Microbial biomass phosphorus contributions to phosphorus solubility in riparian vegetated buffer strip soils

This study tests the hypothesis that microbial biomass phosphorus (P) makes a significant contribution to P solubility in riparian buffer strip soils. In 36 soils collected from buffer strips within three UK soil associations, water-extractable inorganic P solubility was most strongly related to NaHCO₃ extractable inorganic P. However, within individual soil associations where soil pedological properties and management were similar, water-extractable inorganic P was most strongly related to microbial biomass P. These results highlight the difficulty in predicting dissolved P leaching risk based on agronomic soil P tests alone and the dissolved P leaching risk presented by having soils high in organic matter and microbial biomass P in close proximity to surface waters.     

Dynamic connectivity of temporary wetlands in the southern Great Plains

We quantified fluctuations in the status of individual patches (wetlands) in supporting connectivity within a network of playas, temporary wetlands of the southern Great Plains of North America that are loci for regional biodiversity. We used remote sensing imagery to delineate the location of surface waters in >8,000 playa basins in a ~31,900 km² portion of Texas and quantified connectivity in this region from 2007 to 2011. We ranked playas as stepping-stones, cutpoints, and hubs at different levels of environmental conditions (regionally wet, dry, and average periods of precipitation) for dispersal distances ranging from 0.5 to 34 km, representing a range of species’ vagilities, to provide baseline dynamics within an area likely to experience disrupted connectivity due to anthropogenic activities. An individual playa’s status as a stepping-stone, cutpoint, or hub was highly variable over time (only a single playa was a top 20 stepping-stone, cutpoint, or hub in >50 % of all of the dates examined). Coalescence of the inundated playa network usually occurred at ≥10 km dispersal distance and depended on wetland density, indicating that critical thresholds in connectivity arose from synergistic effects of dispersal ability (spatial scale) and wet playa occurrence (a function of precipitation). Organisms with dispersal capabilities limited to <10 km routinely experienced effective isolation during our study. Connectivity is thus a dynamic emergent landscape property, so management to maintain connectivity for wildlife within ephemeral habitats like inundated playas will need to move beyond a patch-based focus to a network focus by including connectivity as a dynamic landscape property.     

Typing of Mycobacterium bovis isolates from cattle and other animals in the same locality

The effects of high doses of the beta-2 agonists iso-prenaline, salbutamol and fenoterol on the myocardium were studied experimentally in sheep. Each drug was given intravenously in progressively increasing doses to four sedated animals and four controls. The experiments were repeated during hypoxaemia and animals were necropsied 3 days later.     

Studies on Sarcocystis species II. Infection in wild and feral animals — prevalence and transmission

Wild and feral animals in New Zealand were examined by a muscle-digest technique, and histology. Sarcocystis spp. were found in red deer, feral goats, feral pigs, rats, mice, and rabbits, and the prevalence of infection recorded. No Sarcocystis spp. were found in 8 wallabies and 62 possums. Sarcocystis spp. in rats and rabbits were transmitted to cats, and a species in goats to dogs.     

DNA typing of Mycobacterium bovis strains from the Castlepoint area of the Wairarapa

Aim. To investigate isolates of Mycobacterium bovis from the Castlepoint area of the Wairarapa using three different methods of DNA typing.

Methods. Isolates of M. bovis, obtained from animals in the Castlepoint area between 1982–l998, were characterised by restriction endonuclease analysis. An isolate representing each restriction type was characterised by two newer DNA typing methods based on the polymorphic GC-rich repetitive sequence (PGRS) and spoligotyping.

Results. Over 300 isolates were distinguished into 26 restriction types.The 24 available restriction types were differentiated into 11 PGRS types and 7 spoligotypes. The three most common restriction types had the same PGRS type and the same spoligotype.

Conclusions. The relatively large number of restriction types found, indicated that restriction endonuclease analysis was well suited for detailed epidemiological studies at Castlepoint. Spoligotyping was less discriminatory than PGRS typing but both methods could be used to group isolates with different restriction types.     

Sequence variation identified in the 18S rRNA gene of Theileria mutans and Theileria velifera from the African buffalo (Syncerus caffer)

The African buffalo (Syncerus caffer) is a natural reservoir host for both pathogenic and non-pathogenic Theileria species. These often occur naturally as mixed infections in buffalo. Although the benign and mildly pathogenic forms do not have any significant economic importance, their presence could complicate the interpretation of diagnostic test results aimed at the specific diagnosis of the pathogenic Theileria parva in cattle and buffalo in South Africa. The 18S rRNA gene has been used as the target in a quantitative real-time PCR (qPCR) assay for the detection of T. parva infections. However, the extent of sequence variation within this gene in the non-pathogenic Theileria spp. of the Africa buffalo is not well known. The aim of this study was, therefore, to characterise the full-length 18S rRNA genes of Theileria mutans, Theileria sp. (strain MSD) and T. velifera and to determine the possible influence of any sequence variation on the specific detection of T. parva using the 18S rRNA qPCR. The reverse line blot (RLB) hybridization assay was used to select samples which either tested positive for several different Theileria spp., or which hybridised only with the Babesia/Theileria genus-specific probe and not with any of the Babesia or Theileria species-specific probes. The full-length 18S rRNA genes from 14 samples, originating from 13 buffalo and one bovine from different localities in South Africa, were amplified, cloned and the resulting recombinants sequenced. Variations in the 18S rRNA gene sequences were identified in T. mutans, Theileria sp. (strain MSD) and T. velifera, with the greatest diversity observed amongst the T. mutans variants. This variation possibly explained why the RLB hybridization assay failed to detect T. mutans and T. velifera in some of the analysed samples.     

Small-scale patch structure in North American and South African grasslands responds differently to fire and grazing

Fire and grazing significantly impact small-scale patch structure and dynamics in savanna grasslands. We assessed small-scale grass-forb associations in long-term fire and grazing experiments in North America (NA) and Southern Africa (SA). Transects of 128 0.25 m² contiguous quadrats were sampled in areas with different combinations of grazing (ungrazed, single grazer, or multiple grazers) and fire frequency (unburned or annually burned). We predicted that (1) the patch structure of each of the dominant grasses in NA and SA would respond similarly to fire and grazing, and (2) that forb richness would be correlated to grass patch structure. Semi-variance analysis was used to determine patch structure of dominant grasses and forb cover. Community structure responded similarly in NA and SA to fire, grazing, and fire-grazing interactions. Species richness, diversity, and community heterogeneity were significantly higher in unburned-grazed sites. Grazing significantly increased forb cover and decreased cover of the dominant grasses, and the effects of fire on community structure depended on the grazing regime. Contrary to our prediction, we found that small-scale patch structure of the dominant grass species in NA and SA responded differently to grazing and fire. We found strong grass patch structure in unburned-ungrazed grasslands in both sites; however, grazing and fire reduced patch structure in NA but not SA, and in no instance did grass patch structure influence forb community structure. We conclude that fire and grazing have larger impacts on small-scale patch structure in NA than they do in SA even though overall community structure responded similarly on both continents.     

Effects of fruit thinning,pollination and paclobutrazol on fruit set and size of persimmon (Diospyros kaki L.) in subtropical Australia

Summary

A factorial combination of three cultural factors (± hand-pollination, ± growth retardant, ± fruit thinning) were evaluated for their effects on fruit set and fruit size of ‘Fuyu’ persimmon (Diospyros kaki L.) in subtropical Australia (Lat. 27° S). Treatments were applied to individual shoots on mature seven year old trees. Fruit set of pollinated flowers was high compared with non-pollinated flowers (91% vs. 47%). Pollinated fruit also grew faster at all stages of fruit development and, at harvest, fresh weights were 25% heavier. Palcobutrazol significantly (P<0.05) increased fruit weight by 7% compared with controls but did not increase fruit set. Irrespective of treatment, fruit weight was not correlated (r<0.3, n.s.) with shoot length, number of nodes per shoot, fruit nodal position, shoot dry weight, leaf area per shoot, and number of leaves per shoot. Fruit fresh weight was only poorly correlated with shoot base diameter (r = 0.41*). Pollinated fruit had significantly (P<0.05) higher concentrations of nutrients (N, K, Ca, and Zn).