Using distribution models to test alternative hypotheses about a species’ environmental limits and recovery prospects

Distribution models are commonly used to generalise across species distributions, to project future potential range changes, and to identify potential areas for species reintroductions and recovery plans. Building several models that incorporate different potential causal factors is a useful way of formalising alternative hypotheses. We developed a series of models to test hypotheses about the factors influencing the distribution of a species of conservation importance - the hen harrier Circus cyaneus.A climate-based model using continental distribution data was consistent with the continental distribution and observational studies in Britain. According to the climate-model the parts of Britain occupied by the hen harrier are the least climatically suitable.Habitat-based models using detailed distribution data from seven Scottish areas explained the recent British distribution well, with birds largely confined to heather dominated areas. These patterns were inconsistent with historical data on the species’ distribution, its habitat use in other parts of its range and with the climate-based model.Our burn intensity index of gamekeeper activity was highly correlated with climatic suitability within the best 25% of 10 km squares by modelled habitat suitability, negatively associated with the productivity data and associated with a decrease in abundances between 1998 and 2004. Gamekeeper activity may be keeping hen harriers out of the most climatically suitable areas with habitat similar to that which they currently occupy within Britain and or keeping the population numbers too low and isolated for the natural re-expansion of the species into parts of the range where it was historically extirpated.     

Nutrient impoverishment and limitation of productivity after 20 years of conservation management in wet grasslands of north-western Germany

European wet grasslands are characterized by high diversity of plant and animal species but are threatened by intensive land use. Although preservation or restoration of species-rich wet grasslands requires low nutrient availability that could be achieved by long-term management, studies monitoring nutrient removal are lacking. Our objective was to assess the long-term effect of management (mowing twice a year without or with PK fertilization for 20 years) on (i) productivity and nutrient removal with the harvest, (ii) the type of nutrient limitation, and (iii) plant species richness in wet grasslands in north-western Germany considering the differences between organic and mineral soils.Initially low nutrient availability in soil led to decreased productivity and base cation removal with harvest particularly on mineral soils after six years of mowing twice a year without fertilization. On mineral soils, N:K ratios indicated limitation of plant growth by K. On organic soils, neither productivity nor K removal with the harvest changed with time suggesting additional K input probably caused by rising groundwater. On organic soils, K:P ratios and a significant decrease of productivity with increasing N:P ratios suggested P limitation. Plant species richness was maintained or even slightly increased by mowing twice a year without fertilization but mainly comprised species that were already present at the study sites.Productivity and N, P, K, and Mg removal with the harvest was significantly increased by mowing twice a year with PK fertilization while species richness was maintained. After 10 years, N:K ratios indicate K limitation even for mowing twice a year with PK fertilization. In case of initially low nutrient availability in soil, cautious PK fertilization and mowing can be recommended to meet demands of agriculture and nature conservation.     

A survey of the trichostrongylid nematode species present on UK sheep farms and associated anthelmintic control practices

A survey of sheep farms from across the UK was conducted to establish information on farming practices, the trichostrongylid nematode species present and anthelmintic usage. Questionnaires and faecal samples were returned from 118 farms. First stage larvae (L(1)) were cultured from faecal samples and used for PCR analysis to determine the presence/absence of selected trichostrongylid species. Teladorsagia circumcincta was the only species present on 100% of farms. Haemonchus contortus was found on ～50% of farms and was widespread throughout the UK. The most common Trichostrongylus spp. was T. vitrinus, found on 95% of farms. Determining the anthelmintic dose rate based on the weight of the heaviest animal in the flock to avoid under dosing was carried out on 58% of farms and was associated with a significantly lower mean epg (p<0.001) in lambs. However, the weight of animals was only estimated (as opposed to animals weighed) on 32% of farms. Macrocyclic lactones (ML) were the most commonly used anthelmintic class for ewes, whilst benzimidazoles (BZ) were the most widely used in lambs. Twenty-two of the surveyed farms had confirmed anthelmintic resistance, of these, 18 had BZ resistance, one had levamisole (LEV) resistance and 3 had resistance to both BZ and LEV. No farms in this survey reported resistance to ML. Location had a significant effect on the incidence of anthelmintic resistance on the farms in this survey (p=0.002). There was evidence of a lower risk of anthelmintic resistance occurring on farms from Scotland compared to those in England (p(f)=0.047) and Wales (p(f)=0.012). Farm type, flock type and open or closed status did not have any significant effect on the incidence of anthelmintic resistance when all other factors were taken into consideration.     

Monitoring of antibiotic consumption in livestock: a German feasibility study

Every application of antibacterial drugs in veterinary medicine may encourage selection for resistant bacteria. In Germany no valid data are available which would be suitable for a species specific estimation of drug consumption especially regarding food producing animals. Therefore, a representative monitoring of consumption of antibacterial drugs in food producing animals should be implemented. As a first step, a feasibility project was conducted to identify the technical preconditions and develop a concept for a regular monitoring system within Germany as a country with a non-central federal state system. The data were collected via the forms obligatory by German law concerning the treatment of animals and the delivery of animal drugs to the animal owners by the veterinarian. 24 veterinary practices and 65 farmers were visited, and all applications of antibiotics to farm animals during the course of one year (September 1, 2006 to August 31, 2007) were entered into a central database. A total of 95,584 records were collected and analysed statistically. Consumption of antibiotics was calculated in kg, but also the number of applications was analysed. The consumption of tetracyclines in kg reached 54.3% of all antimicrobial substances applied to pigs, but only 25.7% of all doses applied to pigs were tetracyclines. For the farms' data, the number of daily doses per animal year (DD(ay)) was estimated based on the number of daily doses recorded and on the number of animals kept in the farm. Correct and detailed data regarding the structures of the farms as well as of veterinary practices are necessary to estimate the consumption of antibiotics reliably. The proposed system is able to function as a monitoring system for antibiotic use in Germany, when the monitoring data are linked to the agricultural data (farm sizes) accounting for differences between German regional agricultural and animal husbandry structures. Furthermore, the results of the antibiotic use analyses may serve as basis to assess the results of the sales data of the pharmaceutical industry. Results are comparable to the outcome of respective systems in other European countries, e.g. the Netherlands and Denmark, and therefore it will contribute to a better understanding and development of strategies for the control of antimicrobial resistances on the European level.     

Study of methicillin resistant Staphylococcus aureus (MRSA) in Danish pigs at slaughter and in imported retail meat reveals a novel MRSA type in slaughter pigs

Methicillin-resistant Staphylococcus aureus (MRSA), especially CC398, have emerged in livestock worldwide. We investigated the occurrence of MRSA in pigs at slaughter and in retail meat. During 2009, nasal swabs (n=789) were taken from pigs at slaughter. Moreover, 866 meat samples [Danish: pork (153), broiler meat (121), beef (142) and; imported: pork (173), broiler meat (193), and beef (84)] were randomly collected in retail stores and outlets. MRSA was isolated from nasal swabs or from meat samples after preenrichment (Mueller Hinton broth with 6.5% NaCl), selective enrichment (tryptone soya broth with 4 mg/L cefoxitine and 75 mg/L aztreonam) and selective plating on Brilliance Chromogenic MRSA agar. The presence of mecA was confirmed by PCR and the MRSA isolates were spa typed. Novel MRSA spa types were characterized by MLST, PFGE and SCCmec typing. Thirteen percent (101/789) of the pigs had MRSA. Based on spa types 93% corresponded to CC398 (spa t011, t034, t1451, t2876, t2974), 4% to CC30 (t1333) and one isolate to CC1 (t0127). The spa type t1333 (CC30), which is common among methicillin susceptible S. aureus (MSSA) from pigs in Denmark, contained a SCCmec cassette type V and czrC zinc resistance gene. Imported broiler meat had the highest occurrence (18%) of MRSA, followed by imported pork (7.5%) and Danish pork (4.6%). MRSA ST398 was found for the first time in Danish beef (1.4%). The finding of MRSA CC30 (spa t1333) suggest possible spread of the SCCmec cassette normally associated with ST398 into another S. aureus lineage common in pigs.     

The influence of rabbit scrapes on dune vegetation

The rabbit, the only grazer of importance in the coastal dunes of northwestern Europe, is thought to stabilize the species composition of the typical dune grasslands. In addition to selectively grazing, it produces shallow scrapes. The function of this scrape-digging behaviour for the rabbit, and the effect on the distribution and abundance of dune grassland species, were analysed. It is concluded that root consumption is one of the main purposes for digging scrapes. The main effect on the vegetation is a comparative increase in the number of individuals of annual plant species, especially where percentage vegetation cover is not very high. The effect on annuals only becomes manifest after the next seed production of these species. Where vegetation cover is high, the effect of scrape digging is less obvious because perennial species have already filled the scrapes before seed production of the annuals. In a sand-dune system rabbit scrapes do not provide unique environments for specific plant species.     

Salt River Project experience in conversion from agriculture to urban water use

Salt River Project (SRP) was established in 1903 to deliver water to farms on about 250,000 ac (100,000 ha) located in South-Central Arizona. While SRP continues to deliver water to the entire area, today only about 10% of that land is still in agriculture. The remainder has been urbanized. Urbanization of the vast majority of water service area has caused SRP to rethink and adjust every aspect of its business, from daily operation and maintenance to the overarching issues of liability and public involvement. Some of the issues being addressed and lessons learned are addressed in this paper.     

Impact of sulfadiazine and chlorotetracycline on soil bacterial community structure and respiratory activity

Veterinary medicines enter agricultural soils by the use of animal excrements as fertilizers. To study their impact on soil bacterial communities, microcosms containing orthic luvisol soil were spiked with the antimicrobial agents sulfadiazine (SDZ) and chlorotetracycline (CTC) at three different concentrations (1, 10, 50 mg kg⁻¹ soil) and incubated for 48 days at 20 °C. The impact on the microbial respiratory activity was measured continuously in a respirometer (Sapromat). Changes in bacterial community structure were visualized by means of PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rDNA derived from soil samples after 1, 7, 11 and 48 days. Additionally, growth inhibitory effects of SDZ and CTC on bacteria previously isolated from the same soil were tested in agar diffusion tests. In microcosms with soil and antibiotics only, no effects could be observed, either on respiratory activity or on bacterial population structure. Therefore, further incubations were conducted in the presence of an additional assimilable carbon source (5 g glucose kg⁻¹ soil). In the presence of glucose, SDZ affected soil respiration as well as the bacterial community structure: Additional bands appeared and some bands already visible at the beginning of incubations increased in intensity. A clear relationship between SDZ concentrations and changes in DGGE patterns became visible. During 48 days of incubation, changes in DGGE patterns were minimal in microcosms with 50 mg SDZ kg⁻¹soil indicating an inhibition of strains, which were capable of growing on glucose in the presence of lower SDZ concentrations. Only a few soil bacterial isolates (5 out of 47 strains tested) were weakly inhibited by SDZ in agar diffusion disk tests. Contrastingly, CTC inhibited growth of 12 soil bacterial isolates significantly in disk tests, but no effects on soil respiration and bacterial community structure could be observed. In the presence of the soil matrix the growth inhibitory potential of CTC decreased due to adsorption or complexation. This was confirmed in growth inhibition experiments with soil suspensions and time-dependent sampling.     

The short-term effects of wood-ash amendment on forest soils

In the heavily forested regions of the northeastern U.S. the potential for producing electricity from wood-fired boilers is also creating a growing supply of wood-ash requiring disposal. Landfill space is expensive and limited, which has resulted in an interest in spreading wood-ash on forest sites. This greenhouse study was designed to provide information on soil and seedling response to wood-ash applications. Red maple (Acer rubrum) seedlings were grown in either O or B horizon forest soil material and amended with six levels of ash (0, 4, 8, 12, 16, and 20 Mg ha^?1) and two levels of N fertilizer (0 and 224 kg ha^?1). Ash amendments increased pH and exchangeable base cations, and decreased extractable Al and Fe concentrations, in both soil materials. Ash treatments increased seedling foliar K and Na concentrations in O horizon soils, but had little effect on growth. No significant effects on seedling properties from ash in B horizon soils were found. Fertilizer N treatments did not improve seedling growth in either soil material. Soil and seedling response to N were notably different for the different soils used. Based on this short-term study it appears that (a) land applications of wood-ash at the rates used may be a viable approach to recycling this solid waste, and (b) long-term studies are required to evaluate this practice under field conditions.