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The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, attacks Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), throughout western North America. Periodic outbreaks cause increased mortality of its host. Land managers and forest health specialists often need to determine population trends of this insect. Bark samples were obtained from 326 trees distributed over 21 stands during a 2- year period in late winter to early spring of 1997 and 1998 in the Colorado Front Range. The variance to mean relationship of brood adults was examined using the Taylor power law, and a...

Hydrothermal time (HTT) describes progress toward seed germination under various combinations of incubation water potential ( ) and temperature (T). To examine changes in HTT parameters during dormancy loss, seeds from two populations of the bunchgrass Elymus elymoides were incubated under seven temperature regimes following dry storage at 10, 20 and 30°C for intervals from 0 to 16 weeks. Fully after-ripened seeds were primed for 1 week at a range of s. Data on germination rate during priming were used to obtain a HTT equation for each seed population, while data obtained following...

This study describes the results of the application of a single dormant season prescribed fire to two southern Ohio forest sites for the purposes of restoring the ecosystem functional properties that existed in these sites prior to major human intervention (clearcutting, fire suppression, and atmospheric deposition). Each forest site was composed of three contiguous watershed units, two of which were burned in April of 1996. The forest sites differed in soil pH and available litter mass prior to the fires, and in both sites pH and available inorganic N varied among landscape positions such...

This paper presents an integrated system to support urban natural resource management. With the application of remote sensing (RS) and geographic information systems (GIS), the paper emphasizes the methodology of integrating information technology and a scientific basis to support ecosystem-based management. First, a systematic integration framework is developed and the major functionality of each component is discussed. Next, an integrated urban storm water management system is discussed at an operational scale. Then, an application of RS and GIS with hydrologic modeling to improve storm...

In the Pacuare River Watershed in Costa Rica, farm size, ownership, and production data were collected and spatially referenced through global positioning surveys and farmer assessments of property boundaries in relation to cadastral maps and air photographs. Using GIs based spatial overlays, this data were integrated with previously collected land use and land degradation data. The resulting integrated database allowed for land use and degradation data to be classified by alternative farm sizes in order to assess the individual needs and relative priority of a soil conservation program...

Stream channels are integral to watershed function and are affected by watershed management decisions. Given an understanding of the relationships among channel and watershed variables, they may serve as indicators of upland condition or used in distributed rainfall-runoff models. This paper presents a quantitative analysis of fluvial morphology as related to watershed characteristics for two disparate sites in Arizona. Detailed geographic information system (GIS) analyses were combined with 297 cross-section surveys. Statistical relationships among GIS-based watershed and field-based...

Information and related literature on watershed management practices is sometimes not widely known nor readily accessible. New electronic technologies provide unique tools for disseminating research findings to scientists, educators, land management professionals, and the public. This paper illustrates how the usefulness and accessibility of research information from the Beaver Creek Experimental watershed in north central Arizona increases using the World Wide Web.

Population increases will continue to severely pressure water resources in the 21st century. Consequently, the importance of watershed management will increase. The potential demand in the next century for information on, and individuals skilled in, watershed management raises several important issues: the need for watershed management to have a central voice to gain the attention of political, government agency, university, and business leaders; the adequacy of watershed management professional training; the need to identify watershed management as a discipline; and the need for a new...

Mining is one of the most important sources of income for the Baja California Sur state. This state is the second most important area for mineral (gold, silver, copper) and non-mineral (salt) mining activities in the Mexican Republic. In the San Antonio-El Triunfo region, mineral-mining activities flourished during the 19th century. Tons of debris containing a high quantity of arsenic were deposited on the soil as a by-product of these activities. In 1998, local inhabitants reported their suspicion of the contamination of the region's wells. For this reason, we developed this study, which...

This study is to develop and apply a practical procedure for the time series analysis of reservoir eutrophication conditions. A multiplicative decomposition method is used to determine the trophic variations including seasonal, circular, long-term and irregular changes. The results indicate that (1) there is a long high peak for seven months from April to October yearly; (2) the long-term trend (T) increases with time (t) as following relationship: T = 51.4231 + 0.0605t; and (3) circular change period decreases from two or three years to about one year. The methodology is feasible to...