Habitat use by the inland carpet python (Morelia spilota metcalfei: Pythonidae): Seasonal relationships with habitat structure and prey distribution in a rural landscape

Abstract Squamate reptiles are significant components of woodland vertebrate communities in eastern Australia, but their ecology is poorly understood. We investigated seasonal variation in habitat use by the Inland Carpet Python, Morelia spilota metcalfei Wells and Wellington (Pythonidae), a threatened snake that inhabits the woodland environments of the Murray–Darling Basin. Nine pythons were radiotracked within and near the Mount Meg Flora and Fauna Reserve in north‐eastern Victoria to investigate how habitat structure and prey distribution (namely, that of the European Rabbit, Oryctolagus cuniculus L. (Leporidae)) influenced seasonal movement patterns. Data were analysed over three spatial scales to allow firm interpretations regarding resource selection. Pythons exhibited distinct seasonal trends in habitat use. During the cooler spring months, snakes chose warm, well‐insulated microhabitats, primarily rocky outcrops on north‐ and north‐west‐facing hillsides. Pythons moved widely during the summer months, apparently in search of prey. Snake localities could be readily linked to rabbit distribution at this time. Specifically, snakes moved to more open, disturbed habitats that contained a high density of rabbits, and consistently selected microhabitats in close proximity to rabbit burrows. In autumn, habitat use was transitional, as snakes progressively returned to the rocky hillsides where they overwintered. Thus, trends in habitat use were influenced by the snakes' thermoregulatory and foraging strategies. Careful management of specific habitats and feral prey populations is required to conserve populations of this endangered snake.     

Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future

The eddy covariance technique ascertains the exchange rate of CO₂ across the interface between the atmosphere and a plant canopy by measuring the covariance between fluctuations in vertical wind velocity and CO₂ mixing ratio. Two decades ago, the method was employed to study CO₂ exchange of agricultural crops under ideal conditions during short field campaigns. During the past decade the eddy covariance method has emerged as an important tool for evaluating fluxes of carbon dioxide between terrestrial ecosystems and the atmosphere over the course of a year, and more. At present, the method is being applied in a nearly continuous mode to study carbon dioxide and water vapor exchange at over a hundred and eighty field sites, worldwide. The objective of this review is to assess the eddy covariance method as it is being applied by the global change community on increasingly longer time scales and over less than ideal surfaces. The eddy covariance method is most accurate when the atmospheric conditions (wind, temperature, humidity, CO₂) are steady, the underlying vegetation is homogeneous and it is situated on flat terrain for an extended distance upwind. When the eddy covariance method is applied over natural and complex landscapes or during atmospheric conditions that vary with time, the quantification of CO₂ exchange between the biosphere and atmosphere must include measurements of atmospheric storage, flux divergence and advection. Averaging CO₂ flux measurements over long periods (days to year) reduces random sampling error to relatively small values. Unfortunately, data gaps are inevitable when constructing long data records. Data gaps are generally filled with values produced from statistical and empirical models to produce daily and annual sums of CO₂ exchange. Filling data gaps with empirical estimates do not introduce significant bias errors because the empirical algorithms are derived from large statistical populations. On the other hand, flux measurement errors can be biased at night when winds are light and intermittent. Nighttime bias errors tend to produce an underestimate in the measurement of ecosystem respiration. Despite the sources of errors associated with long‐term eddy flux measurements, many investigators are producing defensible estimates of annual carbon exchange. When measurements come from nearly ideal sites the error bound on the net annual exchange of CO₂ is less than ±50 g C m^?2 yr^?1. Additional confidence in long‐term measurements is growing because investigators are producing values of net ecosystem productivity that are converging with independent values produced by measuring changes in biomass and soil carbon, as long as the biomass inventory studies are conducted over multiple years.     

Latitudinal patterns of magnitude and interannual variability in net ecosystem exchange regulated by biological and environmental variables

Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the sink are not well known. In this study, we examined latitudinal patterns of interannual variability (IAV) in net ecosystem exchange (NEE) of CO₂ based on 163 site-years of eddy covariance data, from 39 northern-hemisphere research sites located at latitudes ranging from ∼29°N to ∼64°N. We computed the standard deviation of annual NEE integrals at individual sites to represent absolute interannual variability (AIAV), and the corresponding coefficient of variation as a measure of relative interannual variability (RIAV). Our results showed decreased trends of annual NEE with increasing latitude for both deciduous broadleaf forests and evergreen needleleaf forests. Gross primary production (GPP) explained a significant proportion of the spatial variation of NEE across evergreen needleleaf forests, whereas, across deciduous broadleaf forests, it is ecosystem respiration (Re). In addition, AIAV in GPP and Re increased significantly with latitude in deciduous broadleaf forests, but AIAV in GPP decreased significantly with latitude in evergreen needleleaf forests. Furthermore, RIAV in NEE, GPP, and Re appeared to increase significantly with latitude in deciduous broadleaf forests, but not in evergreen needleleaf forests. Correlation analyses showed air temperature was the primary environmental factor that determined RIAV of NEE in deciduous broadleaf forest across the North American sites, and none of the chosen climatic factors could explain RIAV of NEE in evergreen needleleaf forests. Mean annual NEE significantly increased with latitude in grasslands. Precipitation was dominant environmental factor for the spatial variation of magnitude and IAV in GPP and Re in grasslands.     

The Role of Tree Gaps in Maintaining the Population Structure of a Woodland Herb: Cynoglossum virginianum L.

Abstract Tree gaps may be important habitats for the establishment and spread of understory herbs in eastern (US) deciduous forests. Data from past studies, however, have not shown any clear patterns for either species diversity or increased percent cover. The lack of clear patterns of response to gaps by herbs may be due to evolutionary differences among species or, in part, due to the fact that most studies have been short-term and long-term patterns have, therefore, not been observed. In addition, few studies have considered the responses of individual genets and/or ramets. We have been conducting a long-term study of Cynoglossum virginianum , now in its 16th year, to determine subpopulation and individuals' responses in gap and non-gap habitats. A larger percentage of individuals flowered in the gap subpopulation shortly after it was created. Seed production rates were also higher in the gap subpopulation. The long-term benefits gained by the short-term flowering response have, however, been few as all but two of the seedlings produced within a few years of gap formation have died. In addition, all of individuals that flowered and produced seeds decreased in size and most have remained in the smaller size classes. In addition, only one of the individuals in the gap subpopulation has flowered since the initial flowering response while plants in non-gap subpopulations have flowered and produced seeds throughout the study period. Gaps may only be beneficial to C. virginianum if seeds are dispersed into non-gap areas or if seeds can remain dormant in the soil until conditions are more suitable for seedling survival.     

The moult of Barred Warblers Sylvia nisoria in Kenya—evidence for a split wing-moult pattern initiated during the birds' first winter*

The moult of Barred Warblers Sylvia nisoria was studied during three winter seasons in southeastern Kenya at a southward passage site (Ngulia) and a wintering site (Mtito Andei). Most Barred Warblers migrating through Ngulia in November had yet to commence winter moult. These birds probably moulted subsequently in winter in northern Tanzania. In December, birds were found in heavy moult at Mtito Andei, and some of these birds were known to stay throughout the winter. By contrast, most birds reaching southeastern Kenya from late December onwards had already completed part or all of their winter moult, presumably at stopover sites in northern and eastern Kenya or in Ethiopia. Thus, winter moult in Barred Warblers takes place mainly in late November and December, either just before or soon after the final leg of autumn migration. In general, first-year birds renewed all tertials and tail feathers, about three to five secondaries per wing and commonly also the outer one to four large primaries per wing. Adults renewed all tertials and tail feathers, almost all secondaries and only occasionally an outer primary. The replacement of relatively fresh juvenile secondaries during the birds' first winter implies that the split moult pattern of this species (secondaries, tertials and tail moulted in winter; primaries and tertials in summer) is endogenously controlled.     

Migration, stopover and moult of the Great Reed Warbler Acrocephalus arundinaceus in Ghana, West Africa

We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.     

The Incorporation of Glycolytic Intermediates into Lipids by Plastids Isolated from the Developing Endosperm of Castor Oil Seeds (Ricinus communis L.)

Plastids were isolated from the developing endosperm of Ricinuscommunis L. and purified by rate-zonal centrifugation on discontinuoussucrose gradients. Assay conditions were optimized for the uptakeand incorporation of ¹⁴C-acetate into lipids by intact plastids.Using the optimized conditions, the uptake and incorporationof several ¹⁴C-glycolytic intermediates into lipids were examined.Neither sucrose nor glucose-6-phosphate was incorporated intolipids. In order of increasing magnitude of incorporation, glucose,fructose, 3-phosphoglycerate, acetate, and pyruvate were metabolizedto chloroform-methanol (2: 1 v/v) soluble products. Pyridoxal-5'-phosphateinhibited the incorporation of 3-phosphoglycerate into lipidswhereas -cyano-4 hydroxycinnamate was without effect on pyruvateincorporation. Avidin and cerulenin did not inhibit the incorporationof acetate into lipids by intact plastids. Key words: Ricinus communis, Plastids, Lipid synthesis, Glycolytic intermediates     

Field manipulation of populations of individual staphylinid species in cereals and their impact on aphid populations

Abstract.

• 1 Four species of staphylinids were caged separately on wheat and their effect on the population development of the grain aphid, Sitobion avenae (F.), was investigated over two seasons.
• 2 A novel field cage design was used to exclude all but the staphylinid species under investigation.
• 3 Predator effects were compared with total-exclusion cages in which all predators and parasitoids were kept out.
• 4 During a high-density phase of aphid population development only Philonthus cognutus (Stephens) significantly influenced aphid population numbers.
• 5 At low aphid densities, Tachyporus obtusus (L.), T.chrysomelinus (L.) and P.cognatus reduced aphid population levels.
• 6 The experiments showed that Tachyporus spp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and that P.cognatus causes some reduction at both the stages of aphid population growth investigated.

     

Separation of Individual Stages of Trypanosoma cruzi Grown in Cell Culture by Continuous Free-Flow Electrophoresis

The separation of extracellular protozoan parasites from host cells based on a difference in surface charge has been described. However, with Trypanosoma cruzi no method exists for the isolation of pure parasite stages from heterogeneous mixtures. Studies on the electrophoresis of mixed stage populations confirm significant surface charge density differences exist among epimastigotes, trypomastigotes, and amastigotes. In ascending order of electronegativity, amastigotes have the lowest charge density, try-pomastigotes next, followed by epimastigotes. A technique has been developed for the separation of purified populations of parasites based on these charge differences using a continuous free-flow electrophoresis apparatus. The separated populations are morphologically intact and maintain their infectivity to mice. This separation method is applicable for preparative and analytical isolation of pure stages of T. cruzi for biochemical and immunological studies.     

The Effect of Temperature on Photosynthesis of Ryegrass and White Clover Leaves

The rate of photosynthesis of leaves of perennial ryegrass (Loliumperenne L.) and white clover (Trifollum pratense L.) grown atdifferent temperatures was measured at a range of temperatures.There was a small effect of the temperature at which a leafhad grown on its photosynthetic rate, but a large effect ofmeasurement temperature, especially in bright light, where photosyntheticrates at 15°C were about twice those at 5°C. It appearsthat temperature could affect sward photosynthesis in the field.Ryegrass and clover had similar photosynthetic rates which respondedsimilarly to temperature. Lolium perenne L., ryegrass, Trifolium pratense L., white clover, photosynthesis, temperature, irradiance