1,721,091 research outputs found
Soil respiration fluxes in relation to photosynthetic activity in broad-leaf and needle-leaf forest stands
No full textSoil respiration is a combination of CO2 fluxes derived from a diversity of belowground sources, many depending directly on the input of carbon from living plants. Here we present data from two different forest ecosystems, a beech and a spruce forest, where a partitioning of soil respiration was carried out. We used soil cores inside micro-pore meshes together with periodic chamber-based measurements to estimate rhizosphere, mycorrhizal fungal and microbial heterotrophic respiration. Calculated mycorrhizal mycelium respiration was 8% at the spruce forest and 3% at the beech forest. Given the nature of the partitioning method these values represent minimum estimates. The ratio of root-derived carbon respiration to heterotrophic respiration was about 1:1 at both forest types. The relationship of each source with temperature and photosynthesis, measured as gross primary productivity derived from eddy covariance measurements, was subsequently explored. Both factors revealed effects specific to the respiration source and the forest type. A response to temperature was evident in all cases except for mycorrhizal mycelium respiration at the spruce forest (R-2 = 0.06, p = 0.41). Significant correlations of photosynthesis with rhizosphere and mycorrhizal fungal respiration were found in all cases. Peaks in correlation values showed time lags between photosynthetic activity and a respiration response ranging from 1 day for the fungal component and 4 days for the rhizosphere component at the beech forest(R-2 = 0.70, p < 0.01 and R-2 = 0.42, p < 0.05, respectively) to 5 days for both fluxes at the spruce forest (R-2 = 0.44, p < 0.01 and R-2 = 0.72, p < 0.01, respectively). Results show that respiration of the mycorrhizal. component cannot be predicted by common temperature driven models in some ecosystems. They also indicate a strong influence of forest canopy processes on the activity of roots and associated organisms. The specific response in each vegetation type should be ideally explained by physiological mechanisms inherent to different species as a next step towards understanding belowground carbon dynamics. (c) 2007 Elsevier B.V. All rights reserved
Process modelling and direct measurements reveal uncertainties in flux measurements above a tall forest
No full textFluxes and related variables from EddyPro®-Output from eddy-covariance measurements above the forest ecosystem Hohes Holz in 2015
No full textContinuous measurements of carbon, water and energy fluxes are performed using the eddy covariance (EC) method in a mixed-beech forest ecosystem in central Germany (52° 5'12N, 11°13'20E, 193 m asl), accompanied by relevant abiotic measurements. The site was established in the Bode catchment as part of the TERENO Harz/Central German Lowland Observatory, a mesoscale water catchment within the Elbe river basin covering an area of approximately 3300 km². The forest area Hohes Holz is the only larger forested area in the otherwise agriculturally intensively-farmed western part of the Magdeburger Börde with an area of about 1500 ha [Wollschläger et al., 2017]. The forest is a protected area with the centre (150 ha) being a nature reserve (Natura 2000) and is dominated by common beech (Fagus sylvatica L.), sessile oak (Quercus petraea) and hornbeam (Carpinus betulus L.) of about 90 years in age, an average tree height of 23.5 m and a stand density of 260 trees/ha. The long term average of annual precipitation is 563 mm and mean annual temperature is 9.1 °C (1981 – 2010 DWD station Ummendorf, #5158). The eddy covariance system consists of a CSAT-3 anemometer (Campbell Scientific Inc., Logan, UT, USA) and a LI-7500 gas analyser (Li-Cor Inc., Lincoln, NE, USA), established in 2014 in 49 m on a scaffolding tower within the research area. Data presented here comprise energy, water (H and LE), and carbon fluxes (NEE) from the EC-system since 2015 as well as gross primary productivity (GPP) and ecosystem respiration (Reco) derived from partitioning of NEE-data. Complimentary data from the turbulence data set and prioritized driver variables as a basis for ecosystem process analysis are added. High-frequency data (20Hz) were acquired with a Campbell data logger and the Eddymeas data acquisition software [Kolle and Rebmann, 2007]. Flux computation from high frequency raw data was performed with the Eddy-Pro® software (v. 7.0.6). After removing physically unrealistic flux values from the time series, subsequent post-processing steps such as estimating the u*-threshold, gap-filling and flux partitioning were performed according to Wutzler et al. [2018] with the REddyProc package. Full details of site instrumentation, metadata information and R-packages used for processing can be found in the supplementary material. Since January 2019 the site is approved as an ICOS ecosystem class 1 station (DE-HoH). ICOS standard procedures required an additional EC-setup consisting of a Gill HS-50 ultrasonic anemometer (Gill Instruments Ltd., Lymington, Hampshire, UK) and a LI-7200 gas analyser which runs in parallel to the above described system (see ICOS carbon portal: https://www.icos-cp.eu/data-products/ecosystem-release)
Use of remotely sensed land use classification for a better evaluation of micrometeorological flux measurement sites
No full textTime series of climate variables measured in 2020 at the TERENO climate station/flux tower Hordorf (Central Germany) Logger 1
No full textTime series of climate variables (description see HD_variable description.xlsx) at the TERENO flux tower /climate station close to Hordorf (DE-Hod, Latitude/Longitude 52.00128, 11.17769, elevation 80 m) of the entire year 2020, resolution 10 min, quality assured. All variables contain flags in a separate column named 'variable_f', in case this flag column contains '-9999', no quality control is performed at this stage, otherwise the flags are strings initiated by a '9' and then followed by numbers either '0', '1' or '2' on different positions of the string. The positions indicate either the automated test performed or a flag set manually due to maintenance activities (0=good, 1=suspect, 2=bad). The field was cultivated with sugar beet during the vegetation period of 2020.The time base is CET
Time series of climate variables measured in 2020 at the TERENO climate station/flux tower Hordorf (Central Germany) Logger 2
No full textTime series of climate variables (description see HD_variable description.xlsx) at the TERENO flux tower /climate station close to Hordorf (DE-Hod, Latitude/Longitude 52.00128, 11.17769, elevation 80 m) of the entire year 2020, resolution 10 min, quality assured. All variables contain flags in a separate column named 'variable_f', in case this flag column contains '-9999', no quality control is performed at this stage, otherwise the flags are strings initiated by a '9' and then followed by numbers either '0', '1' or '2' on different positions of the string. The positions indicate either the automated test performed or a flag set manually due to maintenance activities (0=good, 1=suspect, 2=bad). The field was cultivated with sugar beet during the vegetation period of 2020.The time base is CET
Post-processed, gap-filled and partitioned carbon and energy fluxes from eddy-covariance measurements above the forest ecosystem Hohes Holz in 2017
No full textAdvection and resulting CO<sub>2</sub> exchange uncertainty in a tall forest in central Germany
No full textPotential losses by advection were estimated at Hainich Forest, Thuringia, Germany, where the tower is located at a gentle slope. Three approaches were used: (1) comparing nighttime eddy covariance fluxes to an independent value of total ecosystem respiration by bottom-up modeling of the underlying processes, (2) direct measurements of a horizontal CO2 gradient and horizontal wind speed at 2 m height in order to calculate horizontal advection, and (3) direct measurements of a vertical CO2 gradient and a three-dimensional wind profile in order to calculate vertical advection. In the first approach, nighttime eddy covariance measurements were compared to independent values of total ecosystem respiration by means of bottom-up modeling of the underlying biological processes. Turbulent fluxes and storage term were normalized to the fluxes calculated by the bottom-up model. Below a u(*) threshold of 0.6 m/s the normalized turbulent fluxes decreased with decreasing u(*), but the flux to the storage increased only up to values less than 20% of the modeled flux at low turbulence. Horizontal advection was measured by a horizontal CO2 gradient over a distance of 130 m combined with horizontal wind speed measurements. Horizontal advection occurred at most of the evenings independently of friction velocity above the canopy. Nevertheless, horizontal advection was higher when u(*) was low. The peaks of horizontal advection correlated with changes in temperature. A full mass balance including turbulent fluxes, storage, and horizontal and vertical advection resulted in an increase of spikes and scatter but seemed to generally improve the results from the flux measurements. The comparison of flux data with independent bottom-up modeling results as well as the direct measurements resulted in strong indications that katabatic flows along the hill slope during evening and night reduces the measured apparent ecosystem respiration rate. In addition, anabatic flows may occur during the morning. We conclude that direct measurements of horizontal and vertical advection are highly necessary at sites located even on gentle hill slopes. [References: 56
Post-processed, gap-filled and partitioned carbon and energy fluxes from eddy-covariance measurements above the forest ecosystem Hohes Holz in 2019
No full textPost-processed, gap-filled and partitioned carbon and energy fluxes from eddy-covariance measurements above the forest ecosystem Hohes Holz in 2016
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