Treesearch

The flora of the San Pedro Riparian National Conservation Area (SPRNCA) consists of 618 taxa from 92 families, including a new species of Eriogonum and four new State records. The vegetation communities include Chihuahuan Desertscrub, cottonwood-willow riparian corridors, mesquite terraces, sacaton grasslands, rocky outcrops, and cienegas. Species richness is enhanced by factors such as perennial surface water, unregulated flood regimes, influences from surrounding floristic provinces, and variety in habitat types. The SPRNCA represents a fragile and rare ecosystem that is threatened by...

The pine-dominated woodlands and forests of the Sky Islands typically sustained surface burns about once per decade until the turn of the 19th to the 20th centuries, when livestock grazing and organized fire suppression effectively ended this centuries-long pattern. Fire scar chronologies from 31 sites in 10 mountain ranges illustrate this history. By combining elevational transects of fire scar chronologies in three of the mountain ranges it is possible to visualize the temporal changes in widespread fire occurrence. Combining all 31 chronologies for the region, it is evident that there...

The goal of this study was to scale up ground-based range assessments to ranch and landscape scales in southeast Arizona using remote sensing and minimum amount of field data collection. Remotely sensed metrics of canopy cover, biomass, and mesquite composition were used to assess soil and site stability and biotic integrity. Ground-based assessments were conducted on 11 field locations and used in conjunction with Natural Resources Conservation Service (NRCS) ecological site descriptions to develop evaluation criteria on two different ecological sites. The data were combined in a GIS and...

We planted 742 greenhouse-grown containerized aspen seedlings in the riparian area of Hurd Creek on the Arapaho National Forest east of Tabernash, Colorado. Objectives were to (1) determine whether aspen seedlings can be planted in an operational setting and survive in sufficient numbers to successfully establish a mature aspen stand and (2) determine the effectiveness of fencing on aspen seedling survival. Five-year survival rates were 18 percent in the fenced area and 23 percent in the unfenced area. Seedling heights were significantly taller in the fenced area than in the unfenced area.

Total numbers of birds and numbers of bird species were significantly (p=0.05 percent) higher in stands of big sagebrush than in stands of greasewood. This was especially true for Brewer’s sparrow, lark sparrow, and mourning dove. The big sagebrush ecosystem appears to support greater number of birds and more species of birds than does the greasewood ecosystem.

This assessment characterizes, at a regional scale, forest biomass that can potentially be removed to implement the fuel reduction and ecosystem restoration objectives of the National Fire Plan for the Western United States. The assessment area covers forests on both public and private ownerships in the region and describes all standing tree volume including stems, limbs, and tops. Analysis of treatment areas and potential removals is included. Additionally, the operational systems necessary to effect the treatments as well as potential erosion impacts, utilization opportunities and market...

Using data obtained in 2002 and 2003 from sites in the Hummingbird Monitoring Network, we investigated the effect of geographic factors—latitude, longitude, and elevation—and year on hummingbird diversity patterns in Southwestern U.S.A. In California, none of these factors affected hummingbird richness but elevation significantly affected abundance. In southeastern Arizona, longitude and elevation significantly affected richness; year affected abundance. For all sites, elevation and longitude affected richness, year and elevation affected abundance. We compared these results with global...

An accuracy assessment of the Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation continuous field (VCF) tree cover product using two independent ground-based tree cover databases was conducted. Ground data included 1176 Forest Inventory and Analysis (FIA) plots for Arizona and 2778 Southwest Regional GAP (SWReGAP) plots for Utah and western Colorado. Overall rms. error was 24% for SWReGAP and 31% for FIA data. VCF bias was positive at low observed tree cover but systematically increased thereafter until at greater than 60% observed tree cover, VCF tree cover was 40% (SWReGAP)...

This report compiles information about recent progress in the application of computer simulation modeling to planning and management of recreation use, particularly in parks and wilderness. Early modeling efforts are described in a chapter that provides an historical perspective. Another chapter provides an overview of modeling options, common data input requirements, and useful model outputs. The bulk of the report consists of case studies that illustrate a broad array of recreational situations and management applications for simulation modeling. A final chapter describes some future...

The USDA Forest Service implemented a more holistic form of ecosystem management than previously practiced in the early 1990s through several ecosystem programs implemented in the Western United States. The ecosystem program that concerns this conference was a collaboration on “Achieving Ecosystem Management in the Borderlands of the Southwestern United States through Research and Management Partnerships” among researchers, managers, conservationists, and local landowners. Concurrent with initiation of this program was the first conference on “Sky Islands of the Madrean Archipelago,” which...