Treesearch

Various human groups have greatly affected the processes and evolution of Middle Rio Grande Basin ecosystems, especially riparian zones, from A.D. 1540 to the present. Overgrazing, clear-cutting, irrigation farming, fire suppression, intensive hunting, and introduction of exotic plants have combined with droughts and floods to bring about environmental and associated cultural changes in the Basin. As a result of these changes, public laws were passed and agencies created to rectify or mitigate various environmental problems in the region. Although restoration and remedial programs have...

Llama use in wilderness is projected to increase over the next 5 years. While the greatest concerns about this increase in use are unexpected impacts to native flora, impacts to native fauna, and conflicts with other user types, there is also concern about how prepared managers are to deal with this increasing recreation demand. This research compares manager attitudes and knowledge to those of hikers, horseback riders, and commercial llama customers in the Intermountain West. With managersí expectations that all packstock use will continue to increase in the near future, this assessment...

We used pitfall traps and time-constrained searches to sample amphibians and reptiles and to describe their habitats in oak woodlands at three areas in California. We captured 766 individuals representing 15 species during pitfall trapping and 333 animals representing 15 species during the time-constrained searches. A total of 19 species were sampled. Across all study areas, several positive relationships were found between animal abundance and the cover of specific tree species. At Tejon Ranch, two salamanders - Batrachoseps nigriventris and Ensatina eschscholtzii croceater -- were...

We studied the relationship between breeding birds and seral stages of green ash (Fraxinus pennsylvanica) woodlands in central South Dakota between 1990 and 1992. Stands of early seral green ash undergoing primary succession had few small trees with western snowberry (Symphoricarpos occidentalis) in the understory. Some early seral green ash stands resulted from retrogression and had large trees with grass understory. Late seral green ash stands were represented by greater overstory cover consisting of green ash and chokecherry (Prunus virginiana) shrubs and small trees in the understory....

Descriptions of morphological characteristics, habitat, and geographic distributions are provided for 114 sedges (Carex spp.) of the Intermountain area. A dichotomous key, color photographs, line drawings, and discussions highlighting differences among similar species aid identification. An illustrated morphology, glossary, and index of common names simplify use. The guide is not inclusive; comprehensive local floras should be checked to confirm identifications.

An estimated global extinction rate that appears to be unprecedented in geological time (May 1990) has heightened concern for the increasing number of rare species. Moreover, this elevated extinction rate is being attributed to the activities of humans rather than to some calamitous natural disaster (Pimm et al. 1995). Conservation efforts to slow biodiversity loss have traditionally focused on species with few remaining individuals, based on the assumption that they are the most vulnerable to extinction (Sisk et al. 1994). Consequently, rarity has been used as an important criterion for...

The method of paired comparison is modified to allow choices between two alternative gains so as to estimate willingness to accept (WTA) without loss aversion. The robustness of WTA values for two public goods is tested with respect to sensitivity of theWTA measure to the context of the bundle of goods used in the paired comparison exercise and to the scope (scale) of the public good project. There was no statistical difference in WTA measures for open space based on independent treatments with different contexts. One treatment involved valuing open space within a set of goods with similar...

The objective of this study was to test the hypothesis that there are no differences in understory production, by species, due to stocking levels of Pinus ponderosa (ponderosa pine). Understory production was estimated by species, on 3 replicates each of 8 growing stock levels, ranging from clearcuts to unthinned stands, in both sapling- and pole-sized stands (48 plots) over 3 nonconsecutive years. All stands were approximately 70 yr old when tinning treatments were applied. Production of many herbaceous species, especially Agropyron spp. (wheatgrasses) and Carex spp. (sedges), declined as...

Poor tree reproduction, sparse shrub cover, and increasing amounts of exotic species such as Kentucky bluegrass (Poa pratensis) are common problems in woody draws in the Northern Great Plains. Although the historic role of fire in maintaining woody draws is unclear, it is likely that these woodlands burned periodically, especially in dry years on hot and windy days. This paper summarizes the first of two studies designed to assess the role of fire in maintaining woody draws in this region.

From 1994 to 1996, researchers monitored 695 nests of nine cavity-nesting bird species and measured vegetation at nest sites and at 90 randomly located sites in burned ponderosa pine forests of southwestern Idaho. Site treatments included two types of salvage logging, and unlogged controls. All bird species selected nest sites with higher tree densities, larger diameter trees, and more heavily decayed snags than that expected based on availability of such trees. This publication is an updated version of a 1997 progress/interim report, and the study is one in a series of long-term studies...