Trees最新文献

Fire damage can significantly impact fruit productivity in orchards. However, the effects of nonlethal fire injuries on the reproductive development of apple trees remain poorly understood. To investigate these effects, we implemented three treatments: trunk girdling to simulate fire injury to xylem, defoliation of a third of the canopy (simulated crown fire injury), and a combined treatment (simulated surface fire injury), alongside a control. The experiment was conducted during the 2021–22 growing season using a randomised block design with four biological replicate plots. Girdling was less effective than crown and surface fire treatments in influencing fruit composition during the current growing season, and flowering and fruiting in the following season. The crown and surface fire treatments induced localised detrimental effects on fruit sugar and titratable acidity while stimulating peel blush. Additionally, these treatments led to reduced starch reserves by harvest, which likely disrupted subsequent flowering and crop load near the previously defoliated sections of the canopy. When surface fires damage leaves near the base of the canopy in addition to the trunk, fruit production in the lower part of the canopy is more likely to be compromised in the following season. Crown fires, which cause leaf loss near the apex of the canopy, appear to be particularly detrimental to tree productivity, as the top defoliation treatment impaired carbohydrate reserves in shoot terminals and roots. In conclusion, fire-induced loss of leaf area during fruit growth alters fruit composition in the current growing season and may lead to lower yields in the subsequent season.

Key message

Tree bark and wood density are highly variable and weakly positively correlated, with species having more or less dense bark than wood to adapt to different environmental stressors.

Tree bark is a complex, multifunctional structure and bark density varies widely across species. While wood density is recognized as a fundamental indicator of the functional ecology of trees, bark density has received much less attention as a key functional trait. Theoretically, bark and wood density should co-vary to some degree, but comprehensive examinations of this covariation are scarce. How do key functional traits of individual trees and species relate to bark and wood density variation/covariation? How does a tree’s life history and evolved tolerance to environmental stress shape variation/covariation in bark and wood density? This study draws from published literature and a large database of individual tree measurements of trees of diverse species and growing conditions, from forest ecosystems across the United States and Canada, to understand covariation between bark and wood density and its relationship to life-history traits and evolved tolerances to environmental stressors. The results of this study show a high tree-to-tree variation in both bark density and wood density, with inherited differences in tissue formation constraining the range of bark and wood densities. All analyses show that bark density was weakly, positively correlated with wood density. Mixed effects modeling showed a strong phylogenetic signal in variation in bark and wood density that was partially explained by the need for species to produce more or less -dense bark and wood to adapt to different environmental stressors (tolerance of drought, shade, frost, waterlogging and fire were all examined), with clearly different relationships for angiosperms versus gymnosperms.

Key Message

In a provenance trial conducted in Serbia, the provenance of the beech trees exhibited a stronger influence on leaf morphology than on survival rate.

Abstract

Provenance trials are crucial for understanding the genetic diversity within beech provenances and advising forestry management practices. In this study, by integrating leaf morphometric analyses and survival data from a 16-year-old provenance trial in Serbia, we aimed to uncover patterns and mechanisms that govern plant–environment interactions in beech (Fagus sylvatica L.) ecosystems. The provenance trial used in this study was established in 2007, as part of the broader European network, from seedlings of 22 provenances originating across Europe. In the fall of 2007 and 2010, and in the summer 2023, plant vitality was recorded within each provenance. For geometric morphometrics, leaves were collected in 2023. The analyses tested the effects of provenance, provenance geographical origin, and provenance survival trend on leaf size and shape. The results showed significant variation in leaf size and shape and revealed that while there was no clear pattern of correlation between survival percentage and leaf morphology, provenance origin did show significant influence on leaf size and shape. Additionally, source stands environmental factors exerted a stronger influence on leaf shape than on leaf size variation. The observed variability in beech leaf morphology on one side, and survival rates on the other side, serve as indicators of the species' resilience and ability to adjust to changing environmental conditions.

Key Message

Although evergreens and deciduous are considered different functional groups due to their dissimilar strategy in canopy maintenance, they exhibit similar leaf heat tolerance to elevated temperatures in Cerrado savannas of Brazil.

Abstract

The escalating temperatures resultant from recent climate shifts have begun to influence the structure and function of tropical ecosystems, according to the Intergovernmental Panel on Climate Change (IPCC). The rise in average temperatures within the tropics implies significant challenges for plant persistence, pushing them beyond the optimal threshold for critical physiological functions, notably photosynthetic process, which temperatures effects can be inferred by measuring leaves chlorophyll fluorescence. Consequently, species lacking leaf traits associated with thermotolerance to high temperatures face heightened risks of permanent damage. The Cerrado is an extremely diverse tropical savanna ecosystem, with an abundance of species exhibiting different foliar habits that are being threatened by such temperature rises. The present study aimed to understand leaf heat tolerance in tree species of different leaf phenologies (evergreens vs. deciduous) exposed to high temperatures (35–65 °C) and to discern any effects and correlations between morphological traits (such as specific leaf area (SLA) and leaf thickness) and heat tolerance capacity measured by the T₅₀. It was hypothesized that evergreen species, with their persistent foliage, might exhibit greater heat tolerance to high temperatures than deciduous species, and that SLA will be correlated with leaf heat tolerance independent of leaf habit. Contrary to the initial hypothesis, the results indicate similar levels of leaf heat tolerance, with deciduous leaves showing a T₅₀ value around 49 °C and evergreens leaves around 50 °C. We did not find differences in the studied morphological traits between the groups, with SLA and leaf thickness not differing between groups, and neither relationships with heat leaf tolerance measured by the T₅₀ values were found. The importance of additional research considering water scarcity is highlighted, as water potential can influence leaf traits and canopy phenology, thus affecting thermotolerance. In summary, our study suggests that, within the context of global warming, leaf phenology alone might not wield substantial influence over the thermotolerance capabilities of these species, at least for the group of Cerrado species studied here.

Key message

SSR-based characterization revealed a high genetic diversity, negligible genetic differentiation, insignificant inbreeding, and subtle genetic structure in Myrica esculenta populations of Western Himalayas, indicating a high adaptive and evolutionary potential.

Myrica esculenta is a high-valued wild edible fruit-bearing tree of sub-Himalayan region experiencing noticeable deterioration in its stand structure. This study aimed to unveil the gene diversity and spatial genetic structure of M. esculenta populations in the Western Himalayas under the state of Uttarakhand (India) using nuclear simple sequence repeat (SSR) markers. By investigating 23 populations at 8 SSR loci, high genetic diversity (expected heterozygosity, He = 0.90; allelic richness, Ar = 13.65) was recorded with little genetic differentiation (fixation index, F_ST = 0. 025). Bayesian analysis revealed a weak genetic structure with no discrete genetic lineages from which ancestry can be inferred. Furthermore, genetic clustering among populations was conspicuous but not in accordance with their spatial distribution. Geographically separated populations are genetically well connected due to long-distance gene flow via pollen as well as seed. Hence, the meta-population in the Western Himalayas demonstrated a subtle spatial genetic structure with negligible genetic divergence, where genetic admixing is not modulated by geographical constraints. Viewing the substantial anthropogenic pressure over wild populations, conservation strategies must be adopted synergistically based on scientific knowledge. As center of diversity is centered toward the Kumaon region capturing higher allelic richness, we recommend the populations of this region to be prioritized for in situ conservation. Further, it will be important to harvest seeds from genetically diverse populations for raising plantations or ex situ field gene banks. As its fruits are mostly harvested from wild, local communities need to be sensitized and encouraged to establish private plantations or orchards.

Key message

Differences in architectural traits of European beech saplings submitted to different levels of competition intensity and neighborhood diversity show a shift toward lateral growth exploration for overtopped trees but less expressed apical control is maintained for beech grown with conifers.

Abstract

Crown plasticity is a fundamental process to optimize the acquisition of light in forests, where it is often the limiting factor for growth. The processes leading to crown dynamics in response to biotic interaction are controlled by the competitive status of a tree, as well as the species diversity of the neighborhood. Yet, the ontogenic diversity of the different branches leading to crown structure makes it difficult to model crown plasticity. In this study, we used single-image photogrammetry and a semi-automatic topology reconstruction software to map the architecture of 3-year-old European beech trees (Fagus sylvatica L.) grown in pure pots or mixed with Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) or Norway spruce (Picea abies L. H.Karst). Further, we investigated the effect of competition intensity (estimated with height rank) and neighbourhood diversity on architectural traits. To do so, we quantified the mean volume, slenderness, number of branches, branching rate, internode length, and diameter ratio for each stem and branch, up to the order three. Overtopped trees developed fewer branches and biomass but allocated more biomass to branches of a higher order than to the stem. The increase in the ramification of the stem and the diameter ratio of the first-order branches for overtopped trees indicate a shift in the growth strategy and a decrease in apical control. As competition intensity and neighbour identity have opposite effects on stem traits, it seems that the positive effect of plant diversity on growth can be attributed to the intrinsic effects of species identity rather than to competition release.

There’s a lack of studies on the structure–function aspect of linking non-structural carbohydrates to temperature, in particular phloem structure is yet a largely neglected subject. We studied gas exchange parameters and in parallel examined functional anatomy and non-structural carbohydrates status in leaf blades, petioles and branches in ‘Cabernet Sauvignon’ grapevines grown under three temperature regimes (22/16 °C, 28/22 °C, 34/28 °C day/night).

After  two months of growth, water use efficiency was the highest at 34 ºC. The individual organs size became progressively smaller as the temperatures increased, and was the smallest at 34 ºC for branch and petiole diameter, and for leaf thickness. The relative xylem cross-sectional area was largely not influenced by the temperature regime. In contrast, phloem cross-sectional area was significantly increased at high temperature in branches and petioles, and became 30% higher at 34 ºC in branches compared to 22 °C. The leaves had the highest non-structural carbohydrates concentration compared to petioles and branches. Sucrose content exhibited a temperature-dependent increase both in branches and petioles, and to some extent also in leaves, while starch, fructose and glucose content did not exhibit any statistically significant temperature trends.

In grapevine, sucrose is the main non-structural carbohydrate used for long-distance transport. Our results indicate temperature dependent increased investment in phloem development in parallel with increased main long-distance transported sugar (sucrose) accumulation. Phloem and xylem development were apparently uncoupled, implying a differential cambium activity for each tissue. Our study could have wide structural–functional implications in the ongoing climate change scenario.

Key message

Early rewetting influenced growth variability and hydraulic uniformity in Pedunculate oak wood on disturbed peatland. Long-term study highlighted vessel widening's importance in adapting to water availability changes.

Abstract

Pedunculate oak (Quercus robur L.) is a widely recognized flood-tolerant tree that thrives on fertile and moist soil conditions, such as on or close to peatland ecosystems. In the frame of climate change counteracting policies, rewetting peatland ecosystems is gaining increasing interest, while the ecological consequences are not always clear. Whereas the effect of flooding on wood anatomical traits of pedunculate oak is widely documented, little is known about the effect of permanent rewetting. In this study, we investigated the wood anatomical responses of 12 pedunculate oak trees located on a formerly drained peatland in NE Germany, that experienced flooding and a consequent rewetting. Wood anatomical traits were analyzed via CARROT, a tool that employs the accuracy and efficiency of artificial intelligence to identify tree rings and vessels. Growth anatomical traits (e.g., tree ring width) showed a sudden increase after the rewetting started in 1995, while hydraulic traits (Dh and Ks) displayed a decreasing trend only after the rewetting process was fostered by the opening of an artificial canal in 2004. Variance analysis highlighted subtle changes in the trait’s distribution over time: high soil water content triggered variability in the growth anatomical traits and, simultaneously, homogeneity in the hydraulic traits. Results suggest the relevance of the “vessel widening” mechanisms to develop coping strategies in response to the later stage of the rewetting, and pose relevant insights concerning the importance of specific site conditions for the implementation of rewetting policies in peatlands with presence of pedunculate oak.