Treesearch

Some fundamental properties of soils that pertain to the concept of soil quality are discussed including a discussion of what can and cannot be changed with management.Case studies showing the effects of N-fixing vegetation and N-enrichment effects on invasive species are provided to illustrate the complications that may arise from applying one soil quality standard to all cases. Finally, the “nitrogen problem is discussed: nitrogen is the most frequently growth-limiting nutrient and yet it is also the nutrient that is often the most problematic to manage without causing deleterious...

Most private and public forest land owners and managers are compelled to manage their forests sustainably, which means management that is economically viable,environmentally sound, and socially acceptable. To meet this mandate, the USDA Forest Service protects the productivity of our nation’s forest soils by monitoring and evaluating management activities to ensure they are both scientifically wise and socially responsive.The purpose of this paper is to review soil quality indicators and models for their possible use in soil management and evaluation programs. The Forest Service has taken...

The resiliency of forest sites after a pulse disturbance is one of the key questions mandated by the National Forest Management Act (NFMA) of 1976. This Act mandated that we maintain the productive capacity of federally managed stands. The original USDA Forest Service soil quality standards were based largely on professional judgment. The North American Long-Term Soil Productivity (LTSP) study was founded to provide a scientific basis for validating or proposing changes to the current standards. Research on the100 field installations centers around how two key properties, site organic...

Many forestry and agricultural agencies and organizations worldwide have developed soil monitoring and quality standards and guidelines to ensure future sustainability of land management. These soil monitoring standards are typically developed in response to international initiatives such as the Montreal Process, the Helsinki Ministerial Conference,or in support of Best Management Practices program development and Code of Forest Practices regulations. This paper describes international (Australia, New Zealand, Canada,and the European Union) and U.S. efforts and perspectives on soil quality...

Many fuel beds, especially live vegetation canopies (conifer forests, shrub fields, bunch-grasses) contain gaps between vegetation clumps. Fires burning in these fuel types often display thresholds for spread that are observed to depend on environmental factors like wind, slope, and fuel moisture content. To investigate threshold spread behaviours, we conducted a set of laboratory burn experiments in artificial fuel beds where gap structure, depth, and slope were controlled. Results revealed that fire spread was limited by gap distance and that the threshold distance for spread was...

Extreme weather often contributes to crown fires, where the fire spreads from one tree crown to the next as a series of piloted ignitions. An important aspect in predicting crown fires is understanding the ignition of fuel particles. The ignition criterion considered in this work is the critical mass flux criterion - that a sufficient amount of pyrolysis gases must be generated for a diffusion flame to be established above the surface. An apparatus was built to measure the critical mass flux for sustained flaming ignition of woody materials for varying environmental conditions (heat flux...

There are a number of situations when fires may occur at low pressures and oxygen concentrations that are different than standard atmospheric conditions, such as in buildings at high elevation, airplanes, and spacecraft. The flammability of materials may be affected by these environmental conditions. Since ignition delay is a measure of material flammability and directly influences whether a fire will occur, experiments were conducted to assess the variation of the ignition delay of PMMA in sub-atmospheric pressures and elevated oxygen concentrations. Three sets of experiments were...

Mountain streams provide important habitats for many species, but their faunas are especially vulnerable to climate change because of ectothermic physiologies and movements that are constrained to linear networks that are easily fragmented. Effectively conserving biodiversity in these systems requires accurate downscaling of climatic trends to local habitat conditions, but downscaling is difficult in complex terrains given diverse microclimates and mediation of stream heat budgets by local conditions. We compiled a stream temperature database (n = 780) for a 2500-km river network in...

Crested wheatgrass (Agropyron cristatum (L.) Gaertn.) is a nonindigenous grass introduced to North America for improving degraded rangelands. It is often criticized for forming nearly monotypic stands. Our objective was to determine the feasibility of restoring native plant species to crested wheatgrass-dominated rangeland. We investigated methods for suppressing crested wheatgrass followed by revegetation with a mix of native species. We tested five suppression treatments: undisturbed, low rate of glyphosate (0.25x recommended rate), high rate of glyphosate (recommended rate), 1-pass...

The purpose of this study was to understand wilderness visitors' perceptions of wildland fire and describe visitors' wilderness recreational experience following wildland fire in the Boundary Waters Canoe Area Wilderness (BWCAW). Qualitative interviews revealed visitors' perceptions of burned areas as well as if and how activities and behaviors were influenced by wildland fire occurrence. Results indicated that BWCAW visitors predominately perceived burned areas as interesting landscape features worthy of exploration. Route choices did not change due to burned areas but site selection and...