Use of Riparian Buffer Strips as Movement Corridors by Forest Birds

We conducted a 3-year field experiment to measure the frequency of bird movements through riparian buffer strips before and after harvesting of adjacent forest. Our study was conducted in the boreal mixed wood forest of Alberta and was designed to determine empirically whether songbirds use riparian buffer strips of forest connecting forest reserves as corridors and if they move along these buffer strips more frequently than they cross adjacent clearcuts. We used mist nets to obtain an index of the frequency of bird movement in the forest, and we observed bird movements across adjacent clearcuts for comparison. We predicted that the frequency of movement would be greater (1) in buffer strips after harvesting of adjacent forest than before harvesting, (2) in buffer strips than across clearcuts and, (3) in buffer strips than at control sites (lakeshore forest with no adjacent clearcuts). After adjusting for year-to-year variation in abundance, we found that capture rates increased significantly from pre- to post-harvest, but only for juveniles. Capture rates of adults decreased immediately after harvesting, probably because of the removal of an adjacent source of birds that previously moved through the lakeside forest. Movement rates of forest species in clearcuts were significantly lower than capture rates in the forest. The number of adults captured was positively correlated with the number of territories in the buffer strips, indicating that most birds captured were probably residents. The number of local territories was a poor predictor of juvenile captures, supporting the notion that juveniles were likely dispersing individuals. Our results indicate that buffer strips enhanced movements of juveniles (i.e., acted as corridors) and maintained movement rates of adults. Furthermore, there appeared to be a threshold distance between reserves below which birds may be less reluctant to fly across openings, making corridor use less important.     

Responses of floaters to removal experiments on wintering chickadees

Summary In response to natural mortality in a local population of wintering black-capped chickadees, Parus atricapillus, high-ranked flock regulars are usually replaced rapidly by flock switchers, while low-ranked regulars are not replaced. A series of removal experiments was done to examine the replacement process. A large outdoor aviary was used to house the removed birds, all of which were returned to their flocks no more than 4 days after removal. Of 10 birds taken, all 6 of the high-ranked ones (3 males, 3 females) were replaced by flock switchers. All inserting switchers made sudden jumps in rank; each was seen to supplant regulars of its sex the day after removal. All 10 removed birds, including the 6 that had been replaced by switchers, regained their former status immediately upon release. The 6 switchers that had inserted into the artificial openings were all driven away, and stayed away from the flock for an average of 15 days. Four removed birds were not replaced. All were males from the bottom-ranked pair in their flock. This is consistent with field observations: of 58 low-ranked regulars disappearing naturally over 7 winters, none was replaced by a switcher, although to do so would be an apparent jump in rank for any switcher.     

REGIONAL AND TEMPORAL PATTERNS OF TOTAL SOLUTES IN THE SASKATCHEWAN RWER BASIN1

ABSTRACT: In the Saskatchewan River Basin (365,000 km²), which drains the Canadian prairie from the Rocky Mountains east to Manitoba, concentrations of total solutes are usually within the range of 100 to 1000 mg/L. Total solutes levels in tributaries increase markedly from west to east across the basin, as mountain snowmelt and dilute surface runoff are replaced by ion-rich ground water and concentrated prairie runoff as the major influences on solute concentrations. In contrast, total solutes concentrations in main-stem rivers are nearly constant, ranging 200–300 mg/L, with only a small increase across the basin. Dilute mountain runoff dominates solute concentrations in main-stem rivers, despite the influx of increasingly ion-rich water from tributaries. The principal long-term trends in total solute concentrations across the basin, as revealed by linear and sine-curve regressions, were due to the construction of reservoirs, which depress the natural winter maximum in solute concentrations and disrupt the sinusoidal annual pattern, while sharply reducing seasonal variation. These regression methods did not show anticipated anthropogenic increases in salt load in the Red Deer or South Saskatchewan Rivers, but a trend of slowly increasing solutes concentrations (2 mg/L/yr) was detected for autumn flows in the lower Bow River. Municipal wastes from the City of Calgary or irrigation return flows are probably responsible for this increase.     

Tolerance to SO2, NO2 and their mixture in Plantago major L. populations

The possible evolution of tolerance to NO2, alone or in combination with SO2 was investigated in three populations of Plantago major L., originating from Hyde Park in central London (polluted site), Ascot (clean site) and The Netherlands. Screening for sensitivity to the pollutants was carried out by means of chronic fumigations with NO2 or NO2 plus SO2 and acute fumigations with SO2, NO2 or their mixture. The Hyde Park population showed smaller growth reductions induced by the pollutant mixture, than did the other populations. In contrast no differential response in terms of foliar injury was observed after an acute fumigation with SO2+ NO2, but the Hyde Park population was the most sensitive to NO2 alone. The results indicate that selection for tolerance to SO2 does not confer tolerance to NO2 alone or the pollutant mixture.     

Defending dissensus: participatory governance and the politics of water measurement in Montana’s Yellowstone River Basin

The role of a particular aspect of collaboration, dissensus, in stimulating critical reconsideration of ‘prior appropriation’, a historically hegemonic condition related to water rights in the western United States, is examined via a collaborative planning effort in Montana. Consensual support for a water-use measuring proposal was undermined by strong libertarian resistance to governmental regulation, and an unwavering embrace of the status quo. However, based on insights from scholars engaged in the ‘post-political’ dimensions of contemporary forms of rule – dissensus – understood as the manifestation of consensus-forestalling disagreement articulated between oppositional voices – is revealed as a condition to be actively nurtured, rather than purged. This case reveals how dissensus can open discursive spaces for hegemony-disrupting modes of inquiry, alternative perspectives, and innovative possibilities, even among sanctioned participant voices operating within otherwise established, depoliticized governing arenas. The study thus deepens our understanding of the complex political dynamics of participatory water planning.     

Mammalian neurohormones: potential significance in reproductive physiology of St. John's wort (Hypericum perforatum L.)?

Melatonin and serotonin are indoleamine neurohormones that function as photoperiod signals in many species and have recently been found in St. John's wort, a medicinal plant used in the treatment of depression. There is no known role for melatonin in higher plants but melatonin functions as a signal of changes in photoperiod in other species. In the current study, serotonin and melatonin were quantified during flower development. Higher concentrations of serotonin were found in flower buds at the tetrad stage of microspore development and higher melatonin concentrations were detected during uninucleate mircosporogenesis. Additionally, the regeneration potential of isolated anthers was highest in the same stage that had elevated melatonin concentrations. These data provide the first evidence of the presence of melatonin during flower development and raise many questions about the potential roles of serotonin and melatonin as regulatory molecules in the reproductive flexibility of higher plants.     

The Influence of Temperature on Norovirus Inactivation by Monochloramine in Potable Waters: Testing with Murine Norovirus as a Surrogate for Human Norovirus

Human noroviral infections are generally more common during winters in temperate regions. This study used a murine norovirus (MNV) as a human norovirus surrogate to test the effect of water temperature (4 and 25°C) on virus survival and its susceptibility to the levels of monochloramine (~1.89 ppm) to terminally disinfect municipally treated potable waters. The titre of MNV remained essentially unchanged for at least 24 h in raw river water at both temperatures. The virus became undetectable in <2 h in monochloramine-containing samples held at 25°C, but its titre remained virtually unaltered at 4°C (P < 0.05) under the same conditions. These findings strongly suggest that water temperature can influence the norovirucidal activity of monochloramine and its possible impact on the seasonality of outbreaks of noroviral infections.