The effect of current velocity and sediment on the drift of the mayfly Ephemerella subvaria Mcdunnough

SUMMARY. Experiments conducted in an artificial stream showed that significantly more nymphs drifted from an inorganic substrate at a mean current velocity of 28.5 cm s⁻¹ than at 18.5 cm s⁻¹. Drift density, however, was not affected. Disproportionately large numbers of nymphs drifted while current velocities were being increased from 18.5 to 28.5 cm s⁻¹.
Both drift numbers and drift density were greater in turbid water, after the addition of large amounts of inorganic sediment, than under clear-flowing conditions during dark periods but not in the light. The interaction of increasing current velocity and sediment levels resulted in a significantly greater number of drifting nymphs under lighted conditions.
Minor spates which do not seriously disturb the stream bed may initiate significant increases in macroinvertebrate drift.     

Chromosome number, karyotype and DNA C-value of the Wollemi Pine (Wollernia nobilis, Araucariaceae)

The Wollemi Pine ( Wollemia nobilis , Araucariaceae) was discovered in 1994 in a remote area of the Wollemi National Park (New South Wales, Australia). With only around 40 adult trees known to be growing in the wild, it is one of the worlds rarest plant species. The results of the first cytological study are reported, including a chromosome count (2n = 2x = 26), karyotype illustration and nuclear DNA C-value (4C = 55.74 pg), obtained using Feulgen microdensitometry. The results are compared with data available on species in the other two genera of the Araucariaceae, Araucaria and Agathis , and with other gymnosperms     

StemBell therapy stabilizes atherosclerotic plaques after myocardial infarction

Background aims. After a myocardial infarction (MI) atherosclerosis is accelerated leading to destabilization of the atherosclerotic plaque. mesenchymal stromal cells are a promising therapeutic option for atherosclerosis. Previously, we demonstrated a novel stem cell delivery technique, with adipose stem cells coupled to microbubbles (i.e., StemBells) as therapy after MI. In this study, we aim to investigate the effect of StemBell therapy on atherosclerotic plaques in an atherosclerotic mouse model after MI. Methods. MI was induced in atherosclerotic Apolipoprotein E–deficient mice that were fed a high-fat Western diet. Six days post-MI, the mice received either 5?×?10⁵/100 µL StemBells or vehicle intravenously. The effects of StemBell treatment on the size and stability of aortic root atherosclerotic plaques and the infarcted heart were determined 28 days post-MI via (immuno)histological analyses. Moreover, monocyte subtypes and lipids in the blood were studied. Results. StemBell treatment resulted in significantly increased cap thickness, decreased intra-plaque macrophage density and increased percentage of intra-plaque anti-inflammatory macrophages and chemokines, without affecting plaque size and serum cholesterol/triglycerides. Furthermore, StemBell treatment significantly increased the percentage of anti-inflammatory macrophages within the infarcted myocardium but did not affect cardiac function nor infarct size. Finally, also the average percentage of anti-inflammatory monocytes in the circulation was increased after StemBell therapy. Discussion. StemBell therapy increased cap thickness and decreased intra-plaque inflammation after MI, indicative of stabilized atherosclerotic plaque. It also induced a shift of circulating monocytes and intra-plaque and intra-cardiac macrophages towards anti-inflammatory phenotypes. Hence, StemBell therapy may be a therapeutic option to prevent atherosclerosis acceleration after MI.     

Australian bird phenology: a search for climate signals

Temporal and climate‐related changes in avian phenology were assessed for seven species of south‐eastern Australia using data obtained from members of the public, naturalist groups and other organizations. Despite significantly warmer temperatures (～0.02–0.03°C per year) and reduced rainfall (～1.6–8.0 mm per year) over much of south‐eastern Australia in recent decades, most species showed no corresponding trends in their timing of migration or breeding, the notable exceptions being the grey fantail (Rhipidura fuliginosa) and the flame robin (Petroica phoenicea), which migrate through Melbourne, Victoria, during autumn and spring. In many species, however, migration or breeding timing appeared to be influenced to some extent by local, rather than regional, climate conditions, particularly local daily maximum and minimum temperatures. Whether these species will noticeably change their phenology to match projected changes in climate, perhaps when a currently unknown climate threshold is crossed, or whether these species are sufficiently flexible in their foraging strategies or food sources to be able to maintain their current timing, remains to be seen.     

Frequent fires reduce tree growth in northern Australian savannas: implications for tree demography and carbon sequestration

Tropical savannas are typically highly productive yet fire‐prone ecosystems, and it has been suggested that reducing fire frequency in savannas could substantially increase the size of the global carbon sink. However, the long‐term demographic consequences of modifying fire regimes in savannas are difficult to predict, with the effects of fire on many parameters, such as tree growth rates, poorly understood. Over 10 years, we examined the effects of fire frequency on the growth rates (annual increment of diameter at breast height) of 3075 tagged trees, at 137 locations throughout the mesic savannas of Kakadu, Nitmiluk and Litchfield National Parks, in northern Australia. Frequent fires substantially reduced tree growth rates, with the magnitude of the effect markedly increasing with fire severity. The highest observed frequencies of mild, moderate and severe fires (1.0, 0.8 and 0.4 fires yr^?1, respectively) reduced tree growth by 24%, 40% and 66% respectively, relative to unburnt areas. These reductions in tree growth imply reductions in the net primary productivity of trees by between 0.19 t C ha^?1 yr^?1, in the case of mild fires, and 0.51 t C ha^?1 yr^?1, in the case of severe fires. Such reductions are relatively large, given that net biome productivity (carbon sequestration potential) of these savannas is estimated to be just 1–2 t C ha^?1 yr^?1. Our results suggest that current models of savanna tree demography, that do not account for a relationship between severe fire frequency and tree growth rate, are likely to underestimate the long‐term negative effects of frequent severe fires on tree populations. Additionally, the negative impact of frequent severe fires on carbon sequestration rates may have been underestimated; reducing fire frequencies in savannas may increase carbon sequestration to a greater extent than previously thought.     

Fire weather risk differs across rain forest—savanna boundaries in the humid tropics of north‐eastern Australia

Alternative stable state theory has been applied to understanding the control by landscape fire activity of pyrophobic tropical rain forest and pyrophytic eucalypt savanna boundaries, which are often separated by tall eucalypt forests. We evaluate the microclimate of three vegetation types across an elevational gradient and their relative fire risk as measured by McArthur's Forest Fire Danger Index (FFDI). Microclimatic data were collected from rain forest, tall eucalypt forest and savanna sites on eight vegetation boundaries throughout the humid tropics in north Queensland over a 3‐year period and were compared with data from a nearby meteorological station. There was a clear annual pattern in daily FFDI with highest values in the austral winter dry season and lowest values in the austral summer wet season. There was a strong association of the meteorological station FFDI values with those from the three vegetation types, albeit they were substantially lower. The rank order of FFDI values among the vegetation types decreased from savanna, tall eucalypt forest, then rain forest, a pattern that was consistent across each transect. Only very rarely would rain forest be flammable, despite being adjacent to highly flammable savannas. These results demonstrate the very strong effect of vegetation type on microclimate and fire risk, compared with the weak effect of elevation, consistent with a fire–vegetation feedback. This study is the first demonstration of how vegetation type influences microclimate and fire risk across a topographically complex tropical forest–savanna gradient.     

The Development of Alternative Storage Sink Sites in Sweet Potato Ipomoea batatas

Sweet potato plants were found to develop three alternativestorage sink sites: adventitious roots, replanted tubers andstems, indicating that the capacity for tuberization is notlimited to the root system. In each case, sink development occurredas a result of meristematic activity of the vascular cambiumand anomalous cambia associated with differentiating vascularbundles in the pith. The involvement of environmental, anatomicaland physiological parameters in the tuberization of sweet potatois discussed. Ipomoea batatas, sweet potato, tuberization, sink site     

Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crussostreu ingens

Mitchell, L., Curry, G.B. & Fallick, A.E. 1995 11 30: Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crassostrea ingens .
Oxygen and carbon stable-isotope profiles and intracrystalline amino acid profiles (free and total) were determined for the New Zealand giant Pliocene oyster Crassostrea ingens by sampling annual growth increments along a sagittal section. These profiles reflect both ontogenetic and environmental change over the life-time of the oyster (approximately 20 years). There is a gradual increase in δ¹⁸O from the umbo towards the shell margin and a subsequent levelling-off about halfway along the shell. This pattern probably reflects a decrease in the growth rate of the oyster rather than a temperature effect. The δ¹³C profile initially increases sharply at the umbo and then gradually decreases towards the shell margin. This may be due to kinetic or metabolic effects associated with the development of a fast-growing juvenile into a slower-growing, sexually mature adult, or it may be due to the influence of ¹³C-depleted carbon derived from the oxidation of organic matter in the surrounding sediment. The amino acid profile reveals a gradual decrease in abundance from the umbo to the shell margin, indicative of a progressive increase in the relative amounts of inorganic carbonate to protein over the life of the oyster, that may also be a consequence of decreasing growth rate. Glycine and alanine are the two most common amino acids in both the free and total amino acid profiles: free (i.e. naturally hydrolysed) amino acids account for about three quarters of the total amino acids present. □ Biogeochemistiy, stable isotopes, amino acids, environment, ontogeny .