Treesearch

Introduction of plant pathogens, insects, parasites, and predators into terrestrial and marine ecosystems is second only to habitat loss among major threats to biodiversity (Torchin et. al. 2002), and the frequency of introductions continues to increase (Flather et al. 1998, Torchin et al. 2002, Wilcove et al. 1998). Despite their detrimental impacts, introductions can also be seen as massive experiments having a defined time of onset, and the possibility to define and monitor changes in genetic structure of both host and parasite across environments over time. As such, introductions of...

The use of molecular genetics in forest pathology has greatly increased over the past 10 years. For the most part, molecular genetic tools were initially developed to focus on individual components (e.g., pathogen, host) of forest pathosystems. As part of broader forest ecosystem complexes, forest pathosystems involve dynamic interactions among living components (e.g., pathogens, hosts, antagonists, hyperparasites, endophytes, epiphytes, symbionts, etc.), as well as responses to their surrounding biophysical environments. These biotic and abiotic components shape and influence overall...

White pine blister rust (Cronartium ribicola) causes extensive damage to white pines and their associated ecosystems across North America. The anatomical and cellular characteristics of C. ribicola colonization in Pinus monticola branch and stem tissues were studied as a basis for understanding host tree reactions that may be related to resistance. Samples examined showed typical fusiform swelling and some had produced aecia. The reaction of phloem and xylem tissues was compared with noninfected tissue using light and electron microscopy. Cortical parenchyma and phloem polyphenolic...

The 2004 Report on the Health of Colorado's Forests begins with an overview of significant incidents and trends in forest insect and disease activity across the state. The remainder of the Report provides an in-depth examination of the ecology, condition and management of Colorado's ponderosa pine forests. Unlike previous editions, which highlighted a range of forest health concerns, this and future Reports will focus on the research related to a particular forest type. These detailed, science-based investigations should effectively deepen Coloradans' understanding of the forested landscape...

The complex topography of the inland northwestern U.S. (58.4 million ha) interacts with continental and maritime air masses to create a highly variable climate, which results in a variety of forest settings. Historically (1850 to 1900), approximately 20% of the area was covered by dry forests (Pinus ponderosa, Pseudotsuga menziesii), and an estimated 18% was covered by moist forests (Pinus monticola, Tsuga heterophylla). Frequent surface fires burned over 75% of the area of dry forests; today, these fires burn approximately 45% of the area. In the dry forests, successful fire exclusion and...

The silvicultural tools applicable for use in forests burned by mixed severity fire regimes are as highly variable as the structures and compositions the fires have historically created. Singly or in combination chunking, chipping, slashing, and piling can alter the character of surface fuels (e.g., small trees, shrubs, branches, and stems). These treatments can be combined with fire to reduce continuity and the amount of ground fuels (e.g., needles, litter, and rotten wood). Ground fuels, especially uncharacteristically deep layers at the base of trees, can be reduced by mechanically...

The moist, cold, and dry forests of the Inland Northwest occupy approximately 144 million acres. Ponderosa pine, lodgepole pine, western white pine, western larch, and Douglas-fir are usually the preferred commercial species of the area. These early-seral species are relatively resistant to endemic levels of insects and diseases. They tend to grow rapidly and in general produce commercial products at a young age, especially using focused management actions packaged in silvicultural systems that are documented in silvicultural prescriptions. Even-aged systems (clearcut, seed-tree, and...

Forest management objectives continue to evolve as the desires and needs of society change. The practice of silviculture has risen to the challenge by supplying silvicultural methods and systems to produce desired stand and forest structures and compositions to meet these changing objectives. For the most part, the practice of silviculture offers a robust set of procedures well suited for the timely and efficient production of timber crops, but often leaving simplified forests that do not necessarily reflect historical conditions, do neither provide a full range of wildlife habitats, nor...

Estimates of the location and extent of the red attack stage of mountain pine beetle (Dentroctonus ponderosae Hopkins) infestations are critical for forest management. The degree of spatial and temporal precision required for these estimates varies according to the management objectives and the nature of the infestation. This paper outlines a hierarchy of information requirements, from the perspectives of forest inventory, planning, and modeling. The capability of remotely sensed data to support these information requirements is presented, with specific focus on medium (Landsat) and high...

The effcacy of verbenone as a stand-level protectant against mountain pine beetle, Dendroctonus ponderosae Hopkins, attacks was tested in lodgepole and whitebark pine stands at five geographically separated sites, including three consecutive years at one site. Forty and 20 high-dose pouches, with a verbenone emission rate up to 50 mg/d per pouch, were spaced in a grid pattern throughout 0.40-ha plots, replicated up to six times at each site. Although the verbenone treatment did not prevent beetles from dispersing through treated stands, attacking large-diameter trees most frequently, the...