Trees最新文献

Key message

Studied beech provenances showed different patterns of inter-annual variability in mean vessel area and ring widths, indicating influence of intraspecific variability and diverse environment on hydraulic conductivity and carbon storage potential.

Abstract

International provenance trials of ecologically and economically important tree species are crucial to deciphering the influence of environmental factors and intraspecific variability on tree growth and performance under climate change to guide assisted gene flow and assisted migration of tree provenances and species. In this context, we compared inter-annual trends in tree-ring widths (carbon sequestration potential) and vessel characteristics (conductivity optimisation) of four beech provenances in two international provenance trials, one in Slovenia (Kamenski hrib, a core beech growing site) and one in Hungary (Bucsuta, a marginal beech site) in 2009–2019. We found different patterns of inter-annual variability in mean vessel area and tree-ring widths among provenances and sites, pointing to diverse genetic background and environmental influence on these two wood-anatomical traits. The average values of the vessel area varied less between provenances at Kamenski hrib than at Bucsuta. Weather conditions differently affected tree-ring width and mean vessel area. Furthermore, the length of the period of response of vessel area to the analysed weather conditions differed in summer and winter periods. The differences in the mean vessel area within the tree ring were more pronounced in the weather-wise extreme years, regardless of the provenance. Consistent with previous studies, we confirmed that site conditions affect the climate sensitivity of trees, which is more pronounced at marginal sites or in extreme years. The findings on how different environmental conditions affect the radial growth of young beech trees of different origin are very important for future forest management.

Key message

A complete system of regeneration, via somatic embryogenesis, from the in vitro culture of leaflets explants of young A. aculeata donor-plants has been reported.

Abstract

In the present study, a complete regeneration protocol of Acrocomia aculeata (Jacq.) Lodd. ex Mart., via somatic embryogenesis is reported, and the influence of the genotype and its age on the induction of the embryogenic process determined. Leaflets explants of 4 genotypes, aged 2 and 5 years, were inoculated in the induction medium consisting of salts and vitamins Y3 supplemented with different concentrations of picloram (9.0, 18.0 and 36.0 µM). In the control, no plant growth regulators were added. Picloram concentrations of 18.0 and 36.0 µM induced greater formation of embryogenic calluses in all genotypes studied. However, 2-year-old genotypes had higher percentages of embryogenic calluses. In addition, at the highest concentration of picloram (36.0 µM), 5-year-old genotypes had the highest oxidation rates. Differentiation of somatic embryos was observed in medium supplemented with 9.0 and 18.0 µM picloram and 1 mM putrescine. However, at a concentration of 9.0 µM, the somatic embryos showed a high degree of fusion. Embryogenic lines were only obtained in medium supplemented with 18.0 µM picloram and 1 mM putrescine. Histochemical analysis showed the presence of pectins in embryogenic cultures and starch grains in peripheral regions of embryogenic calluses, which were not directly involved in regeneration. Somatic embryos were converted into plantlets after 90 days in germination medium containing 0.54 µM NAA, 1 mM putrescine and 3.0 g L⁻¹ activated charcoal, highlighting the potential of the propagation system proposed here for clonal propagation of A. aculeata.

Key message

Bedrock can store appreciable amounts of available water, and some trees apparently use this resource to survive drought.

Abstract

Several forest ecosystems rely on only shallow soil layers overlying more or less compact bedrock. In such habitats, the largest water reservoir can be represented by rock moisture, rather than by soil water. Here, we review evidence for the presence of water available for root water uptake in some rock types, and show examples of the physiological and ecological roles of rock moisture, especially when trees are facing drought conditions. The possible magnitude of rock–root water exchanges is discussed in the frame of current knowledge of rock, soil, and root hydraulic properties. We highlight several areas of uncertainty regarding the role of rock moisture in preventing tree hydraulic failure under drought, the exact pathway(s) available for rock–root water exchange, and the relative efficiencies of water transport in the different compartments of the rock–soil–root continuum. Overall, available experimental evidence suggests that bedrock water should be incorporated into any model describing the forest seasonal water use and tree responses to drought.

Several studies have addressed the role of soil fertility on acorn N remobilization during seedling growth, but have focused on very early development stages or have assessed remobilization at a coarse grain ontogenetic scale making it difficult to know the precise time when seedlings switch from acorn N to soil N use. We cultivated Quercus variabilis seedlings under two distinct soil N fertility and assessed their growth, acorn N remobilization, and absorption of soil N at five distinct development stages, spanning from the incipient shoot emergence to the completion of the second flush of growth. Acorn N contributed more to seedling N content than soil N at all development stages. Seedlings began to uptake substantial amounts of soil N after the completion of leaf expansion during the first shoot flush of growth, coinciding with a fine root area that reached 50% of the maximum value observed at the end of the study. Roots became less dependent on acorn N before shoots. Soil fertility, rather than seedling growth rate, determined soil N uptake after the completion of leaf expansion in the first shoot flush of growth. We conclude that the acorn is the primary N source for Q. variabilis seedlings until the completion of the first shoot flush of growth. Soil fertility does not significantly affect either the amount of N remobilized from acorns or the switch from acorn N to massive soil N use, suggesting a minimal effect of forest microhabitat fertility on acorn N utilization by Q. variabilis seedlings.

Temperature modulating the growing season onset of trees is still not completely understood. We anatomically tracked the growing season onset development of Pinus tabuliformis annual cambium activities in Shenyang during 2019–2021, explored the influencing factors and their regularity on the pine growing season onset, determined the interannual trajectory of the onset date, and simulated the growing season onset trajectory by the physiological process-based tree-ring Vaganov–Shashkin model. We found that the growing season onset date of P. tabuliformis significantly advanced at a rate of 1.5 days/decade in Shenyang during 1951–2021, the mean of which was 6 days earlier in 1981–2021 than in 1951–1980. The April maximum temperature was extremely significantly correlated with the P. tabuliformis growing season onset date. The pine growing season onset is modulated by temperatures, including minimum, mean, maximum temperature and diurnal temperature range (DTR), with corresponding thresholds of 3.2 ± 1.1 °C, 11.4 ± 0.7 °C, 18.1 ± 0.8 °C and 13.0 ± 2.7 °C, respectively, during 11–12 days prior to the growing season onset date. A low DTR during this stage would delay the onset of the pine growing season. The finding of the critical stage, modulating climate variables and their thresholds may help to accurately predict the regional growing season onset of P. tabuliformis.

Key message

Tree species in a temperate floodplain forest had leaf turgor loss point values similar to those of upland forest trees, suggesting physiological drought tolerance in this generally non-water-limited system.

Abstract

Leaf turgor loss point (TLP) is a key plant trait associated with drought tolerance. In the bottomland hardwood (BLH) forests that grow in floodplains of the southeastern USA, drought stress is generally low but may increase with climate change. To address drought tolerance among BLH trees, we measured TLP among 20 species in a BLH forest in Louisiana, USA. We tested whether (1) TLP is higher in BLH tree species than in upland temperate-zone trees; (2) lower TLP is associated with higher drought tolerance among BLH species; (3) TLP drops during the growing season within BLH trees; and (4) within species, TLP is lower in more water limited, non-flooded BLH habitats than in seasonally flooded habitats. Among BLH tree species, TLP was −2.23 ± 0.28 (mean ± SD) and, contrary to our hypothesis, weakly positively correlated with drought tolerance. Within BLH species, TLP was lower in non-flooded habitats than seasonally flooded habitats and TLP decreased between the early and late growing season, more so in the non-flooded habitat. Overall, our results show that TLP among BLH trees is relatively low and plastic for a system that is generally not water limited, which may contribute to drought tolerance in future scenarios.

Key message

This research focused on the interplay between tree structural complexity and drought tolerance, unraveling the crucial role of D_b as an indicator of hydraulic efficiency and vulnerability in several tree species.

Abstract

The potential of trees to adapt to drier and hotter climates will determine the future state of forests in the wake of a changing climate. Attributes connected to the hydraulic network are likely to determine a tree’s ability to endure drought. However, how a tree’s architectural attributes related to drought tolerance remains understudied. To fill this gap, we compared the structural complexity of 71 trees of 18 species obtained from terrestrial laser scanning (TLS) with key hydraulic thresholds. We used three measures of xylem safety, i.e., the water potential at 12%, 50%, and 88% loss of hydraulic conductance (P₁₂, P₅₀, P₈₈) and specific hydraulic conductivity (K_s) to assess the trees’ drought tolerance. TLS data were used to generate 3D attributes of each tree and to construct quantitative structure models (QSMs) to characterize the branching patterns. Fractal analysis (box-dimension approach) was used to evaluate the overall structural complexity of the trees (D_b) by integrating horizontal and vertical extent as well as internal branching patterns. Our findings revealed a significant relationship between the structural complexity (D_b) and the three measures of xylem safety along with K_s. Tree species with low structural complexity developed embolism-resistant xylem at the cost of hydraulic efficiency. Our findings also revealed that the D_b had a stronger and more significant relationship with branch hydraulic safety and efficiency compared to other structural attributes examined. We conclude that D_b seems to be a robust descriptor of tree architecture that relates to important branch hydraulic properties of a tree.

Key message

A significant scaling relationship between the perianth mass and area was detected using 306 flowers of Magnolia × soulangeana, and increases in mass failed to achieve proportional increases in area.

Abstract

The scaling relationship between leaf lamina mass and area has been explored extensively. However, this relationship for floral parts, which are considered homologous with foliage leaves, has not been studied despite the implications of scaling theory and plant morphometry. Toward this goal, a total of 306 flowers and 2759 tepals of Magnolia × soulangeana were collected and measured. The area of each tepal was determined by digitizing its profile, and the perianth area (A_p) was empirically determined by summing the areas of all tepals per flower. The perianth fresh mass (FM) was also measured, and the Montgomery equation (ME) was used to estimate the tepal area (A_t) predicted as proportional to the product of tepal length (L) and width (W) to explore the feasibility of estimating A_t non-destructively. The scaling exponent of FM vs A_p significantly exceeded unity, i.e., increases in mass failed to achieve proportional increases in area, a phenomenon called “diminishing returns”. The estimated proportionality coefficient of ME for non-destructively calculating A_t approximately equaled 0.7 [i.e., A_t ≈ (3/4)LW], and the distributions of A_t, L, W/L, and the tepal centroid ratio were relatively concentrated. The data indicate that (1) scaling relationship between tepal mass and area is statistically indistinguishable from the phenomenon observed for foliage leaves, (2) tepal shape and leaf shape are similar, and (3) the ME predicts tepal area nondestructively. These results encourage the application of the ME to study tepal shape and geometry and support the serial homology between leaves and tepals for this Magnolia hybrid.

Key message

Stem wounds heal most quickly in fast-growing trees. Despite slower growth among savanna species, their wound closure matches forest species, owing to a positive influence of investment in bark production.

Abstract

Stem wounding by fire poses a survival risk to trees in frequently burned environments. Ability to close wounds quickly is important for minimizing exposure of the stem to rot, insects, and future fires, so we investigated factors influencing rates of wound closure. We hypothesized that the rate of wound closure is positively correlated with growth rate, negatively correlated with wood density, and greater for savanna species than forest species. To test these hypotheses, we induced mechanical damage in trunks of 36 tree species in fire-suppressed savanna in southeastern Brazil, and measured subsequent rates of wound closure. There was a strong positive correlation between wound closure and diameter growth, both within and among species. Growth rate varied among functional types, being greatest among forest specialists and lowest among savanna specialists, while the opposite pattern was found for relative bark thickness. Despite differences in growth rate, there was no difference in wound closure among functional types. This apparent inconsistency occurs because of a positive correlation between relative bark thickness and rate of wound closure, after controlling for growth rate. Wound closure was most strongly predicted by the rate of bark increment, which is determined by growth rate and relative bark thickness. There was no effect of wood density on wound closure. These findings enhance our understanding of wound closure dynamics in trees and highlight the importance of growth rate and bark characteristics in determining the ability of trees to recover from damage.

Key message

The leaflet area of acai (Euterpe oleracea) can be estimated by an exponential regression model adjusted by the relationship of leaflet maximum length and width.

Abstract

This work was carried out aiming to fit linear regression models for the non-invasive estimation of leaflet area (LA) in acai (Euterpe oleracea Mart.). Thus, 5010 leaflets were sampled from 403 fronds sampled on 100 acai seedlings. Maximum length (LL) and width (LW) of each leaflet were measured with a ruler and LA was determined using a leaf area meter. Half of the data set was used to adjust the models and the other half was used for model validation. The Jackknife re-sampling method was applied to reduce model bias. Two double-entry models (models A and B) were fitted using LL and LW simultaneously, while these linear dimensions of the leaves were separately considered in single-entry models (models C to F). The adjusted coefficients of determination varied between 0.9075 and 0.9785, with the highest values observed in models A and B, which also showed the lowest standard error of the estimate and Akaike's information criterion (AIC) score. All models were highly accurate in estimating LA, with values above 0.9156; however, the double-entry models A and B showed the best performance regarding the relationship between estimated and observed LA. Comparing the double-entry models, the lowest AIC score in model B indicates that this model is the most parsimonious for non-invasive estimation of acai leaflet area in relation to model A. Therefore, the equation ({text{LA}} = 1.0147 left[{{text{e}}}^{0.3685 + 0.8165 {text{ln}}left({text{LL}} times {text{LW}}right)}right]), deduced from model B, is the more precise model for the non-invasive determination of leaflet area in acai seedlings.