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Plant ecophysiological responses to drought, nocturnal warming and variable climate in the Pannonian sand forest-steppe: results of a six-year climate manipulation experiment

Mojzes, Andrea, Kalapos, Tibor, Kovács-Láng, Edit
Biológia 2017 v.72 no.12 pp. 1431-1445
C3 plants, C4 photosynthesis, C4 plants, Cynodon dactylon, Festuca vaginata, Populus alba, chlorophyll, climate, climate models, drought, drying, ecophysiology, forest steppe, gas exchange, geographical distribution, grasses, leaf area, leaves, photochemistry, physiological response, rain, roots, sand, spring, summer, temperature, Hungary
The impacts of year-round nocturnal warming or late spring rain exclusion on three plant functional types were studied in a plot-scale climate simulation experiment in a semiarid sand forest-steppe of Central Hungary. Ecophysiological traits were followed through six years for the C₃ bunch grass Festuca vaginata, the spreading C₄ grass Cynodon dactylon and shrub-sized root suckers of Populus alba. In general, experimental treatments had slighter effects than weather fluctuations yielding extremities did. Populus alba responded to nocturnal warming with developing slenderer leaves. Rain exclusion reduced leaf physiological activity or growth, but only during or just after the treatment, and in certain years. When assessing treatment and background climatic variation effects together, in spring, leaf area growth was consistently stimulated by increasing temperature, but decreased with longer rainless periods for P. alba and F. vaginata. Physiological responses in spring indicated low temperature limitation for C. dactylon, and both low and high temperature control for P. alba. Longer summer droughts reduced leaf gas exchange, particularly for F. vaginata with substantial drop in photochemical activity and chlorophyll content. These results suggest that shallow rooted C₃ bunch grasses can be the most susceptible to climatic variation, thus their abundance is expected to decline in the Pannonian forest-steppe. In contrast, plants having deeper roots and clonal integration will probably be less affected by the projected warming and drying climate. C₄ photosynthesis or southern geographical distribution may also be beneficial, thus, the abundance of such species is expected to diminish less or even increase.