Treesearch

We present findings from two complementary studies that examine how fire modifies soil organic matter properties, and how these modifications influence rates of decomposition and carbon (C) exchange in black spruce (Picea mariana) ecosystems of interior Alaska. Our laboratory study showed that burning reduced the sensitivity of decomposition to increased temperature, most likely by inducing moisture or substrate quality limitations on decomposition rates. Burning also reduced the decomposability of Sphagnum-derived organic matter, increased the hydrophobicity of feather-moss-derived...

Land surface treatments are often applied after severe wildfires to mitigate runoff and erosion threats. However, questions remain about treatment effectiveness, even as treatment costs continue to rise. We experimentally evaluated the effects of seeding and fertilization treatments on vegetative and total soil cover for two growing seasons after the Pot Peak wildfire in the eastern Cascade Mountains. Without treatments, vegetative cover averaged 15 percent the first year and 27 percent the second year after wildfire. Fertilization significantly increased vascular plant cover and reduced...

Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage. In contrast to nonglacial rivers, we find that the bioavailability of DOM to marine microorganisms is significantly correlated with increasing 14C age. Moreover, the most heavily glaciated watersheds are the source of the oldest...

Predicting plant community responses to changing environmental conditions is a key element of forecasting and mitigating the effects of global change. Disturbance can play an important role in these dynamics, by initiating cycles of secondary succession and generating opportunities for communities of long-lived organisms to reorganize in alternative configurations. This study used landscape-scale variations in environmental conditions, stand structure, and disturbance from an extreme fire year in Alaska to examine how these factors affected successional trajectories in boreal forests...

Scotch broom is a large, leguminous shrub that has invaded 27 U.S. states. The species produces seeds with a hard coat that remain viable in the soil for years. Growth-chamber studies were conducted to determine effects of temperature regime and cold-stratification period on seed germination. Seedling emergence, mortality, and biomass also were studied in response to sulfometuron and metsulfuron herbicides and variation in soil texture and watering regime. Germination was greatest for a dark/light temperature regime of 15/20 C. Initial rates of germination increased as stratification...

Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (FST ~ 0.03) from larger...

We evaluated whether fitting fluorescence excitation-emission matrices (EEMs) to a previously validated PARAFAC model is an acceptable alternative to building an original model. To do this, we built a l0-component model using 307 EEMscollected from southeast Alaskan soil and streamwater. All 307 EEMs were then fit to the existing model (CM) presented in Cory and McKnight (Environ. Sci. Technol. 2005, 39, 8142-8149). The first approach for evaluating whether the EEMs were fit well to the CM model was an evaluation of the residual EEMs, and we found 22 EEMs were fit poorly by the CM model....

Ecological problem solving requires a flexible social infrastructure that can incorporate scientific insights and adapt to changing conditions. As applied to watershed management, social infrastructure includes mechanisms to design, carry out, evaluate, and modify plans for resource protection or restoration. Efforts to apply the best science will not bring anticipated results without the appropriate social infrastructure. For the Long Tom Watershed Council, social infrastructure includes a management structure, membership, vision, priorities, partners, resources, and the acquisition of...

In 2003 to 2008, we conducted surveys to document the eastern and northern range limits of red tree voles (Arborimus longicaudus) in the Columbia River Gorge and Hood River basin, Oregon. Our survey indicated the current range of the vole includes the area from Wahkeena Creek, 20 km east of Troutdale to Seneca Fouts State Park, 6 km west of Hood River. We also found a concentration of red tree vole nests in the headwaters of the Lake Branch of Hood River, 27 km southwest of the town of Hood River. Of the 70 vole nests located, 36 (52 percent) were old unoccupied nests with no evidence of...

Root morphology and stem size were evaluated as predictors of height and basal-area growth (measured at groundline) of 1-1 Oregon white oak (Quercus garryana Dougl. ex Hook.) seedlings planted in raised beds with or without an additional irrigation treatment. Seedlings were classified into three root classes based on a visual assessment of the fibrosity of their root systems. Early-season and late-season height and basal-area growth differed significantly among root classes after accounting for initial seedling size. Irrigation significantly increased late-season height growth, but not the...