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Structure and Function of Ephemeral Streams in the Arid and Semiarid Southwest: Implications for Conservation and Management

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Technical Report,26 Apr 2010,31 Aug 2015

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Arizona State University Tempe United States

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This projects goal was to improve understanding of the hydroclimatic drivers of biotic communities and ecosystem processes in ephemeral stream channels as a basis for projecting response to regional climate change. Data were collected on stream hydrology, litter decomposition, nutrients, vegetation, seed banks, and ground-dwelling soil arthropods. Relationships between rainfall and stream flow permanence varied by stream flow type. Duration of flow and precipitation were decoupled for intermittent and semiperennial streams because of contributions from groundwater discharge and the vadose zone. Decomposition and nutrient release were tightly coupled to stream flow for the narrow band along the stream channel, but not for the associated riparian zone. Along the continuum from ephemeral to semiperennial stream flow, trade-offs were apparent between riparian plant biomass high at wetter sites and plant species diversity high at dry sites with sparse canopy. Ground dwelling arthropods were strongly influenced by flow permanence, with effects being seasonally dynamic. The results demonstrate the need to conserve a variety of stream flow types to meet the sometimes mutually exclusive goals of high ecosystem productivity and high species richness. The many small, unnamed ephemeral streams in the piedmont of the Huachuca Mountains and Barry Goldwater Range have high conservation value.

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