Climatic Drivers of Revegetation Management Practices in Australia: Analysis of a Social Survey

Investment in small and large-scale revegetation in Australia is growing in response to concerns regarding the sustainability and productivity of agricultural landscapes. Site preparation and management––such as soil cultivation, weed control, fertilising, mulching, use of treeguards and watering––are major costs associated with small-scale revegetation. The aim of this study has been to investigate local revegetation knowledge and practices to determine the usefulness of each management practice for achieving success and to determine whether some practices are more suited to particular climatic zones. A national online revegetation survey was conducted to ascertain current small-scale revegetation practices and the factors that drive these choices. Management practices were found to be strongly associated with climate. Mulch, fertiliser, weed control and watering were applied more frequently in higher rainfall and higher temperature zones. Soil cultivation and treeguards were used more frequently in lower rainfall and lower temperature zones. These findings suggest that there may be some benefit in modifying existing revegetation guidelines to reflect climatic zones and management flexibility.

Survival and growth of upland oak and co-occurring competitor seedlings following single and repeated prescribed fires

Studies within and outside the U.S. indicate recurring oak (Quercus spp.) regeneration problems. In deciduous forests of the eastern U.S., a prevailing explanation for this trend is fire suppression leading to high competitor abundance and low understory light. In response, prescribed fire is increasingly used as a management tool to remedy these conditions and encourage future oak establishment and growth. Within eastern Kentucky, we implemented single and repeated (3×) prescribed fires over a 6-yr period (2002–2007). Pre- and post-burn, we quantified canopy cover and oak seedling survival and growth compared to other woody seedlings deemed potential competitors, primarily red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees.). Burning temporarily decreased canopy cover 3–10%, but cover rebounded the subsequent growing season. Repeated burning ultimately produced canopy cover about 6% lower than sites unburned and burned once, suggesting a cumulative effect on understory light. Red maple exhibited low survival (∼40%) following single and repeated burns, but growth remained similar to unburned seedlings. Burning had little impact on sassafras survival and led to total height and basal diameters 2× greater than unburned seedlings. A single burn had no impact on red oak (Erythrobalanus spp.) survival and increased height and basal diameters 25–30%, but this positive growth response was driven by seedlings on several plots which experienced high burn temperatures and consequently high overstory mortality. White oaks (Leucobalanus spp.), however, exhibited twice as high mortality compared to those unburned, with no change in growth parameters. Repeated burning negatively impacted survival and growth of both oak groups compared to unburned seedlings. With both burn regimes, oaks with smaller pre-burn basal diameters exhibited the lowest post-burn survival. Thus, despite the ability of prescribed burns to temporarily increase understory light and reduce red maple survival, neither single or repeated burns placed oaks in an improved competitive position. These findings result from a combination of highly variable yet interdependent factors including the (1) life history traits of oaks compared to their co-occurring competitors, (2) pre-burn stature of pre-existing oak seedlings, and (3) variability in fire temperature and effects on understory light.     

Coastal Prairie Recovery in Response to Shrub Removal Method and Degree of Shrub Encroachment

Shrub encroachment into grasslands is a worldwide phenomenon with no signs of abating and numerous ecological consequences. In South Texas, honey mesquite (Prosopis glandulosa Torr.) and huisache (Vachellia farnesiana [L.] Wight & Arn.) are two shrubs encroaching into coastal prairies, reducing cover of the dominant native grass, gulf cordgrass (Spartina spartinae [Trin.] Merr. ex Hitchc.), and decreasing habitat for the endangered Aplomado Falcon (Falco femoralis), which requires grasslands or savannas for survival. To determine the best management approach for deterring shrub encroachment and restoring native grasslands, the US Fish and Wildlife Service used several shrub removal techniques within coastal prairies of the Bahía Grande Wetland Complex of the Laguna Atascosa National Wildlife Refuge, a core site for Aplomado Falcon reintroductions. Here, we assess native grass recovery over a 2-yr period in response to these shrub removal methods (mechanical plus prescribed fire and/or herbicide treatments) and degree of shrub encroachment before treatment. In general, areas with high levels of shrub encroachment before treatment had the highest amount of bare ground and lowest grass cover immediately following an initial mechanical treatment; this legacy effect persisted throughout the study irrespective of shrub removal treatment. Regardless of degree of shrub encroachment before treatment, grasses in areas treated with either mechanical or mechanical followed by herbicide methods recovered the slowest, likely due to residual woody material that hindered seed germination. Herbicide treatment following mechanical removal or mechanical removal plus fire effectively hindered shrub regrowth. Overall, mechanical treatment followed by prescribed fire and then herbicide application most effectively promoted grass recovery while hindering shrub regrowth. These findings suggest that grassland recovery following shrub encroachment into South Texas coastal prairies may be promoted through the application of shrub removal methods that combine mechanical, fire, and herbicide treatments.     

Suspected myelodysplastic/myeloproliferative neoplasm in a feline leukemia virus‐negative cat

A 10‐year‐old castrated Domestic Short‐Haired cat was presented to a primary care veterinarian for a wellness examination and laboratory examination for monitoring of diabetes mellitus. The CBC revealed marked thrombocytosis, leukopenia and macrocytic, normochromic anemia. The cat tested negative for FeLV and feline immunodeficiency virus, but was positive for Mycoplasma haemominutum by PCR. Hematologic abnormalities were not responsive to therapy, so a repeat CBC and a bone marrow aspiration for cytology were performed. Additional blood smear findings included anisocytosis with megaloblastic erythroid precursors, large platelets, eosinophilic myelocytes and metamyelocytes, and rare unidentified blasts. The bone marrow smear was highly cellular, and the cytologic pattern was consistent with myelodysplastic syndrome with an erythroid predominance. At that time, 15% blasts were present. The cat was treated with a vitamin K₂ analog, doxycycline, and prednisolone, but without a clinical response. Within 3 months, euthanasia was elected due to declining quality of life, and a necropsy was performed. Postmortem bone marrow smears were highly cellular and dominated by monomorphic blasts of unknown line of origin (52%), persistent marked erythroid and megakaryocytic dysplasia, and ineffective erythropoiesis and granulopoiesis. Immunohistochemical, immunocytochemical, and cytochemical stains resulted in a diagnosis of acute myeloid leukemia of unclassified type. Additional histologic findings included mixed hepatitis with trematode infestation and lymphoplasmacytic interstitial nephritis with fibrosis. The marked thrombocytosis with myelodysplastic syndrome and the FeLV‐negative status of this cat were unusual. The difficulty in classifying the myelodysplasia and subsequent leukemia highlights a need for further reporting and characterization of these types of disease.     

Epidemiologic survey of thrombocytopenia in dogs: a report on 987 cases

Thrombocytopenia was documented in 987 of 18,910 (5.2%) dogs admitted to North Carolina State University, College of Veterinary Medicine, Veterinary Teaching Hospital, between 1983 and 1989. Classifying thrombocytopenic dogs by etiologic groups revealed the following proportionate ratios: 5% (48/987) immune-mediated thrombocytopenia; 13% (130/987) neoplasia-associated thrombocytopenia; 23% (224/987) inflammatory/infectious thrombocytopenia; and 59% (585/987) miscellaneous thrombocytopenia. Dogs with immune-mediated thrombocytopenia had significantly (P < 0.05) lower platelet counts (mean 36,760 +/- 50,288 microliter) than dogs in the other three groups, and Doberman Pinschers were overrepresented in all groups except the immune-mediated thrombocytopenic group. We conclude that thrombocytopenia is a prevalent and potentially important diagnostic finding in a variety of disease states.     

Idiopathic arterial medial calcification of the thoracic arteries in an adult horse

A 6-year-old, gelded, Paint horse displayed clinical signs of muscle wasting and limb stiffness for a 6-month period. The horse's clinical signs abated with corticosteroid therapy, but returned upon cessation of treatment. Upon necropsy, severe lesions of aortic thickening and aortic valve rigidity were observed. Histologically, the tunica media of the aorta, coronary arteries, and pulmonary arteries were expanded by foci of elastin fiber calcification and extracellular matrix with lacunae formation. The vascular lesions are comparative to what has been described as medial arterial calcification, seen in humans suffering from chronic renal failure or diabetes mellitus. No exposure to vitamin D-containing plants or feedstuff could be documented at the time of onset or during the period of clinical signs. The current case describes dramatic lesions of arterial medial calcification of the aorta, coronary, and pulmonary arteries of undetermined cause.     

Profitable and Sustainable Cattle Grazing Strategies Support Reptiles in Tropical Savanna Rangeland

Rangelands are areas used primarily for grazing by domestic livestock; however, because they support native vegetation and fauna, their potential role in conservation should not be overlooked. Typically, “off-reserve” conservation in agricultural landscapes assumes a trade-off between maintaining the ecological processes that support biodiversity and successful food production and profitability. To evaluate this potential biodiversity trade-off in rangelands, we need to understand the effect of different livestock grazing strategies on biodiversity, in relation to their performance in terms of profitability and land condition. We monitored reptile community responses to four cattle-grazing strategies (heavy, moderate, and variable stocking rates and a rotational wet season spelling treatment) in a replicated, long-term grazing trial in north Queensland, Australia. Simultaneously, measures of profitability and land condition were collected for the different grazing strategies. Overall, reptile abundance was not negatively impacted by the more sustainably managed treatments (moderate, variable, and rotational) compared with heavy stocking, although the effect of grazing treatment alone was not significant. Profitability and land condition were also higher in these treatments compared with the heavy stocking rate treatment. As drought conditions worsened over the 3 yr, the negative impact of the heavy stocking treatment on both profitability and biodiversity became more pronounced. Heavy stocking negatively impacted reptiles and was also the least profitable grazing strategy over the long term, resulting in the worst land condition. This suggests that in this tropical savanna rangeland there was no trade-off between economic performance and reptile abundance and diversity. Grazing regimes with a moderate stocking rate or flexible management strategies were better able to buffer the effects of climate variability. The consequence was a more resilient reptile community and better economic outcomes in dry years.