The impact of cattle grazing and treading on soil properties and the transport of phosphorus, sediment and E. coli in surface runoff from grazed pasture

Contaminant loss from grazed pasture can negatively affect freshwater quality. There is, however, little data on the impact of different levels of grazing/treading on contaminant loss measured under field conditions. This study quantified phosphorus (P), sediment and Escherichia coli (E. coli) loss in surface runoff from plots grazed by cattle for 0, 16 or 28 h to create different pasture/treading damage. Results showed an increase in grazing/treading duration decreased soil macroporosity (30%) and saturated hydraulic conductivity (96%), and increased surface roughness (71%) and depression water storage capacity (388%). These changes in soil physical condition contributed to greater volumes of surface runoff in the 16 h (31%) and 28 h (55%) treatments. Contaminant concentrations and loads in runoff also tended to increase with grazing/treading, although the increases were not statistically significant. An exception was total P (TP) which increased from 0.323 to 1.222 kg ha¯¹, principally due to increased dissolved P, probably released from plants due to grazing and from the deposition of dung. Management of animals to minimise the number, duration and frequency of grazing wet soils that are vulnerable to physical damage are likely key factors to reducing TP, and probably SS and E. coli transport in surface runoff

Effect of humidity and temperature on conidial germination and appressorium development of two Philippine isolates of the mango anthracnose pathogen Colletotrichum gloeosporioides

A comparison of rates of germination and appressorium formation by an isolate of Colletotrichum gloeosporioides on mango leaves, fruit surfaces and cellophane membranes showed that behaviour was broadly similar on all three substrates. Frequency of appressorium formation was slightly higher on cellophane membranes, and both hyaline and melanized appressoria were formed. Only melanized appressoria were formed on mango surfaces. In vitro experiments on membranes showed comparative differences in physiological behaviour with temperature for two Philippine isolates of C. gloeosporioides. The most stimulatory temperature for production of appressoria differed in isolates I-2 and I-4 (25 and 20 degrees C, respectively). At 30 degrees C more appressoria became melanized than at lower temperatures, but the frequency of formation of penetration pegs was highest at 25 degrees C. Conidia of C. gloeosporioides germinated on cellophane membranes at relative humidities as low as 95%, but the percentage of conidia germinating and forming appressoria increased as the RH approached 100%. Approximately 18% of conidia of C. gloeosporioides I-2 held at 62 and 86% RH for 4 weeks retained viability, and some were capable of forming appressoria when placed at 100% RH. These results have implications for epidemiological models for disease control

Virtual Reconstruction and Prey Size Preference in the Mid Cenozoic Thylacinid, <i>Nimbacinus dicksoni</i> (Thylacinidae, Marsupialia)

<div><p>Thylacinidae is an extinct family of Australian and New Guinean marsupial carnivores, comprizing 12 known species, the oldest of which are late Oligocene (∼24 Ma) in age. Except for the recently extinct thylacine (<i>Thylacinus cynocephalus</i>), most are known from fragmentary craniodental material only, limiting the scope of biomechanical and ecological studies. However, a particularly well-preserved skull of the fossil species <i>Nimbacinus dicksoni</i>, has been recovered from middle Miocene (∼16-11.6 Ma) deposits in the Riversleigh World Heritage Area, northwestern Queensland. Here, we ask whether <i>N. dicksoni</i> was more similar to its recently extinct relative or to several large living marsupials in a key aspect of feeding ecology, i.e., was <i>N. dicksoni</i> a relatively small or large prey specialist. To address this question we have digitally reconstructed its skull and applied three-dimensional Finite Element Analysis to compare its mechanical performance with that of three extant marsupial carnivores and <i>T. cynocephalus</i>. Under loadings adjusted for differences in size that simulated forces generated by both jaw closing musculature and struggling prey, we found that stress distributions and magnitudes in the skull of <i>N. dicksoni</i> were more similar to those of the living spotted-tailed quoll (<i>Dasyurus maculatus</i>) than to its recently extinct relative. Considering the Finite Element Analysis results and dental morphology, we predict that <i>N. dicksoni</i> likely occupied a broadly similar ecological niche to that of <i>D. maculatus</i>, and was likely capable of hunting vertebrate prey that may have exceeded its own body mass.</p></div