Smoke derived from burnt vegetation stimulates germination of arable weeds

A commercially available smoke-water solution (Seed Starter (R)) stimulated the germination of caryopses and intact florets of Avena fatua L. The solution was most effective when diluted (5-50%) and presented to intact or dehulled grain that had received a short period of dry after-ripening. It was less effective when applied at full strength or to grains that had been freshly harvested. The same stimulatory effect was observed in par-fly after-ripened caryopses of nine different wild oat biotypes obtained from three different cropping regions of the world. When freshly harvested caryopses were re-tested with the commercial solution (100%) for just 7 days prior to placement on to distilled water, a much higher germination percentage was possible than seen with continuous smoke-water incubation. The stimulatory ability of smoke water was more closely matched to that of gibberellic acid than to potassium nitrate, which had little or no effect on freshly harvested caryopses. The smoke-water solution (5-100%) was tested on the germination of 18 other cool temperate arable weed species. All monocotyledonous species tested (viz. Avena sterilis ssp. ludoviciana L., Alopecurus myosuroides, Sorghum halepense, Phalaris paradoxa) responded positively, while those of the dicotyledonous species were either strongly stimulated (greater than or equal to 40% stimulation Malva neglecta), moderately stimulated (greater than or equal to 20% stimulation Galium aparine, Veronica persica), slightly stimulated (Polygonum persicaria, P pennsylvanicum, Fallopia convolvulus), unaffected (P. aviculare, Sinapis arvensis, Heracleum sphondylium, Angelica sylvestris, Mercurialis annua, Veronica hederifolia) or inhibited (Lamium purpureum). The optimal concentrations required to stimulate germination of the monocotyledonous species were similar to those observed for A. fatua (5-10%). However, for the dicotyledonous species slightly stronger solutions were required (10-20%). When the unaffected species were retested using a 10-day pre-chilling treatment, smoke water showed a small promotive response in three (S. arvensis, P. aviculare and V hederifolia) of the six species. When four different smoke-water solutions (Seed Starter (R), Regen 2000 (R), charred-wood solution and wheat-straw solution) were tested on two representative species (A. fatua and M. neglecta), three formulations were effective in promoting the germination of both species, while the fourth (charred-wood solution) was only active on A. fatua. The active concentrations were different for the four solutions. Three solutions were active in the 2-20% dilution range, while the fourth (Regen 2000 (R)) was only active in the 1-2% dilution range and was inhibitory at higher concentrations. These observations are discussed in the context that smoke may play an important ecological role in the management and control of introduced weeds in native and arable communities.

'Neighbourhood' size, dispersal and density estimates in the prickly forest skink (Gnypetoscincus queenslandiae) using individual genetic and demographic methods

Dispersal, or the amount of dispersion between an individual's birthplace and that of its offspring, is of great importance in population biology, behavioural ecology and conservation, however, obtaining direct estimates from field data on natural populations can be problematic. The prickly forest skink, Gnypetoscincus queenslandiae, is a rainforest endemic skink from the wet tropics of Australia. Because of its log-dwelling habits and lack of definite nesting sites, a demographic estimate of dispersal distance is difficult to obtain. Neighbourhood size, defined as 4 piD sigma (2) (where D is the population density and sigma (2) the mean axial squared parent-offspring dispersal rate), dispersal and density were estimated directly and indirectly for this species using mark-recapture and microsatellite data, respectively, on lizards captured at a local geographical scale of 3 ha. Mark-recapture data gave a dispersal rate of 843 m(2)/generation (assuming a generation time of 6.5 years), a time-scaled density of 13 635 individuals * generation/km(2) and, hence, a neighbourhood size of 144 individuals. A genetic method based on the multilocus (10 loci) microsatellite genotypes of individuals and their geographical location indicated that there is a significant isolation by distance pattern, and gave a neighbourhood size of 69 individuals, with a 95% confidence interval between 48 and 184. This translates into a dispersal rate of 404 m(2)/generation when using the mark-recapture density estimation, or an estimate of time-scaled population density of 6520 individuals * generation/km(2) when using the mark-recapture dispersal rate estimate. The relationship between the two categories of neighbourhood size, dispersal and density estimates and reasons for any disparities are discussed.

Effectiveness of brown planthopper predators: Population suppression by two species of spider, Pardosa pseudoannulata (Araneae, Lycosidae) and Araneus inustus (Araneae, Araneidae)

The most abundant natural enemies found in Cambodian rice field are spiders, mostly Araneus inustus and Pardosa pseudoannulata. These two hunting and wolf spider, respectively, are believed to actively contribute to brown planthopper (BPH) population control. However, how much each species attacks prey in Cambodian field condition is unknown. We conducted field experiments in Cambodia during the wet season at two locations, a famner's fields at Takeo and at CARDI, using both field cages and natural conditions. Cages were sprayed with insecticide to remove all pre-existing insects in the cages and then washed after 10 days to reduce insecticide residue. Results confirmed BPH inside the cage were killed by the insecticide. A known BPH population was reared inside the cages starting with 3 pairs of adults. Temporary cages were removed after counting second instar BPH and permanent cages were left in place. Spiders were released into the cages for 15 days. In permanent cages either two individual A. inustus or P. pseudoannulata were allowed to feed on BPH prey. Both spider species have the same killing ability in dense prey populations, but predation is higher for Pardosa at low prey density. In uncaged field environments (where more than just BPH prey are available) with a spider/BPH ratio 1:3 to 1:11 BPH mortality was 78–91%. Within 15 days in permanent cages spiders caused 100% BPH mortality at an average predator/prey ratio of 1:5 to 1:14. At a ratio of 1:18 or higher there was some BPH survival in cages.

Can long-distance dispersal be inferred from the New Zealand plant fossil record?

New Zealand is generally thought to have been physically isolated from the rest of the world for over 60 million years. But physical isolation may not mean biotic isolation, at least on the time scale of millions of years. Are New Zealand's present complement of plants the direct descendants of what originally rafted from Gondwana? Or has there been total extinction of this initial flora with replacement through long-distance dispersal (a complete biotic turnover)? These are two possible extremes which have come under recent discussion. Can the fossil record be used to decide the relative importance of the two endpoints, or is it simply too incomplete and too dependent on factors of chance? This paper suggests two approaches to the problem-the use of statistics to apply levels of confidence to first appearances in the fossil record and the analysis of trends based on the entire palynorecord. Statistics can suggest that the first appearance of a taxon was after New Zealand broke away from Gondwana-as long as the first appearance in the record was not due to an increase in biomass from an initially rare state. Two observations can be drawn from the overall palynorecord that are independent of changes in biomass: (1) The first appearance of palynotaxa common to both Australia and New Zealand is decidedly non-random. Most taxa occur first in Australia. This suggests a bias in air or water transport from west to east. (2) The percentage of endemic palynospecies in New Zealand shows no simple correlation with the time New Zealand drifted into isolation. The conifer macrorecord also hints at complete turnover since the Cretaceous.

Pre- and postsynaptic actions of ATP on neurotransmission in rat submandibular ganglia

The pre- and postsynaptic actions of exogenously applied ATP were investigated in intact and dissociated parasympathetic neurotics of rat submandibular ganglia. Nerve-evoked excitatory postsynaptic potentials (EPSPs) were not inhibited by the purinergic receptor antagonists, suramin and pyridoxal-phosphate-6-azophenyl-2 ' ,4 ' -disulphonic acid (PPADS), or the desensitising agonist, alpha,beta -methylene ATP. In contrast. EPSPs were abolished by the nicotinic acetylcholine receptor antagonists, hexamethonium and mecamylamine. Focal application of ATP (100 muM) had no effect on membrane potential of the postsynaptic neurone or on the amplitude of spontaneous EPSPs. Taken together, these results suggest the absence of functional purinergic (P2) receptors on the postganglionic neurone in situ. In contrast, focally applied ATP (100 muM) reversibly inhibited nerve-evoked EPSPs. Similarly, bath application of the non-hydrolysable analogue of ATP, ATP gammaS, reversibly depressed EPSPs amplitude, The inhibitory effects of ATP and ATP gammaS on nerve-evoked transmitter release were antagonised by bath application of either PPADS or suramin, suggesting ATP activates a presynaptic P2 purinoceptor to inhibit acetylcholine release from preganglionic nerves in the submandibular ganglia. In acutely dissociated postganglionic neurotics from rat submandibular ganglia. focal application of ATP (100 LM) evoked an inward current and subsequent excitatory response and action potential firing, which was reversibly inhibited by PPADS (10 muM). The expression of P2X purinoceptors in wholemount and dissociated submandibular ganglion neurones was examined using polyclonal antibodies raised against the extracellular domain of six P2X purinoceptor subtypes (P2X(1-6)). In intact wholemount preparations, only the P2X(5) purinoceptor subtype was found to be expressed in the submandibular ganglion neurones and no P2X immunoreactivity was detected in the nerve fibres innervating the ganglion. Surprisingly, in dissociated submandibular ganglion neurones, high levels of P2X(2) and P2X(4) purinoceptors immunoreactivity were found on the cell surface. This increase in expression of P2X(2) and P2X(4) purinoceptors in dissociated submandibular neurones could explain the increased responsiveness of the neurotics to exogenous ATP. We conclude that disruption of ganglionic transmission in vivo by either nerve damage or synaptic blockade may up-regulate P2X expression or availability and alter neuronal excitability. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.

Dispersal strategies in Tasmanian native hens (Gallinula mortierii)

Individuals in cooperatively breeding species face a complex set of decisions when they reach reproductive maturity. During an 8-year study, we examined the histories of 214 Tasmanian native hens (Gallinula mortierii) from hatching to examine the strategies they used to acquire breeding positions and the reproductive success they experienced in those breeding positions. Two-thirds of young delayed dispersal from their natal groups for at least a year. Ecological constraints were a partial cause of delayed dispersal; high-quality territories were rare and remained occupied due to high adult survivorship. There were also clear benefits of philopatry. Individuals that inherited breeding positions on their natal territories gained better quality positions and experienced higher reproductive success in their first breeding attempts than did individuals who dispersed to other groups. Multivariate analyses showed that the method of acquisition of breeding positions was the only factor significantly related to the quality of the breeding positions attained. Males were more likely to inherit breeding positions in their natal groups than were females. The compositions of individuals' natal groups had no effect on whether they inherited breeding positions or dispersed. In contrast, the compositions of groups did appear to affect whether other birds dispersed into them, with birds rarely moving into groups that contained breeders or nonbreeders of the same sex as the potential dispersers. Short-term removals of breeders confirmed this finding. These results suggest that both ecological constraints and benefits of philopatry explain delayed dispersal in this species.

Do female rainbowfish (Melanotaenia spp.) prefer to shoal with familiar individuals under predation pressure?

Shoaling with familiar individuals may have many benefits including enhanced escape responses or increased foraging efficiency. This study describes the results of two complimentary experiments. The first utilised a simple binary choice experiment to determine if rainbowfish (Melanotaenia spp.) preferred to shoal with familiar individuals or with strangers. The second experiment used a free range situation where familiar and unfamiliar individuals were free to intermingle and were then exposed to a predator threat. Like many other small species of fish, rainbowfish were capable of identifying and distinguishing between individuals and choose to preferentially associate with familiar individuals as opposed to strangers. Contrary to expectations. however. rainbowrish did not significantly increase their preference for familiar individuals in the presence of a stationary predator model. Griffiths [J Fish Biol (1997) 51:489-4951 conducted similar studies under semi-natural conditions examining, the shoaling preferences of European minnows and showed similar results. Both the current study and that of Griffiths were conducted using predator wary populations of fish. It is suggested that, in predator sympatric populations, the benefits of shoaling with familiar individuals are such that it always pays to stay close to familiar individuals even when the probability If predator attack is remote.

Productivity growth in pre-1990 Mongolian agriculture: Spiralling disaster or emerging success?

The reasons for the spectacular collapse of so many centrally-planned economies are a source of ongoing debate. In this paper, we use detailed farm-level data to measure total factor productivity (TFP) changes in Mongolian grain and potato farming during the 14-year period immediately preceding the 1990 economic reforms. We measure TFP growth using stochastic frontier analysis (SFA) and data envelopment analysis (DEA) methods. Our results indicate quite poor overall performance, with an average annual TFP change of - 1.7% in grain and 0.8% in potatoes, over the 14-year period. However, the pattern of TFP growth changed substantially during this period, with TFP growth exceeding 7% per year in the latter half of this period. This suggests that the new policies of improved education, greater management autonomy, and improved incentives, which were introduced in final two planning periods in the 1980s, were beginning to have a significant influence upon the performance of Mongolian crop farming. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Seed dormancy mechanisms in warm season grass species

Available evidence suggests that there are at least two locations for dormancy mechanisms in primary dormant seeds: mechanisms based within the embryo covering structures, and mechanisms based within the embryo. Mechanisms within the covering structures may involve mechanical, permeability and chemical barriers to germination. Mechanisms within the embryo may involve the expression of certain genes, levels of certain plant growth regulators, the activity of important respiratory pathways or the mobilisation and utilisation of food reserves. In addition, some embryos may be too immature to germinate immediately and must undergo a further growth phase before germination is possible. An individual species could have one or several of these various dormancy mechanisms and these mechanisms need to be understood when selecting treatments to overcome dormancy. The way in which certain dormancy breaking agents are thought to work is discussed and practical applications of such agents in field situations are explained.

Predation of brown tree snakes (Boiga irregularis) in Australia

We conducted a literature review to address the potential for using a native, vertebrate predator of brown tree snakes (Boiga irregularis) as a biological control method on Guam. Both actual and potential predators were included in our review. We located two actual predators (red-bellied black snakes (Pseudechis porphyriacus) and cane toads (Bufo marinus)) and 55 potential predators of brown tree snakes. However, none of the native predators of brown tree snakes appear likely candidates as a biological control method on Guam due to their lack of selectivity in their feeding habits and unknown aspects of their natural history. (C) 2002 Elsevier Science Ltd. All rights reserved.

Hydrofluoric acid pre-treatment for improving 13C CPMAS NMR spectral quality of forest soils in south-east Queensland, Australia

Hydrofluoric acid (HF) was used to pre-treat forest soils of south-east Queensland for assessing the effectiveness of iron (Fe) removal, carbon (C) composition using C-13 cross-polarisation (CP) with magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) before and after the HF pre-treatment, and the improvement of C-13 CPMAS NMR spectra. Soil samples were collected from 4 experimental sites of different soil types, harvest residue management or prescribed burning, and tree species. More than 86% of Fe was in all soil types removed by the HF treatment. The C-13 NMR spectral quality was improved with increased resolution, especially in the alkyl C and O-alkyl C regions, and reduced NMR run-time (1-5 h per sample compared with >20 h per sample without the pre-treatment). The C composition appeared to alter slightly after the pre-treatment, but this might be largely due to improved spectrometer conditions and increased resolution leading to more accurate NMR spectral integration. Organic C recovery after HF pre-treatment varied with soil types and forest management, and soluble soil organic matter (SOM) could be lost during the pre-treatment. The Fourier Transform-Infrared (FT-IR) spectra of HF extracts indicated the preferential removal of carboxylic C groups during the pre-treatment, but this could also be due to adsorbed water on the mineral matter. The NMR spectra revealed some changes in C composition and quality due to residue management and decomposition. Overall, the HF treatment was a useful pre-treatment for obtaining semi-quantitative C-13 CPMAS NMR spectra of subtropical Australian forest soils.