OPERATING INSTITUTE: University of Helsinki, Helsinki.
MAIN PURPOSE: Biosphere/atmosphere interaction and climate change.
ECOSYSTEM TYPE: Pine forest.
EXPERIMENTAL TREATMENTS: Prescribed burning.
LOCALISATION: 61.8527363190335 24.29443359375
FACILITIES: The SMEAR site (Station for Measuring Ecosystem-Atmosphere Rela-tions) is situated at the Hyytiälä Forestry Field Station of the University of Helsinki. The site consists of a managed, 50 years old Scots pine forest stand, two open oligotrophic fen sites and a humic lake with forested catchment. The main idea of SMEAR-type infrastructures is continuous, comprehensive measurements of fluxes, storages and concentrations in the land ecosystem–atmosphere continuum. The forest measurements have been operated continuously since 1996, and include leaf, stand and ecosystem scale measurements of green-house gases, volatile organic com-pounds, pollutants (e.g. O3, SO2, NOx) and aerosols, in addition to a full suite of meteo-rological measurements. The biogeochemical cycles and vegetation-soil-atmosphere intera-ctions are studied both experimentally and with long-term observations. The site has full carbon, water and nitrogen budgets made over 10 years, and it is a full ICOS ecosystem station.
In summer 2012, 18 trenching plots were established in the pine stand, in order to analyse how plant input of recently assimi-lated carbohydrates to soil is linked to the decomposition of soil organic matter and utilisation of soil organic nitrogen sources.
In summer 2013, measurements of carbonyl sulfide (COS) fluxes started in the forest, in order to obtain improved estimates of the magnitude and variability of ecosystem-scale photosynthesis, respiration and transpiration. The lake eddy covariance measurements have been complemented with campaign wise turbulence, VOC and CH4 measure-ments. The nearby spruce swamp forest was drained in order to analyse the effect of water level on GHG fluxes and ecosystem carbon balance.
● Korhonen, J. F. J. , Pihlatie, M., Pumpanen, J., Aaltonen, H., Hari, P., Levula, J., Kieloaho, A. J. , Nikinmaa, E., Vesala, T., and Ilvesniemi, H. (2013) Nitrogen balance of a boreal Scots pine forest. - Biogeosciences 10: 1083–1095.
● Aaltonen, H., Aalto, J., Kolari, P., Pihlatie, M., Pumpanen, J., Kulmala, M., Nikinmaa, E., Vesala, T. & Bäck, J. (2012) Continuous VOC flux measurements on boreal forest floor. Plant and Soil DOI 10.1007/s11104-012-1553-4.
● Bäck, J., Aalto, J., Henriksson, M., Hakola, H., HE, Q. & Boy, M. (2012) Chemodiversity of a Scots pine stand and implications for terpene air concentrations. - Biogeosciences 9: 689–702.
TA PROJECTS: Methane (CH4) and nitrous oxide (N2O) fluxes from boreal tree species (MENOFLUX)
TA User (visit): Katerina Machacova, Global Change Research Centre, Academy of Sciences of the Czech Republic (February / March, 2015 – 16 days)
Project Description: Boreal upland forests have been considered to be an important natural sink of CH4 and a natural source of N2O. However, measurement campaigns in boreal upland forest in Hyytiala, Southern Finland, showed for the first time that Scots pine (Pinus sylvestris), European spruce (Picea abies), and silver birch (Betula pendula), as typical boreal tree representatives, can emit both N2O and CH4, and can significantly contribute to the N2O and CH4 exchange of the boreal forest (Machacova et al. 2013a, 2014). However, the question is whether all three tree species emit N2O and CH4 all year long.
Therefore, the proposed project will continue the successful measurement campaigns in 2013 and 2014 to study the seasonal changes of tree CH4 and N2O flux rates. The main objective will be to characterize and quantify the CH4 and N2O fluxes from stems of P. sylvestris, P. abies and B. pendula in winter. We assume that the CH4 and N2O fluxes from stems will be significantly reduced due to decreased transpiration. This hypothesis is based on the assumption of a transpiration stream as a pathway for N2O and CH4 (Macháčová 2013b). The gas fluxes will be investigated on mature trees under natural field conditions using stem chamber systems and subsequent gas chromatographic analyses of emitted trace gases. Forest floor fluxes of CH4 and N2O will be determined parallel to stem fluxes to enable their comparison. Continuously measured micro-climatic data will be used for correlation analyses to investigate their effects on tree fluxes of N2O and CH4.
Methane (CH4) and nitrous oxide (N2O) emissionsfromstemsofpine, spruce and birchtrees (MENOTREE)
ExpeER TA Site: Hyytiala, FINLAND
TA User (visit): Katerina Machacova, Global Change Research Centre, Academy of Sciences of the Czech Republic (October, 2014 – 17 days)
Project Description: The boreal forests with area of about 920 million ha represent 29 % of the total world forest cover. Based on soil chamber measurements, boreal upland forests have been considered to be an important natural sink of CH4 and a natural source of N2O. However, last year measurement campaign in boreal upland forest in Hyytiala, Finland, showed for the first time that Scots pine trees (Pinus sylvestris) can emit both N2O and CH4 from their stems and shoots and can significantly contribute to the N2O and CH4 exchange of the boreal upland pine forest (Machacovaet al. 2013a). Moreover, based on results obtained from the measurement campaign in Hyytiala from May to July 2014, spruce (Picea abies) and birch (Betulapendula) trees, as further important representatives of the boreal forest, emit both gases from their stems.The stem emissions seem to be dependent on soil water content. However, the question is whether all three tree species emit CH4 and N2O all year long.
Therefore, the main objective of the proposed project will be to characterize and quantify the CH4 and N2O emissions from stems of P. sylvestris, P. abies and B. pendulain autumn after the loss of foliage by birch trees. We assume that CH4 and N2O emissions from stems of B. penduladecrease with loss of the foliage. This hypothesis is based on the assumption of a transpiration stream as a pathway for N2O and CH4 (Macháčová 2013b). The experiments will continue the successful measurement campaign in summer 2014 (financially supported by ExpeER project). The gas fluxes will be investigated on mature trees under natural field conditions using stem chamber systems and subsequent gas chromatographic analyses of emitted trace gases. Forest floor emissions of CH4 and N2O will be determined parallel to stem emissions to enable their comparison. Continuously measured micro-climatic data will be used for correlation analyses to investigate their effects on tree emissions of N2O and CH4. At the end of the campaign, the applicant will de-install the stem chamber systems installed in May 2014.
COS as a new tracer for photosynthesis (photoCOS).
TA User (visit): Dan Yakir, Weizmann Institute of Science (Earth & Planetary Sciences), ISRAEL (September, 2014 - 5 days).
Project Description: With this research visit, we aim at exchanging experience and information, and at developing collaboration on COS measurements as a novel tracer of photosynthetic CO2 flux in two contrasting environments. Future applications of COS exchange for modelling photosynthesis and tree water relations will be discussed.
The expected results are to establish common methodology for COS measurement in Finland and Israel; make joint research plans for the incorporation of COS measurements into on going ecosystem research on the partitioning of ecosystem-atmosphere net CO2 fluxes into its main components. Establish a new comparative research framework to assess the response of contrasting ecosystem to change: coniferous forests in high (Finland) and low (Israel) latitudes.
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Methane (CH4) and nitrous oxide (N2O) emissions from different tree species of boreal upland forest (MENOBUF).
TA User (visit): Katerina Machacova, CzechGlobe Global Change Research Centre ASCR, Czech Republic (May, 2014 – 60 days).
Project Description: The boreal forests with area of about 920 million ha represent 29 % of the total world forest cover and 73 % of the world coniferous forests. Based on soil chamber measurements, boreal upland forests have been considered to be an important natural sink of CH4 and a natural source of N2O. However, last year measurement campaign in boreal pine forest in Hyytiala, Finland, showed for the first time that Scots pine (Pinus sylvestris) can emit not only N2O but also significant amount of CH4 from stems and shoots (Machacova et al. 2013). This highly important finding revealed one of the missing unknown CH4 sources in the upland boreal forest of Hyytiala and can partially explained preliminary determination of small positive CH4 fluxes above this ecosystem during summer time (Peltola et al. 2012).
The boreal forest of the experimental station in Hyytiala consists of a mix of Scots pine, European spruce (Picea abies), birch (Betula pendula) and common aspen (Populus tremula). To my knowledge, data on the CH4 and N2O emissions from three last mentioned tree species are not available; however, these are highly required for the understanding and quantification of trace gas fluxes in boreal forests.
Therefore, the main objective of the proposed project will be to characterize and quantify the CH4 and N2O emissions from stems of P. abies, B. pendula and P. tremula as affected by different soil humidity. Moreover, additional measurements on P. sylvestris will be performed. The gas fluxes will be investigated on mature trees under natural field conditions using stem chamber systems and subsequent gas chromatographic analysis of emitted trace gases. Forest floor emissions of CH4 and N2O will be determined parallel to stem emissions to enable their comparison. Continuously measured micro-climatic data will be used for correlation analyses to investigate their effects on tree emissions of N2O and CH4. Finally, the applicant will be involved in comparison campaign of static soil chambers used for measurements of N2O emissions from soil.
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Using the Photochemical Reflectance Index (PRI) as proxy of seasonal variation in biogenic Volatile Organic Compounds (VOCs) emission capacity (PRITOVOC).
TA User (visit): Josep Penuelas, CREAF/Universitat Autonoma de Barcelona, Spain (April, 2014 – 60 days).
Project Description: The purpose of the project is to evaluate the connection between VOC emissions, leaf pigment contents, pigment and terpenoid precursors (DMAPP), and the photochemical reflectance index (PRI) during the spring-to-summer recovery of photosynthesis in boreal Scots pine. The work is based on preliminary evidence that suggests that the PRI could be used as a remote sensing proxy of VOC emission capacity. This project validates the hypothesis in a real case scenario. The Transnational Access includes a 2 month visit for MSc. Chao Zhang to conduct leaf-level spectral measurements and collect needle samples in Hyytiälä Forest Research Station during the period 1 April 2014 - 31 May 2014, as well as a 1 week visit for Prof. Josep Peñuelas and Dr Iolanda Filella to start-up measurements and plan data analysis and upcoming publications. The resulting spectral and biochemical data will be combined with data from ongoing measurements in SMEAR-II/Hyytiälä Station: VOC monitoring, Gas exchange measurements, Chlrophyll fluorescence measurements, eddy covariance data, as well as tower based Spectral Reflectance. Hyytiälä offers the required infrastructure for this activity. This TA is part of a collaborative project between Prof. Peñuelas, Prof. Jaana Bäck (UHEL) and Dr. Porcar-Castell (UHEL). Pigment and DMAPP analysis will be carried out in Helsinki during summer 2014 in collaboration with Dr. Albert Porcar-Castell (UHEL). Analysis costs will be covered by ongoing projects of Bäck and Porcar-Castell. The visit is expected to yield at least one high-profile publication.
BVOC measurements in a boreal forest using PTR-MS.
TA User (visit): Dušan Materić, The Open University, UK (February, 2014 – 5 days).
Project Description: The aim of the short visit to SMEAR II, Finland, is to obtain valuable experience in the following areas: branch enclosure techniques for VOCs emission research, PTR-MS set up and its use for research in the field, dealing with issues connected to sample piping, simultaneous photosynthesis and VOC measurement in the field, application of gas standards in the open systems due the calibration, models for tower estimation of VOCs emission.Furthermore, potential long-term collaboration as a part of the applicant’s PhD project will be discussed together with associated logistics. It is expected that initial measurement will be done, as well.
Shrub-Tree INTeractions in peat bogs (STINT).
TA User (visit): Juul Limpens, Wageningen University, The Netherlands (July, 2013 – 21 days).
Project Description: Peatlands cover only 3% of the Earth’s land surface but store approximately 30% of all terrestrial soil carbon (Turunen et al. 2002), particularly in moss-dominated peat bogs (Rydin & Jeglum 2006). Most peat bogs are situated at high latitudes in the northern hemisphere where climate warming is expected to peak (Solomon et al. 2007). Changes in temperature and precipitation patterns are expected to lower the water table and speed up peat mineralization with potentially profound consequences for the ecological functioning and plant species composition (Heijmans et al. 2013). Whether climate change can turn moss-dominated peatlands into shrub- or tree lands remains speculative. It has been hypothesised that expansion of shrubs and trees may set in motion positive plant-soil feedback (Ohlsen et al. 2001), accelerating succession into forest (Eppinga et al. 2009). However, current hypotheses do not take into account the effect of ericaceous evergreen shrubs, which often colonise dry microsites before trees arrive (Rydin & Jeglum, 2006). Shrubs can either facilitate or depress tree recruitment and growth (Berkowitz et al. 1995, Holmgren et al. 1997, Gómez-Aparicio et al. 2004, Holmgren et al. 2012), sometimes even arresting succession (Mallik 2003, Acacio et al. 2007).
We are conducting a field experiment to assess the interactions between shrubs and trees in Siikaneva. Preliminary results suggest that shrubs facilitate pine seedling recruitment. This research proposal aims to assess the ecophysiological performance, growth and survival of pine seedlings under different shrub density treatments in 2013.
Developing the methods for online BVOC measurements from boreal ecosystems.
TA User (visit): Miguel Portillo Estrada, Dept. Plant Physiology, Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences, Estonia (May, 2013 – 4 days).
Project Description: The aim of this application is to strengthen the relationship between the field station SMEAR II in Hyytiälä (Finland) and the SMEAR station in Estonia, particularly in relation to ecosystem VOC exchange techniques with PTR-TOF-MS (Proton Transfer Reactor Time-of-Flight Mass Spectrometry). Our department has purchased one device and we need to learn how to use it from experienced scientists. This device analyzes the dynamics of sesquiterpene fluxes, and is capable of identifying these very reactive compounds in sufficiently short temporal resolution.
The visit to the field station SMEAR II will be driven by a training course on how to perform PTR-TOF-MS measurements of ambient air in the field. It also will provide first-hand information about the characteristics of the VOC exchange in the boreal coniferous ecosystem of Hyytiälä field station.
Nitrous oxide (N2O) and methane (CH4) emissions from Pinus sylvestris and Populus tremula (NOME).
TA User (visit): Katerina Machacova, CzechGlobe - Global Change Research Centre, Czech Republic (May, 2013).
Project Description: Nitrous oxide (N2O) and methane (CH4) are important greenhouse gases contributing to global climate change. N2O and CH4 can be emitted from surfaces of riparian plants. However, data on the emissions of these greenhouse gases by trees, especially by upland tree species, are scarce. To our knowledge, no data are available for coniferous tree species. Therefore, the main objective of the proposed project will be the characterisation and quantification of N2O and CH4 emissions from tree surfaces (stem and leaves) of Pinus sylvestris, representative of coniferous tree species. The gas fluxes will be investigated on mature trees under field conditions using chamber systems (stem and leaves chambers) and gas chromatographic analyses. Moreover, determined soil emissions of N2O and CH4 will be used for comparison with emissions of both trace gases from tree surfaces. Furthermore, measurements of sap flow rates will enable further correlation analyses with N2O and CH4 emission rates from P. sylvestris. Finally, the influence of soil and air characteristics (e.g. soil and air humidity and temperature) on trace gas emissions will be analysed.
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Measuring and modelling soil CO2 concentrations, production and diffusion (MMCO2).
ExpeER TA Site: with Hesse, France.
TA User (visit): Markus Herndl, AREC Raumberg-Gumpenstein, Austria (February, 2013).
Project Description: The role of soil CO2 efflux from ecosystems in the terrestrial carbon cycle and its feedbacks to climate change is well known and there are several scientific efforts to characterize and quantify soil respiration across different environments. For ecosystems such as forests there exist a lot of studies, but comparatively little is known for agricultural systems such as cultivated grassland. In the Expeer project, knowledge regarding measuring and modeling CO2 efflux across Europe will be bundled and cross-linked. Moreover, the determination of soil CO2 produced in the different horizons by respiration from efflux data needs the measurement of soil CO2 storage. At the Hesse and Hyytialla sites there are continuous measurements of CO2 in soil pore space to quantify soil CO2 storage using Membrane Tube Technique. Also on both sites expertise is consisting about using and developing the soil CO2 gradient method. The main aim of the of the project MMCO2 is, to acquire site specific knowledge of modeling with the soil CO2 gradient method and the method of measuring CO2 in soil pore space. In the course of the project the two site approaches will be compared and the essential regarding technique and scientific methods transferred to grassland based system. The findings of the project will be used to establish a facility to measure and model CO2 efflux from cultivated grassland in Austria. The expertise exchange can help cross-linking systems and approaches from ecosystem science to application in agricultural sciences.
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