Another example we show is the ambient median NO mixing ratio Figure 6A and its dependency on height. One of the natural sources of NO is the soil emission Kesik et al. At the same time NO2 Figure 6B remained almost constant at both heights indicating that larger scale processes determine its atmospheric mixing ratio.
Binned monthly median CO2 A and water vapour B mixing ratios are for the period August to July , measured at 30 m height. While median CO2 mixing ratios vary around ppm lower in summer, higher in winter the photosynthetic activity of the trees lead to higher variability during the growing season. Water vapour follows to large extent the air temperature Fig. Joonis 4. CO2 A ja veeauru B kontsentratsioonide kuude mediaanid vaatlusperioodil august kuni juuli moodetuna Apna mastis 30 meetri korguselt. Kui CO2 kontsentratsioon ohus varieerub ppm lahedal suvel on madalam ja talvel korgem , siis puude fotosunteetiline aktiivsus suuren-dab kasvuperioodi jooksul kuusisest varieeruvust.
Veeauru kontsentratsioon ohus jargib valdavalt ohutemperatuuri muutumisi vt joonis 3C ning on madalaim kulmadel talvekuudel. Figure 5. Example of the seasonal dynamic of monthly median ozone mixing ratios measured at 30 m height above the canopy A. Besides the seasonal dynamic, ozone changes according to the energy input by sunlight on a diurnal scale B.
Comparing the diurnal dynamics for different seasons the impact of light availability, temperature and trace gases participating the photochemical ozone formation process are visible. Joonis 5. Osooni kontsentratsioon oopaevasel skaalal muutub olenevalt paikesekiirgusest B. Figure 6. Example of differences in NO and NO2 mixing ratios as dependent on the height of the measurement 2 m vs. NO concentrations are more influenced by the local situation within-canopy position, turbulence conditions, radiation intensity, concentrations of reactive trace gases, emissions from soil processes.
NO2, on the contrary, seems to be influenced by atmospheric larger-scale processes. Joonis 6. For volatile organic compounds VOC we characterized their spatial and seasonal variability in ambient air Noe et al. Especially for ambient monoterpene concentrations that play a role in the formation and growth of aerosol particles Spracklen et al.
Isoprene, monoterpene and sesquiterpene emissions from the vegetation surface leaves and needles where measured using branch enclosure cuvettes Noe et al. Energy fluxes are assessed by measuring the total and diffuse direct and reflected solar radiation, the photo-synthetically active radiation and the latent heat in the atmosphere. Fluxes of matter in the form of water vapour, biomass. The measurement techniques for particulate matter aerosol particles fluxes are under development see section: Atmospheric particulate matter and air ions and currently only vertical gradients of particle concentration can be estimated.
Prior Eddy flux measurements root back to Noe et al. Carried out on 30 m and 70 m heights, the footprint areas covered by the flux measurements at the m mast reach up to 1. Within these fetch areas, the protected primeval forest quarter and different forest site types under different forest management regimes are located.
This heterogeneity provides the possibility to study changes in carbon. Figure 7. Negative fluxes denote the carbon uptake by the forest within the fetch area and positive fluxes denote the ecosystem respiration flux. The error bars are standard deviations of the monthly mean CO2 fluxes to visualize the spread of the data. Overall, it is visible that the higher 70 m measurements, corresponding to a distance from the mast of up to 4. The larger fetch and less impact of forest floor respiration fluxes and canopy shape lead to a "smoother" flux result.
Joonis 7. Negatiivsed voovaartused on iseloomulikud metsaokosusteemi susiniku sidumisele ning positiivne voog on iseloomulik okosusteemi aktiivse hingamise voogudele. Usaldusnivooga on esitatud kuude keskmiste CO2 voogude standardhalved. Jooniselt on naha, et korgemalt 70 m tehtud mootmised vastavad arvestuslikule neeluala ulatusele kuni 4,5 km, neid ei mojuta kohalikud mojutused niivord kui madalamalt 30 m tehtud mootmised, mis vastavad neeluala ulatusele kuni 1,5 km.
Mida su-urem on neeluala ulatus ning vaiksem mulla ja alustaimestiku hingamise voo moju, seda uhtlasem on moodetud voog. Measurements of air ion and aerosol particles size distributions during last three years provided a valuable database for studies of new particle formation and growth properties of secondary organic aerosol particles SOA in the atmosphere.
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These measurements Figures. This database enables statistical classification of the NPF-events in accordance with characteristic shapes of the aerosol and air ion size distribution evolution Hirsikko et al, , ; Manninen et al. The most pronounced NPF-event, with a typical diurnal behaviour of appearance of newly formed particles followed by their. Figure 8.
Examples of the classification of new particle formation events obtained from the data recorded in using classification scheme developed by Hirsikko et al. Joonis 8. Uute aineosakeste tekke klassifitseerimise naited oopaevaste mootekaikude mootmisandmetel aastast Hirsikko et al. Kulmala et al, , , In these environments, sulphuric acid and possibly stabilizing bases together with extremely low volatile organic vapours are responsible for the formation and growth of the aerosol particles Kulmala et al. One specificity of our data is that it includes also cluster ion data and therefore, it enables to study the new particle formation by ion-induced nucleation Laakso et al.
However, these events need future investigations and experimental proof to make any final conclusions. The data from SMEAR Estonia has been used for a comparative analysis of the aerosol nucleation burst events in widely spaced stations in Jarveslja, Estonia and in Hyytiala and Varrio, Finland during an intensive course held in Autumn in Jarvselja Kulmala et al, a. There are two different types of plots depending on when they were established.
Within the fetch area of the atmospheric measurement mast, there are a few old permanent experimental plots established long before the SMEAR station became functional. There are also forest monitoring plots established with the purpose to cover the footprint area of the station.
Old long-term monitoring plots are located in close vicinity of the Apna site. The establishment of forest monitoring plots specifically for SMEAR Estonia started in at the Liispollu site and continued in at the newly established Apna. Liispollu plots have been re-measured once in for growth monitoring. For Apna a plot grid was established to ensure consistent point descriptions within the footprint area.
Soil temperature and moisture are the important drivers that control many ecosystem processes Davidson et al. Being the biggest source of carbon emitted back to the atmosphere, the soil CO2 fluxes Figure 10A are needed to assess the ecosystems carbon budget in combination with the Eddy covariance fluxes. Soil water content and soil temperature are the major driving forces of the soil respiratory activity Figures 10B and 10C. While some soil variables had been available since , these data correspond to shorter campaign measurements and did not cover a full vegetation cycle.
Since , the situation has changed and the soil characteristics have been measured on a regular basis through the year. Figure 9. All measurements on the SMEAR Estonia footprint area follow a systematic grid, where the basic measurement unit is circular plot. Both stand, understory and field flora A and tree storey B measurements are carried out spatially explicitly. Joonis 9. Puistu alustaimestiku mootekohad A ja uksik-puud B kaardistatakse ruumiliselt.
Figure Soil CO2 flux was measured with the manual chambers, and soil water content and soil temperature were measured at the soil depth of 5 cm. Joonis Mulla CO2 voogude mootmised on tehtud manuaal-kambritega ning mulla niiskusesisaldus ja temperatuur on moodetud 5 cm sugavuselt. Long-term, comprehensive and continuous integrated soil-plant-atmosphere measurements are of key importance for understanding the dynamics of natural ecosystems and for gaining an insight into the feedback mechanisms between the ecosystems and the environment Kulmala et al.
Furthermore, there are increasing efforts to integrate the long-term measurement sites into a worldwide consortium with standardized measurement protocols and data quality controls, e. SMEAR Estonia covers an important part of Earth biomes, hemiboreal forest, and therefore significantly enlarges the coverage of worldwide networks e.
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The SMEAR Estonia station gives opportunity to study diverse forestry management activities and forest type specific differences, e. Already the efforts of building the station led to increased possibilities for national and international cooperation. Further development of the station will increase the set of measurements, improve the quality of observations, and ensure the use of the data produced in research and policymaking.
Increasing the level of automation allows for long-term comprehensive measurements and increases the impact of Estonian science on international level and thereby providing possibilities to contribute to world-class research activities. Aalto, P. Physical characterization of aerosol particles during nucleation events.
Ahti, T. Vegetation zones and their sections in northwestern Europe. Atkinson, R. Part A. General Topics, 24, Bourtsoukidis, E. Chen, X. Responses of the atmospheric concentration of radon to the vertical mixing and spatial transportation.
Rennenberg, H. (Heinz) [WorldCat Identities]
Curiel Yuste, J. Micro-bial soil respiration and its dependency on carbon inputs, soil temperature and moisture. Davidson, E. Soil water content and temperature as independent or confounded factors controlling soil respiration in a temperate mixed hardwood forest. Ehn, M.
A large source of low-volatility secondary organic aerosol. Factors influencing the contribution of ion-induced nucleation in a boreal forest, Finland. Hari, P. A comprehensive network of measuring stations to monitor climate change. Structure, radiation and photosynthetic production in coniferous stands. Nonlinear dependence of photosynthetic rate on irradiance and its consequences for estimates of the amount of saccharides formed. Conceptual design of a measurement network of the global change. Hewitt, C. Ground-level ozone influenced by circadian control of isoprene emissions.
Hirsikko, A. Identification and classification of the formation of intermediate ions measured in boreal forest. Atmospheric ions and nucleation: a review of observations. Mobility spectrum of air ions at Tahkuse Observatory. Bursts of intermediate ions in atmospheric air. Statistical characterization of air ion mobility spectra at Tahkuse Observatory: Classification of air ions. Cambridge University Press, Cambridge.
Kadastik, E. Estonian research infrastructures roadmap Eesti teaduse infra-struktuuride teekaart Haridus- ja Teadus-ministeerium, Tartu. In Estonian. Kent, M. Kerminen, V. Cloud condensation nuclei production associated with atmospheric nucleation: a synthesis based on existing literature and new. Kesik, M. Kiviste, A. Kratz, T. Kull, O. Shoot structure and growth along a vertical profile within a Populus-Tilia canopy.
Kulmala, M. The Legacy of Finnish-Estonian air ion and aerosol workshop. V, Smith, J. Mentel, T. Direct observations of atmospheric aerosol nucleation. CO2-induced terrestrial climate feedback mechanism: From carbon sink to aerosol source and back. Toward Direct Measurement of Atmospheric Nucleation. A new feedback mechanism linking forests, aerosols, and climate.
Finnish-Estonian air ion and aerosol workshops. University of West Hungary Press, Sopron, Laakso, L. Kinetic nucleation and ions in boreal forest particle formation events. Laan, B. Estimating the origin of background aerosol pollution in Estonia. Leaves that exposed to south and west directions were found to exhibit twice as high net assimilation In this case, lowest net assimilation rates were measured in west exposed 3.
Adaptations of the photosynthetic apparatus to light intensities are explaining that behavior Niinemets et al. Directions given in the bars refer to the direction in which the leaves measured have been exposed. Error bars denote standard errors. Although P. The expositions of the branches measured have been West, South and North. Net assimilation rates of B. For B. Another typical pattern in forest ecosystems are gaps due to fallen or removed trees.
We measured also in such gap situations. The net assimilation rate of Betula leaves were very variable, ranging between 5. Of the species measured in the understory 3 species shown in Table 6 , Tilia had higher net assimilation rates than the two Betula species. The gap offered a niche for those species, which were not found in the understory, like Quercus robur and Populus tremula. In general, the canopy discriminates the irradiative energy input strongly. Manual chamber measurements resulted in a mean soil CO 2 efflux of 3. The average air temperature recorded on the soil surface was Mean soil CO 2 efflux was 4.
Average volumetric soil moisture was The average daytime temperature from h was very stable at Results of the additional single measurements are presented in Table 7. In both cases, manual and automatic chamber measurements, we found rather stable emissions over the course of the day which is in accordance with the stable soil temperature during the measurements. As the chambers have been operated under shade conditions in the understory, the average temperature change during measurements have been 0.
The data, obtained on both plots, give hints about the plasticity which occurs through changes in soil type and canopy structure and may be reflected by substantial changes in soil CO 2 efflux. Even though soil respiration is known to correlate positive with soil temperature which is influenced by soil moisture and PAR Lloyd and Taylor, ; Ruehr and Buchmann, , we found only weak correlations which is mainly caused by the limited number of the measurements during the campaign in Time of measuring was between 12—17 h.
Comparison of the two methods of continuous measurement cycles Fig. Even though, the mean daytime air temperature was by 5. Given the temperature dependency of soil respiration, this is a contradictory result, which may be reconciled based on differences in the sampling and analysis techniques employed. Among the technical explanations, site heterogeneity, different depth or the time of collar installation might have played a role as well. The inset shows a one day data set of soil respiration fluxes measured with the manual chamber system. Given the differences in footprint between both methods Baldocchi, , the random and systematic uncertainties associated with each method Hollinger and Richardson, , and finally the differing time frames during which these measurements were made, we consider these results as very encouraging.
Fluxes of methane and nitrous oxide were measured using the manual chamber system. We found negative methane fluxes during the campaign in , which indicates a possible net consumption of CH 4 in soil Chan and Parkin, ; Mori et al. It is further known, that dry soils are sinks and wet soils act as sources for atmospheric methane as well as that tree species affect the source and sink properties of forest soils Saari et al.
The inverse relationship between the CO 2 and CH 4 fluxes may support the idea of methane consumption by methanotrophic bacteria in the soil as a reason for the flux.
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We found daytime nitrous oxide emissions that averaged 0. N 2 O is mainly produced by denitrification process in soils. In deeper layers, given wet and anaerobic conditions denitrification may occur frequently Ball et al. In our groundwater influenced study site, the soil temperature should positively correlate with the N 2 O efflux Schindlbacher et al. Due to the limited number of measurements we observed only a weak positive correlation. While this is likely to be correct, we strongly believe that the two measurement campaigns already unearthed a number of encouraging results which may serve as building blocks upon which we aim to continue research at this site.
Combining these two lines of information, experimental field data and simulation analysis, will be critical in order to finally assess the role this and similar forests in this region are playing in modulating climate and how sensitive these ecosystems are to likely future climate. We further thank Endla Reintam for identifying soil types, Sandra Metslaid and Ahto Kangur for their data on forest description and the experimental design of the circular sample plots and Toomas Tamm for comments on the soil water regime.
We further thank the unknown reviewers for their helpful and encouraging comments. Financial support by the European Science Foundation grant Vocbas ref. We describe the concentration change in time by the flux from soil into a chamber by an exponential relation Pedersen et al. To calculate the molar flow F c , we apply:.
We further assumed that the pressure stayed constant throughout the sampling period and corrected for the temperature changes by multiplying equation 2 with:. We conducted also the BVOC sampling by usage of the manual chamber system. Rearranging equation 1 and application of the logarithm leaded to:. While the amounts of aliquot we took from the manual chambers volume 23 L with the syringes are neglectable if compared to the total chamber volume that is not true in case of the BVOC measurements where we took an aliquot of five liters per sample over a period of 20 minutes.
To prevent underpressure we let stream in background air to the bottom of the chamber with a small tube while sampling and by that changing instantaneously the concentration within the chamber. That resembles the open flow chamber system as described by Pumpanen et al. Integration of equation 5 and rearranging with respect to Q leads to a timely description of the flux added while sampling:.
With that, we could account for the portion of soil efflux that have been generated during the 20 minutes sampling period and have been added to chamber. The automatic chamber system measured the fluxes directly relative to a CO 2 free air standard and resembles in its operation therefore also a closed static system Pumpanen et al. The software of the automatic chamber system used the method as given by Pedersen et al. Measurements that did not reach a stable fluxes have been discarded by the system.
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Figure 1. Table 1 Overview on the measurement series conducted throughout both campaigns. Table 2 Description of the dominant canopy layer of sample plots at the atmosphere - forest measurement campaign site.
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Figure 2. Eddy fluxes upper panel and storage fluxes lower panel. Table 3 Mean values and standard errors of the ecosystem CO 2 fluxes August Figure 3. Comparison between the ozone mixing ratios above and below the canopy. Figure 4. Relationship between the wind direction and the mixing ratios of nitrogen oxides NO and NO 2 and ozone during the measurement campaign in Darker color refers to higher mixing ratios.
Figure 5. Monoterpene emissions from the main tree species B. Figure 6. Photosynthetic net assimilation rate of B. Figure 7. Daily mean soil respiration measured over 3 days during the campaign by the automatic chamber system. Appendix 1 We describe the concentration change in time by the flux from soil into a chamber by an exponential relation Pedersen et al.
References Arold I. Atkinson R. Atmospheric Environment. Atkinson R, Arey J. Gas-phase tropospheric chemistry of biogenic volatile organic compounds: a review. Baldocchi DD. Flux footprints under forest canopies. Boundary-Layer Meteorology. Measuring biosphere-atmosphere exchanges of biologically related gases with micrometeorological methods.
Soil Till. Spruce forests Norway and Sitka Spruce : Carbon and water fluxes, balances, ecological and ecophysiological determinants. In: Valentini R, editor. Fluxes of carbon, water and energy of European forests, Ecological Studies. Springer Verlag; Berlin: Nucleation and Atmospheric Aerosols. Borken W, Beese F. Methane and nitrous oxide fluxes of soils in pure and mixed stands of European beech and Norway spruce. European Journal of Soil Science. Coniferous forests Scots and Maritime Pine : Carbon and water fluxes, balances, ecological and ecophysiological determinants.
Microbial consumption of atmospheric isoprene in a temperate forest soil. Applied and Environmental Microbiology. Gas Chromatography-mass spectrometry method for determination of monoterpene and sesquiterpene emissions from stressed plants. Studia Universitatis Babes-Bolyai, Chemia. Comparison of horizontal and vertical advective CO 2 fluxes at three forest sites. Agricultural and Forest Meteorology. Frenzel P, Karofeld E. CH 4 emission from a hollow-ridge complex in a raised bog: The role of CH 4 production and oxidation.
Deciduous forests Beech : Carbon and water fluxes, balances, ecological and ecophysiological determinants. Seasonal variation of VOC concentrations above a boreal coniferous forest. This result is in contrast with conclusions from previous studies suggesting that increasing WUE is an important aspect of plant acclimation to high light . In species of the genus Acer , acclimation to high light can be characterized by traits that maximize WUE rather than only maximizing leaf net carbon gain .
In our study, Gaafour seedlings grown under HL have higher A max and g s , which is generally found in light-demanding species  , . However, there was a trend toward higher stomatal control of water loss in HL Feija seedlings.
In conclusion, a distinct difference in photosynthetic plasticity was observed in response to the light environment between both of the studied populations. Gaafour seedlings exhibited the highest photosynthetic rate in high light, and there was a difference in carbon assimilation across light regimes that is consistent with high physiological plasticity.
However, Feija seedlings were better acclimated to low and medium-light environments. This suggests that populations originating from semi-arid sites can benefit more from high light conditions than populations from humid sites. Additional studies of more populations are necessary to corroborate this hypothesis.
We wish to thank Dr. The constructive comments of two anonymous referees are gratefully acknowledged. Light acclimation of leaf gas exchange in two Tunisian cork oak populations from contrasting environmental conditions. Total Article Views: from publication date up to now.
Web Metrics Days since publication: Overall contacts: Avg. Article citations are based on data periodically collected from the Clarivate Web of Science web site last update: Aug Adjustment of photosynthetic carbon assimilation to higher growth irradiance in three-year-old seedlings of two Tunisian provenances of Cork Oak Quercus suber L. Drought tolerance in cork oak is associated with low leaf stomatal and hydraulic conductances. Photosynthesis of three evergreen broad-leaved tree species, Castanopsis sieboldii, Quercus glauca , and Q. A new approach to ozone plant fumigation: The Web-O 3 -Fumigation.
Isoprene response to a gradient of ozone stress in leaves of Quercus pubescens. Variation in growth, photosynthesis and water-soluble polysaccharide of Cyclocarya paliurus under different light regimes. The use of branch enclosures to assess direct and indirect effects of elevated CO 2 on photosynthesis, respiration and isoprene emission of Populus alba leaves. A comparison between stomatal ozone uptake and AOT40 of deciduous trees in Japan. Testing a dual isotope model to track carbon and water gas exchanges in a Mediterranean forest.
References 1. Shade-sun responses: compromises between acclimation and photoinhibition. Elsevier, Amsterdam, The Netherlans, pp. Low temperature during winter elicits differential responses among populations of the Mediterranean evergreen cork oak Quercus suber. Tree Physiology CrossRef Gscholar. Arnon DI Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta vulgaris. Plant Physiology Population divergence in the plasticity of the response of Quercus coccifera to the light environment.
Functional Ecology Boardman NK Comparative photosynthesis of sun and shaded plants. Annual Review of Plant Physiology Effects of shade treatments on the photosynthetic capacity, chlorophyll fluorescence content of Tetrastigma hemleyanum Diels et Gilg. Environmental and experimental Botany Evans JR Leaf anatomy enables more equal access to light and CO 2 between chloroplasts. New phytologist Diurnal changes in photoprotective mechanisms in leaves of cork oak Quercus suber during summer. Tree Physiology 16 : Differences in the response of carbon assimilation to summer stress water deficits, high light and temperature in four Mediterranean tree species.
Physiologia Plantarum Flexas J, Medrano H Drought inhibition of photosynthesis in C3 plants: stomatal and non-stomatal limitations revisited. Annals of Botany Thermal optima of photosynthetic functions and thermostability of photochemistry in crok oak seedlings. Differential light responses of Mediterranean tree saplings: linking ecophysiology with regeneration niche in four co-occuring species. Hall A A model of leaf photosynthesis and respiration for predicting carbon dioxide assimilation in different environments.
Trace Gas Exchange in Forest Ecosystems
Oecologia The effect of growth irradiance on leaf anatomy and photosynthesis in Acer species differing in light demand. Plant, Cell and Environment Holmgren P Leaf factors affecting light-saturated photosynthesis in ecotypes of Solidago virgaurea from exposed and shaded habitats. Stomatal conductance and photosynthesis vary linearly with plant hydraulic conductance in ponderosa pine. Photoacclimation of photosynthesis irradiance response curves and photosynthetic pigments in microalgae and cyanobacteria.
Journal of Phycology Effects of growth irradiance and nitrogen limitation on photosynthetic energy conversion in photosystem II. A new scenario for the Quaternary history of European beech populations: palaeobotanical evidence and genetic consequences.