External factors of eco-technological water management - influences of land use and climate change
Final Report Abstract
The aim of the project was to test, whether anticipated climate change effects on water (and matter, e.g., N) fluxes can be mitigated or balanced by land use change. Influences of land use and climate change where investigated as external factors of eco-technological water management. For this purpose, example area (Tharandter Wald and its vicinity) flux data of nitrogen, carbon, and water were compiled in a relational data base. Recent and future climate data from statistical and deterministic downscaling were provided by ReKIS (Regionales Klimainformationssystem, www.rekis.org). Furthermore, specific measurements of water, carbon, and nitrogen fluxes were done in 2009 and 2010 within the investigation area at the cropland site Klingenberg. A detailed analysis of differences of the eddy covariance (EC) and modified Bowen ratio (MBR) system showed that MBR systems are useful to obtain fluxes of NOx and NH3. It demonstrated the potential of the method to address more exotic fluxes which are currently not covered by fast sensors (necessary for EC). Measurements from this site also showed that the energy balance closure gap, which was detected in the EC fluxes of H and LE, does not seem to propagate completely to the flux of CO2, as the underestimation of FCO2 by EC was by about 10%; compared to 32.5% for the fluxes of H and LE. Therefore, the closure gap correction (following Twine et al. 2000) cannot be directly applied for the flux of CO2 or N species, at least for the Klingenberg site. The simulation of evapotranspiration (ET) was done by the water balance model BROOK90 for different land uses with measured (until 2010) and simulated data from 1961 until 2100. Most of the simulated crops show increasing ET with time, while forests increase until mid of the century but decrease for the last 30 year period of 2071 to 2100. To evaluate the influence of land use on evapotranspiration, different land uses and also two different maximum LAI (5.2 & 7.2) for spruce were applied. Due to reduction in precipitation a small but general reduction in ET is modelled at the end of the climate projection period. However, the systematic difference between the different LAI is decreasing with decreasing LAI, indicating that the lower LAI is more suitable for the future water supply. At the same time, LAI (in other words stand density or tree species) remains an important factor of ET and in turn, a potential tool to stabilize run-off with decreasing precipitation. Regarding evapotranspiration, differences of land use dominate over differences of climate change. Finally, the atmospheric boundary layer model HIRVAC was used to simulate fluxes of energy and CO2 including full feedback with higher CO2 concentration and changing vapour density deficit for different land uses. With the implementation of feedbacks to simulated stomatal conductance, the model is now a useful tool for assessing changes in ecosystem-atmosphere exchange under changing climate conditions. Lower transpiration rates and also fluxes of CO2 are the consequence from elevated CO2 concentrations in atmosphere. Therefore and as shown in FACE (Free Atmospheric Carbon Enrichment) experiments, elevated CO2 will probably increase water use efficiency lower water demand and will balance (partially) the anticipated increase in ET with climate change.
Publications
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„Die Integration von Kohlenstoff- und Stickstoffflüssen zur Modellierung der Rückkopplung zwischen Oberfläche und Atmosphäre“ AG Hydrologische Modellierung 14-15 Mai 2009 in Freiburg i.Br.
Brust, K., Hehn, H., Bernhofer, C.
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„Integration von Kohlenstoff- und Stickstoffflüssen bei der Modellierung der Rückkopplung zwischen Landnutzung und Atmosphäre“ 13. Workshop der Großskaligen Hydrologischen Modellierung 25-27 November 2009 in Dresden
Brust, K., Goldberg, V. und Bernhofer, C.
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(2010): Land use regulates carbon budgets in eastern Germany: From NEE to NBP. Agric. For. Meteorol. 150, 1016–1025
Prescher, A.-K., Grünwald, T., Bernhofer, C.
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“Matter fluxes between atmosphere and an agricultural surface – Modified Bowen Ratio (MBR) versus Eddy Covariance (EC) Measurements” (1st Place Poster Award) Reactive Nitrogen and the European Greenhouse Gas Balance – Open Science Conference 3-4 February 2010 in Solothurn, Switzerland
Brust, K., Hehn, M., Grünwald, T., C. Bernhofer
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„Implementierung von Kohlenstoffflüssen zur Modellierung der Rückkopplung zwischen Landnutzung und Atmosphäre“ DACH Meteorologen-Tagung 20-24 September 2010 in Bonn
Brust, K., Bernhofer, C.
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(2011): Mikrometeorologische, pflanzenökologische und bodenhydrologische Messungen in Buchen- und Fichtenbeständen des Tharandter Waldes. Waldökologie, Landschaftsforschung und Naturschutz, 12, 17-28
Bernhofer C, Grünwald T, Spank U, Clausnitzer F, Eichelmann U, Feger K-H, Köstner B, Prasse H, Menzer A, Schwärzel K
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„Integrating carbon fluxes for an improved simulation of land use – atmosphere feedback“ EGU General Assembly 3-8 April 2011 Vienna, Austria, EGU2011-7499
Brust, K., Goldberg, V., Bernhofer, C.
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„Integrating carbon fluxes to model land-use atmosphere feedback under changing climate conditions“ iLEAPS Science Conference 18-23 September 2011 in Garmisch-Partenkirchen, Germany
Brust, K., Goldberg, V., Bernhofer, C.
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"Comparative analysis of matter and energy fluxes determined by Bowen Ratio and Eddy Covariance techniques at a crop site in eastern Germany" EGU General Assembly 22-27 April 2012 Vienna, Austria. EGU2012-8806
Brust, K., Hehn, M., Grünwald, T., Bernhofer, C.
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2012. Energie- und Stoffflüsse über verschiedenen Landnutzungen. Promet 38, 59–68
Grünwald, T., Knohl, A., Bernhofer, C.
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(2013): Beschreibung, Messung und Modellierung von Wasserhaushalt und Wasserhaushaltskomponenten von Wäldern. Promet 38; 80-91
Spank, U., Bernhofer, Ch.
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(2013): Evapotranspiration amplifies European summer drought. Geophys. Res. Letters, 40, 2071–2075
Teuling, A. J, Van Loon, A.F., Seneviratne, S.I., Lehner, I., Aubinet, M., Heinesch, B., Bernhofer, C., Grünwald, T., Prasse, H. & U. Spank
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„Hydrological impacts of forest decline and regrowth: a retrospective analysis of the past 60 years in Saxony, Germany” Oral presentation EGU General Assembly 07-12 April 2013 Vienna, Austria. EGU2013-5109
Renner, M., Brust, K., Bernhofer, C.
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(2014): Separating the effects of changes in land cover and climate: a hydro-meteorological analysis of the past 60 yr in Saxony, Germany, Hydrol. Earth Syst. Sci., 18, 389-405
Renner, M., Brust, K., Schwärzel, K., Volk, M., and Bernhofer, C.
