Roberto Salomón

Universidad Politécnica de Madrid | UPM · Departamento de Sistemas y Recursos Naturales

Changes in vapour pressure deficit (VPD) can lead to the depletion and replenishment of stem water pools to buffer water potential variations in the xylem. Yet, the precise velocity at which stem water pools track environmental cues remains poorly explored. Nine eucalyptus seedlings grown in a glasshouse experienced high-frequency environmental osc...

To determine the optimal germination temperature for Pyrus ussuriensis seeds and whether they experienced the phenomenon of thermodormancy and its inciting factors, several germination tests were conducted using non-dormant P. ussuriensis seeds for comparison. The results showed that the highest germination rate of P. ussuriensis seeds was reached...

Stem respiration (RS) substantially contributes to the return of photo-assimilated carbon to the atmosphere and, thus, to the tree and ecosystem carbon balance. Stem CO2 efflux (ECO2) is often used as a proxy for RS. However, this metric has often been challenged because of the uncertain origin of CO2 emitted from the stem due to post-respiratory p...

The carbon isotope composition of respired CO2 (δ13CR) and bulk organic matter (δ13CB) of various plant compartments informs about isotopic fractionation and substrate of respiratory processes, crucial to advance understanding of carbon allocation in plants. Nevertheless, its variation across organs, species, and seasons remains poorly understood....

Tree stem respiration (RS ) is a substantial component of the forest carbon balance. The mass balance approach uses stem CO2 efflux and internal xylem fluxes to sum up RS , while the oxygen-based method assumes O2 influx as a proxy of RS . So far, both approaches have yielded inconsistent results regarding the fate of respired CO2 in tree stems, a...

Forests account for nearly 90 % of the world's terrestrial biomass in the form of carbon and they support 80 % of the global biodiversity. To understand the underlying forest dynamics, we need a long-term but also relatively high-frequency, networked monitoring system, as traditionally used in meteorology or hydrology. While there are numerous exis...

Pinus koraiensis is famous for its high-quality timber production all the way and is much more famous for its high value health-care nut oil production potential since 1990’s, but the less understanding of its reproduction biology seriously hindered its nut productivity increase. Exploring the effects of reproduction on nutrient uptake, allocation...

Nitrogen (N) is essential in regulating plant growth and biomass allocation. Plant N uptake and assimilation influence species adaptation and distribution, yet intra-specific comparisons across environmental gradients are scarce. In this study, white birch (Betula platyphylla) seedlings from three Chinese provenances spanning a wide latitude and te...

Elevated atmospheric CO2 concentration (eCO2) is expected to mitigate the adverse effects of moderate drought on leaf and whole-tree functioning. However, tree responses to eCO2 under severe drought and throughout the growing season remain largely unknown. One-year-old Populus tremula L. trees were grown in two controlled treatment chambers under a...

Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-tempor...

Stem respiration (RS) plays a crucial role in plant carbon budgets. However, its poor understanding limits our ability to model woody tissue and whole-tree respiration. A biophysical model of stem water and carbon fluxes (TReSpire) was calibrated on cedar, maple, and oak trees during spring and late summer. For this, stem sap flow, water potential,...

The timing of abiotic stress elicitors on wood formation largely affects xylem traits that determine xylem efficiency and vulnerability. Nonetheless, seasonal variability of elevated CO2 (eCO2) effects on tree functioning under drought remains largely unknown. To address this knowledge-gap, one-year-old aspen (Populus tremula L.) trees were grown u...

Cone development in conifer species is crucial to ensure sexual regeneration. A better understanding of carbon (C) source-sink relations at the branch level can guide strategies for improving resource allocation to reproduction. In particular, the evaluation of C relations between vegetative and reproductive branches is helpful to test whether tree...

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observatio...

The CO2 efflux from tree stem surfaces to atmosphere (RS) is an important component in the carbon (C) balance of forest ecosystems. Rising atmospheric carbon dioxide concentrations [CO2] are expected to stimulate RS, because of greater C assimilation and carbohydrate supply to stems under rising [CO2]. Growth respiration (Rg) and maintenance respir...

Elevated atmospheric CO2 concentration (eCO2) commonly stimulates net leaf assimilation, decreases stomatal conductance and has no clear effect on leaf respiration. However, effects of eCO2 on whole-tree functioning and its seasonal dynamics remain far more uncertain. To evaluate temporal and spatial variability in eCO2 effects, one-year-old Europe...

Determining the fate of CO2 respired in woody tissues is necessary to understand plant respiratory physiology and to evaluate CO2 recycling mechanisms. An aqueous ¹³C‐enriched CO2 solution was infused into the stem of 3‐4 m tall trees to estimate efflux and assimilation of xylem‐transported CO2 via cavity ring down laser spectroscopy and isotope ra...

At leaf level, elevated atmospheric CO2 concentration (eCO2) results in stimulation of carbon net assimilation and reduction of stomatal conductance. However, a comprehensive understanding of the impact of eCO2 at larger temporal (seasonal and annual) and spatial (from leaf to whole‐tree) scales is still lacking. Here, we review overall trends, mag...

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological,energy and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations...

Woody tissue photosynthesis (Pwt) contributes to the tree carbon (C) budget and generally stimulates radial stem growth under ambient atmospheric CO2 concentration (aCO2). Moreover, Pwt has potential to enhance tree survival under changing climates by delaying negative effects of drought stress on tree hydraulic functioning. However, the relevance...

Photosynthesis in woody tissues (Pwt) is less sensitive to water shortage than in leaves, hence, Pwt might be a crucial carbon source to alleviate drought stress. To evaluate the impact of Pwt on tree drought tolerance, woody tissues of 4‐m‐tall drought‐stressed Populus tremula trees were subjected to a light‐exclusion treatment across the entire p...

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1–5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration⁶. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on bio...

Stem water storage capacity and hydraulic capacitance (CS) play a crucial role in tree survival under drought‐stress. To investigate whether CS adjusts to increasing water deficit, variation in stem water content (StWC) was monitored in vivo for two years and related to periodical measurements of tree water potential in Mediterranean Quercus ilex t...

A substantial portion of locally respired CO2 in stems can be assimilated by chloroplast‐containing tissues. Woody tissue photosynthesis (Pwt) therefore plays a major role in the stem carbon balance. To study the impact of Pwt on stem carbon cycling along a gradient of water availability, stem CO2‐efflux (EA), xylem CO2‐concentration ([CO2]) and xy...

Mechanistic models of plant respiration remain poorly developed, especially in stems and woody tissues where measurements of CO2 efflux do not necessarily reflect local respiratory activity. We built a process‐based model of stem respiration that couples water and carbon fluxes at the organ level (TReSpire). To this end, sap flow, stem diameter var...

Research Highlights: Tree decline can alter soil carbon cycling, given the close relationship between primary production and the activity of roots and soil microbes. Background and Objectives: We studied how tree decline associated to old age and accelerated by land-use change and increased drought in the last decades, affects soil properties and s...

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration. While evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass gr...

Given the importance of carbon allocation for plant performance and fitness, it is expected that competition and abiotic stress influence respiratory costs associated to stem wood biomass production and maintenance. In this study, stem respiration (R) was measured together with stem diameter increment in adult trees of eight co-occurring species in...

Key message Efflux-based estimates of stem respiration in oak trees during the dormant season were biased by axial diffusion of locally respired CO 2 . Light-induced axial CO 2 diffusion along the stem due to woody tissue photosynthesis may lead to equivocal estimates of stem respiratory coefficients during the dormant season, which are generally u...

To quantify stem respiration (RS) under elevated CO2 (eCO2), stem CO2 efflux (EA) and CO2 flux through the xylem (FT) should be accounted for, because part of respired CO2 is transported upwards with the sap solution. However, previous studies have used EA as a proxy of RS, which could lead to equivocal conclusions. Here, to test the effect of eCO2...

Respired CO2 in woody tissues radially diffuses to the atmosphere or it is transported upward with the transpiration stream, making the origin of CO2 in stem CO2 efflux (EA) uncertain, which may confound stem respiration (RS) estimates. An aqueous 13C-enriched solution was infused into stems of Populus tremula L. trees, and real-time measurements o...

Long-term coppicing leads to the development of massive root systems. A disproportionate carbon investment in root maintenance has been pointed as a cause of the widespread decline of abandoned coppices. We aimed at assessing how coppicing has influenced root and shoot development and related carbon loss ascribed to maintenance of woody tissues in...

The balance between photosynthetic carbon (C) assimilation and C loss via respiration (R), emission of volatile organic compounds (VOCs), and rhizodeposition determines plant net primary production and controls to a large extent ecosystem C budgets. Compared to photosynthesis, the physiology, environmental control and ecological importance of proce...

Daytime decreases in temperature‐normalised stem CO 2 efflux ( E A _D ) are commonly ascribed to internal transport of respired CO 2 ( F T ) or to an attenuated respiratory activity due to lowered turgor pressure. The two are difficult to separate as they are simultaneously driven by sap flow dynamics. To achieve combined gradients in turgor pressu...

Reassimilation of internal CO 2 via woody tissue photosynthesis has a substantial effect on tree carbon income and wood production. However, little is known about its role in xylem vulnerability to cavitation and its implications in drought‐driven tree mortality. Young trees of Populus nigra were subjected to light exclusion at the branch and stem...

Genetic, dendrochronological and physiological studies are reviewed to investigate causes of tree stagnation of abandoned Quercus pyrenaica coppices. Tree decline – displayed by slow stem growth, branch dieback and scarce acorn production – has led to advice on the conversion of abandoned oak coppices into high forests by thinning. However, this pr...

Hydraulic modelling is a primary tool to predict plant performance in future drier scenarios. However, as most tree models are validated under non-stress conditions they may fail when water becomes limiting. To simulate tree hydraulic functioning under moist and dry conditions, the current version of a water flow and storage mechanistic model was f...

Spruce budworm (Choristoneura fumiferana Clem.) outbreaks cause extensive mortality and growth reductions throughout boreal forests in eastern North America. As tree vulnerability to defoliation remains partially unexplained by tree and stand attributes, we hypothesized that root grafting might attenuate the negative impact of severe defoliation in...

To accurately estimate stem respiration (RS), measurements of both carbon dioxide (CO2) efflux to the atmosphere (EA) and internal CO2 flux through xylem (FT) are needed because xylem sap transports respired CO2 upward. However, reports of seasonal dynamics of FT and EA are scarce and no studies exist in Mediterranean species under drought stress c...

Since a substantial portion of respired CO2 remains within the stem, diel and seasonal trends in stem CO2 concentration ([CO2]) are of major interest in plant respiration and carbon budget research. However, continuous long-term stem [CO2] studies are scarce, and generally absent in Mediterranean climates. In this study, stem [CO2] was monitored ev...

• Key message: Xylem and soil CO2 fluxes in coppiced oak forests increase with clonal size, suggesting larger expenditures of energy for root respiration. An imbalance between root demand and shoot production of carbohydrates may contribute to the degradation of abandoned coppices. • Context: Our understanding of root respiration is limited, parti...

La respiración del tronco es un proceso complejo; su regulación e implicaciones ecológicas están relativamente poco estudiadas. En este trabajo se ha cuantificado la velocidad de emisión de dióxido de carbono (CO 2) de los troncos de seis especies forestales al final de otoño, seleccionando individuos dominantes y suprimidos para su comparación. Co...

Tree trunks and roots have a variable and often important proportion of live cells. Respiration provides energy and carbon skeletons required by these living cells for their maintenance and proliferation. In the process of respiration, soluble sugars previously synthesized by leaves and young stems are oxidized and carbon dioxide (CO2) is produced...

Stem respiration plays a role in species coexistence and forest dynamics. Here we examined the intra- and inter-specific variability of stem CO2 efflux (E) in dominant and suppressed trees of six deciduous species in a mixed forest stand: Fagus sylvatica L., Quercus petraea [Matt.] Liebl, Quercus pyrenaica Willd., Prunus avium L., Sorbus aucuparia...

Seed recalcitrant behavior influences germination capacity determining establishment and colonization potential of seed desiccation sensitive species. The purpose of this study is to compare acorn recalcitrant behavior of different Iberian Quercus species. Seed lots of Q. suber, Q. canariensis, Q. faginea, Q. pyrenaica and two Q. ilex provenances w...

El presente proyecto ha sido llevado a cabo en la Zona de Reserva del Merendón (Municipalidad de San Pedro Sula, Honduras). Consiste en un estudio de la evolución de los usos de suelo presentes en la reserva: asentamientos humanos, agricultura tradicional, pastizales, terrenos forestales, matorral y suelos desnudos. Para la realización del estudio...