Treesearch

Results are presented of a 12-year monitoring program on the Coral Pink Sand Dunes and Sand Hills populations of the threatened Welsh's milkweed, Asclepias welshii N & P Holmgren. The species is an early sera1 member of the dune flora, colonizing blowouts and advancing with shifting dunes. When an area stabilizes and other vegetation encroaches, A. welshii is crowded out. Reproduction is by seeds and rhizomes, with the latter being more important. Three growth forms and their significance in colony dynamics are recognized. Monitoring has measured fluctuations in stem counts, vegetative...

Yellow-flowered columbines (Aquilegia chrysantha Gray) are usually found in small, isolated populations near streams and pools in mountain ranges throughout the southwestern United States. To study the long-term dynamics of these populations, which are vulnerable to extinction, we have monitored the demography of a population in Fillmore Canyon in the Organ Mountains of southern New Mexico. Annual estimates of growth, survival, and reproduction were recorded for 2,152 individuals in 15 one-meter square plots for 6 years. We estimated a seed bank survival rate from experimental plots and...

Plant conservation in the United States benefits directly and indirectly from national and international conservation initiatives. The United Nations Convention on Biological Diversity, which began in December 1993, serves as a guiding force for conservation in the United States even though the U.S. is not a party to the convention. An international meeting in 1998 of leaders concerned with biological collections and the field of systematics addressed what was called the Taxonomic Impediment, consisting of gaps of knowledge in our taxonomic system, a shortage of trained taxonomists, and...

Fire is being experimentally reintroduced to the forests of southern Ohio to determine its effectiveness in restoring and maintaining mixed-oak (Quercus spp.) forest communities. We studied the effects of repeated burning (1-4 years of annual burning) and recovery (1 year after burning) on the breeding bird community. Burning resulted in incremental but temporary reductions in the availability of leaf litter, shrubs, and saplings, but it did not affect trees, snags, or understory vegetation cover. Of 30 bird species monitored, 4 were affected negatively and 2 were affected positively by...

Concern for declines in big game habitat throughout the West and the pioneering work of revegetation researchers in the mid twentieth century led to increased use of native shrubs, grasses, and forbs for revegetation, and the 1975 establishment of the U.S. Department of Agriculture, Forest Service, Shrub Sciences Laboratory in Provo, Utah. During this period revegetation objectives shifted from an emphasis on production of commodities to conservation of biodiversity and ecosystem functions. Plant resource development altered from an agronomic approach focusing on plant improvement to one...

This guide describes all the 131 species of Carex known to occur in Wyoming, Colorado, and western portions of Kansas, Nebraska, and South Dakota. A dichotomous key is provided for identification in the field. Each species is described, with diagrams of the plant, head, pistillate scale, and perigynium. A distribution map appears for each species, as well as a table of characteristics and index.

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, causes considerable mortality in Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, forests. Within-stand distribution of mortality was examined in affected stands using geostatistical techniques. A 10 x 10 m grid was established in two 4-ha study sites. Live and beetle-killed host basal area was measured at each node. In a 16-ha stand, a variable-resolution grid was established and the same information collected. The relationship between Douglas-fir basal area and Douglas-fir basal area killed was examined using non-spatially...

Contemporary carrying capacity frameworks, such as Limits of Acceptable Change and Visitor Experience and Resource Protection, rely on formulation of standards of quality, which are defined as minimum acceptable resource and social conditions in parks and wilderness. Formulation of standards of quality involves elements of both science and values, and both of these elements must be integrated into "informed judgments" on the part of park and wilderness managers. That is, managers must ultimately make value-based judgments about the maximum acceptable level of visitor-caused impacts to the...

Wilderness is a special place that provides opportunity for unique and profound experiences. An essential task for the maintenance of these recreational opportunities is the definition and monitoring of experience quality. Four approaches to the measurement of the wilderness experience have developed in over 30 years of research: satisfaction approaches (which focus on evaluation of onsite conditions), benefits-based approaches (focusing on psychological outcomes), experience-based approaches (describing cognitive states experienced in wilderness), and meanings-based approaches (documenting...

As wilderness use levels have changed, managers have often considered implementation of use limits to control the impacts of use density. Use limits are generally intended to protect natural qualities and/or to ensure opportunities for solitude, although the second goal appears to have become more common over time, and may be the central use-related concern for certain high-use wildernesses. The goal of this paper is briefly to review the evolution of use limit systems in wilderness and then raise three key questions about use limits, with which managers and researchers must grapple before...