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Microcomputed tomography (µCT) is a nondestructive X-ray imaging method used in plant physiology to visualize in situ plant tissues that enables assessments of embolized xylem vessels. Whereas evidence for X-ray-induced cellular damage has been reported, the impact on plant physiological processes such as carbon (C) uptake, transport, and use is unknown. Yet, these damages could be particularly relevant for studies that track embolism and C fluxes over time. We examined the physiological consequences of µCT scanning for xylem embolism over 3 mo by monitoring net photosynthesis (Anet), diameter growth, chlorophyll (Chl) concentration, and foliar nonstructural carbohydrate (NSC) content in 4 deciduous tree species: hedge maple (Acer campestre), ash (Fraxinus excelsior), European hornbeam (Carpinus betulus), and sessile oak (Quercus petraea). C transport from the canopy to the roots was also assessed through 13C labeling. Our results show that monthly X-ray application did not impact foliar Anet, Chl, NSC content, and C transport. Although X-ray effects did not vary between species, the most pronounced impact was observed in sessile oak, marked by stopped growth and stem deformations around the irradiated area. The absence of adverse impacts on plant physiology for all the tested treatments indicates that laboratory-based µCT systems can be used with different beam energy levels and doses without threatening the integrity of plant physiology within the range of tested parameters. However, the impacts of repetitive µCT on the stem radial growth at the irradiated zone leading to deformations in sessile oak might have lasting implications for studies tracking plant embolism in the longer-term., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Stable carbon and oxygen isotope ratios of raw pollen sampled from nine abundant tree species growing in natural habitats of central and northern Europe were investigated to understand the intra- and inter-specific variability of pollen-isotope values. All species yielded specific δ13Cpollen and δ18Opollen values and patterns, which can be ascribed to their physiology and habitat preferences. Broad-leaved trees flowering early in the year before leaf proliferation (Alnus glutinosa and Corylus avellana) exhibited on average 2.6‰ lower δ13Cpollen and 3.1‰ lower δ18Opollen values than broad-leaved and coniferous trees flowering during mid and late spring (Acer pseudoplatanus, Betula pendula, Carpinus betulus, Fagus sylvatica, Picea abies, Pinus sylvestris and Quercus robur). Mean species-specific δ13Cpollen values did not change markedly over time, whereas δ18Opollen values of two consecutive years were often statistically distinct. An intra-annual analysis of B. pendula and P. sylvestris pollen revealed increasing δ18Opollen values during the final weeks of pollen development. However, the δ13Cpollen values remained consistent throughout the pollen-maturation process. Detailed intra-individual analysis yielded circumferential and height-dependent variations within carbon and oxygen pollen-isotopes and the sampling position on a tree accounted for differences of up to 3.5‰ for δ13Cpollen and 2.1‰ for δ18Opollen. A comparison of isotope ranges from different geographic settings revealed gradients between maritime and continental as well as between high and low altitudinal study sites. The results of stepwise regression analysis demonstrated, that carbon and oxygen pollen-isotopes also reflect local non-climate environmental conditions. A detailed understanding of isotope patterns and ranges in modern pollen is necessary to enhance the accuracy of palaeoclimate investigations on δ13C and δ18O of fossil pollen. Furthermore, pollen-isotope values are species-specific and the analysis of species growing during different phenophases may be valuable for palaeoweather reconstructions of different seasons., Competing Interests: The authors have declared that no competing interests exist.

In many woody dicot plant species, colder temperatures correlate with a greater degree of leaf dissection and with larger and more abundant leaf teeth (the serrated edges along margins). The measurement of site-mean characteristics of leaf size and shape (physiognomy), including leaf dissection and tooth morphology, has been an important paleoclimate tool for over a century. These physiognomic-based climate proxies require that all woody dicot plants at a site, regardless of species, change their leaf shape rapidly and predictably in response to temperature. Here we experimentally test these assumptions by growing five woody species in growth cabinets under two temperatures (17 and 25°C). In keeping with global site-based patterns, plants tend to develop more dissected leaves with more abundant and larger leaf teeth in the cool treatment. Overall, this upholds the assumption that leaf shape responds in a particular direction to temperature change. The assumption that leaf shape variables respond to temperature in the same way regardless of species did not hold because the responses varied by species. Leaf physiognomic models for inferring paleoclimate should take into account these species-specific responses., Competing Interests: The authors have declared that no competing interests exist.

Dendrometers offer a useful tool for long-term, high-resolution monitoring of tree responses to environmental fluctuations and climate change. Here, we analyze a 4-year dendrometer dataset (2014-17) on European beech (Fagus sylvatica L.), common hornbeam (Carpinus betulus L.) and pedunculate oak (Quercus robur L.), co-occuring in a mixed broadleaved forest in northeastern Germany. In our analyses, we focus both on seasonal growth dynamics as well as on the environmental forcing of daily stem-size variations. Over the study period with contrasting weather conditions, we observed species- and year-specific differences in growth phenology (i.e., growth onset, cessation and duration). Oak was characterized by early growth onset and long growth duration in all years as compared with beech and hornbeam. The analysis on the environmental forcing of daily stem dynamics revealed, however, highly similar responses for the studied species, with current-day vapor pressure deficit and sunshine duration negatively, and relative humidity and precipitation positively affecting stem size. When considering lagged effects, environmental conditions often oppositely affected stem-size changes. No consistent seasonality in environmental responses was detected, though specific weather conditions were found to affect temporal patterns in individual years. We suggest that the high similarity in environmental forcing observed between tree species can be explained by daily stem-size changes mainly reflecting tree water status rather than tree growth. Our results stress that correcting dendrometer series for reversible stem hydrological changes is of utmost importance to better quantify tree growth from dendrometers in future.

In temperate deciduous forests, vertical gradients in leaf mass per area (LMA) and area-based leaf nitrogen (Narea) are strongly controlled by gradients in light availability. While there is evidence that hydrostatic constraints on leaf development may diminish LMA and Narea responses to light, inherent differences among tree species may also influence leaf developmental and morphological response to light. We investigated vertical gradients in LMA, Narea and leaf carbon isotope composition (δ13C) for three temperate deciduous species (Carpinus caroliniana Walter, Fagus grandifolia Ehrh., Liriodendron tulipifera L.) that differed in growth strategy (e.g., indeterminate and determinate growth), shade tolerance and leaf area to sapwood ratio (Al:As). Leaves were sampled across a broad range of light conditions within three vertical layers of tree crowns to maximize variation in light availability at each height and to minimize collinearity between light and height. All species displayed similar responses to light with respect to Narea and δ13C, but not for LMA. Light was more important for gradients in LMA for the shade-tolerant (C. caroliniana) and -intolerant (L. tulipifera) species with indeterminate growth, and height (e.g., hydrostatic gradients) and light were equally important for the shade-tolerant (F. grandifolia) species with determinate growth. Fagus grandifolia had a higher morphological plasticity in response to light, which may offer a competitive advantage in occupying a broader range of light conditions throughout the canopy. Differences in responses to light and height for the taller tree species, L. tulipifera and F. grandifolia, may be attributed to differences in growth strategy or Al:As, which may alter morphological and functional responses to light availability. While height was important in F. grandifolia, height was no more robust in predicting LMA than light in any of the species, confirming the strong role of light availability in determining LMA for temperate deciduous species., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

This study examines the role of dorsiventral leaf measurements in reflectance-based air quality estimation. The dorsiventral asymmetry is used to describe the difference between the upper (adaxial) and lower (abaxial) leaf side. Spectral characteristics of dorsiventral asymmetry and both adaxial and abaxial leaf reflectance are investigated for a typical dicotyledonous species Carpinus betulus used in an urban environment. The link with traffic-related air pollution is established and the potential for monitoring of air quality is evaluated. We conclude that dorsiventral reflectance asymmetry is a factor that should not be ignored in canopy measurements and modeling. On the other hand, the benefits of dorsiventral asymmetry indices as a tool for reflectance-based air quality seem limited.

In deciduous trees growing in temperate forests, bud break and growth in spring must rely on intrinsic carbon (C) reserves. Yet it is unclear whether growth and C storage occur simultaneously, and whether starch C in branches is sufficient for refoliation. To test in situ the relationships between growth, phenology and C utilization, we monitored stem growth, leaf phenology and stem and branch nonstructural carbohydrate (NSC) dynamics in three deciduous species: Carpinus betulus L., Fagus sylvatica L. and Quercus petraea (Matt.) Liebl. To quantify the role of NSC in C investment into growth, a C balance approach was applied. Across the three species, >95% of branchlet starch was consumed during bud break, confirming the importance of C reserves for refoliation in spring. The C balance calculation showed that 90% of the C investment in foliage (7.0-10.5 kg tree(-1) and 5-17 times the C needed for annual stem growth) was explained by simultaneous branchlet starch degradation. Carbon reserves were recovered sooner than expected, after leaf expansion, in parallel with stem growth. Carpinus had earlier leaf phenology (by ∼25 days) but delayed cambial growth (by ∼15 days) than Fagus and Quercus, the result of a competitive strategy to flush early, while having lower NSC levels., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

In the present study, the effect of some pre-treatments implemented on seeds of Oriental hornbeam (Carpinus orientalis), which has wide geographical variation along Turkey on germination percentage values were investigated. For this purpose, 13 different pre-treatments were implemented to seeds obtained from 17 different populations. According to the obtained results (except control seeds), pre-treatments leading to lowest germination percentage value (8.1%) in Oriental hornbeam seeds was PT10: Keeping seeds for 90 min in sulfuric acid, while highest germination percentage (86.58%) has been obtained with pre-treatment PT13: Implementation of 40% dose of Baikal EM1 + Biohoumous mixture to the seeds, while lowest germination percentage (40.50%) was observed on seeds collected from P7 (Bartin-Kozcağiz) population, highest germination percentage was observed in seeds obtained from P17 (Artvin-Hopa) population.

Revegetation patterns after quarry abandonment have been widely studied from several ecological points of view, but a trait-based approach is still lacking. The aim of this study was to characterise the plant species assemblages and the associated functional traits filtered on different geomorphological surfaces in abandoned limestone quarry areas: artificial cliffs, embankments, and platforms. We then verified if species with certain traits were better able to overcome the dispersal and environmental filters necessary for establishment. To this aim, we analyzed 113 vegetation plots and collected data on 25 morphological, ecological, and dispersal traits to detect species adaptaions across these man-made environments. As a case study, we investigated the extraction basin of Botticino (Lombardy, Italy), the second largest in Italy. The results obtained by SIMPER and CCA analyses showed that rockiness, stoniness, slope, elevation, and time of surfaces are the main filters that varied across quarries and affected plant assemblages at the macro-scale level. Across the three geomorphological surfaces (meso-scale) of quarries, more specific abiotic filters selecting species were found. In turn, traits differentiation according to the three main geomorphological surfaces of quarry emphasized that further filters acting at the micro-scale imply differences in dispersal mechanisms and resource availability. This work highlighted the utility to study species assemblages and environmental filters to address quarry restoration according to the type of geomorphological surface. The investigation of some traits (chorological form, life forms, seed dispersal,s and plant height) can furnish some interesting indications for practice individuating further abiotic filters acting at the micro-scale.

Tree ring analysis investigates growth processes at time horizons of several weeks to millennia, but lacks the detail of short-term fluctuation in cambial activity. This study used electronic high-precision dendrometry for analyzing the environmental factors controlling stem diameter variation and radial growth in daily resolution in five co-existing temperate broad-leaved tree species (genera Fraxinus, Acer, Carpinus, Tilia and Fagus) with different growth and survival strategies. Daily stem radius change (SRC(d)) was primarily influenced by the atmospheric demand for water vapor (expressed either as vapor pressure deficit (D) or relative air humidity (RH)) while rainfall, soil matrix potential, temperature and radiation were only secondary factors. SRC(d) increased linearly with increasing RH and decreasing D in all species. The positive effect of a low atmospheric water vapor demand on SRC(d) was largest in June during the period of maximal radial growth rate and persisted when observation windows of 7 or 21 days instead of 1 day were used. We found a high synchronicity in the day-to-day growth rate fluctuation among the species with increment peaks corresponding to air humidity maxima, even though the mean daily radial growth rate differed fivefold among the species. The five -species also differed in the positive slope of the growth/RH relationship with the steepest increase found in Fraxinus and the lowest in Fagus. We explain the strong positive effect of high RH and low D on radial stem increment by lowered transpiration which reduces negative pressure in the conducting system and increases turgor in the stem cambium cells, thereby favoring cell division and expansion. The results suggest that mechanistic models of tree growth need to consider the atmospheric water status in addition to the known controlling environmental factors: temperature, soil moisture and precipitation. The results further have implications for sensitivity analyses of tree growth to climatic changes.

The objective of this paper is to give an account of the evaluation of the effect of urban habitat quality on dorsi-ventral leaf reflectance asymmetry to bio-monitor urban habitat pollution. Reflectance in the RGB bands of a reflex camera is measured at the adaxial and abaxial sides of Carpinus betulus L. leaves for two contrasting urban habitats, e.g.; suburban green and industrial habitats in the city of Gent (Belgium). Abaxial leaf reflectance is consistently higher than adaxial leaf reflectance. We quantified leaf dorsi-ventral reflectance asymmetry with a newly defined Normalized Dorsi-ventral Asymmetry Index (NDAI). The NDAI is significantly higher in industrial habitats as opposed to suburban green ones. Our optical observations indicate that changes in Carpinus betulus L. leaf morphology are related to urban habitat quality. Hence, we suggest that leaf dorsi-ventral reflectance asymmetry allows the estimation of the magnitude and spatial extent of environmental pollution in urban environments., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The regeneration structure and biodiversity of trees and shrub species in under story of pure and mixed Oak plantations were investigated in Chamestan Forest and Rangeland Research Station of Iran. Planted species including Oak (as main species) and Hornbeam (as associated species). This species were planted in five proportions (100Q, 70Q:30C, 60Q:40C, 50Q:50C, 40Q:60Z) in Northern of Iran in 11 years ago. All of regenerating seedlings and saplings of woody plants were divided into two height classes of 15-200 cm and more than 200 cm. In biodiversity study dominance index of Berger-Parker, diversity index of Fisher alpha, richness index of Margalef and evenness index of Equitability J were used. The results showed that abundance and diversity of regenerated species in under story of all plantations of oak were more than unplanted control plots and also under 50Q:50C were more than pure stand of oak. The presence of primary forest species in under stories of mixed plantation showed the usage of these plantations in development of succession in natural

In trees, leaf life span is closely related to successional status. Although leaves are attached to shoots, shoot life span has been insufficiently studied in the context of ecological systems. Interspecific variation in shoot survivorship was investigated over 27 months in 15 temperate hardwood tree species. Relationships between shoot architecture and shoot survival were also investigated. Shoot life span was shortest in early successional species, and longest in late successional species, in each of the families Betulaceae and Fagaceae. In Salicaceae, all of which were early successional species, shoot life span was longer in mountainous than in riparian species. Early successional or riparian species distributed longer shoots densely, even in proximal positions on mother shoots, resulting in mutual shading and consequent early and massive shoot shedding. By contrast, late successional or mountainous species concentrated shoots in distal positions, allowing shoots to receive equally favorable light, resulting in a longer life span. These results reveal close relationships between shoot life span and environmental resource availability or successional status and suggest a causal relationship between shoot shedding and shoot architecture.

Background and Aims: It is generally known that fertilization is delayed for more than a few weeks after pollination in Fagales. Recent studies showed that, during that period, pollen tubes grew in pistils in close association with the development of the ovule in a five-step process in Casuarina (Casuarinaceae) and a four-step process in Alnus (Betulaceae). The number of pollen tubes was reduced from many to one, a fact suggesting that delayed fertilization plays a role for gametophyte selection. Myrica (Myricaceae) also shows delayed fertilization for >2 weeks after pollination, but nothing is known of how pollen tubes grow in the pistil during that period., Methods: Pollen-tube growth and the development of the ovule in pistils was investigated by fluorescent and scanning electron microscopy and analysis of microtome sections of the pistils., Key Results: Developmental study of the pollen-tube growth in the pistil of M. rubra showed that the tip of the pollen tube was branched or lay in a zigzag pattern in the upper space of the ovarian locule or near the tip of the integument, and subsequently was swollen on the nucellar surface. Such morphological changes indicate that the pollen-tube growth was temporarily arrested before fertilization. The pollen-tube growth in M. rubra can therefore be summarized as occurring in three steps: (1) from the stigma to the ovarian locule; (2) from the ovarian locule to the nucellar surface; and (3) from the nucellar surface to the embryo sac., Conclusion: Myrica differs from other families in that the pollen tubes arrest their growth on the nucellar surface, probably digesting nutrient from nucellar cells. There is little information on five other families of Fagales. An extensive study is needed to better understand the diversity and function of the mode of pollen-tube growth within the order.

Based on the 1985 - 2003 fixed-position data in 9 runoff plots of Caijiachuan watershed in the Jixian county of Shanxi Province in loess area, this paper discussed the relationships between vegetation and runoff and sediment production on sloping lands of loess area. The results showed that natural-secondary forest had better function in soil and water conservation than artifical Robinia pseudoacacia forest, with runoff and sediment produced 65% - 82% and 23% - 92%, respectively. Multiple regression analysis indicated that runoff and sediment production had a significant correlation with rainfall and its intensity, but this relationship was decreased gradually with increasing canopy density. Different land-use type had different runoff and sediment production, e. g., Ostryopsis davidiana and natural-secondary forests had the least runoff and sediment production, artificial Robinia pseudoacacia and Pinus tabulaeformis forests had 5 folds of it as much as Ostryopsis davidiana forest, mixed apple trees and crops had 17.14 and 3.96 folds of it than Ostryopsis davidiana forest, respectively, while high-standard soil preparation could decrease the production obviously. Gray correlation analysis suggested that the stand canopy density and the biomass of herb and litter were the most important factors affecting the runoff and sediment production on sloping land, whose gray correlation degrees all exceeded 0.6. Mixed forest with multi-layer stand structure and shrub forest should be developed in vegetation re-construction of loess area, which could help to increase the coverage and litter thickness to dramatically decrease the runoff and sediment production on sloping land.

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.

In 2003, Central Europe experienced the warmest summer on record combined with unusually low precipitation. We studied plant water relations and phenology in a 100-year- old mixed deciduous forest on a slope (no ground water table) near Basel using the Swiss Canopy Crane (SCC). The drought lasted from early June to mid September. We studied five deciduous tree species; half of the individuals were exposed to elevated CO(2) concentration ([CO(2)]) (530 ppm) using a free-air, atmospheric CO(2)-enrichment system. In late July, after the first eight weeks of drought, mean predawn leaf water potential about 30 m above ground was -0.9 MPa across all trees, dropping to a mean of -1.5 MPa in mid-August when the top 1 m of the soil profile had no plant accessible moisture. Mean stomatal conductance and rates of maximum net photosynthesis decreased considerably in mid-August across all species. However, daily peak values of sap flow remained surprisingly constant over the whole period in Quercus petraea (Matt.) Liebl., and decreased to only about half of the early summer maxima in Fagus sylvatica L. and Carpinus betulus L. (stomatal down- regulation of flux). Although we detected no differences in most parameters between CO(2)-treated and control trees, predawn leaf water potential tended to be less negative in trees exposed to elevated [CO(2)]. Leaf longevity was greater in 2003 compared with the previous years, but the seasonal increase in stem basal area reached only about 75% of that in previous years. Our data suggest that the investigated tree species, particularly Q. petraea, did not experience severe water stress. However, an increased frequency of such exceptionally dry summers may have a more serious impact than a single event and would give Q. petraea a competitive advantage in the long run.

A unique mode of fertilization called "chalazogamy", whereby the pollen tube passes through the chalaza instead of the micropyle, is known in several species of derived genera in Casuarinaceae. In this paper we report the occurrence of chalazogamy in Gymnostoma ( G. poissonianum), the most primitive genus in the family. We also show that the pollen tube grows discontinuously from the stigma to ovules in about 3 months. At the time of pollination, the ovules have not yet formed in the ovary, and require a long time to develop. The pollen tube(s) lie in a zigzag line and are branched in the upper region of the style, and their growth is arrested there until the ovary develops further. Studies of the relevant literature further revealed discontinuous pollen-tube growth in relation to a prolonged period between pollination and fertilization, as well as chalazogamy, in Betulaceae, Juglandaceae and/or Fagaceae that are closely related to Casuarinaceae. This feature may have derived early in the evolution of Fagales.