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1.
Isotopes Environ Health Stud ; : 1-21, 2021 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-34846959

RESUMO

Stable isotope analyses are the leading method for geographic origin determination, especially of plant-based agricultural products. Origin analysis is typically done by comparing a suspicious sample to reference materials with known geographic origin. Reference materials are usually collected at the species level, assuming different varieties of a species to have comparable isotope compositions within a given location. We evaluated whether different phenotypes that are expressed in different varieties of winter wheat (Triticum aestivum L.) influence the oxygen (δ18O) and hydrogen (δ2H) isotope composition of plant tissue water and organic compounds. We found that mean δ18O and δ2H values among winter wheat varieties did not differ significantly in leaf water, however, differed significantly in bulk dried grain tissue. The differences in bulk dried grain δ18O and δ2H values among varieties can be related to differences in phenotypic trait expression among varieties. Despite this substantial phenotypic variability, the overall variability of bulk dried grain δ18O and δ2H values among varieties was small (SD 0.54 ‰ for oxygen, 3.60 ‰ for hydrogen). We thus conclude that reference materials collected at the species level should be sufficient for geographic origin analysis of winter wheat and possibly other cereals using δ18O and δ2H values.

2.
Sci Rep ; 11(1): 17314, 2021 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-34453087

RESUMO

Fraudulent food products, especially regarding false claims of geographic origin, impose economic damages of $30-$40 billion per year. Stable isotope methods, using oxygen isotopes (δ18O) in particular, are the leading forensic tools for identifying these crimes. Plant physiological stable oxygen isotope models simulate how precipitation δ18O values and climatic variables shape the δ18O values of water and organic compounds in plants. These models have the potential to simplify, speed up, and improve conventional stable isotope applications and produce temporally resolved, accurate, and precise region-of-origin assignments for agricultural food products. However, the validation of these models and thus the best choice of model parameters and input variables have limited the application of the models for the origin identification of food. In our study we test model predictions against a unique 11-year European strawberry δ18O reference dataset to evaluate how choices of input variable sources and model parameterization impact the prediction skill of the model. Our results show that modifying leaf-based model parameters specifically for fruit and with product-independent, but growth time specific environmental input data, plant physiological isotope models offer a new and dynamic method that can accurately predict the geographic origin of a plant product and can advance the field of stable isotope analysis to counter food fraud.

3.
J Chem Ecol ; 47(10-11): 889-906, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34415498

RESUMO

How climate change will modify belowground tritrophic interactions is poorly understood, despite their importance for agricultural productivity. Here, we manipulated the three major abiotic factors associated with climate change (atmospheric CO2, temperature, and soil moisture) and investigated their individual and joint effects on the interaction between maize, the banded cucumber beetle (Diabrotica balteata), and the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora. Changes in individual abiotic parameters had a strong influence on plant biomass, leaf wilting, sugar concentrations, protein levels, and benzoxazinoid contents. Yet, when combined to simulate a predicted climate scenario (Representative Concentration Pathway 8.5, RCP 8.5), their effects mostly counter-balanced each other. Only the sharp negative impact of drought on leaf wilting was not fully compensated. In both current and predicted scenarios, root damage resulted in increased leaf wilting, reduced root biomass, and reconfigured the plant sugar metabolism. Single climatic variables modulated the herbivore performance and survival in an additive manner, although slight interactions were also observed. Increased temperature and CO2 levels both enhanced the performance of the insect, but elevated temperature also decreased its survival. Elevated temperatures and CO2 further directly impeded the EPN infectivity potential, while lower moisture levels improved it through plant- and/or herbivore-mediated changes. In the RCP 8.5 scenario, temperature and CO2 showed interactive effects on EPN infectivity, which was overall decreased by 40%. We conclude that root pest problems may worsen with climate change due to increased herbivore performance and reduced top-down control by biological control agents.

4.
Proc Natl Acad Sci U S A ; 118(26)2021 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-34162705

RESUMO

Hydrogen and oxygen isotope values of precipitation are critically important quantities for applications in Earth, environmental, and biological sciences. However, direct measurements are not available at every location and time, and existing precipitation isotope models are often not sufficiently accurate for examining features such as long-term trends or interannual variability. This can limit applications that seek to use these values to identify the source history of water or to understand the hydrological or meteorological processes that determine these values. We developed a framework using machine learning to calculate isotope time series at monthly resolution using available climate and location data in order to improve precipitation isotope model predictions. Predictions from this model are currently available for any location in Europe for the past 70 y (1950-2019), which is the period for which all climate data used as predictor variables are available. This approach facilitates simple, user-friendly predictions of precipitation isotope time series that can be generated on demand and are accurate enough to be used for exploration of interannual and long-term variability in both hydrogen and oxygen isotopic systems. These predictions provide important isotope input variables for ecological and hydrological applications, as well as powerful targets for paleoclimate proxy calibration, and they can serve as resources for probing historic patterns in the isotopic composition of precipitation with a high level of meteorological accuracy. Predictions from our modeling framework, Piso.AI, are available at https://isotope.bot.unibas.ch/PisoAI/.

5.
New Phytol ; 231(5): 1708-1719, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34028817

RESUMO

Hydrogen isotope ratios of plant lipids are used for paleoclimate reconstruction, but are influenced by both source water and biosynthetic processes. Measuring 2 H : 1 H ratios of multiple compounds produced by different pathways could allow these effects to be separated, but hydrogen isotope fractionations during isoprenoid biosynthesis remain poorly constrained. To investigate how hydrogen isotope fractionation during isoprenoid biosynthesis is influenced by molecular exchange between the cytosolic and plastidial production pathways, we paired position-specific 13 C-pyruvate labeling with hydrogen isotope measurements of lipids in Pachira aquatica saplings. We find that acetogenic compounds primarily incorporated carbon from 13 C2-pyruvate, whereas isoprenoids incorporated 13 C1- and 13 C2-pyruvate equally. This indicates that cytosolic pyruvate is primarily introduced into plastidial isoprenoids via glyceraldehyde 3-phosphate and that plastidial isoprenoid intermediates are incorporated into cytosolic isoprenoids. Probably as a result of the large differences in hydrogen isotope fractionation between plastidial and cytosolic isoprenoid pathways, sterols from P. aquatica are at least 50‰ less 2 H-enriched relative to phytol than sterols in other plants. These results provide the first experimental evidence that incorporation of plastidial intermediates reduces 2 H : 1 H ratios of sterols. This suggests that relative offsets between the 2 H : 1 H ratios of sterols and phytol can trace exchange between the two isoprenoid synthesis pathways.


Assuntos
Hidrogênio , Isótopos , Lipídeos , Esteróis , Terpenos
6.
Proc Natl Acad Sci U S A ; 118(16)2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33846261

RESUMO

Understanding the vulnerability of trees to drought-induced mortality is key to predicting the fate of forests in a future climate with more frequent and intense droughts, although the underlying mechanisms are difficult to study in adult trees. Here, we explored the dynamic changes of water relations and limits of hydraulic function in dying adults of Norway spruce (Picea abies L.) during the progression of the record-breaking 2018 Central European drought. In trees on the trajectory to drought-induced mortality, we observed rapid, nonlinear declines of xylem pressure that commenced at the early onset of xylem cavitation and caused a complete loss of xylem hydraulic conductance within a very short time. We also observed severe depletions of nonstructural carbohydrates, though carbon starvation could be ruled out as the cause of the observed tree death, as both dying and surviving trees showed these metabolic limitations. Our observations provide striking field-based evidence for fast dehydration and hydraulic collapse as the cause of drought-induced mortality in adult Norway spruce. The nonlinear decline of tree water relations suggests that considering the temporal dynamics of dehydration is critical for predicting tree death. The collapse of the hydraulic system within a short time demonstrates that trees can rapidly be pushed out of the zone of hydraulic safety during the progression of a severe drought. In summary, our findings point toward a higher mortality risk for Norway spruce than previously assumed, which is in line with current reports of unprecedented levels of drought-induced mortality in this major European tree species.

7.
Tree Physiol ; 41(5): 697-707, 2021 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-33079190

RESUMO

Drought alters allocation patterns of carbon (C) and nutrients in trees and eventually impairs tree functioning. Elevated soil nutrient availability might alter the response of trees to drought. We hypothesize that increased soil nutrient availability stimulates root metabolism and C allocation to belowground tissues under drought stress. To test this hypothesis, we subjected 3-year-old Pinus sylvestris L. saplings in open-top chambers during two subsequent years to drought using three different water treatments (100, 20 and 0% plant available water in the soil) and two soil nutrient regimes (ambient and nitrogen-phosphorus-potassium (N-P-K) fertilization corresponding to 5 g N m-2 year-1) and released drought thereafter. We conducted a 15N and 13C labeling experiment during the peak of the first-year drought by injecting 15N labeled fertilizer in the soil and exposing the tree canopies to 13C labeled CO2. The abundance of the N and C isotopes in the roots, stem and needles was assessed during the following year. Carbon uptake was slightly lower in drought-stressed trees, and extreme drought inhibited largely the N uptake and transport. Carbon allocation to belowground tissues was decreased under drought, but not in combination with fertilization. Our results indicate a potential positive feedback loop, where fertilization improved the metabolism and functioning of the roots, stimulating C allocation to belowground tissues. This way, soil nutrients compensated for drought-induced loss of root functioning, mitigating drought stress of trees.


Assuntos
Secas , Árvores , Carbono , Nitrogênio , Nutrientes , Raízes de Plantas , Solo
8.
Nature ; 589(7840): 76-81, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33208944

RESUMO

Adaptive radiation is the likely source of much of the ecological and morphological diversity of life1-4. How adaptive radiations proceed and what determines their extent remains unclear in most cases1,4. Here we report the in-depth examination of the spectacular adaptive radiation of cichlid fishes in Lake Tanganyika. On the basis of whole-genome phylogenetic analyses, multivariate morphological measurements of three ecologically relevant trait complexes (body shape, upper oral jaw morphology and lower pharyngeal jaw shape), scoring of pigmentation patterns and approximations of the ecology of nearly all of the approximately 240 cichlid species endemic to Lake Tanganyika, we show that the radiation occurred within the confines of the lake and that morphological diversification proceeded in consecutive trait-specific pulses of rapid morphospace expansion. We provide empirical support for two theoretical predictions of how adaptive radiations proceed, the 'early-burst' scenario1,5 (for body shape) and the stages model1,6,7 (for all traits investigated). Through the analysis of two genomes per species and by taking advantage of the uneven distribution of species in subclades of the radiation, we further show that species richness scales positively with per-individual heterozygosity, but is not correlated with transposable element content, number of gene duplications or genome-wide levels of selection in coding sequences.


Assuntos
Evolução Biológica , Ciclídeos/classificação , Ciclídeos/genética , Somatotipos/genética , África , Animais , Calibragem , Ciclídeos/anatomia & histologia , Feminino , Especiação Genética , Genômica , Heterozigoto , Arcada Osseodentária/anatomia & histologia , Lagos , Masculino , Fenótipo , Fatores de Tempo
9.
Proc Natl Acad Sci U S A ; 117(40): 24885-24892, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32958662

RESUMO

Drought alters carbon (C) allocation within trees, thereby impairing tree growth. Recovery of root and leaf functioning and prioritized C supply to sink tissues after drought may compensate for drought-induced reduction of assimilation and growth. It remains unclear if C allocation to sink tissues during and following drought is controlled by altered sink metabolic activities or by the availability of new assimilates. Understanding such mechanisms is required to predict forests' resilience to a changing climate. We investigated the impact of drought and drought release on C allocation in a 100-y-old Scots pine forest. We applied 13CO2 pulse labeling to naturally dry control and long-term irrigated trees and tracked the fate of the label in above- and belowground C pools and fluxes. Allocation of new assimilates belowground was ca. 53% lower under nonirrigated conditions. A short rainfall event, which led to a temporary increase in the soil water content (SWC) in the topsoil, strongly increased the amounts of C transported belowground in the nonirrigated plots to values comparable to those in the irrigated plots. This switch in allocation patterns was congruent with a tipping point at around 15% SWC in the response of the respiratory activity of soil microbes. These results indicate that the metabolic sink activity in the rhizosphere and its modulation by soil moisture can drive C allocation within adult trees and ecosystems. Even a subtle increase in soil moisture can lead to a rapid recovery of belowground functions that in turn affects the direction of C transport in trees.


Assuntos
Carbono/metabolismo , Pinus sylvestris/metabolismo , Solo/química , Árvores/metabolismo , Carbono/análise , Mudança Climática , Secas , Ecossistema , Florestas , Pinus sylvestris/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Rizosfera , Árvores/crescimento & desenvolvimento , Água/análise , Água/metabolismo
10.
Rapid Commun Mass Spectrom ; 34(19): e8854, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32511807

RESUMO

RATIONALE: The oxygen isotopic composition (here shown as the δ18 O value) of soluble sugars in leaves and phloem tissue holds valuable information about plant functions in response to climatic changes. However, δ18 O analysis of sugars is prone to error, and thoroughly tested methods are lacking. METHODS: We performed three experiments to test if sample preparation modifies the δ18 O values of sugars. In experiment 1, we tested the effects of oven-drying versus freeze-drying, whereas in experiment 2 we focused on the extraction and purification of leaf sugars. In experiment 3, we investigated the exudation and purification of twig phloem sugars as a function of exudation time and different ethylenediaminetetraacetic acid (EDTA) exudation media. RESULTS: Freeze-drying produced more consistent δ18 O values than oven-drying for sucrose but not for phloem sugars. The extraction and purification of leaf sugars can be performed without a significant modification of their δ18 O values; yet the purified leaf and phloem sugars possessed higher δ18 O values than the fraction of water-soluble compounds. Moreover, the exudation time significantly modulated the δ18 O values of phloem sugars, which is probably related to changes in the sugar composition. The addition of EDTA did not improve the determination of the δ18 O values of phloem sugars. CONCLUSIONS: We show that the sample preparation of plant sugars for the reliable determination of δ18 O values requires a strict protocol, which is described in this paper. For phloem sugar, we recommend a maximum exudation time of 1 h to reduce the degradation of sucrose and minimise oxygen isotope exchange reactions between the resulting hexoses and water.


Assuntos
Técnicas de Química Analítica/métodos , Isótopos de Oxigênio/análise , Floema/química , Folhas de Planta/química , Açúcares/isolamento & purificação , Ácido Edético , Açúcares/análise , Açúcares/química
11.
PLoS One ; 15(2): e0228993, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32053664

RESUMO

Bioirrigation has been defined as the transfer of hydraulically lifted water by a deep-rooted plant to a neighbouring shallow-rooted plant which cannot access deep soil moisture. In this study, we tested if facilitative effects of bioirrigation or the competition for water dominate the interaction of two intercropped plants-deep-rooted pigeon pea (PP) and shallow-rooted finger millet (FM) before and during a drought. Additionally, we tested how the presence of a common mycorrhizal network (CMN) affects the balance between facilitative (i.e. bioirrigation) and competitive interactions between two intercropping species. Our results show that PP can indeed promote the water relations of FM during a drought event. Specifically, stomatal conductance in FM controls dropped to low values of 27.1 to 33.6 mmol m-2s-1, while FM in intercropping treatments were able to maintain its stomatal conductance at 60 mmol m-2s-1. In addition, the presence of PP reduced the drought-induced foliar damage and mortality of FM. The observed facilitative effects of PP on FM were partially enhanced by the presence of a CMN. In contrast to the facilitative effects under drought, PP exerted strong competitive effects on FM before the onset of drought. This hindered growth and biomass production of FM when intercropped with PP, an effect that was even enhanced in the presence of a CMN. The results from our study thus indicate that in intercropping, deep-rooted plants may act as "bioirrigators" for shallow-rooted crops and that a CMN can promote these facilitative effects. However, the interspecific competition between the intercropped plants under conditions of abundant moisture supply can be strong and are enhanced by the presence of a CMN. In more general terms, our study shows that the extent by which the antagonistic effects of facilitation and competition are expressed in an intercropping system strongly depends on the availability of resources, which in the case of the present study was water and the presence of biotic interactions (i.e. the presence of a CMN).


Assuntos
Secas , Milhetes/fisiologia , Ervilhas/metabolismo , Ervilhas/fisiologia , Raízes de Plantas/metabolismo , Raízes de Plantas/fisiologia , Água/metabolismo , Biomassa , Milhetes/metabolismo
12.
Plant Cell Environ ; 43(2): 510-523, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31732962

RESUMO

The 18 O signature of atmospheric water vapour (δ18 OV ) is known to be transferred via leaf water to assimilates. It remains, however, unclear how the 18 O-signal transfer differs among plant species and growth forms. We performed a 9-hr greenhouse fog experiment (relative humidity ≥ 98%) with 18 O-depleted water vapour (-106.7‰) on 140 plant species of eight different growth forms during daytime. We quantified the 18 O-signal transfer by calculating the mean residence time of O in leaf water (MRTLW ) and sugars (MRTSugars ) and related it to leaf traits and physiological drivers. MRTLW increased with leaf succulence and thickness, varying between 1.4 and 10.8 hr. MRTSugars was shorter in C3 and C4 plants than in crassulacean acid metabolism (CAM) plants and highly variable among species and growth forms; MRTSugars was shortest for grasses and aquatic plants, intermediate for broadleaf trees, shrubs, and herbs, and longest for conifers, epiphytes, and succulents. Sucrose was more sensitive to δ18 OV variations than other assimilates. Our comprehensive study shows that plant species and growth forms vary strongly in their sensitivity to δ18 OV variations, which is important for the interpretation of δ18 O values in plant organic material and compounds and thus for the reconstruction of climatic conditions and plant functional responses.


Assuntos
Isótopos de Oxigênio/metabolismo , Folhas de Planta/metabolismo , Plantas/metabolismo , Água/metabolismo , Oxigênio/metabolismo , Desenvolvimento Vegetal , Poaceae/metabolismo , Chuva , Árvores/metabolismo , Volatilização , Tempo (Meteorologia)
13.
Oecologia ; 191(2): 389-396, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31435756

RESUMO

Habitats with fluctuating resource conditions pose specific challenges to plants, and they often favor a small subset of species that includes exotic invaders. These species must possess a superior ability to capitalize on resource pulses through faster resource uptake or greater resource-use efficiency. We addressed this question in an experiment with invasive knotweed, a noxious invader of temperate ecosystems that is known to benefit from nutrient fluctuations. We used stable isotopes to track the uptake and use efficiency of a nitrogen pulse in competition pairs between knotweed and five native competitors. We found that nitrogen pulses indeed promoted knotweed invasion and that this is explained by a superior efficiency in turning the taken-up extra nitrogen into biomass, rather than capturing an overproportional share of the nitrogen. Thus, temporary increases in nutrient availability might help knotweed to invade natural environments, such as river banks or nitrogen-polluted margins and wastelands, where nutrient fluctuations occur. Our experiment shows that resource-use efficiency can drive invasion under fluctuating resource conditions, and that stable isotopes help to understand these processes.


Assuntos
Nitrogênio , Polygonum , Biomassa , Ecossistema , Plantas
15.
Plant Cell Environ ; 42(5): 1674-1689, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30536787

RESUMO

Conifers growing at high elevations need to optimize their stomatal conductance (gs ) for maximizing photosynthetic yield while minimizing water loss under less favourable thermal conditions. Yet the ability of high-elevation conifers to adjust their gs sensitivity to environmental drivers remains largely unexplored. We used 4 years of sap flow measurements to elucidate intraspecific and interspecific variability of gs in Larix decidua Mill. and Picea abies (L.) Karst along an elevational gradient and contrasting soil moisture conditions. Site- and species-specific gs response to main environmental drivers were examined, including vapour pressure deficit, air temperature, solar irradiance, and soil water potential. Our results indicate that maximum gs of L. decidua is >2 times higher, shows a more plastic response to temperature, and down-regulates gs stronger during atmospheric drought compared to P. abies. These differences allow L. decidua to exert more efficient water use, adjust to site-specific thermal conditions, and reduce water loss during drought episodes. The stronger plasticity of gs sensitivity to temperature and higher conductance of L. decidua compared to P. abies provide new insights into species-specific water use strategies, which affect species' performance and should be considered when predicting terrestrial water dynamics under future climatic change.


Assuntos
Estômatos de Plantas/fisiologia , Transpiração Vegetal/fisiologia , Traqueófitas , Adaptação Fisiológica , Secas , Larix/fisiologia , Pinus/fisiologia , Solo , Temperatura , Traqueófitas/fisiologia , Água/fisiologia
16.
PLoS One ; 13(12): e0209031, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30576332

RESUMO

Soil respiration plays a crucial role in global carbon cycling. While the response of soil respiration to abiotic drivers like soil temperature and moisture is fairly well understood, less is known about the effects of biotic drivers, such as plant above- and belowground productivity or plant diversity, and their interactions with abiotic drivers on soil respiration. Thus, current predictions of soil respiration to summer droughts might miss relevant biological drivers and their interactions with abiotic drivers. Since drought events are expected to increase in Central Europe in the future, we simulated early summer drought using rainout shelters at 19 grassland sites, which differed in plant productivity and species richness in central Germany in 2002 and 2003. We tested the potentially interacting effects of drought with biotic drivers, i.e. annual above-ground productivity, species richness and root biomass, on the drought response of soil respiration in temperate grasslands. In both years, drought led to a significant reduction in soil respiration. The drought-induced reduction in soil respiration was largely driven by the reduction in above-ground productivity in response to drought. The extent of the drought response of soil respiration was dependent on the species richness level of the site and this interacting effect was explainable by the variation in root biomass (root biomass and species richness were positively correlated). Our findings highlight the importance of biotic drivers for the quantification of the drought response of soil respiration in grasslands.


Assuntos
Secas , Poaceae/crescimento & desenvolvimento , Solo/química , Biomassa , Ciclo do Carbono , Pradaria , Poaceae/metabolismo , Estações do Ano , Temperatura
17.
Sci Rep ; 8(1): 15006, 2018 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-30301936

RESUMO

The water status of transpiring tree crowns depends on a hydraulic continuum from the soil matrix around roots to the sub-stomatal cavity of leaves, with a multitude of hydraulic resistances along this path. Although the stem xylem path may not be the most critical of these resistances, it had been suggested that a >50% interruption of that path by drought-stress-induced embolization (air filling) of conduits is critical for tree survival. Here we show that cutting the sapwood of mature, 35 m tall trees in half hardly affects crown water status and transpiration. Counter expectation, this first adult tree sapwood interception experiment revealed that shoot water potential in the canopy (assessed by using a 45 m canopy crane) either remained unaffected (spruce) or became less negative (beech), associated with small reductions in leaf diffusive conductance for water vapour. We conclude that the stem xylem of these trees has a large overcapacity and the tree hydraulics debate requires a critical re-visitation.


Assuntos
Fenômenos Fisiológicos Vegetais , Transpiração Vegetal , Árvores , Folhas de Planta , Raízes de Plantas , Xilema
18.
New Phytol ; 219(4): 1283-1299, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29862531

RESUMO

Trees play a key role in the global hydrological cycle and measurements performed with the thermal dissipation method (TDM) have been crucial in providing whole-tree water-use estimates. Yet, different data processing to calculate whole-tree water use encapsulates uncertainties that have not been systematically assessed. We quantified uncertainties in conifer sap flux density (Fd ) and stand water use caused by commonly applied methods for deriving zero-flow conditions, dampening and sensor calibration. Their contribution has been assessed using a stem segment calibration experiment and 4 yr of TDM measurements in Picea abies and Larix decidua growing in contrasting environments. Uncertainties were then projected on TDM data from different conifers across the northern hemisphere. Commonly applied methods mostly underestimated absolute Fd . Lacking a site- and species-specific calibrations reduced our stand water-use measurements by 37% and induced uncertainty in northern hemisphere Fd . Additionally, although the interdaily variability was maintained, disregarding dampening and/or applying zero-flow conditions that ignored night-time water use reduced the correlation between environment and Fd . The presented ensemble of calibration curves and proposed dampening correction, together with the systematic quantification of data-processing uncertainties, provide crucial steps in improving whole-tree water-use estimates across spatial and temporal scales.


Assuntos
Reologia , Temperatura , Traqueófitas/fisiologia , Incerteza , Calibragem , Modelos Lineares , Especificidade da Espécie , Fatores de Tempo , Árvores/fisiologia , Água
19.
New Phytol ; 219(4): 1300-1313, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29888480

RESUMO

We assessed how the seasonal variability of precipitation δ2 H and δ18 O is propagated into soil and xylem waters of temperate trees, applied a hydrological model to estimate the residence time distribution of precipitation in the soil, and identified the temporal origin of water taken up by Picea abies and Fagus sylvatica over 4 yr. Residence times of precipitation in the soil varied between a few days and several months and increased with soil depth. On average, 50% of water consumed by trees throughout a year had precipitated during the growing season, while 40% had precipitated in the preceding winter or even earlier. Importantly, we detected subtle differences with respect to the temporal origin of water used by the two species. We conclude that both current precipitation and winter precipitation are important for the water supply of temperate trees and that winter precipitation could buffer negative impacts of spring or summer droughts. Our study additionally provides the means to obtain realistic estimates of source water δ2 H and δ18 O values for trees from precipitation isotope data, which is essential for improving model-based interpretations of δ18 O and δ2 H values in plants.


Assuntos
Fagus/fisiologia , Florestas , Marcação por Isótopo , Picea/fisiologia , Solo/química , Água/metabolismo , Deutério , Isótopos de Oxigênio , Raízes de Plantas/metabolismo , Chuva , Análise de Regressão , Fatores de Tempo , Xilema/fisiologia
20.
Tree Physiol ; 38(7): 941-952, 2018 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-29554370

RESUMO

Direct evidence for the link between stem diameter variations (SDV) and the daily canopy water status, i.e., daily water potentials (Ψ), is rare, particularly for tall trees. It thus remains unclear up to what degree SDV readings are useful to estimate daily canopy Ψ. We measured SDV with point dendrometers at the stem base of tall, mature individuals of six European forest tree species in a near-natural temperate forest and compared them with daily canopy Ψ during the growing seasons of 2014 (wet) and 2015 (dry). Stem diameter variations were de-trended for growth with two different approaches leading to the so-called tree water deficit (TWD). We found that midday Ψ can be predicted from TWD, independent of the growth-de-trending procedure to obtain TWD from SDV. Further, daily TWD was a better indicator for daily midday Ψ, particularly under dry conditions, than maximum daily shrinkage, another common quantity derived from SDV. Based on data from six temperate tree species, we conclude that TWD measured at the stem base is a consistent proxy for daily canopy midday Ψ of tall trees over the entire range of measured conditions.


Assuntos
Caules de Planta/anatomia & histologia , Árvores/anatomia & histologia , Água , Europa (Continente) , Caules de Planta/fisiologia , Transpiração Vegetal , Árvores/fisiologia
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