Treesearch

Critical to conservation efforts and other investigations at low taxonomic levels, DNA sequence data offer important insights into the distinctiveness, biogeographic partitioning, and evolutionary histories of species. The resolving power of DNA sequences is often limited by insufficient variability at the intraspecific level. This is particularly true of studies involving plant organelles, as the conservative mutation rate of chloroplasts and mitochondria makes it difficult to detect polymorphisms necessary to track genealogical relationships among individuals, populations, and closely...

Competition with barred owls (Strix varia varia) is an important factor contributing to the continued decline of threatened northern spotted owl (Strix occidentalis caurina) populations in the Pacific Northwest, USA, but basic information on habitat selection and space use patterns of barred owls is lacking for much of the region. We investigated space use and habitat selection by tracking radiotagged barred owls in the eastern Cascade Range of Washington, USA, from 2004 to 2006. We surveyed for barred owls across the 309-km2 study area and confirmed presence of barred owl pairs at 21...

Early-successional forest ecosystems that develop after stand-replacing or partial disturbances are diverse in species, processes, and structure. Post-disturbance ecosystems are also often rich in biological legacies, including surviving organisms and organically derived structures, such as woody debris. These legacies and postdisturbance plant communities provide resources that attract and sustain high species diversity, including numerous early-successional obligates, such as certain woodpeckers and arthropods. Early succession is the only period when tree canopies do not dominate the...

Sap flow techniques, such as thermal dissipation, involve an empirically derived relationship between sap flux and the temperature differential between a heated thermocouple and a nearby reference thermocouple inserted into the sapwood. This relationship has been widely tested but mostly with newly installed sensors. Increasingly, sensors are used for extended periods. After several months, tree growth, wounding, or other changes in water flow path may impair sensor performance. To quantify changes in sensor performance over time, we installed 23 sensors (1 per tree) in 16-year-old...

Young basalt terrains offer an exceptional opportunity to study landscape and hydrologic evolution through time, as the age of the landscape itself can be determined by dating lava flows. These constructional terrains are also highly permeable, allowing one to examine timescales and process of geomorphic evolution as they relate to the partitioning of hydrologic flowpaths between surface and subsurface flow. The western slopes of the Cascade Range in Oregon, USA, are composed of a thick sequence of lava flows ranging from Holocene to Oligocene in age, and the landscape receives abundant...

By measuring the isotopic signature of soil respiration, we seek to learn the isotopic composition of the carbon respired in the soil (δ13CR-S) so that we may draw inferences about ecosystem processes. Requisite to this goal is the need to understand how (δ13CR-S) is affected by both contributions of multiple carbon sources to respiration and fractionation owing to soil gas transport. In this study, we measured potential isotopic sources to determine their contributions to (δ13CR-S) and we performed a series of experiments to investigate the impact of soil gas transport on (δ13CR-S)...

Site factors predispose yellow-cedar (Chamaecyparis nootkatensis D. Don (Spach)) to a widespread climate-induced mortality in southeast Alaska. We investigated the influence of canopy cover and snow on microclimate at two small watersheds across a range of declining yellow-cedar stands on Baranof and Chichagof Islands in southeast Alaska. Two measures of canopy cover, derived from hemispherical photography and LIDAR, were correlated at the two sites; both had significant relationships with basal area of live trees on plots. Reduced canopy cover increases soil warming in spring and leads to...

This study considered three aspects of residential wood energy use in Alaska: current conditions and fuel consumption, knowledge and attitudes, and future use and conditions. We found that heating oil was the primary fuel for home heating in southeast and interior Alaska, whereas natural gas was used most often in south-central Alaska (Anchorage). Firewood heating played a much more important role as a secondary (vs. primary) heating source in all regions of Alaska. In interior Alaska, there was a somewhat greater interest in the use of wood energy compared to other regions. Likewise,...

This study had three objectives: (1) to determine if there are correlations between aboveground vegetation and belowground soil properties within large 50-m-diameter gaps, (2) to determine how large gaps influence forest soils compared with nongap soils, and (3) to measure the effects of differently sized gaps on gap soils. Circular canopy gaps were created in old-growth Douglas-fir forests of the H.J. Andrews Experimental Forest in the western Oregon Cascade Mountains. Within-gap soil spatial patterns were compared with aboveground distributions of both vegetation and large woody debris...

Deforestation globally accounts for about 20 percent of total greenhouse gas emissions. One of the major forestry challenges in the United States is reducing the loss of forest land from development. Foresters have a critical role to play in forest management and carbon sequestration to reduce greenhouse gas emissions, and forestry can be part of the solution. A recent national silviculture workshop demonstrated the importance of collaborative efforts between researchers and forest practitioners and an assessment of the potential linkage between forest management, carbon sequestration, and...