Treesearch

A sequential extraction technique for compartmentalizing mercury (Hg) in leaves was developed based on a water extraction of Hg from the leaf surface followed by a solvent extraction of the cuticle. The bulk of leaf Hg was found in the tissue compartment (90-96%) with lesser amounts in the surface and cuticle compartments. Total leaf concentrations of Hg varied among species and was most closely correlated with the number of stomates per sample, supporting the hypothesis that stomatal uptake of atmospheric Hg (most likely Hg0) is a potential uptake pathway. Mercury concentrations in leaves...

Successful modeling of the carbon (C) cycle requires empirical data regarding species-specific root responses to edaphic characteristics. We address this need by quantifying annual root production of three bioenergy systems (continuous corn, triticale/sorghum, switchgrass) in response to variation in soil properties across a toposequence within a Midwestern agroecosystem. Using ingrowth cores to measure annual root production, we tested for the effects of topography and 11 soil characteristics on root productivity. Root production significantly differed among cropping systems. Switchgrass...

Restoring the forest herbaceous layer in remnant forests throughout the Midwestern United States (U.S.) is limited by the lack of seed and propagules for many plant species. As a result, restorationists often have limited material to work with and must seek out plant material at a regional rather than a local scale, without knowing whether regional provenances are ecologically appropriate. We conducted greenhouse and field experiments to examine persistence, growth, and reproduction of three herbaceous perennials (wild ginger, Virginia waterleaf, and James' sedge) that could be used for...

1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year. 2. To more completely describe thermal regimes, we developed several descriptors of magnitude, variability, frequency, duration and timing of thermal events throughout a year. We evaluated how these descriptors change over time using long-term (1979–2009), continuous...

We used a new ecohydrological model, Visualizing Ecosystems for Land Management Assessments (VELMA), to analyze the effects of forest harvest on catchment carbon and nitrogen dynamics. We applied the model to a 10 ha headwater catchment in the western Oregon Cascade Range where two major disturbance events have occurred during the past 500 years: a stand-replacing fire circa 1525 and a clear-cut in 1975. Hydrological and biogeochemical data from this site and other Pacific Northwest forest ecosystems were used to calibrate the model. Model parameters were first calibrated to simulate the...

As the climate changes and invasive species continue to spread, proactive management may be needed to conserve native plant populations. Selecting appropriate plant material for restoration or other actions that will sustain populations is an integral part of any such plan and must take into account genetic differentiation to limit maladaptation. Common garden studies are used to determine the genetic basis of trait variation among populations from different geographic sources. However, maternal effects, the effect of environment during offspring development, can also affect performance,...

High-elevation, five-needle white pines are among the most picturesque trees in many national parks as well as other federal, state, and private lands in western North America. These trees often live to a great age; the trees' gnarled trunks give testimony to fierce winds that buffet them on exposed rocky sites. Ancient limber pines (Pinus flexilis) in Rocky Mountain National Park occupy the edge of Trail Ridge Road, and a remarkable old giant stands sentinel on the shore of Lake Haiyaha. Limber pines accompany Rocky Mountain bristlecone pines (P. aristata) on the exposed ridges around...

This report from the Washington State Academy of Sciences (WSAS) is in response to a request from the Washington State Department of Natural Resources (DNR) to "identify approaches and opportunities ripe for research on understanding and managing root diseases of Douglas-fir." Similar to the process used by the National Research Council, the WSAS upon agreeing to undertake a project such as requested by the DNR assembles a committee of state, regional, national, and/or international experts, as needed; develops a statement of task to guide the study; conducts the study; and makes recommenda...

Reliable predictions of regional-scale population connectivity are needed to prioritize conservation actions. However, there have been few examples of regional connectivity models that are empirically derived and validated. The central goals of this paper were to (1) evaluate the effectiveness of factorial least cost path corridor mapping on an empirical resistance surface in reflecting the frequency of highway crossings by American black bear, (2) predict the location and predicted intensity of use of movement corridors for American black bear, and (3) identify where these corridors cross...

Stream pollution by nutrient loading is a chronic problem in the Midwest, United States, and greater impacts on water quality are expected as agricultural production and urban areas expand. Remnant riparian forests are critical for maintaining ecosystem functions in this landscape context, allowing water infiltration and capture of nutrients before they are lost from the system. Our objective was to identify linkages between riparian forest plant community composition and water quality in remnant forested headwater streams. We identified watersheds with embedded headwater streams in three...