Treesearch

Nocturnal increases in water potential and water content in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution (HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the daily recovery in water content, confounding efforts to determine the actual magnitude of HR. We estimated liquid and vapor soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of water potential, water content, and...

Disease is often implicated as a factor in population declines of wildlife and plants. Understanding the characteristics that may predispose a species to infection by a particular pathogen can help direct conservation efforts. Recent declines in amphibian populations world-wide are a major conservation issue and may be caused in part by a fungal pathogen, Batrachochytrium dendrobatidis (Bd). We used Random Forest, a machine learning approach, to identify species-level characteristics that may be related to susceptibility to Bd. Our results suggest that body size at maturity, aspects of egg...

Biogeochemical reactions associated with stream nitrogen cycling, such as nitrification and denitrification, can be strongly controlled by water and solute residence times in the hyporheic zone (HZ). We used a whole-stream steady state 15N-Iabeled nitrate and conservative tracer addition to investigate the spatial and temporal physiochemical conditions controlling the denitrification dynamics in the HZ of an upland agricultural stream. The findings demonstrate that the HZ is an active nitrogen sink in this system and that the distinction between net nitrification and denitrification in the...

Demand for clean water for a variety of uses will increase. Watersheds are where we live, grow crops and create various forms of industry. As the Pacific Northwest's human population expands, competition for water and the ecological goods and services that water provides will grow more intense. With this in mind it is helpful to review emerging issues that are of interest to small woodland owners: climate change, wildfires and invasive species. That climate is changing is beyond scientific dispute, even though the causes of change may continue to be publicly debated. With climate change...

During a long-term demography study of Northern Spotted Owls (Strix occidentalis caurina) in the eastern Cascade Range of Washington State in 1989 to 2008, we documented 276 nests of Northern Spotted Owls at 73 different territories. Of these nests, 90.2% were on platforms, mostly in clumps of deformed limbs caused by dwarf mistletoe (primarily Arceuthobium douglasii), and 9.8% were in cavities in trees. Of the nests associated with dwarf mistletoe, 8.4% were nests built by other raptors and 91.6% were either natural accumulations of debris or debris accumulated by other birds or mammals....

We investigated the population dynamics of the keystone symbiotic N-fixing species Alnus tenuifolia (thinleaf alder) and the patterns of primary succession on the Tanana River floodplains of interior Alaska, USA. The goals of this study were to characterize (i) the variation in the population structure of thinleaf alder and its influence on ecosystem function; (ii) the role of a fungal disease outbreak in driving the population dynamics of thinleaf alder; (iii) the patterns of landscape-scale thinleaf alder recruitment; and (iv) the variation in successional pathways across the landscape....

Given that ecological effects of disturbance have been extensively studied in many ecosystems, it is surprising that few quantitative syntheses across diverse ecosystems have been conducted. Multi-system studies tend to be qualitative because they focus on disturbance types that are difficult to measure in an ecologically relevant way. In addition, synthesis of existing studies across systems or disturbance types is challenging because sufficient information needed for analysis is not easily available. Theoretical advances and improved predictions can be advanced by generalizations...

Assessments of watershed condition for aquatic and riparian species often have to rely on expert opinion because of the complexity of establishing statistical relationships among the many factors involved. Such expert-based assessments can be difficult to document and apply consistently over time and space. We describe and reflect on the process of developing a computer based decision support application from expert judgments for assessing aquatic and riparian conditions over the 100,000 km2 managed by the US federal government under the Northwest Forest Plan. The decision support system...

Despite improvements in understanding biophysical response to climate change, a better understanding of how such changes will affect societies is still needed. We evaluated effects of climate change on the coupled human-environmental system of the McKenzie River watershed in the Oregon Cascades in order to assess its vulnerability. Published empirical and modeling results indicate that climate change will alter both the timing and quantity of streamflow, but understanding how these changes will impact different water users is essential to facilitate adaptation to changing conditions. To...

Clark's Nutcracker (Nucifraga Columbiana) is one of the most specialized scatter-hoarding birds, considered a seed disperser for four species of pines (Pinus spp.), as well as an obligate coevolved mutualist of White bark Pine (P. albicaulis). Cache-site selection has not been formally studied in Clark 's Nutcrackers, which are considered effective seed dispersers for pines because past studies have found that they harvest and store large quantities of seeds. Although many seeds are placed in sites suitable for germination and establishment, information is lacking on the proportions of...