Experimental Site

ClimGrass – Climate impact research on grassland

Hardly another issue than climate change and its consequences have been dominating media and public discussion over years. Since 1995 annual climate conferences are taking place under the patronage of the United Nations. Berlin, Geneva and Kyoto were the first venues in the nineties whereas Paris, Marrakesch and Bonn hosted the climate conference in the recent past. The predicted increase of temperature and enhancement of atmospheric CO2-concentration as well as the intensified appearance of weather extremes will cause massive impact on society and on the entire environment during the next decades. As many of weather- and climate-determining parameters are likewise important growing factors for plants, the Austrian grassland and its management will particularly be affected by climate change. For many years climate and climate impact research has intensively studied causes and effects of climate change on various areas of life and economy. Research is mainly based on modelling as well as on experimental approaches whereat the latter are very time- and labour intensive. Climate change experiments are either performed under laboratory conditions or outdoor, mostly including and regulating a limited number of weather-/climate factors like temperature or precipitation. Outdoor experiments for climate impact research provide a specific challenge, particularly when several factors are altered at the same time.

Setup and design of the ClimGrass-experiment

Over the past years this world-wide unique, multi-factorial outdoor experiment has been developed and realised at AREC Raumberg-Gumpenstein with the support of numerous internal and foreign experts. On at all 54 experimental plots (each with 4 x 4 m size) temperature (eT) and atmospheric CO2-concentration (eC) can be regulated at different levels and combinations including the most likely scenario that is predicted for the end of this century (see Figure 1).  For the ClimGrass experiment a completely randomized response surface design was used, which allows a more efficient estimation of treatment effects due to more parsimonious modelling (Piepho et al., 2017). Warming is realised by six infrared heaters per plot and is varied in three assembly levels namely ambient (= current temperature), + 1.5°C and + 3°C (+ means the increase compared to the current temperature). Warming treatments are performed full-time all-the year and only stopped when the snow cover exceeds a height of 10 cm. The enhancement of atmospheric CO2 is realised with fumigation rings (diameter of 2 m) by which air enriched with CO2 streams in the plot vegetation. The isotopic signature (13C) of the added CO2 is different to that of the atmospheric carbon dioxide and allows specific allocation analyses. CO2-fumigation is only done during the vegetation season from begin of April to end of November and during the day when global radiation is higher than 50 W m-2.

       

Monolith Lysimeter

Monolith-lysimeter

Infrared Heater

Infrared-heater

Fumigation Ring

Fumigation ring

Rainout Shelter

Rainout-shelter

Picture series 1: functional and technical devices of the ClimGrass-experiment

Six of the experimental plots are equipped with weighable monolith-lysimeters (1 m² surface, 1.5 m depth), which allow detailed investigations on the hydrological cycle (Slawitsch et al., 2016). On another eight plots each 12 mesocosm (30 cm diameter, 60 cm depth) are installed to realize different fertilization levels and to conduct pulse labelling with 13C to trace carbon dynamics and carbon allocation in soil and plants. Three rainout-shelters each covering four experimental plots are used for simulating drought events, which are also expected to increase in terms of climate change.

ClimGrass Experimental Design

Figure 1: Experimental design of the ClimGrass experiment (47°29`38`` S, 14°06`03`` E, 710 m.a.s.l.)

Recordings and analysis

The plot size of 16 m² requires accurate spatial partition and planning in terms of sampling and in situ measurements as there are many project partners and scientists involved. Beside typical methods of investigations, non-invasive methods like ultrasonic and spectroscopy are used to dynamically determine yield and quality of aboveground biomass. Strong emphasis is given on soil nutrient dynamics and on changes in hydrological, carbon and nitrogen cycle. For this reason automated chambers (LICOR8100) and in addition manual measurements (PP-System EGM4) are used to determine soil respiration. On six plots a complex gas hose system was installed at five different soil depths to monitor concentrations of N2O, CH4 and CO2 online. Investigations of root system as well as gas measurements in soil, vegetation and atmosphere amend the ambitious program of measurements and recordings.

     

Respiration Chamber

Respiration chamber

Spectroscopy and Ultrasonic

Spectroscopy and ultrasonic

Visual Rating

Visual rating

     

Mesocosm

Mesocosm

Microsensors

Microsensors

Membrane Tubes

Membrane tubes

Picture series 2: measurement devices and recording activities in the ClimGrass-experiment

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