Trees最新文献

Key message

Resource-limited environments showed a tendency towards conservative and coupled leaf and wood traits, while displaying an acquisitive and decoupled pattern in resource-rich ones. Water and elevation were the most studied gradients.

Abstract

In the Neotropics, spatial and temporal environmental gradients subject plants to distinct abiotic conditions, requiring functional adjustments. This promotes changes in trait expression, resulting in individual trait variation or covariation. We have systematically reviewed the literature focusing on leaf and wood traits in the Neotropics along major abiotic gradients (water, irradiance, temperature, soil fertility, and elevation), and assessed their spatial and temporal variation and covariation trends. Thus, we compiled 141 published papers from 2010 to 2022. Most of the studies of leaf and wood traits were related to: (1) the gradients of water avalability and elevation, (2) leaf traits at the expense of wood traits, with specific leaf area and wood density the most studied traits, respectively, (3) the morphological leaf traits to a greater extent than to biochemical, ecophysiological, or anatomical ones. In general, more conservative traits were observed in environments with lower resource availability. Although there is still no consensus, coupling was predominantly linked to water balance during periods of water restriction or in dry ecosystems, and papers have focused on single ecosystems rather than making comparisons across multiple ecosystems. This systematic review highlights the tendency for systems with fewer resources to show a bias towards greater coordination between leaf and wood traits compared to systems with more resources. This review also adresses how traits are expressed based on the integration of more than one environmental driver and the qualitative variation of these resources. Finally, we emphasize the importance of analyzing different aspects of trait expression when assessing species’ responses to environmental gradients, especially in megadiverse regions such as the Neotropics.

Key message

Mediterranean forest stands manifest diverse flammability traits according to their potential ecological successional stage and promoting a gradient from flammable to less flammable ecosystem.

From a general consideration of vegetation as ‘fuel’, it has been well proven that plant traits have the potential to promote the forest stand gradient from flammable to less flammable. While the ever-growing literature helps to assess the relationship between plants and their flammability at species level, at the landscape scale this relationship should be evaluated along with a variety of forest features such as structural and stand parameters and from the perspective of successional forest stages. To this end, we clustered several forest stands in Southern Europe (Apulia region, Italy), characterized by oaks, conifers, and arboreal shrub species, according to their flammability traits. We hypothesized that flammability traits change along different horizontal and vertical structural features of forest stands, shifting from high to low-flammability propensity. The results confirmed that forest stands with greater height and diameter classes are associated with traits with a low-flammability propensity. It is worth highlighting the importance of shrub coverage in differentiating the clusters denoting their strong influence in increasing fuel load (litter and fuel bed traits). Finally, our findings lead us to assume that high-flammability propensity traits are associated with typical pioneer successional stages, supporting the notion that later successional forest stands are less flammable and, therefore, that flammability decreases along with succession.

Key message

At the eastern range limit of silver fir, there is moderate population differentiation in tolerance to frost damages. Differentiated management measures accounting for climate change are required, as some populations are not responding similar to drought and frost damage.

Abstract

Under ongoing climate change, it is expected that in Europe 35% of forests will be at risk of frost, especially in the eastern part. In trees, frost effects are imprinted in rings and our study was conducted in juvenile individuals of silver fir from a trial comprising nine provenances from the eastern species distribution range. We analyzed the main characteristics of frost rings, their climate determinants and influence on height growth. Compared with other species, we found a slightly higher proportion of frost rings, and that the tracheid form was significantly influenced by the position within the ring and the intensity of damage. The climate covariates best explaining the frost damage in the initial and late frost rings were the March minimum temperature and the May mean temperature, respectively. A test of local adaptation indicated two characteristics related to the climatic determined late frost—the growing degree days accumulations until late frost and its day of the year, as significant triggers of the initial and late frost rings. In the initial frost ring, the height growth was negatively influenced by the proportion of annual rings affected over 50% by frost; in the late frost ring, an unexpected-positive influence on height growth of the proportion of total damaged annual rings was identified, possibly related to favorable growing seasons with prolonged autumn activity. Our study identified differentiation between provenances, which was more evident in the initial frost ring, suggesting maladaptation of eastern populations to frost-related events.

Key Message

The agar–agar panel method identified circumferential, vertical, and temporal variations in the bark pH of a Japanese cedar tree in detail, including high-resolution distribution reflecting the bark’s microrelief.

Abstract

The morphology of bark surfaces is heterogeneous on any given tree, especially rough-barked trees, often changing along a vertical gradient from top to bottom and circumferentially. This study sought to better understand the intricacies of the spatiotemporal changes of bark pH distribution on the bole of a mature Cryptomeria japonica D. Don (Japanese cedar) tree in Taiwan by using agar–agar panels. Agar–agar panels were positioned at the four cardinal directions at seven different heights along the tree bole on six separate sampling dates ((n = 134)) to study the temporal variation of bark pH, while an additional 48.5 agar–agar panels were arranged radially at three tree heights (in zones 2 (30 m), 4 (20 m), and 7 (5 m)) to study the circumferential variation of bark pH. The changes in bark pH were found to vary across time, direction, height, and circumferential position, presumably due to the abiotic factors (e.g., fog) prior to sampling as well as changes in bark morphological patterns around the tree bole. This study demonstrates the highly dynamic temporal and spatial variability of bark pH. In particular, bark pH was found to be lower in the furrows as compared to the bark ridges, albeit with differing pH at different times. Future work should couple the use of agar–agar panels with mathematical modeling to quantify the interrelationships among bark morphology, bark pH, solute leaching, and mass flux along the complex network of interconnected furrows and ridges of tree stems.

Key message

Pistil abortion in Prunus sibirica was associated with insufficient supply of nutrient, auxins, and gibberellins in flower buds, which promotes pistil development, and accumulation of cytokinins, which inhibits pistil development.

Abstract

Prunus sibirica is an important ecological and economic tree species with high utilization potential and broad application prospects. However, pistil abortion affects its fruit setting, yield, and quality, restricting its industrial development. In this study, the type and stage of pistil abortion in P. sibirica were identified using flower buds with abortive and fertile pistil. The effects of different nutrients and endogenous hormones on pistil abortion were analyzed. The pistil abortion type of P. sibirica clone belonged to abnormal style structure, and the key stage of pistil abortion was the dew white stage, characterized by pistil degeneration and dissolution at the dew white stage and complete pistil disintegration and disappearance at the full blooming stage. The soluble protein, soluble sugar, and total sugar contents of flower buds with abortive pistils were significantly lower than those of flower buds with fertile pistils at the dew white, initial blooming, and full blooming stages. Among the 44 hormones detected in flower buds of P. sibirica, majority were cytokinins (CKs 25), followed by auxins (13). At the dew white stage, the CK content in flower buds with abortive pistils was significantly higher than that in flower buds with fertile pistils. Pistil abortion in P. sibirica was mainly due to insufficient supply of soluble protein, soluble sugar, and total sugar in flower buds; insufficient supply of auxins and gibberellins, which promotes pistil development; and accumulation of cytokinins, which inhibits pistil development.

Key message

Provenance controls conductive area of stem secondary xylem, leaf area, and stable isotope (C, N, and O) ratios of beech leaves, while no significant effects were observed for ectomycorrhizal community composition.

Abstract

Beyond growth parameters and drought tolerance, comparatively little is known about the functioning of different beech (Fagus sylvatica L.) provenances. We investigated properties of leaves, stem secondary xylem, and ectomycorrhiza (ECM), and explored their interdependencies to identify the best performing beech provenance in optimal growth conditions. The study was conducted on 23-year-old trees in a provenance trial. The investigated provenances originated from Atlantic (Belgium—BE), Alpine (Italy—IT, Slovenia—SI), and continental climates (the Czech Republic—CZ). A significant effect of provenance was observed for stem vessel diameters and conductive area, as well as for foliar %C, δ¹³C, δ¹⁵N, and δ¹⁸O. δ¹³C as a proxy of intrinsic water use efficiency (iWUE) showed that the highest iWUE was achieved in BE provenance. Individuals with a better iWUE had wider growth rings regardless of provenance. Better iWUE was associated with lower specific leaf area (SLA). ECM community composition and diversity indices did not differ significantly among the provenances. Specific ECM taxa were associated with individuals with high SLA, δ¹³C, δ¹⁵N, and δ¹⁸O. In optimal growth conditions with no stress events, BE is a promising provenance due to an efficient water conducting system with high vessel diameters and conductive area, and high iWUE, while Alpine provenances showed an adaptation of their water conducting system to freezing conditions at their original locations. Integrating findings from different compartments improves our understanding of functioning of different beech provenances.

Key message

This study not only provide a theoretical basis for screening drought-resistant yellowhorn rootstocks but also lay the foundation for the research on the drought resistance mechanism of yellowhorn.

Abstract

Drought is a major limiting factor in the production and cultivation of yellowhorn, an important woody oil species in China. It is important to select excellent drought-resistant rootstocks, and the current reproduction of rootstocks of yellowhorn is mainly through seed propagation. In this study, we analyzed the phenotypes, physiology and anatomy of the F1 generation of five yellowhorn varieties (‘Zhongshi 1’, ‘Zhongshi 4’, ‘Zhongshi 7’, ‘Zhongshi 9’ and ‘Yuanda’) which are currently the main promoted varieties of yellowhorn. The changes in physiological traits were used to comprehensively rank drought resistance by the membership function method. The results showed that the drought resistance of different varieties was in the order ‘Zhongshi 9’ > ‘Zhongshi 4’ >  ‘Yuanda’ >  ‘Zhongshi 7’ >  ‘Zhongshi 1’. In addition, we investigated the molecular signature of two yellowhorn varieties exhibiting a large difference in levels of drought resistance using transcriptome data. A total of 119 differentially expressed genes (DEGs) were found between the 2 yellowhorn varieties under drought stress. Based on KEGG analysis, DEGs were mostly enriched in three pathways. According to the correlation analysis between weighted gene co-expression network analysis (WGCNA) and physiological traits, a total of four co-expression networks with high correlation were constructed, and some hub genes of yellowhorn in response to drought stress were found. We carried out a comprehensive evaluation of yellowhorn drought tolerance based on parental lines. It solves the current problems faced in the breeding of yellowhorn and lays the foundation for studying the molecular mechanism of drought resistance in yellowhorn.

Key message

Norway spruce operates with larger hydraulic safety margins (HSM) than beech and Douglas-fir despite the known drought sensitivity of spruce, questioning a pivotal role of HSM in drought tolerance.

Abstract

The exceptional 2018/2019 drought exposed Central Europe’s forests to severe stress, highlighting the need to better understand stomatal regulation strategies and their relationship to xylem safety under extreme drought. We studied diurnal, seasonal, and inter-annual variation in stomatal conductance (g_s) and leaf water potential (Ψ_Leaf) in co-occurring European beech (F. sylvatica), Norway spruce (P. abies), and Douglas-fir (P. menziesii) trees in the two summers and related them to hydraulic traits characterizing drought resistance. In 2018, F. sylvatica exhibited a continuous Ψ_Leaf decline from June to September, as is characteristic for an anisohydric strategy, while P. abies closed stomata early and reached the least negative Ψ_Leaf-values at the end of summer. P. menziesii showed low Ψ_Leaf-values close to P₁₂ (the xylem pressure at onset of embolism) already in July. Both conifers closed stomata when approaching P₁₂ and maintained low g_s-levels throughout summer, indicative for isohydric regulation. In 2019, all three species showed a linear decline in Ψ_Leaf, but F. sylvatica crossed P₁₂ in contrast to the conifers. The three species exhibited similar water potentials at turgor loss point (− 2.44 to − 2.51 MPa) and branch P₅₀ (xylem pressure at 50% loss of hydraulic conductance; − 3.3 to − 3.8 MPa). Yet, F. sylvatica and P. menziesii operated with smaller hydraulic safety margins (HSM means: 0.79 and 0.77 MPa) than P. abies (1.28 MPa). F. sylvatica reduced leaf size and specific leaf area in 2019 and increased Huber value. Our species comparison during extreme drought contradicts the general assumption that conifers operate with larger HSMs than angiosperm trees. Contrary to expectation, P. abies appeared as hydraulically less vulnerable than Douglas-fir.

Key message

The high-wood-density species displays greater water limitation tolerance, as it maintains leaf transpiration under drought conditions.

Abstract

The relationship between environmental conditions and plant hydraulic safety is essential to understand species’ strategies to minimize damage to their hydraulic structure yet maintain function. In the Brazilian semi-arid, the relationships between rainfall seasonality, hydraulic conductivity, wood density, stomatal conductance, and phenology in different species still needs to be clarified. To better understand these relationships, we selected two deciduous trees species with contrasting wood density: (1) Commiphora leptophloeos (Mart.) J.B. Gillett (low wood density) and (2) Cenostigma pyramidale (Tul.) E. Gagnon & G. P. Lewis (high wood density) from the Caatinga dry forest of northeast Brazil. We tracked monthly measurements of whole-tree hydraulic conductivity, leaf stomatal conductance, leaf transpiration rate, xylem water potential, and phenology. We found that the low-wood-density species had a higher whole-tree hydraulic conductivity and an early leaf flush and fall. In addition, lower leaf transpiration rate and higher water storage capacity maintained high xylem water potential and stomatal conductance values, especially in the rainy season. On the other hand, the high-wood-density species had a lower whole-tree hydraulic conductivity and higher leaf transpiration rate, even during the dry season. These results point to the divergent hydraulic strategies employed by each species, further suggesting opposing hydraulic safety pathways during drought.

Key message

In upland forests, trunk CH₄ emissions exhibit significant intra-individual spatial variability, which was explained by variations in both CH₄ concentration and CH₄ production rates in the sapwood.

Abstract

Methane (CH₄) emissions from tree trunks in upland forests should be scaled accurately to assess the role of tree trunk in the forest CH₄ budget. As the chambers used to measure emissions cover only a small part of the large surface area of tree trunks, it is necessary to understand the intra-individual spatial variability of trunk CH₄ emissions. To assess this spatial variability, we measured trunk CH₄ flux at nine locations per individual on four trees in a cool-temperate upland forest for which microbial production of CH₄ inside the trunk is likely an important source of the emission. To know the origin of this variability and the underlying processes, we also measured the potential rate of CH₄ production and CH₄ concentrations in both sapwood and characterized wood and bark. Up to 15-fold intra-individual spatial variations in CH₄ fluxes were observed in target trees. The variability in emissions within an individual was primarily shown by the variation of the sapwood CH₄ concentration which was further explained by the variation in potential CH₄ production rate. The radial CH₄ diffusivity calculated from concentration gradients and emissions was not related to the measured characteristics of either wood or bark. We emphasized the importance of sampling trunk CH₄ flux at multiple locations on the surface of a tree trunk in order to capture the spatial variability, a prerequisite for estimating tree-level CH₄ emissions.