Experimental design of multifactor climate change experiments with elevated CO₂, warming and drought: the CLIMAITE project

Abstract

Summary 1.Recent findings indicate that the interactions among CO 2 , temperature and water can be substantial, and that the combined effects on the biological systems of several factors may not be predicted from experiments with one or a few factors. Therefore realistic multifactorial experiments involving a larger set of main factors are needed. 2. We describe a new Danish climate change-related field scale experiment, CLIMAITE, in a heath/ grassland ecosystem. CLIMAITE is a full factorial combination of elevated CO 2 , elevated temperature and prolonged summer drought. The manipulations are intended to mimic anticipated major environmental changes at the site by year 2075 as closely as possible. The impacts on ecosystem processes and functioning (at ecophysiological levels, through responses by individuals and communities to ecosystem-level responses) are investigated simultaneously. 3. The increase of [CO 2 ] closely corresponds with the scenarios for year 2075, while the warming treatment is at the lower end of the predictions and seems to be the most difficult treatment to increase without unwanted side effects on the other variables. The drought treatment follows predictions of increased frequency of drought periods in summer. The combination of the treatments does not create new unwanted side effects on the treatments relative to the treatments alone.

Design and Manual to Construct Rainout-Shelters for Climate Change Experiments in Agroecosystems

“…After an initial phase with similar soil water content in each of the three treatments, soil water content was constantly lower under the rainout-shelter as compared to the ambient control and the rainout-shelter control plots. The soil water content in the experimental treatments started to differ after the first heavy rain events supporting results of previous studies (Mikkelsen et al, 2008;Vogel et al, 2013). Although the early summer 2017 was characterized by several short drought-like periods, the developed rainout-shelters still resulted in differences in soil water content, making the design also suitable for regions with drier climatic conditions.…”

“…One group of shelter types provides a complete or almost complete exclusion of precipitation by permanently closed roofs (Svejcar et al, 1999;Fay et al, 2000;Poll et al, 2013;Prechsl et al, 2015) or by roofs that are closing automatically during rain events (Mikkelsen et al, 2008;Parra et al, 2012). Roofs that only close during rain events minimize unintended shelter effects on the microclimate, as they are only closed for short periods of time (closed for <5% of daytime, Mikkelsen et al, 2008). Yet, these roofs do not operate during strong wind, which often coincides with rainfall events and therefore do not exclude 100% of precipitation.…”

Root growth and N dynamics in response to multi-year experimental warming, summer drought and elevated CO2 in a mixed heathland-grass ecosystem

“…The treatments were initiated in October 2005. See Mikkelsen et al (2008) and Larsen et al (2011) for further details of the experimental design and set-up. Fig.…”

Response of temperate grasslands at different altitudes to simulated summer drought differed but scaled with annual precipitation

“…Sternberg et al, 1999;Greco and Cavagnaro, 2003;Köchy and Wilson, 2004;English et al, 2005;Schwinning et al, 2005;HeislerWhite et al, 2008;Sherry et al, 2008) but also in temperate grasslands where drought is not a severe problem today (e.g. Grime et al, 2000;Morecroft et al, 2004;Kahmen et al, 2005;Mikkelsen et al, 2008). A number of studies focused on the effects of changes in precipitation timing and amounts on C 4 dominated grasslands (e.g.…”