A sub-continental scale living laboratory: Spatial patterns of savanna vegetation over a rainfall gradient in northern Australia

Savanna landscapes across north Australia are characterised by limited topographic variation, and in the Northern Territory, by a relatively constant decline in rainfall with distance inland. The North Australian Tropical Transect (NATT) traverses this 1000 km gradient of largely intact vegetation which provides an ideal ‘living laboratory’ and framework to investigate the influence of vegetation structural and floristic change and climate drivers on land-atmosphere exchange at a regional scale. We conducted a multidisciplinary program examining carbon, water and energy fluxes as a function of climate and vegetation change along a sub-continental environmental gradient. Initial findings are reported in this Special Issue. During the program, an intensive field campaign was undertaken during the dry season to characterise vegetation and soil properties of eight flux tower sites used to describe spatial and temporal dynamics of fluxes across this gradient. This paper provides an overview of the savanna landscapes of north Australia detailing vegetation structural and physiological change along this gradient. Above-ground woody biomass, stem density, overstorey LAI and canopy height declined along sites that spanned an 1100 mm annual rainfall gradient. Biomass ranged from 35 to 5 t C ha⁻¹ with dry season LAI ranging from ∼1 to 0.05 across savanna sites both intact and cleared for grazing. Across open-forest and woodland savanna, basal area ranged from 9.7 to 5.3 m² ha⁻¹. While structural change was significant and correlated with rainfall, leaf scale physiological properties (maximal photosynthesis, V_cmax, c_i/c_a, light use efficiency) of the dominant woody species showed little variation, despite the significant environmental gradient. It is likely that changes in structural properties dominate spatial patterns of flux as opposed to physiological plasticity or species differences along this gradient.     

Hepatozoon spp. (Apicomplexa: Hepatozoidae) infection and selected hematological values of the neotropical rattlesnake, Crotalus durissus collilineatus (Linnaeus, 1758) (Serpentes: Viperidae), from Brazil

This study aims to establish the hematological values of Crotalus durissus collilineatus snakes captured in Brazil as well as to verify the effects of hematozoan infection on these snakes. Eighty-three blood samples were drawn from C. d. collilineatus specimens for analysis. The sample set was composed of 30 males and 30 females, recently caught from the wild, and 11 males and 12 females bred in captivity. Blood samples were used to determine red blood cell counts, white blood cell counts, thrombocyte counts, hematocrit values, hemoglobin concentration, and total plasma protein. Blood smears were used to diagnose Hepatozoon spp. infection and to calculate the parasitic load in the sample as well as the percentage of immature red cells. Results obtained for the wild-caught animals, with and without parasites, were compared among themselves and with the values obtained for the captive-bred animals. Hematological values for C. durissus were established. Wild-caught snakes had an infection rate of 38.3%, while no Hepatozoon sp. infection was detected in the captive-bred animals. The snakes which were not infected by the Hepatozoon sp. exhibited average weight, length, and weight-length ratios higher than those of the infected animals. An increase in immature red cells was noted in the Hepatozoon-infected snakes.     

Pharmacokinetics of intramuscular ketamine in young ostriches premedicated with romifidine

Ketamine is a short-acting dissociative anaesthetic for chemical restraint and surgical anaesthesia in domestic and non-domestic animals. The present study was designed to determine the pharmacokinetics of a single dose of ketamine (10 mg/kg) after intramuscular (i.m.) administration to young ostriches premedicated with romifidine. Ketamine was rapidly absorbed after i.m. administration. Maximal ketamine concentration (C(max)) of 2.93 +/- 0.61 microg/ml was reached at 12.5 +/- 2.50 min and thereafter ketamine concentrations decreased rapidly. The elimination half-life (t(1/2 z)) obtained was 62.37 +/- 17.37 min and mean residence time (MRT) was 77.33 +/- 19.12 min. The area under the curve (AUC) was 114.19 +/- 15.76 microg x min/ml.