Analysis of fine-scale spatial pattern of a grassland from remotely-sensed imagery and field collected data

An important practical problem in the analysis of spatial pattern in ecological systems is that requires spatially-intensive data, with both fine resolution and large extent. Such information is often difficult to obtain from field-measured variables. Digital imagery can offer a valuable, alternative source of information in the analysis of ecological pattern. In the present paper, we use remotely-sensed imagery to provide a link between field-based information and spatially-explicit modeling of ecological processes. We analyzed one digitized color infrared aerial photograph of a serpentine grassland to develop a detailed digital map of land cover categories (31.24 m × 50.04 m of extent and 135 mm of resolution), and an image of vegetation index (proportional to the amount of green biomass cover in the field). We conducted a variogram analysis of the spatial pattern of both field-measured (microtopography, soil depth) and image-derived (land cover map, vegetation index, gopher disturbance) landscape variables, and used a statistical simulation method to produce random realizations of the image of vegetation index based upon our characterization of its spatial structure. The analysis revealed strong relationships in the spatial distribution of the ecological variables (e.g., gopher mounds and perennial grasses are found primarily on deeper soils) and a non-fractal nested spatial pattern in the distribution of green biomass as measured by the vegetation index. The spatial pattern of the vegetation index was composed of three basic components: an exponential trend from 0 m to 4 m, which is related to local ecological processes, a linear trend at broader scales, which is related to a general change in topography across the study site, and a superimposed periodic structure, which is related to the regular spacing of deeper soils within the study site. Simulations of the image of vegetation index confirmed our interpretation of the variograms. The simulations also illustrated the limits of statistical analysis and interpolations based solely on the semivariogram, because they cannot adequately characterize spatial discontinuities.     

Cross species transmission of ovine Johne's disease from sheep to cattle: an estimate of prevalence in exposed susceptible cattle

OBJECTIVE: To determine the prevalence of infection of cattle with the sheep strain of Mycobacterium avium subsp paratuberculosis at least two years after exposure at < 6 months old. DESIGN: Prospective survey One thousand seven hundred and seventy-four cattle from 12 properties (Farms A to L) were sampled by ELISA and faecal culture to detect evidence of infection with M a paratuberculosis. All properties had a known history of Johne's disease (JD) in sheep, and sampled cattle were likely to be susceptible to JD at the time they were first exposed, being at an age of 6 months or less. In addition, opportunistic investigations were undertaken of ELISA reactor cattle discovered during testing for the Australian Johne's Disease Market Assurance Program for Cattle (Farms M and N). RESULTS: All animals in the survey gave negative results on serology while one animal from a herd of 349 gave a positive faecal culture result. Follow-up faecal culture, post-mortem and histopathology on the latter animal were negative, suggesting that it was a passive faecal shedder or carrier. Two occurrences of OJD transmission to cattle were detected during the opportunistic investigations. CONCLUSION: These observations confirm existing beliefs about the risk of transmission of OJD to cattle, that the risk of transmission is low. However transmission occurs sporadically. An estimated upper limit of prevalence of S strain M a paratuberculosis infection in susceptible exposed cattle in the OJD high prevalence area of New South Wales is 0.8%, assuming a common prevalence within herds.     

Allogenic blood patch pleurodesis for management of pneumothorax in a Cavalier King Charles Spaniel puppy with multiple pulmonary blebs and bullae

A 9‐week‐old male intact Cavalier King Charles Spaniel was presented for evaluation of acute onset dyspnea caused by left‐sided pneumothorax. Thoracic computed tomography (CT) identified multiple pulmonary bullae and blebs in multiple lung lobes. Rupture of ≥1 pulmonary blebs or bullae, precipitated by low impact trauma, was the suspected cause of pneumothorax. A volume of 7.5 mL/kg of fresh whole blood was collected from a type‐matched donor dog and administered into the left pleural space using a thoracostomy tube. The pneumothorax was successfully resolved and no adverse effects of blood patch pleurodesis were noted. The dog was clinically normal 12 months later.     

Relative Exposure Index: an important factor in sea turtle nesting distribution

• 1. The threatened status of many sea turtle populations and their vulnerability to coastal development and predicted climate change emphasize the importance of understanding the role of environmental factors in their distribution and ecological processes. The factors driving the distribution of sea turtle nesting sites at a broad spatial scale is poorly understood.
• 2. In light of the lack of understanding about physical factors that drive the distribution of turtle nesting, the relationship between nesting site distribution and the exposure of coastal areas to wind and wind‐generated waves was analysed. To achieve this, a Relative Exposure Index (REI) was developed for an extensive area in north‐eastern Australia and values of the index for nesting sites of five different sea turtle species and randomly selected non‐nesting sites were compared.
• 3. Although there are differences between species, the results show that sea turtles nest in areas of higher REI values suggesting that wind exposure is related to the spatial distribution of sea turtle nesting sites, and it may also influence nest site selection in female turtles and/or the dispersal of hatchlings towards oceanic currents.
• 4. The combination of these results with further research on other driving environmental factors, like oceanic currents, has the potential to allow for the identification and prediction of future nesting sites, for which conservation and management may become essential. Copyright © 2009 John Wiley & Sons, Ltd.

     

Some Factors Associated With Fertility of Thoroughbred Stallions

The results of 3 years (2005–2007) of observations and mating (5,646 estrous cycles of 3,788 mares bred to 1 of 15 stallions) at one Thoroughbred breeding farm in central Kentucky were analyzed by a multiple logistic regression model using Bayesian statistics to evaluate the relationship between data entries (factors) and pregnancy outcomes. Factors found to be significantly (P < .05) associated with pregnancy outcome included stallion (one stallion had lower OR for pregnancy higher odds ratio [OR] for pregnancy, and one had, than other stallions), date of mating (OR for pregnancy declined slightly in May – July), mare age (OR for pregnancy were higher for mares <13 years old, and lower for mares >18 years old), mare beginning status (foaling mares had a higher OR for pregnancy), mating on foal heat (lowered OR for pregnancy), mating of the day for the stallion (OR for pregnancy was 4.16 times lower for fifth compared with first mating of day), reinforcement breeding (increased OR for pregnancy), dismount semen neutrophil score (lowered OR for pregnancy when neutrophils were present in dismount semen samples), and tranquilization before breeding (lowered OR for pregnancy in foaling and barren mares). The influence of dismount sample sperm motility scores on OR for pregnancy was weak, so motility scores were not included in the final logistic regression model. The majority of variation in pregnancy outcome was because of mare factors, with only approximately one-third of the variation in fertility explained by stallion.     

Assessing the value of forestry to the Irish economy — An input–output approach

Input–output analysis was used to evaluate the total economic impact (i.e. the sum of the direct, indirect and induced impacts) of the forestry and wood products sectors on the Irish economy. The total impact of the forestry sector on a number of regional economies was also examined, as were the short-term economic consequences of an afforestation scenario. Only economic activity associated with timber production was considered, and externalities associated with the sector were not accounted for. The results show that in 2003, forestry produced a direct output of €255.4 million. For every euro of output from forestry, a further €0.85 of economic activity was generated, yielding a total output of €472.4 million and total employment level of 7182. The wood products sector generated a total output of €1.6 billion and a total employment level of 12,246. These estimates of the economic impact of the forestry and wood products sectors cannot be added due to an overlap in indirect and induced impacts. The gross total value of an afforestation programme amounting to 15,000 ha per annum over 5 years was shown to be €475.0 million. Accounting for the fact that almost all land currently afforested is in agriculture, the net total value of this afforestation programme ranged from €157.8 million to €340.4 million, depending on the farming system being replaced and whether stacking of direct payments to farmers under the Single Payment Scheme applies to the land being planted.     

Remediation of upstream passage for migrating Galaxias (Family: Galaxiidae) through a pipe culvert

Movement through streams is critical for the maintenance of diadromous fish populations. Numerous fish passage improvement techniques exist, and knowledge of their effectiveness is required to conserve target species. An existing 70‐m pipe culvert was considered a barrier to the passage success of young‐of‐year (YOY) Galaxias spp. as a result of high water velocity (0.9 m/s). Water velocity in the pipe culvert was reduced by installing a concrete weir downstream of the culvert. A lateral ridge rock‐ramp fishway was installed to provide for the passage of fish over the weir, and baffles were installed in the upstream portion of the culvert to provide refuge from higher water velocity at this location. A BACI design was used to determine whether passage success, measured using a mark–recapture technique, improved as a result of the remediation works. The probability of successful passage of YOY Galaxias spp. through the culvert increased from 0.03 to 0.41 following remediation works and was similar to levels observed at a control site (0.33). The success of the fishway and baffles at this culvert provides an important case study for managers to adopt this technique to improve fish passage on a broader scale and range of other sites.     

Hierarchical factors impacting the distribution of an invasive species: landscape context and propagule pressure

Distribution of invasive species is the outcome of several processes that interact at different hierarchical levels. A hierarchical approach is taken here to analyze the landscape level distribution pattern of Purple loosestrife (Lythrum salicaria), an aggressive wetland invader. Using land use/land cover (LULC) data and loosestrife presence records we were able to identify and characterize the key processes that resulted in the observed large-scale distribution. Herbaceous wetlands, edges of open water sites, and developed open spaces were identified as loosestrife’s preferred LULC types. Analysis of spatial neighborhoods of these key land cover types revealed that disturbance modified open water edges and herbaceous wetlands were more likely to be invaded by loosestrife. Moreover, developed open spaces appear to hold loosestrife only if there is water rich conditions in the immediate neighborhood. Neighborhood analyses also showed that wetlands and open water edges embedded within a neighborhood matrix of grassland and agricultural environments is less likely to contain loosestrife. Finally, there is strong evidence of propagule pressure. Open water edges and wetlands invaded by loosestrife had on an average more loosestrife as neighbors than uninvaded lake edges and wetlands. Taken together, it is apparent that loosestrife’s landscape level distribution is the outcome of three nested hierarchical factors: habitat preference, the spatial neighborhood and propagule pressure. The patterns characterized suggests that occurrence of an invasive species is not merely contingent on availability of suitable habitat but is also influenced by human actions within its proximity, and is further constrained by dispersal limitation.     

Digestion and nitrogen metabolism in beef cattle and in vitro rumen fermentation of autumn grass differing in fertilizer nitrogen application rate

Beef cattle partition dietary nitrogen (N) into meat or excrete it mainly in faeces and urine, which can contribute significantly to water and air pollution. The effects of two inorganic nitrogen (N) fertilizer application rates—15 (LN) or 80 (HN) kg N/ha—to Lolium perenne‐dominant swards in autumn, on herbage chemical composition, intake, digestion and N balance in beef cattle, and in vitro fermentation and methane production were studied. Four growing beef steers used in a 2 × 2 crossover design experiment were offered zero‐grazed grass harvested 21 days post‐N application between July and October. The same grasses were incubated in an eight‐vessel rumen simulation technique in a randomized complete block experiment. Grass dry‐matter (DM) concentration was 26 g/kg lower and crude protein (CP) concentration was 35 g/kg DM higher for HN compared to LN. There was no difference in herbage DM intake or in vivo DM digestibility between treatments. Nitrogen intake and the digestibility of N were higher for HN compared to LN. Total and urine N loss were 41 and 45 g/day greater, respectively, for HN compared to LN, but faecal N loss did not differ between treatments. The quantity of N retained and therefore N‐use efficiency did not differ between LN and HN (25% vs. 22%). In vitro rumen pH and ammonia‐N concentrations were higher for HN compared to LN, whereas volatile fatty acid concentrations and molar proportions did not differ between treatments. In vitro methane and total gas production were 0.9 mmol/day and 280 ml/day lower for HN than LN respectively. Under the particular conditions of this experiment, reducing fertilizer N application rate reduced total and urinary N excretion, which has potential environmental benefits; however, methane output measured in vitro was increased.