Treesearch

Ecosystems and landscapes change over time as a function of vegetation characteristics and disturbance regimes, including fire. Interactions between disturbance events and forest development (succession) create patterns of vegetation across landscapes. These patterns result from, and change with respect to, species compositions and structures that arise from disturbance events interrupting successional pathways at ditlerent points during forest development. Vegetation patterns and disturbance regimes are modified by the effects of topography on the biotic and abiotic processes that drive...

During the last 2 years, many people from numerous government agencies and private institutions compiled a scientific assessment of the natural and human resources of the Interior Columbia River Basin (Jensen and Bourgeron 1993). This assessment is meant to guide the development of a coarse-scale Environmental Impact Statement for all 82 million hectares comprising the Interior Columbia River Basin (fig. 1). A myriad of spatial data products has been generated from this immense effort, including a wide variety of coarse-scale GIs data layers that describe historical, current, and fbture...

Stand replacement prescribed burning has been applied in Alaska on several occasions. Based on that experience, perspectives can be provided, issues can be discussed, and keys to success can be identified that are applicable to stand replacement prescribed burning activities in areas outside Alaska.

Many of the ponderosa pine (Pinus ponderosa) mixed conifer stands in the Methow Valley of north-central Washington have developed understories of Douglas-fir (Pseudotsuga rnenziesii) as a result of fire exclusion. Most of the forest floor has not yet become cluttered with dead woody fuel. Instead, the live biomass has increased and created more ladder fuels (branches near enough to the ground to carry a surface into the crowns). Consequently, crown fires can be initiated by fires of lower intensity. There is an increase in dwarf mistletoe (Arceuthobiurn spp.), root rot, and other associated...

Fire has influenced both the morphology of species and their distribution for millions of years. Prescribed fire may be necessary to meet ecological restoration objectives, but reintroducing fire is a complex task. Fire may have undesirable effects if it is reintroduced outside of its "historical range of variability," or where the ecosystem has undergone major shifts in species composition or structure due to fire exclusion. Oregon white oak or Garry oak (Quercus garryana) woodlands and their associated prairies are a good example of this problem (Griffin 1977).

The Oregon Coast Range supports some of the most dense and productive forests in North America. In the pre-harvesting period these forests arose as a result of large fires-the largest covering 330,000 ha (Teensma and others 1991). These fires occurred mostly at intervals of 150 to 300 years. The natural disturbance regime supported a diverse fauna and large populations of anadromous salmonids (salmon and related fish). In contrast, the present disturbance regime is dominated by patch clearcuts of about 10-30 ha superimposed on most of the forest land with agriculture on the flats near...

For thousands of years fire has been a major, natural disturbance in the forest landscape from the Cascade Range westward to the coast in Oregon and Washington (Agee 1993; Brubaker 1991). Viewing the landscape of the central western Cascades in Oregon from a high point, one can see that fires of variable intensity and areal extent have created a complex mosaic of forest patches (Morrison and Swanson 1990).

Several decades of fire suppression following logging around the turn-of-the-century has produced dense, evenage stands of ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii). They contrast with the original forests where frequent, low-intensity fires gave rise to open, parklike, and often uneven-age stands of ponderosa pine. Forests in current conditions are prone to insect infestations, disease outbreaks, and severe wildfires. As residential development and recreational use of this forest type continues to increase, the need for low-impact treatments for mitigating...

Ecological research has implicated the practice of fire exclusion as a major contributor to forest health problems in the semiarid ponderosa pine (Pinus ponderosa) zone of the Inland West (Mutch and others 1993; Sampson and others 1994). Prior to 1900, frequent, low-intensity fires occurred on upland forests in this forest zone at intervals of 5 to 30 years. With fire exclusion, dense understories and thickets of conifers have developed, producing stands that are highly susceptible to a variety of insect and disease epidemics-and severe wildfires. These concerns have led to proposals and a...

Seral, fire dependent lodgepole pine (Pinus contorta Dougl.) communities are an important component of upper elevation forests throughout the Northern Rockies, where they cover 4 million acres, or about 17 percent of the land base. On the Bitterroot National Forest, lodgepole pine occurs mostly between 5,500 and 7,500 feet.