Treesearch

The composition and biodegradability of streamwater dissolved organic matter (DOM) varies with source material and degree of transformation. We combined PARAFAC modeling of fluorescence excitation-emission spectroscopy and biodegradable dissolved organic carbon (BDOC) incubations to investigate seasonal changes in the lability of DOM along a soil-stream continuum in three soil types: bog, forested wetland and upland forest. The percentage of BDOC ranged from 7 to 38 across all sites, and was significantly greater in soil compared to streamwater in the bog and forested wetland, but not in...

This study compares initial understory vegetation response among three thinning treatments and a control in 30 - to 50-year-old even-aged Pseudotsuga menziesii (Mirbel) Franco (Douglas-fir) stands. It was conducted on four sites on the western slope of the central Oregon Cascades. Treatments included a control (no thinning), a light thinning, and two treatments designed to encourage development of understory vegetation: a light thinning with gap creation and a heavy thinning. Vegetation response was measured during the first posttreatment growing season and 5 to 7 years later. Vegetation...

Dissolved organic matter (DOM) is an important component of aquatic food webs. We compare the uptake kinetics for NH4-N and different fractions of DOM during soil and salmon leachate additions by evaluating the uptake of organic forms of carbon (DOC) and nitrogen (DON), and proteinaceous DOM, as measured by parallel factor (PARAFAC) modeling of DOM fluorescence. Seasonal DOM slug additions were conducted in three headwater streams draining a bog, forested wetland, and upland forest using DOM collected by leaching watershed soils. We also used DOM collected from bog soil and salmon carcasses...

We examined the impact of permafrost on dissolved organic matter (DOM) composition in Caribou-Poker Creeks Research Watershed (CPCRW), a watershed underlain with discontinuous permafrost, in interior Alaska. The stream draining the high permafrost watershed had higher DOC and dissolved organic nitrogen (DON) concentrations, higher DOCDON and greater specific ultraviolet absorbance (SUVA) than the streams draining the low and medium permafrost watersheds. All sites had a high proportion of humic components, a low proportion of protein components, and a low fluorescence index value (1.3 -...

We developed temporally and spatially explicit relationships between air temperature and fuel moisture codes derived from the Canadian Fire Weather Index System to estimate annual area burned at 2.5o (latitude x longitude) resolution using a Multivariate Adaptive Regression Spline (MARS) approach across Alaska and Canada. Burned area was substantially more predictable in the western portion of boreal North America than in eastern Canada. Burned area was also not very predictable in areas of substantial topographic relief and in areas along the transition between boreal forest and tundra....

We use a gridded data set developed with a multivariate adaptive regression spline approach to determine how area burned varies each year with changing climatic and fuel moisture conditions. We apply the process-based Terrestrial Ecosystem Model to evaluate the role of future fire on the carbon dynamics of boreal North America in the context of changing atmospheric carbon dioxide (CO2) concentration and climate in the A2 and B2 emissions scenarios of the CGCM2 global climate model. Relative to the last decade of the 20th century, decadal total carbon emissions from fire increase by 2.5-4.4...

Resource managers must deal increasingly with land use and conservation plans applied at large spatial scales (watersheds, landscapes, states, regions) involving multiple interacting federal agencies and stakeholders. Access to a geographically focused and application-oriented database would allow users in different locations and with different concerns to quickly access similar types of information in a consistent format. Agencies could pool their resources, thereby saving costs, increasing availability of the highest resolution data and most advanced tools, and providing smaller groups...

Marbled murrelets (Brachyramphus marmoratus) nest predominantly in the canopies of large old-growth conifers, and are listed as Threatened in Canada and three U.S. states mainly as a consequence of reductions in this habitat owing to logging. We assessed the re-use of nest sites (nest trees) by murrelets in British Columbia using three types of data: (1) evidence of return of adults to the same nest site, (2) evidence of multiple nests within the same tree, and (3) re-checking known nest trees in subsequent seasons for evidence of re-use. All three methods showed evidence of re-use of nest...

Barred owls (Strix valia) have recently expanded their range and now encompass the entire range of the northern spotted owl (Strix ocddentalis caulina). This expansion has led to two important issues of concern for management of northern spotted owls: (1) possible competitive interactions between the two species that could contribute to population declines of northern spotted owls and (2) possible changes in vocalization behavior and detection probabilities of northern spotted owls induced by presence of barred owls. We used a two-species occupancy model to investigate whether there was...

Size-related changes in hydraulic architecture, carbon allocation, and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ~6 m tall exhibited more branch damage, larger numbers of dead individuals, higher wood density, greater leaf mass per area, lower leaf area to sapwood area ratio (LA/SA), lower stomatal conductance, and lower net CO2 assimilation than small trees. Stem-specific hydraulic conductivity...