Deconstructing key dimensions of climate variability in Semi-Arid Grasslands
Climate Change is expected to alter precipitation patterns across the Great Plains region leading to fewer but larger rainfall events with longer dry intervals between events. Results from past precipitation manipulation experiments suggest that this shift in rainfall patterns will lead to increases in primary production in arid grasslands. These past experiments often use weekly watering treatments which fail to represent the natural stochastic patterns of precipitation. The Precipitation Evenness Project addresses this issue through the use of full rainfall exclusion shelters and irrigation treatments that vary in the evenness of rainfall patterns imposed. Set up in the shortgrass steppe of Colorado, this experiment mimics the exact rainfall pattern of a historic year with high variability in precipitation event size and timing. Additional treatments impose the same rainfall amount but alter rainfall pattern to be more even (i.e. weekly watering treatments of the same amount). Whole ecosystem responses as well as physiological responses of the dominant grass species are measured within each treatment. Results from this experiment will inform and improve the design of future precipitation manipulation experiments.
Click HERE to see results published in Journal of Ecology |
Linking climate of origin with Drought Strategies of central Australian grasses
Plant species vary in their stomatal strategies for coping with drought and can be classified as either risky or conservative. Risky species (anisohydric) keep their stomata open as soil dries maintaining high photosynthetic rates at the risk of hydraulic failure (see video above). Conservative species (isohydric) close their stomata at the first signs of soil drying to protect their hydraulic transport system at the cost of reduced photosynthesis. The goal of this project is to determine how historical rainfall patterns have affected the evolution of these drought strategies. The Australian outback is characterized by extremely high inter-annual variability in precipitation. Taking advantage of an established experiment assessing drought along a gradient of mean annual rainfall and inter-annual variability in rainfall (Fig. 1), this project quantifies dominant species' drought strategies along the isohydry spectrum through detailed measurements of hydraulic vulnerability to cavitation and stomatal closure. This project is funded by the Hawkesbury Institute for the Environment and is part of Drought-Net (sala.lab.asu.edu/research/drought-net/).
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