Directionality, Magnitude, and Duration of Precipitation Extremes Within a Mesic Grassland

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Locally and globally, climate extremes are expected to become an increasingly important determinant of terrestrial ecosystem structure and functioning. In particular, precipitation anomalies are likely to have the most pronounced impacts on biodiversity (Tilman and El haddi 1992), carbon storage (Ciais et al. 2005) and cycling (Reichstein et al. 2013). As a consequence, an expressed need has been for a next generation of experiments designed to elucidate the causes and consequences of ecosystem responses to precipitation extremes (Smith 2011, Reichstein et al. 2013). While studies on the ecology of climate extremes have grown, we still lack a basic understanding of how specific attributes of an extreme (e.g., directionality, magnitude, and duration) may independently and interactively affect ecosystem processes. To address this, we installed a growing season (May-August) precipitation manipulation experiment on intact plant communities within the Konza Prairie Biological Station in northeastern Kansas. This project will assess how the duration (1 yr. vs. 2 yrs.) and extremity (1^st, 5^th, 10^th, 15^th, 85^th, 90^th, 95^th and 99^th percentiles of the long-term climate record) of growing season precipitation will interact to affect the resistance and resilience of the tallgrass prairie ecosystem. Measurements are scaled from the physiological responses of the dominant plant species, plant community structure, to key components of ecosystem functioning such as carbon cycling and resource supply. Preliminary results of the first field season suggest nonlinear dynamics of ecosystem responses to increasing climatic extremity. In total, the proposed application of this study is to contribute an understanding towards the determinants of terrestrial ecosystem responses to climate extremes, with particular emphasis on the ecological role of climate extreme characteristics.