Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead ( Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook ( O . tshawytscha ) in the California Central Valley, coho ( O . kisutch ) in California and southern Oregon, sockeye ( O . nerka ) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. In heterogeneous landscapes, a species' habitat may be partitioned into sources and sinks. Conceptually, three kinds of habitat have been described: (1) "sources" are consistent net exporters of organisms; "true sinks" are net importers, and without immigration their populations go extinct; and (3) "pseudosinks" are also net importers, but without immigration they can sustain populations and sometimes can even become net exporters (sources). Previously, I have described sources and pseudosinks in a metapopulation of the butterfly Euphydryas editha and reported the extinction of populations in sources due to an unusual frost. Here, I describe the recolonization of the former sources by migrants from extant populations in the former pseudosinks. For comparison, a series of vacant patches was created in the former pseudosinks. Recolonization was tracked by sampling the population density in the vacant patches. Patches were sampled for 5 years.Contrary to theoretical expectations, the establishment rate of new populations was 10 times higher in outcrops, the former pseudosinks, than in clearings, the former sources. Initial population density was 150 times higher in outcrops (measured as number of larval webs per square meter). Yet in clearings, only the immigrants had poor reproductive success. On those occasions when a resident population was established, the residents had high reproductive success, and the population grew rapidly. The low recolonization rate of clearings could not be attributed to effects of patch size or spatial barriers. A temporal barrier was hypothesized, in which immigrants arrived too late each year to reproduce successfully on host plants in clearings. The host plant in clearings, Collinsia torreyi, typically senesced during the breeding season, but the host plant in outcrops, Pedicularis semibarbata, did not. The hypothesis proposed that immigrants oviposited later than residents because the immigrants originated in outcrops, which had a different microclimate that delayed adult eclosion. The hypothesis was supported: the newly established resident populations in clearings tended to oviposit 10 d earlier than populations in nearby outcrops. An experiment showed earlier eclosion times in clearings than in outcrops. Another experiment showed much higher larval survival in early clearings than in late clearings. Mortality was correlated with host-plant senescence.The temporal barrier was strong enough to keep clearings as net importers of butterflies from outcrops, meaning that the net flow of butterflies reversed after the frost destroyed th...
Climate change affects seasonal weather patterns, but little is known about the relative importance of seasonal weather patterns on animal population vital rates. Even when such information exists, data are typically only available from intensive fieldwork (e.g., mark-recapture studies) at a limited spatial extent. Here, we investigated effects of seasonal air temperature and precipitation (fall, winter, and spring) on survival and recruitment of brook trout (Salvelinus fontinalis) at a broad spatial scale using a novel stage-structured population model. The data were a 15-year record of brook trout abundance from 72 sites distributed across a 170-km-long mountain range in Shenandoah National Park, Virginia, USA. Population vital rates responded differently to weather and site-specific conditions. Specifically, young-of-year survival was most strongly affected by spring temperature, adult survival by elevation and per-capita recruitment by winter precipitation. Low fall precipitation and high winter precipitation, the latter of which is predicted to increase under climate change for the study region, had the strongest negative effects on trout populations. Simulations show that trout abundance could be greatly reduced under constant high winter precipitation, consistent with the expected effects of gravel-scouring flows on eggs and newly hatched individuals. However, high-elevation sites would be less vulnerable to local extinction because they supported higher adult survival. Furthermore, the majority of brook trout populations are projected to persist if high winter precipitation occurs only intermittently (≤3 of 5 years) due to density-dependent recruitment. Variable drivers of vital rates should be commonly found in animal populations characterized by ontogenetic changes in habitat, and such stage-structured effects may increase population persistence to changing climate by not affecting all life stages simultaneously. Yet, our results also demonstrate that weather patterns during seemingly less consequential seasons (e.g., winter precipitation) can have major impacts on animal population dynamics.
Genetic analyses of coastal Oncorhynchus mykiss, commonly known as steelhead/rainbow trout, at the southern extreme of their geographic range in California are used to evaluate ancestry and genetic relationships of populations both above and below large dams. Juvenile fish from 20 locations and strains of rainbow trout commonly planted in reservoirs in the five study basins were evaluated at 24 microsatellite loci. Phylogeographic trees and analysis of molecular variance demonstrated that populations within a basin, both above and below dams, were generally each other's closest relatives. Absence of hatchery fish or their progeny in the tributaries above dams indicates that they are not commonly spawning and that above-barrier fish are descended from coastal steelhead trapped at dam construction. Finally, no genetic basis was found for the division of populations from this region into two distinct biological groups, contrary to current classification under the US and California Endangered Species Acts.
[1] We address the growing need for accurate water temperature predictions in regulated rivers to inform decision support systems and protect aquatic habitats. Although many suitable river temperature models exist, few simultaneously model water temperature dynamics while considering uncertainty of predictions and assimilating observations. Here, we employ a stochastic dynamics approach to water temperature modeling that estimates both the water temperature state and its uncertainty by propagating error through a physically based dynamical system. This method involves converting the governing hydrodynamic and heat transport equations into a state space form and assimilating observations via the Kalman Filter. This model, called the River Assessment for Forecasting Temperature (RAFT), closes the heat budget by tracking heat movement using a robust semi-Lagrangian numerical scheme. RAFT considers key thermodynamic processes, including advection, longitudinal dispersion, atmospheric heat fluxes, lateral inflows, streambed heat exchange, and unsteady nonuniform flow. Inputs include gridded meteorological forecasts from a numerical weather prediction model, bathymetric crosssectional geometry, and temperature and flow measurements at the upstream boundary and tributaries. We applied RAFT to an $100 km portion of the Sacramento River in California, downstream of Keswick Dam (a regulatory dam below Shasta Dam), at a spatial resolution of 2 km and a temporal resolution of 15 min. Model prediction error over a 6 month calibration period was on the order of 0.5 C. When temperature and flow gage data were assimilated, the mean prediction error was significantly less (0.25 C). The model accurately predicts the magnitude and timing of diel temperature fluctuations and can provide 72 h water temperature forecasts when linked with meteorological forecasts and real-time flow/ temperature monitoring networks. RAFT is potentially scalable to model and forecast finegrained one-dimensional temperature dynamics covering a broad extent in a variety of regulated rivers provided that adequate input data are available.
In heterogeneous landscapes, a species’ habitat may be partitioned into sources and sinks. Conceptually, three kinds of habitat have been described: (1) “sources” are consistent net exporters of organisms; “true sinks” are net importers, and without immigration their populations go extinct; and (3) “pseudosinks” are also net importers, but without immigration they can sustain populations and sometimes can even become net exporters (sources). Previously, I have described sources and pseudosinks in a metapopulation of the butterfly Euphydryas editha and reported the extinction of populations in sources due to an unusual frost. Here, I describe the recolonization of the former sources by migrants from extant populations in the former pseudosinks. For comparison, a series of vacant patches was created in the former pseudosinks. Recolonization was tracked by sampling the population density in the vacant patches. Patches were sampled for 5 years. Contrary to theoretical expectations, the establishment rate of new populations was 10 times higher in outcrops, the former pseudosinks, than in clearings, the former sources. Initial population density was 150 times higher in outcrops (measured as number of larval webs per square meter). Yet in clearings, only the immigrants had poor reproductive success. On those occasions when a resident population was established, the residents had high reproductive success, and the population grew rapidly. The low recolonization rate of clearings could not be attributed to effects of patch size or spatial barriers. A temporal barrier was hypothesized, in which immigrants arrived too late each year to reproduce successfully on host plants in clearings. The host plant in clearings, Collinsia torreyi, typically senesced during the breeding season, but the host plant in outcrops, Pedicularis semibarbata, did not. The hypothesis proposed that immigrants oviposited later than residents because the immigrants originated in outcrops, which had a different microclimate that delayed adult eclosion. The hypothesis was supported: the newly established resident populations in clearings tended to oviposit 10 d earlier than populations in nearby outcrops. An experiment showed earlier eclosion times in clearings than in outcrops. Another experiment showed much higher larval survival in early clearings than in late clearings. Mortality was correlated with host‐plant senescence. The temporal barrier was strong enough to keep clearings as net importers of butterflies from outcrops, meaning that the net flow of butterflies reversed after the frost destroyed the resident populations in clearings. Thus, “early” clearings had been sources, but “late” clearings were true sinks, giving the system two kinds of source–sink relationships. After the frost, the metapopulation as a whole underwent a demographic source–sink inversion from one locally stable state to the other. The findings suggest that asymmetric constraints on dispersal, due to temporal structure, may be a mechanism for complex source–sink dynamics in h...
Dam removal provides a valuable opportunity to measure the fluvial response to changes in both sediment supply and the processes that shape channel morphology. We present the first study of river response to the removal of a large (32‐m‐high) dam in a Mediterranean hydroclimatic setting, on the Carmel River, coastal California, USA. This before‐after/control‐impact study measured changes in channel topography, grain size, and salmonid spawning habitat throughout dam removal and subsequent major floods. During dam removal, the river course was re‐routed in order to leave most of the impounded sediment sequestered in the former reservoir and thus prevent major channel and floodplain aggradation downstream. However, a substantial sediment pulse occurred in response to base‐level fall, knickpoint migration, and channel avulsion through sediment in the former reservoir above the newly re‐routed channel. The sediment pulse advanced ~3.5 km in the first wet season after dam removal, resulting in decreased riverbed grain size downstream of the dam site. In the second wet season after dam removal, high flows (including a 30‐year flood and two 10‐year floods) transported sediment > 30 km downstream, filling pools and reducing cross‐channel relief. Deposition of gravel in the second wet season after dam removal enhanced salmonid spawning habitat downstream of the dam site. We infer that in dam removals where most reservoir sediment remains impounded and where high flows follow soon after dam removal, flow sequencing becomes a more important driver of geomorphic and fish‐habitat change than the dam removal alone. © 2018 John Wiley & Sons, Ltd.
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