REU: LTREB: Short-term Climate Change and Variable Response to Disturbance in an Arid Land Watershed-stream Ecosystem

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This project comprises a long-term investigation of the capacity of various components of a desert stream ecosystem to respond to a disturbance which itself varies with interannual variation in climate. Climate interacts with this ecosystem by providing, through runoff, both water and nutrients to the stream channel. In particular, nitrogen, a key element in desert ecosystems, varies in stream water as a function of extended (several years) dry or wet periods. Nitrogen availability has a strong influence on both algal succession and the capacity of invertebrates to recover after disturbance. Climatic forcers affecting precipitation and runoff provide the predominant form of disturbance in this ecosystem, flash floods and drought. Therefore, climate, by influencing precipitation, evapotranspiration, and resulting runoff, both alters inputs of essential materials to the ecosystem and is a major disrupter of biotic structure. Both the mechanisms of terrestrial-aquatic linkage and interannual patterns of disturbance response in Sycamore Creek, Arizona, will be studied using a combination of manipulative and experimental approaches. This research will rely heavily upon and will extend an existing long-term database describing structure and functioning of this ecosystem.