower WD than primary forests. Carbon stocks positively correlated with species abundance and functional trait variation. In conclusion, our results highlight that after 12 years, restored forests have not yet matched the AGC stocks or functional composition of primary forests, remaining dominated by a few species and functional groups. The dominance of AGC stocks by sown species underscores the effectiveness of direct seeding in facilitating revegetation and the positive relationships between carbon stocks and functional trait variation emphasize their importance as indicators of forest recovery.

Graphical abstract

Key message

A 4-day or more duration of flooding is considered a critical stress period for tree tomato plants, as they do not recover their plant water status, electron transport in photosystems, or growth during the post-stress period.

Abstract

The tree tomato (Solanum betaceum Cav.) is a tropical fruit tree affected by climate variability, especially by flooding phenomena, which are projected to increase in the coming years, causing damage to the physiology and development of crops. Therefore, the objective of this research was to characterize the physiological response of the tree tomato in the vegetative stage under different days of flood duration (0, 2, 4, and 6 days) and later in the recovery period (14 days), in plants grown under controlled shade conditions. Stomatal conductance (g_s), leaf water potential (Ψ_leaf), leaf insertion angle, pigment concentration, chlorophyll a fluorescence, and plant growth were quantified. The results indicated that with 2 days of flooding, g_s, total chlorophyll concentration, root dry weight, and leaf area decreased slightly compared to the control. With 4 days of flooding, the plants showed more significant reductions in g_s and Ψ_leaf, which allowed the tree tomato to be classified as an isohydric plant. The 6-day flooding completely dehydrated the leaves. In addition, for the 4 and 6 days of flooding, the OJIP curves showed that the plants had lower photosynthetic efficiency, which was reflected in the reduction of the maximum photochemical quantum efficiency Fv/Fm, quantum yields, energy fluxes per reaction center, and linear electron flow (LEF). These parameters were more affected in the recovery period. The carotenoid concentration and non-photochemical dissipation Φ_NPQ increased as a photoprotective mechanism to dissipate excess energy. The biomass of the root and the aerial part decreased significantly as the intensity of the flooding increased. These results show that a time greater than or equal to 4 days of flooding with shade in tree tomato plants is considered a critical stress period.

Assessing carbon stocks in forest ecosystems is key to developing effective climate change mitigation strategies. However, the role of plant traits, particularly bark, sapwood, and heartwood, in biomass accumulation remains poorly understood. Clarifying these relationships can improve predictions of tropical forest carbon storage and management strategies. This study investigated the contributions of these stem layers to aboveground biomass in four vegetation types in Benin: semi-deciduous forest, gallery forest, swamp forest, and woodland. Data were collected using a non-destructive method; 470 trees across 25 species with diameters ranging from 5 to 77 cm were sampled from 111 plots. Multiple linear regressions and analysis of variance were performed to determine the contribution of each stem layer to aboveground biomass. The findings revealed significant variations in bark, sapwood, and heartwood characteristics across different vegetation types and among species. Woodland species presented the thickest bark (1.38 cm), whereas semi-deciduous forest species at seasonally flooded sites had the thinnest bark (0.80 cm). Bark and sapwood thickness were identified as key predictors of biomass accumulation (p < 0.000 and adj R² between 53.04 and 76.39%). Lower bark mass density was generally observed in semi-deciduous forest, gallery forest, and woodland species than in sapwood and heartwood. Notably, Daniellia oliveri in woodland revealed an atypical pattern, with the bark mass density exceeding that of the inner wood layers. A consistent increase in wood mass density from the bark to the pith was observed in the swamp forest. These findings highlight the importance of incorporating bark and sapwood traits into tropical biomass models to enhance carbon stock estimates and guide more effective, ecosystem-specific forest management for climate change mitigation.