J. Ammann results 33
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Global maps of soil temperatureNARA Subscribed
Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1‐km 2 r...
Outmigration survival of wild Chinook salmon smolts through the Sacramento River during historic drought and high water conditionsNARA Subscribed
Populations of wild spring-run Chinook salmon in California’s Central Valley, once numbering in the millions, have dramatically declined to record low numbers. Dam construction, habitat degradation, and altered flow regimes have all contributed to depress populations, which currently persist in only a few tributaries to the Sacramento River. Mill Creek (Tehama County) continues to support these threatened fish, and contains so...
Statistics of multi‐year droughts from the method for object‐based diagnostic evaluationNARA Subscribed
This study uses the method for object‐based diagnostic evaluation (MODE) technique to examine and compare the statistics of drought attributes over the upper Colorado River basin (UCRB). The drought objects are based on the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) on a 36‐month timescale (SPI36 and SPEI36, respectively). The drought indicators are calculated usin...
Extreme variability in abundance of California salmon populations is often ascribed to ocean conditions, yet relatively little is known about their marine life history. To investigate which ocean conditions influence their distribution and abundance, we surveyed juvenile Chinook salmon ( Oncorhynchus tshawytscha ) within the California Current (central California [37°30′N) to Newport, Oregon (44°00′N]) for a 2‐week period over...
Innate predator recognition and fright response in related populations of Oncorhynchus mykiss under different predation pressureNARA Subscribed
Innate predator recognition and fright response behaviours were compared in a laboratory study between second generation offspring from two related populations of steelhead trout Oncorhynchus mykiss from Sashin Creek, Alaska. The stream population was anadromous and co‐occurred with Dolly Varden Salvelinus malma , a piscivore and salmonid predator. Sashin Lake, formerly fishless, was stocked with fish from the stream populatio...