Prioritising sites for pollinators in a fragmented coastal nectar habitat network in Western Europe

Landscape Ecology - Habitat loss and fragmentation contribute significantly to pollinator decline and biodiversity loss globally. Conserving high quality habitats whilst restoring and connecting...     

Non-intertidal habitat use by shorebirds: a reflection of inadequate intertidal resources?

Many species of shorebird typically forage almost exclusively on intertidal habitats. When such strongly maritime species choose to forage on non-intertidal habitats, it may either be a response to deteriorating intertidal conditions or to the discovery of more profitable resources in non-intertidal areas. Methods which allow distinction between these two will clearly be important for identifying problems in intertidal habitats. Since January 1998, turnstone (Arenaria interpres) on the Wash estuary, eastern England have been foraging on the docksides of Port Sutton Bridge (mainly on spilt wheat and fishmeal), fields and river edges, resulting in concern that intertidal food supplies were no longer sufficient to support the population. We quantified the distribution and behaviour of turnstone within the Wash in relation to season, tidal state and weather and used a depletion model to predict the number of turnstone that could be supported by the port, under a range of resource densities and environmental conditions. Numbers of turnstone on non-intertidal habitats increased over the winter and use of the port was significantly greater around high tide and on colder days. The depletion model showed that under virtually all conditions, the port could support a much greater proportion of the turnstone population than current peak numbers. The use of non-intertidal habitats therefore suggests that the preferred intertidal food supplies are not currently capable of supporting the turnstone population throughout the winter. Habitat switches such as this can potentially be important advance warnings of ecological changes for species, which have not yet led to reductions in population size.     

Long-Term Production and Profitability From Grazing Cattle in the Northern Mixed Grass Prairie

Conventional wisdom among rangeland professionals has been that for long-term sustainability of grazing livestock operations, rangeland should be kept in high good to low excellent range condition. Our objective was to analyze production parameters, costs, returns, and profit using data generated over a 34-yr period (1969–2002) from grazing a Clayey range site in the mixed-grass prairie of western South Dakota with variable stocking rates to maintain pastures in low–fair, good, and excellent range condition classes. Cattle weights were measured at turnout and at the end of the grazing season. Gross income · ha^?1 was the product of gain · ha^?1 and price. Prices were based on historical National Agricultural Statistics Services feeder cattle prices. Annual variable costs were estimated using a yearling cattle budget developed by South Dakota State University agricultural economists. All economic values were adjusted to a constant dollar using the Bureau of Labor Statistics' Consumer Price Index. Stocking rate, average daily gain, total gain, net profit, gross revenue, and annual costs · ha^?1 varied among range condition classes. Net income for low–fair range condition ($27.61 · ha^?1) and good range condition ($29.43 · ha^?1) were not different, but both were greater than excellent range condition ($23.01 · ha^?1). Over the life of the study, real profit (adjusted for inflation) steadily increased for the low–fair and good treatments, whereas it remained level for the excellent treatment. Neither drought nor wet springs impacted profit differently for the three treatments. These results support generally observed rancher behavior regarding range condition: to maintain their rangeland in lower range condition than would be recommended by rangeland professionals. Ecosystem goods and services of increasing interest to society and associated with high range condition, such as floristic diversity, hydrologic function, and some species of wildlife, come at an opportunity cost to the rancher.     

Estimation of actual evapotranspiration in winegrape vineyards located on hillside terrain using surface renewal analysis

Sensible and latent heat flux densities were estimated in a level vineyard, a northeast aspect vineyard and a southwest aspect vineyard in the Napa Valley of California using the eddy covariance and surface renewal methods. Surface renewal is theoretically not limited to level or extensively homogeneous terrain because it examines a more localized process of scalar exchange as compared with eddy covariance. Surface renewal estimates must be calibrated against eddy covariance data to account for unequal heating of the air parcels under a fixed measurement height. We calibrated surface renewal data against eddy covariance data in a level vineyard, and the calibration factor (α) was applied to the surface renewal measurements on the hillside vineyards. Latent heat flux density was estimated from the residual of the energy balance. In the level vineyard, the average daily actual evapotranspiration (ET _a ) for the period of June through September was 2.4?mm per day. In the northeast aspect vineyard, the average daily ET _a was 2.2?mm per day, while in the southwest aspect vineyard it was 2.7?mm per day. The net radiation values for the level vineyard, the northeast aspect vineyard, and the southwest aspect vineyard were compared against the Ecosystem Water Program with good agreement.     

Bracken effects on inorganic nitrogen leaching from an upland podzol

Leaching of inorganic N species to stream waters from upland areas of the UK is increasing, reflecting the increases in atmospheric deposition of nitrogen species due to increased levels of vehicular emissions. Bracken cover in UK uplands is also increasing overall ( Taylor, 1986 ), and the architectural nature of bracken has been shown to both increase deposition of atmospheric constituents to soils and change their chemical and physical nature. We have tested the nutrient status of upland podzols from the Lake District, Cumbria, UK, from under both moorland grass and bracken. The results show reduced levels of base cations and nitrate throughout the profile and decreases in the organic matter content of surface horizons as a consequence of bracken encroachment. We also report increased ammonium concentrations in lower soil horizons under bracken, possibly leading to increased leaching to stream waters. These results suggest either increased leaching of soil nutrients due to bracken encroachment or increased storage of nutrients within the bracken rhizome system. Results also suggest changes in either microbial activity or the microbial community of podzols, possibly due to the allelopathic nature of bracken. This may have caused changes in the soil nutrient dynamics, possibly accounting for some of the changes seen. We hypothesize that increased bracken cover within the British uplands has the potential to increase leaching of inorganic nitrogen to upland streams.     

rep-PCR-Mediated Genomic Fingerprinting: A Rapid and Effective Method to Identify Clavibacter michiganensis

ABSTRACT The genomic DNA fingerprinting technique known as repetitive-sequence-based polymerase chain reaction (rep-PCR) was evaluated as a tool to differentiate subspecies of Clavibacter michiganensis, with special emphasis on C. michiganensis subsp. michiganensis, the pathogen responsible for bacterial canker of tomato. DNA primers (REP, ERIC, and BOX), corresponding to conserved repetitive element motifs in the genomes of diverse bacterial species, were used to generate genomic fingerprints of C. michiganensis subsp. michiganensis, C. michiganensis subsp. sepedonicus, C. michiganensis subsp. nebraskensis, C. michiganensis subsp. tessellarius, and C. michiganensis subsp. insidiosum. The rep-PCR-generated patterns of DNA fragments observed after agarose gel electrophoresis support the current division of C. michiganensis into five subspecies. In addition, the rep-PCR fingerprints identified at least four types (A, B, C, and D) within C. michiganensis subsp. michiganensis based on limited DNA polymorphisms; the ability to differentiate individual strains may be of potential use in studies on the epidemiology and host-pathogen interactions of this organism. In addition, we have recovered from diseased tomato plants a relatively large number of naturally occurring avirulent C. michiganensis subsp. michiganensis strains with rep-PCR fingerprints identical to those of virulent C. michiganensis subsp. michiganensis strains.     

Genetic Change Within Populations of Phytophthora infestans in the United States and Canada During 1994 to 1996: Role of Migration and Recombination

ABSTRACT Dramatic changes occurred within populations of Phytophthora infestans in the United States and Canada from 1994 through 1996. Occurrence of the US-8 genotype, detected rarely during 1992 and 1993, increased rapidly and predominated in most regions during 1994 through 1996. US-7, which infected both potato and tomato and made up almost 50% of the sample during 1993, was detected only rarely among 330 isolates from the United States analyzed during 1994. It was not detected at all in more limited samples from 1996. Thus, ability to infect both potato and tomato apparently did not increase the fitness of this genotype relative to US-8, as predicted previously. US-1, the previously dominant genotype throughout the United States and Canada, made up 8% or less of the samples analyzed during 1994 through 1996. A few additional genotypes were detected, which could indicate the beginnings of sexual reproduction of P. infestans within the United States and Canada. However, clonal reproduction still predominated in all locations sampled; opportunities for sexual reproduction probably were limited, because the A1 and A2 mating types usually were separated geographically. The high sensitivity of the US-1 genotype to the fungicide metalaxyl also could have reduced opportunities for contact between the mating types in fields where this compound was applied. The previous correlation between metalaxyl sensitivity and genotype was confirmed and extended to a new genotype, US-17: all US-1 isolates tested were sensitive; all isolates of the US-7, US-8, and US-17 genotypes tested to date have been resistant. Isolates of P. capsici and P. erythroseptica, two other species often found on tomato and potato, could be easily distinguished from each other and from P. infestans using a simple allozyme assay for the enzyme glucose-6-phosphate isomerase. This technique could be useful for rapid identification of species, in addition to genotype of P. infestans. It generally was not possible to predict which genotypes would be present in a location from 1 year to the next. Long-distance movement of US-8 in seed tubers was documented, and this was probably the primary means for the rapid spread of this genotype from 1993 through 1996.