Evolutionary consequences of habitat loss for Pacific anadromous salmonids

Large portions of anadromous salmonid habitat in the western United States has been lost because of dams and other blockages. This loss has the potential to affect salmonid evolution through natural selection if the loss is biased, affecting certain types of habitat differentially, and if phenotypic traits correlated with those habitat types are heritable. Habitat loss can also affect salmonid evolution indirectly, by reducing genetic variation and changing its distribution within and among populations. In this paper, we compare the characteristics of lost habitats with currently accessible habitats and review the heritability of traits which show correlations with habitat/environmental gradients. We find that although there is some regional variation, inaccessible habitats tend to be higher in elevation, wetter and both warmer in the summer and colder in the winter than habitats currently available to anadromous salmonids. We present several case studies that demonstrate either a change in phenotypic or life history expression or an apparent reduction in genetic variation associated with habitat blockages. These results suggest that loss of habitat will alter evolutionary trajectories in salmonid populations and Evolutionarily Significant Units. Changes in both selective regime and standing genetic diversity might affect the ability of these taxa to respond to subsequent environmental perturbations. Both natural and anthropogenic and should be considered seriously in developing management and conservation strategies

Annual climate assessment.

Description based on: 5th (1993).Mode of access: Internet.Prepared by: the Climate Analysis Center.Electronic serial mode of access: World Wide Web

Improved understanding of climate change impact to Pennsylvania dairy pasture

Pasture can be either a source or a sink for atmospheric carbon dioxide, depending primarily on climate and land management. In the absence of specific data on pasture in the northeastern United States, the parameterization of ecosystem models for carbon and energy flux has been based on data from grasslands in the Great Plains (United States), where climate is more arid and less management intensive than in the eastern United States. Models have not been adequately parameterized to simulate carbon dynamics under managed dairy grasslands in the humid eastern United States. This paper aims to provide TEM-Hydro2—a terrestrial ecosystems model—with region-specific dairy pasture parameterization in Pennsylvania to more realistically determine humid grassland dynamics under a changing climate. Through this study, we highlight the importance of considering region-specific calibration data in reporting realistic ecosystem response to climate change through the comparison to a simulation based on a xeric parameterization. Our field observations indicate that Pennsylvania’s more humid climate results in higher carbon and nitrogen flux exchanges between grassland and the atmosphere, but the soil carbon pool is significantly lower compared with the semiarid grassland. Moreover, Pennsylvania pasture is simulated to be more sensitive to climate change based on the region-specific parameterization. Projected to the end of the 21st century, dairy pasture in Pennsylvania will probably experience increased carbon uptake and soil carbon accumulation under continuous grazing management, while hay production would drastically reduce Pennsylvania dairy pasture’s capacity to sequester carbon