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Bothell, WA, United States

Larson A.J.,University of Montana | Lutz J.A.,Utah State University | Donato D.C.,111 Washington St. SE | Freund J.A.,University of Washington | And 4 more authors.
Ecology | Year: 2015

Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially autocorrelated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a threedecade record of tree mortality from replicated mapped permanent plots located in young (<60-year-old) and old-growth (>300-year-old) Abies amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strongly density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatially aggregated, but was density independent and did not change the spatial pattern of surviving trees. These results extend current theory by demonstrating that densitydependent competitive mortality leading to increasingly uniform tree spacing in young forests ultimately transitions late in succession to a more diverse tree mortality regime that maintains spatial heterogeneity through time. © 2015 by the Ecological Society of America.

Creutzburg M.K.,Oregon State University | Halofsky J.S.,111 Washington St. SE | Hemstrom M.A.,Forestry science Laboratory | Hemstrom M.A.,Oregon State University
USDA Forest Service - General Technical Report PNW-GTR | Year: 2012

Many threats are jeopardizing the sagebrush steppe of the Columbia Basin, including the spread of invasive species such as cheatgrass (Bromus tectorum L.) and the expansion of western juniper (Juniperus occidentalis Hook.) into historic shrub steppe. Native sagebrush steppe provides productive grazing lands and important habitat for many wildlife species, and managers are in need of landscapescale tools to assess shrub steppe conversion risk and management options to maintain native shrub steppe. We used a state-and-transition modeling approach to project changes in sagebrush steppe vegetation across the landscape of southeastern Oregon. Models were constructed using both empirical data, including empirically derived fire probabilities, and expert opinion for processes that are still poorly documented, such as livestock grazing effects. With unrestricted grazing and no restoration treatments, future invasion by exotic annual grasses in warm, dry sagebrush steppe and juniper expansion into cool, moist sagebrush steppe are likely to accelerate in the next 50 years under current climatic conditions. Invasions are also likely to be spatially heterogeneous, depending on the mix of sagebrush steppe environments, current rangeland condition, disturbances, and management activities across the landscape. We conclude that state-and-transition models provide a useful framework for conceptualizing vegetation dynamics of sagebrush steppe systems, identifying gaps in knowledge, projecting future vegetation conditions, and identifying potential areas for restoration at landscape scales.

Looney C.,111 Washington St. SE | Zack R.S.,Washington State University | LaBonte J.R.,35 Capitol Street N.E
ZooKeys | Year: 2014

In this paper we report on ground beetles (Coleoptera: Carabidae) collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site), which is located in southcentral Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte), and Stenolophus lineola (Fabricius). Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity. © C. Looney et al.

Looney C.,111 Washington St. SE | Smith D.R.,U.S. Department of Agriculture | Collman S.J.,Washington State University | Langor D.W.,Natural Resources Canada | Peterson M.A.,Western Washington University
Journal of Hymenoptera Research | Year: 2016

Examination of museum specimens, unpublished collection data, and field surveys conducted between 2010 and 2014 resulted in records for 22 species of sawflies new to Washington State, seven of which are likely to be pest problems in ornamental landscapes. These data highlight the continued range expansion of exotic species across North America. These new records also indicate that our collective knowledge of Pacific Northwest arthropod biodiversity and biogeography is underdeveloped, even for a relatively well known and species-poor group of insects. Notable gaps in the knowledge of Washington State's Symphyta remain for the Olympic Peninsula, the Cascade Mountain Range, and the arid interior of the state. Washington's shrub-steppe appears to be particularly poorly surveyed for sawflies.

Lindenmayer D.B.,Australian National University | Franklin J.F.,University of Washington | Lohmus A.,University of Tartu | Baker S.C.,University of Tasmania | And 14 more authors.
Conservation Letters | Year: 2012

Approximately 85% of the global forest estate is neither formally protected nor in areas dedicated to intensive wood production (e.g., plantations). Given the spatial extent of unprotected forests, finding management approaches that will sustain their multiple environmental, economic, and cultural values and prevent their conversion to other uses is imperative. The major global challenge of native forest management is further demonstrated by ongoing steep declines in forest biodiversity and carbon stocks. Here, we suggest that an essential part of such management-supplementing the protection of large reserves and sensitive areas within forest landscapes (e.g., aquatic features)-is the adoption of the retention approach in forests where logging occurs. This ecological approach to harvesting provides for permanent retention of important selected structures (e.g., trees and decayed logs) to provide for continuity of ecosystem structure, function, and species composition in the postharvest forest. The retention approach supports the integration of environmental, economic, and cultural values and is broadly applicable to tropical, temperate, and boreal forests, adaptable to different management objectives, and appropriate in different societal settings. The widespread adoption of the retention approach would be one of the most significant changes in management practice since the onset of modern high-yield forestry. © 2012 Wiley Periodicals, Inc.

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