Treesearch

The genus Armillaria (2) and Armillaria mellea sensu lato (3) have been reported previously from Hawaii. However, Armillaria species in Hawaii have not been previously identified by DNA sequences, compatibility tests, or other methods that distinguish currently recognized taxa. In August 2005, Armillaria rhizomorphs and mycelial bark fans were collected from two locations on the island of Hawaii.

Nuclear ribosomal DNA regions (i.e. large subunit, internal transcribed spacer, 5.8S and intergenic spacer) were sequenced using a direct-polymerase chain reaction method from Armillaria ostoyae genets collected from the western USA. Many of the A. ostoyae genets contained heterogeneity among rDNA repeats, indicating intragenomic variation and likely intraspecific hybridization. Intragenomic variation was verified by visually editing base-sequence offsets in regions with insertions/deletions, and using sequence-specific internal primers to resequence heterogeneous regions. Phylogenetic...

Naturally occurring Cronartium ribicola infections were discovered in August and September, 2004 on Pedicularis racemosa and Castilleja miniata in a mixed stand of white pine blister rust-infected whitebark pine (Pinus albicaulis) and western white pine (P. monticola) in northern Idaho, at Roman Nose Lakes, ca 30 km west of Bonners Ferry. Infections were confirmed by ITS rDNA sequencing of teliospores. The ability of these species to act as host was confirmed by laboratory inoculations using aeciospores from whitebark pine. Isolates recovered from P. racemosa after artificial inoculations...

The moist forests of the Rocky Mountains typically support late seral western hemlock, moist grand fir, or western redcedar forests. In addition to these species, Douglas-fir, western white pine, western larch, ponderosa pine, and lodgepole pine can occur creating a multitude of species compositions, structures, and successional stages that can be arrayed in a variety of fine to coarse mosaics. Weather, insects and diseases are often the most frequent and persistent disturbances. Large high severity wildfires do occur but their intervals have been lengthened by successful fire suppression...

Cold-induced mortality is a key factor driving mountain pine beetle, Dendroctonus ponderosae, population dynamics. In this species, the supercooling point (SCP) is representative of mortality induced by acute cold exposure. Mountain pine beetle SCP and associated cold-induced mortality fluctuate throughout a generation, with the highest SCPs prior to and following winter. Using observed SCPs of field-collected D. ponderosae larvae throughout the developmental season and associated phloem temperatures, we developed a mechanistic model that describes the SCP distribution of a population as a...

Removal of deep litter and duff from the base of mature southwestern ponderosa pine trees is commonly recommended to reduce mortality following prescribed burns, but experimental studies that quantify the effectiveness of such practices in reducing mortality are lacking. Following a pilot study, on each of four sites in northern Arizona we monitored 15-16 sets of 8 matched trees (N=488) on areas designated to be burned and adjacent unburned sites and randomly assigned one of four litter removal treatments: 1) to 9" with raking, 2) to 9" with a leaf blower, 3) to 40" with raking, and 4) no...

Hanging gardens are island-like habitats dominated by mesophytic-hydrophytic plant communities, growing on seeps on the xeric canyon walls of the Colorado Plateau in the American West. We measured the abundance of species and physical microhabitat characteristics of 73 individual hanging gardens during the growing seasons of 1991-1993. Cluster analysis of a simplified Morisita community similarity index matrix produced four distinct clusters of herbaceous vegetation: Adiantum capillus-veneris, Aquilegia micrantha, Calamagrostis scopulorum, and Cirsium rydbergii Herbaceous Associations....

Ponderosa pine forests of the southwestern United States were historically characterized by relatively open, parklike stands with a bunchgrass-dominated understory. This forest structure was maintained by frequent, low-intensity surface fires. Heavy livestock grazing, fire suppression, and favorable weather conditions following Euro-American settlement in the late 19th century resulted in a dramatic increase in pine regeneration. Today, many of these forest stands have high stand densities with low understory production, and are susceptible to infrequent, stand-replacing fires. The primary...

With fire exclusion and the consequent absence of fire-associated floods, many river and stream ecosystems throughout the Rocky Mountains have undergone hydrologic and vegetation changes.

Pool-breeding amphibian populations operate at multiple scales, from the individual pool to surrounding upland habitat to clusters of pools. When metapopulation dynamics play a role in long-term viability, conservation efforts limited to the protection of individual pools or even pools with associated upland habitat may be ineffective over the long term if connectivity among pools is not maintained. Connectivity becomes especially important and difficult to assess in regions where suburban sprawl is rapidly increasing land development, road density, and traffic rates. We developed a model...