Competition for territories in red-winged blackbirds: Is resource-holding potential realized?

Summary In resource-defence mating systems we intutively expect that the most competitive males should win the best resources so that, in territorial species, male quality and territory quality will be highly correlated. In the polygyny threshold model (PTM) of mate choice this expectation has become an assumption. We performed a removal experiment using red-winged blackbirds to test the validity of this assumption. On the basis of two morphological and two behavioral indices of competitive ability we found only weak correlation between male competitive ability and territory quality. Factors potentially contributing to this result include habitat quality perception, site dominance, and site fidelity. However, both our experimental design and measurement of male competitive ability may have caused us to underestimate the real correlation between male quality and territory quality. Nevertheless, our results suggest that male quality is not perfectly correlated with territory quality as is assumed in the PTM. Therefore, male quality and territory quality should be treated independently when modelling mate choice in this and other territorial species.     

POSSIBILITIES OF INCREASED WATER SUPPLY FROM CLOUD SEEDING1

ABSTRACT. A review of the development of weather modification to augment precipitation including the cloud-physical foundation is presented. Recent work has tended to re-emphasize the importance of physical understanding of storm systems and of the effects of cloud seeding. The Pyramid Lake Seeding Project is discussed.     

Spatial and time variations of radon-222 concentration in the atmosphere of a dead-end horizontal tunnel

The concentration of radon-222 has been monitored since 1995 in the atmosphere of a 2 m transverse dimension, 128 m long, dead-end horizontal tunnel located in the French Alps, at an altitude of 1600 m. Most of the time, the radon concentration is stable, with an average value ranging from 200 Bq m(-3) near the entrance to about 1000 Bq m(-3) in the most confined section, with an equilibrium factor between radon and its short-lived decay products varying from 0.61 to 0.78. However, radon bursts are repeatedly observed, with amplitudes reaching up to 36 x 10(3) Bq m(-3) and durations varying from one to several weeks, with similar spatial variations along the tunnel as the background concentration. These spatial variations are qualitatively interpreted in terms of natural ventilation. Comparing the radon background concentration with the measured radon exhalation flux at the wall yields an estimate of 8+/-2 x 10(-6) s(-1) (0.03+/-0.007 h(-1)) for the ventilation rate. The hypothesis that the bursts could be due to transient changes in ventilation can be ruled out. Thus, the bursts are the results of transient increased radon exhalation at the walls, that could be due to meteorological effects or possibly combined hydrological and mechanical forcing associated with the water level variations of the nearby Roselend reservoir lake. Such studies are of interest for radiation protection in poorly ventilated underground settings, and, ultimately, for a better understanding of radon exhalation associated with tectonic or volcanic processes.     

Lessons learned from recent incidents: Facility siting, atmospheric venting, and operator information systems

Recent incidents have focused attention on a number of technical and management systems that need to be addressed by industry. A multiple layer of protection approach is essential for the prevention of incidents and/or reduction of consequences. Safety culture and operational discipline are the overall embracing factors that influence the safety performance of a facility. However, as recent events have indicated, there are a number of technical and engineering issues that must also be developed and implemented appropriately. Some of these issues that could lead to incidents with catastrophic consequences include facility siting and atmospheric relief venting. Impact of operator information systems on the prevention of releases of hazardous materials from their containment is also another significant factor that should be given appropriate attention.

This paper describes these three topics based on the findings from recent incidents and historical data. Engineering standards, regulatory requirements, and industry practices are discussed for facility siting, atmospheric relief venting, and operator information systems. Finally, a summary of gaps and needs in technology, standards, and practices is presented.     

Ranch Ownership Change and New Approaches to Water Resource Management in Southwestern Montana: Implications for Fisheries1

Abstract:  This article reports on a survey of ranch owners in high amenity areas in southwestern Montana that have experienced marked ownership change over the last two decades. Specifically, we focus on findings from a set of questions targeting water resource and riparian area management. After reviewing the results, we consider how new owners may be managing water resources differently than longtime owners and what the ecological implications of this shift in management might be for Montana’s prized wild fisheries. Uses more closely associated with new owners than with longtime owners include water reallocation to instream uses, aquatic and riparian ecosystem restoration, and fish pond construction. These uses have both positive and negative impacts on the region’s fisheries. Our findings suggest that current laws and institutions guiding the management of water resources and the aquatic and riparian ecosystems they support may not be adequate to address emerging conservation opportunities and challenges.     

Control of Tamarix in the Western United States: Implications for Water Salvage, Wildlife Use, and Riparian Restoration

Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (streamside) vegetation, and to improve wildlife habitat. However, increased water yield might not always occur and has been substantially lower than expected in water salvage experiments, the potential for successful revegetation is variable, and not all wildlife taxa clearly prefer native plant habitats over saltcedar. As a result, there is considerable debate surrounding saltcedar control efforts. We review the literature on saltcedar control, water use, wildlife use, and riparian restoration to provide resource managers, researchers, and policy-makers with a balanced summary of the state of the science. To best ensure that the desired outcomes of removal programs are met, scientists and resource managers should use existing information and methodologies to carefully select and prioritize sites for removal, apply the most appropriate and cost-effective control methods, and then rigorously monitor control efficacy, revegetation success, water yield changes, and wildlife use.     

Urbanization and the Loss of Resource Lands in the Chesapeake Bay Watershed

We made use of land cover maps, and land use change associated with urbanization, to provide estimates of the loss of natural resource lands (forest, agriculture, and wetland areas) across the 168,000 km² Chesapeake Bay watershed. We conducted extensive accuracy assessments of the satellite-derived maps, most of which were produced by us using widely available multitemporal Landsat imagery. The change in urbanization was derived from impervious surface area maps (the built environment) for 1990 and 2000, from which we estimated the loss of resource lands that occurred during this decade. Within the watershed, we observed a 61% increase in developed land (from 5,177 to 8,363 km²). Most of this new development (64%) occurred on agricultural and grasslands, whereas 33% occurred on forested land. Some smaller municipalities lost as much as 17% of their forest lands and 36% of their agricultural lands to development, although in the outlying counties losses ranged from 0% to 1.4% for forests and 0% to 2.6% for agriculture. Fast-growing urban areas surrounded by forested land experienced the most loss of forest to impervious surfaces. These estimates could be used for the monitoring of the impacts of development across the Chesapeake Bay watershed, and the approach has utility for other regions nationwide. In turn, the results and the approach can help jurisdictions set goals for resource land protection and acquisition that are consistent with regional restoration goals.     

Influence of Catchment-Scale Military Land Use on Stream Physical and Organic Matter Variables in Small Southeastern Plains Catchments (USA)

We conducted a 3-year study designed to examine the relationship between disturbance from military land use and stream physical and organic matter variables within 12 small (<5.5 km2) Southeastern Plains catchments at the Fort Benning Military Installation, Georgia, USA. Primary land-use categories were based on percentages of bare ground and road cover and nonforested land (grasslands, sparse vegetation, shrublands, fields) in catchments and natural catchments features, including soils (% sandy soils) and catchment size (area). We quantified stream flashiness (determined by slope of recession limbs of storm hydrographs), streambed instability (measured by relative changes in bed height over time), organic matter storage [coarse wood debris (CWD) relative abundance, benthic particulate organic matter (BPOM)] and stream-water dissolved organic carbon concentration (DOC). Stream flashiness was positively correlated with average storm magnitude and percent of the catchment with sandy soil, whereas streambed instability was related to percent of the catchment containing nonforested (disturbed) land. The proportions of in-stream CWD and sediment BPOM, and stream-water DOC were negatively related to the percent of bare ground and road cover in catchments. Collectively, our results suggest that the amount of catchment disturbance causing denuded vegetation and exposed, mobile soil is (1) a key terrestrial influence on stream geomorphology and hydrology and (2) a greater determinant of in-stream organic matter conditions than is natural geomorphic or topographic variation (catchment size, soil type) in these systems.     

POINT‐NONPOINT SOURCE WATER QUALITY TRADING: A CASE STUDY IN THE MINNESOTA RIVER BASIN1

ABSTRACT: Contrary to the general trend of only a few actual trades occurring within point‐nonpoint source water quality trading programs in the United States, two trading projects in the Minnesota River Basin, created under the provisions of National Pollutant Discharge Elimination System (NPDES) permits, have generated five major trades and numerous smaller ones. In this paper, these two projects are described to illustrate their origins, implementation, and results. It was found that several factors contributed to the relatively high number of trades in these projects, including the offsetting nature of the projects (hence a fixed number of credits that the point sources were required to obtain), readily available information on potential nonpoint source trading partners, and an effectively internal trading scheme used by one of the two projects. It was also found that long term structural pollution control measures, such as streambank stabilization, offered substantial cost savings over point source controls. Estimates of transaction costs showed that the total costs of the trading projects were increased by at least 35 percent after transaction costs were taken into account. Evidence also showed that in addition to pollution reduction, these two trading projects brought other benefits to the watershed, such as helping balance environmental protection and regional economic growth.     

PATTERNS OF WATERSHED URBANIZATION AND IMPACTS ON WATER QUALITY1

ABSTRACT: Urban runoff contributes to nonpoint source pollution, but there is little understanding of the way that pattern and extent of urbanization contributes to this problem. Indicators of type and density of urbanization and access to municipal services were examined in six urban watersheds in Durham, North Carolina. Principal components analysis (PCA) was used to identify patterns in the distribution of these variables across the urban landscape. While spatial variation in urban environments is not perfectly captured by any one variable, the results suggest that most of the variation can be explained using several variables related to the extent and distribution of urban development. Multiple linear regression models were fit to relate these urbanization indicators to total phosphorus, total kjeldahl nitrogen, total suspended solids, and fecal coliforms. Development density was correlated to decreased water quality in each of the models. Indicators of urbanization type such as the house age, amount of contiguous impervious surface, and stormwater connectivity explained additional variation. In the nutrient models, access to city services was also an important factor. The results indicate that while urbanization density is important in predicting water quality, indicators of urbanization type and access to city services help explain additional variation in the models.