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Extreme Cooling Experiment
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Scientific question

The semiarid grasslands in Mongolia Plateau are among the very sensitive ecosystems to the changing climate, including its extremes that are high in their magnitude and frequency. Our analysis of the climate change in the past six decades indicates that the extremes cooling continues with the warming trend in this region. Several large manipulative experiments had been installed to understand the effects of warming and heat waves on ecosystem processes, but none on the role of extreme low temperatures regardless of their similar occurrences to the heat waves. Based on a temperature-controlled experiment in Duolun of Inner Mongolia, our objective is to examine the regulations of seasonal lower temperatures on plant phenology and community prosperity, soil microbial community structure, and major carbon fluxes (i.e., photosynthesis, respiration, and net ecosystem exchange), as well as the underlying mechanisms responsible for the changes. This study is based on the first manipulative experiment on low temperatures in terrestrial ecosystems, suggesting that the results will be foundational to the global change community as its scientific base and firsthand data for future modeling.

 

Fig. 1 Cooling assemblage

Experiment design

This study used complete random design, take the extreme cooling event as the treatment factor (i.e., lower the real-time temperature by 8oC than the ambient environment for about 7 days). The treatment levels included spring cooling (in Apr. 10-20, SP), autumn cooling (in Sep.10-20, AU), spring and autumn cooling (SPAU), and control (i.e., with OTC during the cooling, CK). Each level has six replicates. Thus, twenty-four plots were arranged in 5×5 matrix, with 3×3 m as one plot and a 4-m distance between any two adjacent plots, except for the cooling machine in the middle of region (Fig. 1). During the extreme cooling, polycarbonate sheets were inserted in the OTC frame (i.e., 12 pieces without ceiling), and then take down them after the 7 days (Fig. 2).

 

Fig. 2 Experiment layout

Experiment operator

Juanjuan Han

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Copyright:Laboratory of Global Change Ecology

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