Savanna fires and their impact on net ecosystem productivity in North Australia

Savannas comprise a large area of the global land surface and are subject to frequent disturbance through fire. The role of fire as one of the primary natural carbon cycling mechanisms is a key issue in considering global change feedbacks. The savannas of Northern Australia burn regularly and we aimed to determine their annual net ecosystem productivity (NEP) and the impact of fire on productivity. We established a long‐term eddy covariance flux tower at Howard Springs, Australia and present here 5 years of data from 2001 to 2005. Fire has direct impacts through emissions but also has indirect effects through the loss of productivity due to reduced functional leaf area index and the carbon costs of rebuilding the canopy. The impact of fire on the canopy latent energy exchange was evident for 40 days while the canopy was rebuilt; however, the carbon balance took approximately 70 days to recover. The annual fire free NEP at Howard Springs was estimated at −4.3 t C ha⁻¹ yr⁻¹ with a range of −3.5 to −5.1 t C ha⁻¹ yr⁻¹ across years. We calculated the average annual indirect fire effect as +0.7 t C ha⁻¹ yr⁻¹ using a neural network model approach and estimated average emissions of fine and coarse fuels as +1.6 t C ha⁻¹ yr^‐1. This allowed us to calculate a net biome production of −2.0 t C ha⁻¹ yr^‐1. We then partitioned this remaining sink and suggest that most of this can be accounted for by woody increment (1.2 t C ha⁻¹ yr^‐1) and shrub encroachment (0.5 t C ha⁻¹ yr^‐1). Given the consistent sink at this site, even under an almost annual fire regime, there may be management options to increase carbon sequestration by reducing fire frequency.     

Ecological strategies of Dalbulus leafhoppers

Abstract. 1. Developmental times from egg to adult eclosion were established for eight Dalbulus leafhopper species on maize (Zea mays) and its perennial, gamagrass relative, Tripsacum dactyloides. Experiments were conducted with a 16 h day (25–27°C) and an 8 h night (21–22°C).
2. Developmental times were shortest for the maize specialists, c. 26 days for D. maidis and c. 27 days for D. elimatus, and longest for the Tripsacum specialists, c. 32 days for D. tripsacoides, c. 34 days for D. quinquenotatus and c. 40 days for D. guzmani. Developmental times were intermediate for D. gelbus, D. longulus and D. guevarai, species that utilize both maize and Tripsacum as field hosts.
3. For all species, development was significantly faster on maize (species mean 29 days) than on T. dactyloides (species mean 34 days).
4. D. maidis and D. elimatus developed significantly faster (c. 3 days) on maize than on its close perennial relative, Z. diploperennis.
5. As measured by a 48 h oviposition period, D. maidis, D. elimatus and D. gelbus produced significantly more progeny on maize than on gamagrass. D. quinquenotatus produced more progeny on T. dactyloides than on maize. D. maidis and D. elimatus produced more progeny on maize than on Z. diploperennis.
6. These studies provide support for the hypothesis which predicts that herbivorous insects that specialize on annual plants will have a shorter generation time and be more fecund than perennial specialists. The genus Dalbulus appears to be composed of species that fit an r-K continuum, with maize specialists and Tripsacum specialists at opposite ends of the continuum.     

A New Programmatic Basis for Shell Pigment Patterns in the Bivalve Mollusc Lioconcha castrensis (L.)

This paper proposes that cell division assembles divaricate patterns from alternate states expressed by pigmentation zones in the belt of mantle epithelium which deposits the growing margin of the shell. This model of development derives from two fundamental features of patterns in Lioconcha castrensis (Linné). Its patterns are lineages of standard brown triangular units that double repeatedly and diverge in opposite directions from a common origin over the white surface of the valves. Doubling of pigment, not dilution or subdivision, accounts for patterns, since the width and intensity of the units do not decline, even after long lineages. Hence, cell division is proposed. The second feature concerns the finding that triangular units consist of specific combinations of radial and divergent lines that branch from previous diagonal lines. These lines evidently are deposited by pigmentation zones which assume certain states governing whether they are pigmented and radial or divergent. Eight states are possible, each one a particular combination of three binary cellular properties deduced to be: (1) ability to deposit pigment, (2) ability to move along the margin of the valve, and (3) the direction of movement. Thus, the patterns are divaricate because alternate mobile pigment states double and segregate in the mantle epithelium, possibly through cell division.     

Nitrogen deposition causes widespread loss of species richness in British habitats

We use national scale data to test the hypothesis that nitrogen (N) deposition is strongly negatively correlated with plant species richness in a wide range of ecosystem types. Vegetation plots from a national ecological surveillance programme were drawn from heathland, acid, calcareous and mesotrophic grassland habitats. Mean species number and mean plant traits were calculated for each plot and related to atmospheric N deposition. There was a significant reduction in species richness with N deposition in acid grassland and heathland even after fitting covarying factors. In acid grassland and heathland, evidence from trait changes suggested that acidification rather than increased fertility was responsible for species loss. In contrast, calcareous grassland showed evidence of eutrophication in response to increasing N deposition. Loss of species richness from chronic N deposition is apparent in infertile grasslands and heathland. Mechanisms associated with loss of species richness differ between habitats so mitigation of N deposition should be targeted to habitat type.     

Factors affecting Grey‐headed Flying‐fox (Pteropus poliocephalus: Pteropodidae) foraging in the Melbourne metropolitan area,Australia

Abstract Factors affecting the foraging of mobile native fauna in highly fragmented urban landscapes have seldom been quantified at large spatial scales. We investigated factors affecting foraging by Grey‐headed Flying‐foxes (Pteropus poliocephalus; ‘flying‐foxes’) in the greater Melbourne metropolitan area. Flying‐foxes established a continuously occupied colony site in the Royal Botanic Gardens Melbourne in 1986, and the size of the colony has subsequently increased greatly. We used a stratified‐random sampling design to examine the importance of six variables on the detection of foraging flying‐foxes: (i) distance from the colony site (0–10, 10–20 and 20–30 km); (ii) distance from the Yarra River (0–5 and 5–20 km); (iii) the relative tree density of the municipality; (iv) whether the site was a park or street; (v) whether there was a relatively high or low density of trees at the site; and (vi) whether food was or was not detected at the site. We surveyed 240 sites within a 30‐km radius of the colony site for foraging flying‐foxes in both May and October 2002. The probability of detecting a foraging flying‐fox declined with increasing distance from the colony site, but increased with increasing tree cover, and was higher for parks compared with streets and when food was present. Flying‐foxes were observed foraging in a number of plant genera that have no species that naturally occur in the Melbourne area. Flying‐foxes in Melbourne thus forage on planted resources that are widely distributed within a fragmented landscape, and are an example of a positive response by a native species to the process of urbanization.     

Thanaka (Limonia acidissima) and deet (di-methyl benzamide) mixture as a mosquito repellent for use by Karen women

The prevention and treatment of drug-resistant malaria is becoming increasingly difficult. On the Thai–Myanmar border multi-drug resistant strains of falciparum malaria are increasing and, because the malaria vector Anopheles bite outdoors during early evening, insecticide house-spraying or impregnated bednets provide only limited protection. Therefore, the protective efficacy of repellent formulations containing di-methyl benzamide (deet) and permethrin against local vectors was estimated, when applied to the skin, and their acceptability amongst pregnant Karen women who are at relatively high risk from malaria was assessed. Human landing catches of mosquitoes showed that almost complete protection was achieved using different formulations of 20% deet and 0.5% permethrin for up to 6 h. All-night collections from human subjects indicated that this repellent combination reduced exposure to malaria parasites by at least 65 and 85% for those transmitted by Anopheles minimus and An. maculatus , respectively, the two principal vectors in this area. Pregnant women in the camps preferred repellents which were mixed with 'thanaka', a root paste made from pulp of the wood apple tree, Limonia acidissima , used locally as a cosmetic. Apart from a temporary warming sensation where repellent thanaka was applied to the skin, the repellents were well tolerated. An intervention trial is currently in progress to determine whether deet mixed with thanaka can protect pregnant women against malaria in this part of the world. Bioassays using a laboratory strain of Aedes aegypti demonstrated that thanaka is itself slightly repellent at high dosages and the mixture with deet provides protection for over 10 h. This treatment would therefore also provide some personal protection against dengue, which is increasing locally, transmitted by Ae. aegypti and Ae. albopictus biting during the daytime.     

Schizoplasmodium,a Mycetozoan Genus Intermediate Between Cavostelium and Protostelium; a New Order of Mycetozoa*

SYNOPSIS. Two new species of the simple mycetozoan genus Schizoplasmodium—S. ovatum and S. gracile—are described, the former having ovate spores and the latter spherical ones. All stages of the life cycle are multinucleate. At sporulation the holozoic plasmodium segments into prespore cells which develop directly into long-stalked, single-spored sporocarps. Sexual reproduction was not observed. A new order—the PROTOSTELIDA—is proposed for this and related genera, which are believed to comprise a phylogenetically linked series, beginning with the amoebo-flagellate genus Cavostelium and evolving through Schizoplasmodium to Protostelium. The two families Cavostelidae (Cavostelium) and Protostelidae (Schizoplasmodium, Protostelium) are recognized.