Showing papers by "Cooperative Research Centre published in 2000"

The effects of drying and re-flooding on the sediment and soil nutrient dynamics of lowland river-floodplain systems: A synthesis

Abstract: Lowland river–floodplain systems are characterized by a high degree of variability in both the frequency and period of inundation of various parts of the floodplain. Such variation should profoundly affect the processes underlying nutrient transformations in these systems. This paper explores the effect of various hydrologic regimes on nutrient cycles. Partial drying of wet (previously inundated) sediments will result in an increased sediment affinity for phosphorus and will produce a zone for nitrification coupled with denitrification. Hence, partial drying may reduce the availability of nitrogen (N) and phosphorus (P). Conversely, complete desiccation of sediments may lead to the death of bacteria (and subsequent mineralization of N and P), a decrease in the affinity of P for iron minerals, a decrease in microbial activity and a cessation of all anaerobic bacterial processes (e.g. denitrification). Colonization of exposed sediments by terrestrial plants may lead to N and P moving from the sediments to plant biomass. Re-wetting of desiccated soils and sediments will result in an initial flush of available N and P (which can be incorporated into bacterial or macrophyte biomass), coupled with an increase in bacterial activity, particularly nitrification. Inundation of floodplain soils will result in the liberation of C, N and P from leaf litter and floodplain soils. This will result in an increase in productivity, which ultimately may lead to the onset of anoxia in floodplain soils and, consequently, an increase in anoxic bacterial processes such as P release and denitrification. Copyright © 2000 John Wiley & Sons, Ltd.

Training Captive‐Bred or Translocated Animals to Avoid Predators

Abstract: Animal reintroductions and translocations are potentially important interventions to save species from extinction, but most are unsuccessful. Mortality due to predation is a principal cause of failure. Animals that have been isolated from predators, either throughout their lifetime or over evolutionary time, may no longer express appropriate antipredator behavior. For this reason, conservation biologists are beginning to include antipredator training in pre-release preparation procedures. We describe the evolutionary and ontogenetic circumstances under which antipredator behavior may degenerate or be lost, and we use principles from learning theory to predict which elements can be enhanced or recovered by training. The empirical literature demonstrates that training can improve antipredator skills, but the effectiveness of such interventions is influenced by a number of constraints. We predict that it will be easier to teach animals to cope with predators if they have experienced ontogenetic isolation than if they have undergone evolutionary isolation. Similarly, animals should learn more easily if they have been evolutionarily isolated from some rather than all predators. Training to a novel predator may be more successful if a species has effective responses to similar predators. In contrast, it may be difficult to teach proper avoidance behavior, or to introduce specialized predator-specific responses, if appropriate motor patterns are not already present. We conclude that pre-release training has the potential to enhance the expression of preexisting antipredator behavior. Potential training techniques involve classical conditioning procedures in which animals learn that model predators are predictors of aversive events. However, wildlife managers should be aware that problems, such as the emergence of inappropriate responses, may arise during such training.

Development and evaluation of predictive models for measuring the biological integrity of streams

Abstract: The ratio of the number of observed taxa to that expected to occur in the absence of human-caused stress (OIE) is an intuitive and ecologically meaningful measure of biological integrity. We examined how OIE ratios derived from stream invertebrate data varied among 234 unimpaired reference sites and 254 test sites potentially impaired by past logging. Data were collected from streams in three montane ecoregions in California. Two sets of River Invertebrate Prediction and Classification System (RIVPACS) predictive mod- els were built: one set of models was based on near-species taxonomic resolution; the other was based on family identifications. Two models were built for each level of taxonomic resolution: one calculated 0 and E based on all taxa with probabilities of capture (Pj) > 0; the other calculated 0 and E based on only those taxa with Pc ? 0.5. Evaluations of the performance of each model were based on three criteria: (1) how well models predicted the taxa found at unimpaired sites, (2) the degree to which OIE values differed among unimpaired reference sites and potentially impaired test sites, and (3) the degree to which test site OIE values were correlated with independent measures of watershed alteration. Predictions of species models were more accurate than those of family models, and pre- dictions of the PC ? 0.5 species model were more robust than predictions of the PC > 0 model. OIE values derived from both species models were related to land use variables, but only assessments based on the Pc > 0.5 model were insensitive to naturally occurring differences among streams, ecoregions, and years.

Apical membrane antigen 1 plays a central role in erythrocyte invasion by Plasmodium species

Abstract: Apical membrane antigen 1 (AMA1) is an asexual blood-stage protein expressed in the invasive merozoite form of Plasmodia species, which are the causative agent of malaria. We have complemented the function of Plasmodium falciparum AMA1 (PfAMA1) with a divergent AMA1 transgene from Plasmodium chabaudi (PcAMA1). It was not possible to disrupt the PfAMA1 gene using 'knock-out' plasmids, although we demonstrate that the PfAMA1 gene can be targeted by homologous recombination. These experiments suggest that PfAMA1 is critical, perhaps essential, for blood-stage growth. Importantly, we showed that PcAMA1 expression in P. falciparum provides trans-species complementation to at least 35% of the function of endogenous PfAMA1 in human red cells. Furthermore, expression of this transgene in P. falciparum leads to more efficient invasion of murine erythrocytes. These results indicate an important role for AMA1 in the invasion of red blood cells (RBCs) across divergent Plasmodium species.

Responses of ant communities to dry sulfur deposition from mining emissions in semi‐arid tropical Australia, with implications for the use of functional groups

Abstract: The impact of dry deposition of SO2 emissions on ant abundance, diversity and composition was investigated at Mount Isa in the semiarid tropics of northern Australia. Forty plots were sampled, stratified at two levels: sulfur deposition zones (high, medium, low, and two control zones) and habitat (Ridge and Plain). The two habitats supported distinctly different ant communities. Ants had clear responses to SO2 emissions. Ant abundance was lowest in the high and medium sulfur zones in both habitats. Species richness in high SO2 plots (up to 5 km from the source) was approximately half that of control plots in Ridge habitat, and was substantially less than controls in the Plain habitat. Ant community composition in the high sulfur zone was clearly separated from those of other zones in ordinations. Vector fitting showed soil SO4 concentration as a primary correlative factor in this separation. Ant abundance and richness were both negatively correlated with soil SO4 concentration, and positively correlated with plant species richness and distance away from the smelters. The abundance of 10 of the 21 most common species showed significant responses to emissions. Five species showed positive responses, and all belong to species-groups known to be abundant at disturbed sites throughout northern Australia. Relative abundance and richness of Eyrean (arid adapted) taxa collectively responded positively to sulfur, and Torresian (tropical) and Widespread species responded negatively. Despite large changes in species composition and abundances, there was relatively little change in the abundance of functional groups that have been widely used in studies of Australian ant communities. Ants are sensitive to SO2 emissions and appear to be good candidates as an indicator group in this context. However, an alternative functional group framework is required for the identification of recurrent responses of arid zone ant communities to disturbance.

Using ants as bioindicators in land management: simplifying assessment of ant community responses

Abstract: Summary 1. The indicator qualities of terrestrial invertebrates are widely recognized in the context of detecting ecological change associated with human land-use. However, the use of terrestrial invertebrates as bioindicators remains more a topic of scientific discourse than a part of land-management practice, largely because their inordinate numbers, taxonomic challenges and general unfamiliarity make invertebrates too intimidating for most land-management agencies. Terrestrial invertebrates will not be widely adopted as bioindicators in land management until simple and efficient protocols have been developed that meet the needs of land managers. 2. In Australia, ants are one group of terrestrial insects that has been commonly adopted as bioindicators in land management, and this study examined the reliability of a simplified ant assessment protocol designed to be within the capacity of a wide range of land managers. 3. Ants had previously been surveyed intensively as part of a comprehensive assessment of biodiversity responses to SO 2 emissions from a large copper and lead smelter at Mt Isa in the Australian semi-arid tropics. This intensive ant survey yielded 174 species from 24 genera, and revealed seven key patterns of ant community structure and composition in relation to habitat and SO 2 levels. 4. We tested the extent to which a greatly simplified ant assessment was able to reproduce these results. Our simplified assessment was based on ant ‘bycatch’ from bucket-sized (20-litre) pitfall traps used to sample vertebrates as part of the broader biodiversity survey. We also greatly simplified the sorting of ant morphospecies by considering only large (using a threshold of 4 mm) species, and we reduced sorting time by considering only the presence or absence of species at each site. In this manner, the inclusion of ants in the assessment process required less than 10% of the effort demanded by the intensive ant survey. 5. Our simplified protocol reproduced virtually all the key findings of the intensive survey. This puts effective ant monitoring within the capacity of a wide range of land managers.

Old radiocarbon ages in the southwest Pacific Ocean during the last glacial period and deglaciation

Abstract: Marine radiocarbon (14C) dates are widely used for dating oceanic events and as tracers of ocean circulation, essential components for understanding ocean-climate interactions. Past ocean ventilation rates have been determined by the difference between radiocarbon ages of deep-water and surface-water reservoirs, but the apparent age of surface waters (currently approximately 400 years in the tropics and approximately 1,200 years in Antarctic waters) might not be constant through time, as has been assumed in radiocarbon chronologies and palaeoclimate studies. Here we present independent estimates of surface-water and deep-water reservoir ages in the New Zealand region since the last glacial period, using volcanic ejecta (tephras) deposited in both marine and terrestrial sediments as stratigraphic markers. Compared to present-day values, surface-reservoir ages from 11,900 14C years ago were twice as large (800 years) and during glacial times were five times as large (2,000 years), contradicting the assumption of constant surface age. Furthermore, the ages of glacial deep-water reservoirs were much older (3,000-5,000 years). The increase in surface-to-deep water age differences in the glacial Southern Ocean suggests that there was decreased ocean ventilation during this period.

Speech Perception as a Function of Electrical Stimulation Rate: Using the Nucleus 24 Cochlear Implant System

Abstract: This is a publisher’s version of an article published in Ear and Hearing 2000. This version is reproduced with permission of Lippincott Wilkins & Williams.

A "Mouth-feel Wheel": terminology for communicating the mouth-feel characteristics of red wine

Abstract: A hierarchically structured vocabulary of mouth-feel sensations elicited by red wines has been produced. Represented as a wheel, this structured vocabulary should assist tasters in their interpretation and use of terminology relating to 'in mouth' sensations produced by red wines. These terms and their definitions were generated by consulting the opinions of experienced wine tasters following exposure to an extensive range of commercial red wines. Logical relationships among the derived terms were formulated by analysis of 'sorting data' provided by a combined group of experienced winemakers and wine-tasters.

Micronucleus induction and chromosome loss in transformed human white cells indicate clastogenic and aneugenic action of the cyanobacterial toxin, cylindrospermopsin

Abstract: Cylindrospermopsin (CYN) is a potent inhibitor of protein synthesis produced by a number of cyanobacterial species, the most common being Cylindrospermopsis raciborskii . CYN contains a uracil moiety attached to a sulphated guanidino moiety, suggesting that it may have carcinogenic activity. This report describes the use of the WIL2-NS lymphoblastoid cell-line in the well-validated cytokinesis-block micronucleus (CBMN) assay to test this hypothesis. Centromeres (CENs) were identified in micronuclei (MNi) of binucleated cells (BNCs) by fluorescent in situ hybridisation of alpha centromeric DNA sequence repeats. The results indicate that CYN induced a significant increase in the frequency of MNi in BNCs exposed to 6 and 10 μg/ml, and a significant increase in CEN-positive MNi at all concentrations of CYN tested (1, 3, 6, and 10 μg/ml). However, despite this apparently greater sensitivity of WIL2-NS cells to induction of CEN-positive MNi at low CYN concentrations, at the higher concentrations the magnitude of the increase in CEN-positive MNi did not account for the greater increase in MNi in BNCs, indicating that both CEN-positive and CEN-negative MNi were induced. This suggests that CYN acts to induce cytogenetic damage via two mechanisms, one at the level of the DNA to induce strand breaks, the other at the level of kinetochore/spindle function to induce loss of whole chromosomes (aneuploidy). C. raciborskii occurs in a number of human drinking water sources worldwide and so these findings may have important public health implications.

Moth assemblages as indicators of environmental quality in remnants of upland Australian rain forest

Abstract: Summary 1. Despite great concern about the effects of fragmentation on biodiversity, quantitative studies are still scarce with respect to many major groups and important environments. Well-studied natural reference sites are few. 2. Extensive light trapping surveys for moths were thus carried out in both dry and wet seasons in nine remnants of complex notophyll vine forest on basalt on the Atherton Tablelands in tropical north Queensland, Australia. Three sites had never been cleared, three secondary sites had substantial regrowth, and three sites were newly cleared. 3. A total of 15 632 moths of 835 species was collected, counted and identified. These represent more than 17% of the named Australian fauna of our target families. 4. A principal components analysis (PCA) indicated clear discrimination among assemblages based on forest type. This discrimination did not differ qualitatively between seasons (although abundance levels of moths did) but the pattern was most evident in the smaller dry season samples. 5. Taxa, the relative abundance of which increased significantly with disturbance, were the Arctiinae, Amphipyrinae, Catocalinae, Hadeninae, Heliothinae, Hypeninae, Noctuinae, Plusiinae, Hermeniidae and Phycitinae. In contrast, a number of subfamilies showed a marked decrease in relative abundance with increased disturbance, namely Ennominae, Geometrinae, Larentiinae, Oenochrominae, Epipaschiinae, Lymantriidae and Anthelidae. 6. A weighted sum with importance values based on the eigenvalues associated with each of these taxa derived from the PCA is a powerful predictor set of forest quality. 7. These differential responses may be explained on the basis of broad known and expected host-plant patterns. The results show how moth assemblages are powerful indicators of forest disturbance, and should prompt parallel studies elsewhere in the world.

Differential screening indicates a dramatic change in mRNA profiles during grape berry ripening. Cloning and characterization of cDNAs encoding putative cell wall and stress response proteins.

Abstract: We used differential screening to isolate ripening-associated cDNAs from a Shiraz grape (Vitis vinifera L.) berry cDNA library. A rapid increase in the mRNA levels of a number of cDNAs not present in unripe fruit occurred in grape berries at the onset of ripening. The putative translation products of some of these clones had homologs in other species that are involved in cell wall structure. These included four proline-rich proteins, a small protein that is similar to the non-catalytic, N-terminal domain of some pectin methylesterases, and two other glutamate-rich proteins. The remainder of the clones encoded putative stress response proteins. These included two thaumatin-like proteins, a metallothionein, a transcription factor, a cytochrome P450 enzyme, and proteins induced by water, sugar, and/or cold stress in other species. Many of the homologs of the grape cDNAs thought to be involved in cell wall structure or stress-related responses also accumulate in a developmental manner in other plants. This may indicate that the grape mRNAs accumulate in response to stresses such as the storage of high concentrations of sugars and rapid cell expansion, or they may accumulate as part of the ripening developmental program.

Sediment transport capacity relations for overland flow

Abstract: Nearly all physically based models of soil erosion and landform evolution include an equation for the sediment transport capacity of flow, yet the choice of relation varies from one model to anothe

The potential of knitting for engineering composites—a review

Abstract: Current literature on knitted composites tends to address the aspects of manufacture and characterisation separately. This paper aims to bring together these two sets of literature to provide the reader with a comprehensive understanding of the subject of knitted composites. Consequently, this paper contains a detailed outline of the current state of knitting technology for manufacturing advanced composite reinforcements. Selected mechanical properties of knitted composites, and some of the predictive models available for determining them are also reviewed. To conclude, a number of current and potential applications of knitting for engineering composites are highlighted. With a comprehensive review of the subject, it is believed that textile engineers would be able to better understand the requirements of advanced composites for knitting, and, by the same token, composites engineers can have a better appreciation of the capability and limitations of knitting for composite reinforcement. This should lead to more efficient usage and expanded application of knitted composites.

The Classical Arabinogalactan Protein Gene Family of Arabidopsis

Abstract: Arabinogalactan proteins (AGPs) are extracellular proteoglycans implicated in plant growth and development. We searched for classical AGPs in Arabidopsis by identifying expressed sequence tags based on the conserved domain structure of the predicted protein backbone. To confirm that these genes encoded bona fide AGPs, we purified native AGPs and then deglycosylated and deblocked them for N-terminal protein sequencing. In total, we identified 15 genes encoding the protein backbones of classical AGPs, including genes for AG peptides—AGPs with very short backbones (10 to 13 amino acid residues). Seven of the AGPs were verified as AGPs by protein sequencing. A gene encoding a putative cell adhesion molecule with AGP-like domains was also identified. This work provides a firm foundation for beginning functional analysis by using a genetic approach.

Fish larvae and the management of regulated rivers

Abstract: Alterations to the natural hydrologic regime in regulated rivers can disrupt cues that initiate the maturation and spawning of riverine fish, or they can change the conditions which are suitable for the recruitment of larvae into juvenile populations. Observations of fish larvae have the potential to provide insights into the effects of flow regulation, showing whether it has had a greater impact on fish by preventing spawning or by reducing or eliminating recruitment. We investigated historical and current records of native fish in the highly regulated Campaspe River and the moderately regulated Broken River, Murray-Darling Basin, Australia, and compared these with the results from sampling of fish larvae over three consecutive years to assess the likely impact that river regulation has had on fish populations in lowland Australian rivers. Of the 12 native species of fish that have been recorded historically from the Campaspe River, eight still occur, generally in low abundance, but only three of these were recorded as larvae in this experiment. From recent records, ten native fish species are extant in the Broken River from a suite of 15 that have been recorded there; of these, nine were collected as larvae. The presence of Murray cod larvae in this river was a significant finding. Thus, the less regulated Broken River is in a much healthier state than the Campaspe River. The results of sampling in both rivers indicated that most species of fish spawned each year, despite high inter-annual variation in antecedent hydrological conditions. This suggests that for the species present in these two rivers, the hydrology (pattern of daily discharge) during the winter and spring preceding breeding was unlikely to be a cue for final maturation and spawning. These findings are only preliminary, but they may show that river regulation has had more of an impact on post-spawning recruitment than on prevention of spawning. This has important implicatons for the remediation of the effects of river regulation, with targeting of recruitment processes and the factors influencing these, a priority. Copyright © 2000 John Wiley & Sons, Ltd.

Plant genetics affects arthropod community richness and composition: evidence from a synthetic eucalypt hybrid population.

Abstract: To examine how genetic variation in a plant population affects arthropod community richness and composition, we quantified the arthropod communities on a synthetic population of Eucalyptus amygdalina, E. risdonii, and their F1 and advanced-generation hybrids. Five major patterns emerged. First, the pure species and hybrid populations supported significantly different communities. Second, species richness was significantly greatest on hybrids (F1 > F2 > E. amygdalina > E. risdonii). These results are similar to those from a wild population of the same species and represent the first case in which both synthetic and wild population studies confirm a genetic component to community structure. Hybrids also acted as centers of biodiversity by accumulating both the common and specialist taxa of both parental species (100% in the wild and 80% in the synthetic population). Third, species richness was significantly greater on F1s than the single F2 family, suggesting that the increased insect abundance on hybrids may not be caused by the breakup of coadapted gene complexes. Fourth, specialist arthropod taxa were most likely to show a dominance response to F1 hybrids, whereas generalist taxa exhibited a susceptible response. Fifth, in an analysis of 31 leaf terpenoids that are thought to play a role in plant defense, hybrids were generally intermediate to the parental chemotypes. Within the single F2 family, we found significant associations between the communities of individual trees and five individual oil components, including oil yield, demonstrating that there is a genetic effect on plant defensive chemistry that, in turn, may affect community structure. These studies argue that hybridization has important community-level consequences and that the genetic variation present in hybrid zones can be used to explore the genetic-based mechanisms that structure communities.

Hydrological persistence and the ecology of dryland rivers

Abstract: The flow regime of Cooper Creek, central Australia, is subject to a summer-monsoonal climate and aseasonal cycles associated with the El Nino–Southern Oscillation (ENSO). Analysis of a 48-year hydrograph indicates that floods tend to occur in clusters associated with La Nina episodes. The influence of ENSO is apparent in lagged correlations between discharge and values of the Southern Oscillation Index (SOI), and in measures of coherency derived from cross-spectrum analysis. Hydrological persistence is indicated by partial auto-correlations between floods in successive years. In a cluster of five floods over 1987–1991, cumulative effects were apparent in wetland habitat areas, in water temperature and transparency, and in the recruitment patterns of five fish species: Nematalosa erebi (Clupeidae), Hypseleotris klunzingeri (Gobiidae), Melanotaenia splendida tatei (Melanotaeniidae), Retropinna semoni (Retropinnidae) and Gambusia holbrooki (Poeciliidae). During serial floods, native fish appear to have a recruitment advantage over the exotic Gambusia. Hydrological persistence and its ecological correlates warrant consideration in research, planning and management, particularly in regard to the water resources of arid and semi-arid regions. Copyright © 2000 John Wiley & Sons, Ltd.

Identification and Analysis of Error Types in High-Throughput Genotyping

Abstract: Although it is clear that errors in genotyping data can lead to severe errors in linkage analysis, there is as yet no consensus strategy for identification of genotyping errors. Strategies include comparison of duplicate samples, independent calling of alleles, and Mendelian-inheritance-error checking. This study aimed to develop a better understanding of error types associated with microsatellite genotyping, as a first step toward development of a rational error-detection strategy. Two microsatellite marker sets (a commercial genomewide set and a custom-designed fine-resolution mapping set) were used to generate 118,420 and 22,500 initial genotypes and 10,088 and 8,328 duplicates, respectively. Mendelian-inheritance errors were identified by PedManager software, and concordance was determined for the duplicate samples. Concordance checking identifies only human errors, whereas Mendelian-inheritance-error checking is capable of detection of additional errors, such as mutations and null alleles. Neither strategy is able to detect all errors. Inheritance checking of the commercial marker data identified that the results contained 0.13% human errors and 0.12% other errors (0.25% total error), whereas concordance checking found 0.16% human errors. Similarly, Mendelian-inheritance-error checking of the custom-set data identified 1.37% errors, compared with 2.38% human errors identified by concordance checking. A greater variety of error types were detected by Mendelian-inheritance-error checking than by duplication of samples or by independent reanalysis of gels. These data suggest that Mendelian-inheritance-error checking is a worthwhile strategy for both types of genotyping data, whereas fine-mapping studies benefit more from concordance checking than do studies using commercial marker data. Maximization of error identification increases the likelihood of linkage when complex diseases are analyzed.

Seedling dynamics over thirty-two years in a tropical rain forest tree

Abstract: We examined patterns of seedling recruitment and their underlying mechanisms in a population of Chrysophyllum sp. nov. (Sapotaceae), a shade-tolerant canopy species in mature tropical rainforest in Queensland, Australia. We considered spatial scales ranging from 1 m2 to 1 ha, and temporal scales ranging from 1 to 32 yr. Over the 32-yr study period there were six episodes of very high seedling recruitment (masts) at intervals ranging from 4 to 10 yr. Less than 2% of new recruits were found in the nine censuses in other years. We found no significant correlations between the numbers of seedlings per census and either seasonal or annual rainfall, number of dry months per year, or El Nino Southern Oscillation (ENSO) events but found two correlations with mean seasonal air temperatures in the years preceding flowering. There were long-term changes in abundance in both time and space. In 1965 there were 163 seedling-sized plants in two dense patches, whereas in 1996, there were 4000 in 15 patches. Once a new patch became established, seedlings recruited there in each succeeding mast episode. Adult trees varied in their production of seedlings. Only 25% of the trees in the sample analyzed participated in all mast years; others had few seedlings for up to 28 yr before beginning to produce many seedlings. Seedlings were shade tolerant. They grew extremely slowly in the shaded understory, mean height only doubling in 27 yr. They were also quite long-lived; 6% of seedlings recruited in 1969 were still alive 27 yr later. There was little effect of natural enemies on seeds or seedlings. We found weak positive and negative effects of density on seed germination, seedling mortality, and growth. Mortality rates of Chrysophyllum seedlings did not show any trends with time, nor with distance from conspecific adults. These results suggest that abundance of older stages is determined by recruitment as well as subsequent growth and mortality. Mortality rates of seedlings of species other than Chrysophyllum decreased with distance from adult Chrysophyllum trees. Under present conditions, the Chrysophyllum population may be increasing in relation to that of other species, perhaps leading to a reduction in tree diversity in this tropical rainforest.

Ryk-deficient mice exhibit craniofacial defects associated with perturbed Eph receptor crosstalk

Abstract: Ryk-deficient mice exhibit craniofacial defects associated with perturbed Eph receptor crosstalk

Development of seed polyphenols in berries from Vitis vinifera L. cv. Shiraz.

Abstract: Polyphenols extracted from the seeds of Vitis vinifera L. cv. Shiraz berries were monitored during berry development. Initially seeds were green, plump and had pliable seed coats, but beginning at veraison the seeds browned in colour, became desiccated and the seed coats hardened. Isolated polyphenols consisted of flavan-3-ol monomers ((+)-catechin, (-)-epicatechin and (-)-epicatechin-3-O-gallate) and procyanidins. The procyanidins were maximal in the 3 weeks prior to veraison, increasing little during this period. The amounts of flavan-3-ol monomers increased 5-fold during this same period of time, indicating that the procyanidins and the flavan-3-ol monomers accumulate at different stages. Beginning at veraison, amounts of all polyphenols declined and changed in composition. The decrease in amount followed second-order kinetics. Polyphenol changes after veraison could be explained by oxidation and therefore, electron paramagnetic resonance (EPR) spectroscopy was used to follow the potential development of radical species in the developing seeds. Spectra consistent with a phenoxyl radical were observed in the developing seeds. The concentration of radicals remained low until veraison but then increased, reaching a maximum three weeks later, declining slowly thereafter. Changes in radical intensity together with other documented changes in the seed are consistent with an oxidative event occurring during fruit ripening.

Eddy Variability and Energetics from Direct Current Measurements in the Antarctic Circumpolar Current South of Australia

Abstract: Two-year time series measurements of current velocity and temperature in the Subantarctic Front (SAF) south of Australia from 1993 to 1995 provide estimates of eddy fluxes of heat and momentum across the Antarctic Circumpolar Current (ACC) and further insight into the variability of the ACC. The SAF was found to be an energetic, meandering jet with vertically coherent fluctuations varying on a timescale of 20 days with typical amplitude 30 cm s21 at 1150 dbar. A daily varying coordinate frame that follows the direction of flow allowed mesoscale variability of the SAF to be isolated from variability due to meandering of the front and proved very successful for examining eddy fluxes. Vertically averaged cross-stream eddy heat flux was 11.3 kW m 22 poleward and significantly different from zero at 95% for fluctuations in the 2‐90 day band. Zonally integrated, this eddy heat flux ( 50.9 PW) is more than large enough to balance heat lost south of the Polar Front and is as large as cross-SAF fluxes found in Drake Passage. Cross-stream eddy momentum fluxes were small, not significantly different from zero, and of indeterminate sign, but tending to decelerate the mean flow. A relationship between vertical motion and meander phase identified in the Gulf Stream was found to hold for the ACC. Eddy kinetic energy levels were similar to those in Drake Passage and southeast of New Zealand. Eddy potential energy was up to an order of magnitude larger than at other ACC sites, most likely because meandering of the front is more common here. Baroclinic conversion was found to be the dominant mechanism by which eddies grow south of Australia. Typical eddy growth time is estimated to be 30 days, approximately twice as fast as in Drake Passage, consistent with eddy energy growing rapidly downstream.

Evapotranspiration from eucalypt open-forest savanna of northern australia

Abstract: 1. Using three independent methods (eddy covariance, heat pulse and open-top chambers), diurnal and seasonal measurements of evapotranspiration were made in a wet–dry Eucalypt savanna of the Northern Territory, Australia. 2. Total annual dry-canopy water loss was estimated to be 870 mm and understorey evapotranspiration contributed 557 mm to this flux. Understorey evapotranspiration occurred predominantly during the wet season as bare soil evaporation and transpiration of Sorghum spp., a C4 grass. 3. Annual transpiration from trees was 313 mm, significantly less than the grassy understorey. Despite a very high degree of seasonality in distribution of rainfall and large changes to soil and atmospheric water content, water use by the trees did not differ between wet and dry seasons. This suggests that mature trees exploit a large soil volume and this may include extraction from the capillary fringe of the shallow water table (2–10 m below the ground surface). 4. The open canopy created an aerodynamically rough surface well coupled to the atmosphere with the coupling coefficient, Ω, ranging from 0·40 to 0·11 over a wet–dry cycle. 5. Leaf area index (LAI) of the overstorey was typically 1·0 in the wet season and 0·65 in the dry season. The decline in tree LAI occurred when evaporative demand showed a similar proportional increase. Consequently overstorey water use remained relatively unchanged throughout the year. 6. Given the very high rainfall intensities of the monsoonal climate and low LAI of the site, canopy interception was set at 5% of rainfall. Including this amount gives an annual evapotranspiration of 958 mm for this savanna.

Monitoring river health

Abstract: Photo 1. Richard Norris has concentrated his research on biological assessment of rivers. He recently ran an international conference on river health and has played a major role in developing Australia’s National River Health Program. He is Associate Professor in freshwater Ecology at the University of Canberra in Australia’s national capital and leads a program on water quality and ecological assessment for the Cooperative Research Centre for Freshwater Ecology

A Scaling Rule for Landscape Patches and How It Applies to Conserving Soil Resources in Savannas

Abstract: Scaling issues are complex, yet understanding issues such as scale dependencies in ecological patterns and processes is usually critical if we are to make sense of ecological data and if we want to predict how land management options, for example, are constrained by scale. In this article, we develop the beginnings of a way to approach the complexity of scaling issues. Our approach is rooted in scaling functions, which integrate the scale dependency of patterns and processes in landscapes with the ways that organisms scale their responses to these patterns and processes. We propose that such functions may have sufficient generality that we can develop scaling rules—statements that link scale with consequences for certain phenomena in certain systems. As an example, we propose that in savanna ecosystems, there is a consistent relationship between the size of vegetation patches in the landscape and the degree to which critical resources, such as soil nutrients or water, become concentrated in these patches. In this case, the features of the scaling functions that underlie this rule have to do with physical processes, such as surface water flow and material redistribution, and the ways that patches of plants physically “capture” such runoff and convert it into plant biomass, thereby concentrating resources and increasing patch size. To be operationally useful, such scaling rules must be expressed in ways that can generate predictions. We developed a scaling equation that can be used to evaluate the potential impacts of different disturbances on vegetation patches and on how soils and their nutrients are conserved within Australian savanna landscapes. We illustrate that for a 10-km2 paddock, given an equivalent area of impact, the thinning of large tree islands potentially can cause a far greater loss of soil nitrogen (21 metric tons) than grazing out small grass clumps (2 metric tons). Although our example is hypothetical, we believe that addressing scaling problems by first conceptualizing scaling functions, then proposing scaling rules, and then deriving scaling equations is a useful approach. Scaling equations can be used in simulation models, or (as we have done) in simple hypothetical scenarios, to collapse the complexity of scaling issues into a manageable framework.