Effects of contrasting seasonal growth patterns on composition and persistence of mixed grass‐legume pastures over 5 years in a semi‐arid Australian cropping environment

Perennial grass‐based pastures are uncommon in phased cropping rotations in south‐eastern Australia, where rainfall often limits production and persistence. The high reliance on pure legume‐based pastures limits overall pasture productivity and has adverse effects on environmental parameters such as weed incursion and ground cover. A field experiment was monitored over 5 years to examine the relative productivity of the temperate perennial grasses, phalaris (Phalaris aquatica) and cocksfoot (Dactylis glomerata) and determine whether contrasting seasonal activity enhances their persistence when grown in mixtures with lucerne (Medicago sativa) and annual legumes. Phalaris swards were shown to increase cumulative aboveground biomass by up to 96% and 32%, and in year 5 reduce annual grass emergence by between sevenfold and threefold compared to annual legume and lucerne/annual legume mixed swards, respectively. Only swards that included phalaris maintained ground cover above 70% in each autumn of the experimental period. Swards based on the highly summer dormant cocksfoot cultivar, Kasbah, were generally less productive over all, despite the cocksfoot showing a high level of persistence and good recovery following drought. Grass‐based swards that included lucerne were observed to produce ~35% greater legume biomass than a sward sown only to annual legumes. Cumulative legume biomass was greatest in lucerne swards in the absence of perennial grasses. The experiment was unable to demonstrate a consistent benefit in production and persistence associated with contrasting seasonal growth patterns. However, mixtures containing a range of functional types were consistently shown to enhance productivity over the duration of the experiment compared to less diverse swards. The potential to substantially increase forage productivity and ground cover, while reducing incursion by annual grass weeds, by including well‐adapted perennial grasses in mixtures with lucerne and annual legumes should be utilized.     

Subtotal scapulectomy as the treatment for scapular tumour in the dog: a report of six cases

The medical records of six dogs treated by sub-total scapulectomy for tumours involving the scapula were reviewed. The mean age of dogs in this study was 8 years and 4 months. Clinical signs on presentation included lameness of the affected forelimb and a palpable mass over the scapular area on physical examination. Pre-operative chest and affected forelimb radiographs were taken in most cases in addition to a biopsy. Subtotal scapulectomy was performed, ensuring margins clear of neoplastic tissue of at least 2 cm, preservation of the glenoid cavity and thus retention of the scapulo-humeral joint. On histopathological examination the tumours where diagnosed as chondrosarcoma (one), haemangiosarcoma (two), anaplastic malignant neoplasia (one) and osteosarcoma (one). Limb function was found to be good in all cases postoperatively. Prognosis was related to histopathological diagnosis of the tumour, favourable with chondrosarcoma and poor with the other tumour types.     

Destruction of Ammophila breviligulata by pedestrian traffic: Quantification and control

Ammophila breviligulata is the most common grass stabilising dunes north of Cape Hatteras on the eastern shore of the United States. Various levels and types of pedestrian traffic were tested to determine their effects on the standing crop of A. breviligulata. Levels of use as low as 200 shod passages in 45 days significantly reduced plant mass. The results of these tests are used to develop both formulae for predicting visitor impact and recommendation for controlling it.     

Changes in Concentrations of Major Elements and Trace Metals in Northeastern U.S.-Canadian Sub-Alpine Forest Floors

The forest floor at high elevation spruce-fir sites from southern Vermont, U.S. to the Gaspé Peninsula, Québec, Canada was sampled and analyzed in 1979 and re-sampled and analyzed in 1996 to study temporal changes in the impacts of atmospheric pollutants. We determined organic matter mass, pH, and concentrations of Al, Ca, Fe, K, Mg, Na, Cd, Cu, Hg, Pb, and Zn for the litter (L = fresh litter plus Oi horizon) and fermentation plus humic horizons (F+H) (= Oe plus Oa horizons) of the forest floor. There were no trends for Al or Fe concentrations in the 1979 or 1996 L along the transect. Several sites had significantly lower Al and Fe values in 1996 than in 1979, likely indicating less mineral soil in the 1996 samples. The 1996 concentrations of Ca in L increased along the transect from 0.22% dry weight (dw) in Vermont to 0.60% dw in Québec. Concentrations of Mg in L were relatively constant along the transect. Neither Ca nor Mg changed at sites from 1979 to 1996, indicating unchanged base status. Concentrations of Cd did not vary spatially along the transect but decreased at all sites from 1979 to 1996. Cu and Zn did not vary spatially or with time. In 1979, the concentration of Hg in L ranged between 150 and 300 μg kg^?1 dw, with no spatial gradient. By 1996, Hg concentrations were 25 to 50% lower in L, with decreases generally proportional to the concentration in 1979. The concentration of Pb in 1979 L decreased significantly from 200 mg kg^?1 dw in southern Vermont to 60 mg kg^?1 dw in Québec. By 1996, the Pb concentration in L ranged between 32 and 66 mg kg^?1 dw with no spatial trend along the transect. Decreases in Pb concentrations at sites were proportional to the absolute value in 1979. The concentrations of Cd, Hg, and Pb have declined in litter from 1979 to 1996, indicating a decline in atmospheric deposition. Higher Hg and Pb accumulation rates to the southwest are suggested for the past as indicated by (F+H) concentrations and inventories of Hg and Pb. The decline of Pb in L is consistent with the decreased use of leaded gasoline starting in the 1970s; the declines in Cd and Hg probably reflect lower emissions over the same period. Declining concentrations of Cd, Hg, and Pb in L parallel those documented in recent lake and peat sediments in the northeastern United States.     

A review of the chemical record in lake sediment of energy related air pollution and its effects on lakes

Inter-lake variation in accumulation rates of energy-related elements is a function of gross sedimentation rate (sediment focusing), position on pollution gradients, and water chemistry. Accumulation rates of Pb in lake sediments from profundal area cores in the Adirondack Mountains of New York and northern New England range from 0.1 to 0.2 ug/cm²/y (pre-1800 A.D.) to as much as 2 μg/cm²/y (recent sediment). Rates increase from the late 1800's to nearly the present, in parallel. Accumulation rates for V remain at background values which range up to 0.5 ug/cm²/y and increase 5 to 10 × background in Adirondack Mountain lakes. Chronically acidic lakes have a subsurface maximum. Of these three metals, only Pb has elevated deposition rates in high elevation lakes in the Rocky Mountains of Colorado. Mining activity is believed responsible for the implied air pollution there.     

Food selection and internal processing in Archegozetes longisetosus (Acari: Oribatida)

The nutritional biology of the oribatid mite Archegozetes longisetosus Aoki was examined using a control (starvation) and four types of food: Protococcus sp. algae from tree bark, two fungi—Stachybothrys sp. and Alternaria sp.—and filter paper. Direct observations, histology, enzymology and plating techniques were employed to record contact with food, contents and structure of the alimentary tract, presence and viability of bacterial microorganisms inside the mite body, and chitinase and cellulase activity of mite homogenates. Algae were highly palatable, resulting in high apocrine secretion and guts that were continuously full. Initially there was no evidence of chitinase or cellulase production. Chitinase activity started after 10 days, probably due to consumption of fungi that invaded the algal cover, and correlated with the presence of chitinolytic bacteria (Serratia rubidea) in the mite homogenate. Alternaria was grazed intensively, but cell walls of spores and hyphae remained intact and no chitinase was detected suggesting that only cell contents were enzymatically digested. Stachybothrys sp. was rejected as food. The bacterium Alcaligenes faecalis was dominant in homogenates in each of the treatments, but under starvation Achromobacter xylosoxidans became co-dominant. Cellulase activity was not detected in any treatment, but strong chitinase activity was induced with a filter paper (colonized by invasive fungi) diet. Furthermore, bacteria were common in mesenchyme between the internal organs in the filter paper and starvation treatments.     

Identifying potential novel resistance to the foliar disease ‘Scald’ (Rhynchosporium commune) in a population of Scottish Bere barley landrace (Hordeum vulgare L.)

Journal of Plant Diseases and Protection - Barley ‘Scald’ is an economically damaging fungal disease that is a global problem, causing significant yield and economical losses in the UK...