Phenological variation in Heteropogon contortus and its relation to climate

1966 ◽  
Vol 14 (1) ◽  
pp. 35 ◽  
Author(s):  
JC Tothill
Keyword(s):  
Seasonal Pattern ◽  
Natural Populations ◽  
Late Summer ◽  
Day Length ◽  
Tropical Region ◽  
Wet Season ◽  
Early Maturity ◽  
Heteropogon Contortus ◽  
Rainfall Season ◽  
Eastern Australia

Heteropogon contortus Beauv. ex Roem. & Schult. (spear grass or tanglehead) exhibits conisiderable: morphological and phenoiogicai variation. Wniie the morphological variation is apparently unrelated to geographic distribution, the phenological variation appears to be closely associated with differences in climate. Flowering is largely governed by day length, but the seasonal pattern of rainfall distribution has selected only those day lengths which promote flowering within the rainfall season. In the tropical region of north-eastern Australia flowering occurs in late summer and short days, since the wet season prevails over the second half of the summer. When northern material is grown in uniform grass gardens south of this tropical region, late maturity still prevails; hence this behavioural pattern is genetically fixed. In the subtropics, on the other hand, adequate rain may fall over the entire potential growing season or any part of it. In the garden great variation of phenology marks the southern material. Furthermore, sampling within local populations may also show great variation from early maturity through to late. It is suggested that in Australia H. contortus is naturally a species of the semi-arid tropics. It has spread into the subtropics through its ability to match the extended but more uncertain rainfall season by producing types of differing day length response. This variation is fixed by the predominantly apomictic mode of reproduction, while the perenniality of the plants ensures survival over periods of unsuitable climate. A long-term equilibrium is therefore established between the flowering behaviour of the population and its climate. A knowledge of the patterns of behaviour within and between populations is likely to be Important for increased pastoral efficiency, firstly, in preventing natural populations from deteriorating towards earlier maturity, and secondly, in lengthening the productive season of pasture growth.

Conservation value of solar salt ponds in coastal tropical eastern Australia to waterbirds and migratory shorebirds.

2012 ◽  
Vol 18 (2) ◽  
pp. 100 ◽  
Author(s):  
Wayne Houston ◽  
Robert Black ◽  
Rod Elder ◽  
Leif Black ◽  
Richard Segal
Keyword(s):  
Seasonal Pattern ◽  
River Estuary ◽  
Conservation Value ◽  
Wet Season ◽  
Salinity Regime ◽  
Solar Salt ◽  
Migratory Shorebirds ◽  
Complementary Resources ◽  
Eastern Australia ◽  
Natural Wetlands

Some human-altered habitats such as saltfields support significant numbers of shorebirds and waterbirds, but their values in tropical eastern Australia are poorly understood. With the continuing loss of shorebird habitats in the East Asian-Australasian Flyway, identification of important habitats and management is important for their conservation. The habitat value of two saltfields associated with the Fitzroy River estuary, Queensland (23.520S, 150.860E) was evaluated by monthly surveys over 33 months and by comparison to previous surveys of nearby natural wetlands. Saltfields supported as many waterbirds and species as freshwater and naturally saline lagoons. Numbers of migratory shorebirds peaked during the southern migration period (September to November), when wetlands in tropical northern Australia are at their lowest extent, thus elevating the conservation value of tropical saltfields to shorebirds. Sharp-tailed Sandpipers were regularly present in numbers exceeding international levels for staging, while Red-necked Stints were just below the staging criterion. Salinity regime was found to influence waterbird communities associated with saltfield pools: piscivores dominating metasaline pools, and shorebirds hypersaline pools. A seasonal pattern of occurrence occurred in some guilds with greatest numbers in the drier months (cormorants, pelicans, ducks and egrets, all significantly negatively correlated with the previous month’s rainfall), most of which bred in nearby natural wetlands during the wet season. Furthermore, cormorants were abundant in the saltfields and fluctuated less compared with natural lagoons during the critical drier months. Overall, saltfields are an integral component of the ecology of the landscape, providing complementary resources to that of the natural wetlands.

The production and life span of seed of subterranean clover (Trifolium subterraneum L.)

1959 ◽  
Vol 10 (6) ◽  
pp. 771 ◽  
Author(s):  
CM Donald
Keyword(s):  
Seed Production ◽  
Genetic Difference ◽  
Seasonal Pattern ◽  
Subterranean Clover ◽  
Late Summer ◽  
Trifolium Subterraneum ◽  
Daily Minimum Temperature ◽  
South Wales ◽  
Eastern Australia ◽  
Carry Over

At an elevation of 2040 ft on the southern tablelands of Kew South Wales, seed production by swards of subterranean clover was apparently governed by mininnnn temperatures (frequency and intensity of frosts) during the flowering period. The aggregate deficit of the daily minimum temperature below 40°F in the 21 days from the commencement of flowering showed a high correlation with seed production per unit area in four successive seasons. Spring frosts account for the altitudinal limit of about 4000 ft to which subterranean clover grows in the alps of south-eastern Australia. Lateness of flowering has specific survival value at high altitudes in this region and in such areas as the high parts of the plateau of Spain. On the average 92 per cent. of the seed crop germinated in the year following its production, with 6.3 per cent. in the second year, and with falling values to 0.07 per cent. in the fifth year. Germination thereafter was nil or negligible. The early-flowering variety Dwalganup appeared to show a genetic difference in the persistence of more of its seed into the second and subsequent years. There was a regular seasonal pattern of seed germination, with the peak of germination occurring in the late summer and autumn. The "carry over" of seed into the second and subsequent years, and the germination peak in the autumn, have each considerable ecological significance.

Temperature modulation of photoperiodism: an adaptation for long-distance dispersal in the aphid, Acyrthosiphon pisum (Hemiptera: Aphididae)

2013 ◽  
Vol 145 (3) ◽  
pp. 302-316
Author(s):  
M.A.H. Smith ◽  
P.A. MacKay ◽  
R.J. Lamb
Keyword(s):  
Acyrthosiphon Pisum ◽  
Seasonal Pattern ◽  
Local Population ◽  
Late Summer ◽  
Photoperiodic Response ◽  
Day Length ◽  
Temperature Modulation ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Critical Photoperiod

AbstractVariation in the seasonal occurrence of asexual and sexual phenotypes of Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) is quantified for a local population in southern Manitoba, Canada. To survive winter, summer asexual generations must produce a sexual generation in a timely way at the end of the season, so that females can lay overwintering eggs. This transition is controlled by day length, which varies in a fixed seasonal pattern with latitude, and the local pattern of day length selects for an appropriate photoperiodic response. Substantial variation in the timing of production of males and mating females occurs among locally collected genotypes. Some of the variation is due to the arrival of long-distance dispersers (1000 km or more), and some is consistent with shorter but still long-distance dispersal. Some of the variation is due to year-to-year changes in late summer temperature. The critical day length in nature, which corresponds to critical photoperiod, increases as the average temperature decreases. This temperature modulation is adaptive because it allows many genotypes to produce some sexual phenotypes before the end of the season, although their photoperiodic responses are characteristic of long-distance dispersers and inappropriate to local day lengths.

Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum

1992 ◽  
Vol 43 (2) ◽  
pp. 241 ◽  
Author(s):  
JJ Mott ◽  
MM Ludlow ◽  
JH Richards ◽  
AD Parsons
Keyword(s):  
Growing Season ◽  
Close Correlation ◽  
Dry Season ◽  
Carbon Gain ◽  
Panicum Maximum ◽  
Wet Season ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Moisture Conditions ◽  
Sheath Material

The close correlation between grazing-induced mortality and major climatic patterns in Australian savannas, led us to the hypothesis that moisture conditions during the dry, non-growing season could affect sensitivity to grazing in the subsequent growing season. Using three widespread savanna species (Themeda triandra, Heteropogon contortus and Panicum maximum), this hypothesis was tested experimentally and the mechanisms controlling this response examined and quantified. In T. triandra drought during the dry season led to major mortality in defoliated plants in the next growing season. This mortality was caused by a synchrony of tillering at the commencement of the wet season, leaving few buds for replacement once parent tillers were killed by defoliation. T. triandra was also the most sensitive species to defoliation. This sensitivity was due to the poor ability of the plant to maintain positive carbon gain after defoliation. Several factors contributed to this poor ability, including: low total photosynthetic rate, low specific leaf area, and a large proportion of sheath material with poor photosynthetic capacity remaining after cutting. Both H. contortus and P. maximum growing under irrigated and fertilized conditions did not display any effects of previous moisture treatments when defoliated during the next wet season and were much less sensitive to defoliation than T. triandra.

Fungal deterioration of second-growth Douglas-fir logs in coastal British Columbia

1970 ◽  
Vol 48 (9) ◽  
pp. 1541-1551 ◽  
Author(s):  
R. B. Smith ◽  
H. M. Craig ◽  
D. Chu
Keyword(s):  
Seasonal Pattern ◽  
Wood Decay ◽  
Late Summer ◽  
Douglas Fir ◽  
White Rot ◽  
Decay Fungi ◽  
Deterioration Rate ◽  
Second Growth ◽  
Autumn And Winter ◽  
Fungal Deterioration

Fungal deterioration of second-growth Douglas-fir logs, felled each month from August 1961 to May 1962, was studied 2, 4, and 6 years after felling. Decay increased from 10% of log volumes after 2 years to 47% after 6 years. The rate of decay, particularly for the brown cubical type, was greater for autumn- and winter-felled logs than for those felled in the spring and late summer, and closely paralleled the seasonal pattern of ambrosia beetle attack.Decay rates increased with decreasing log size, increasing percentage of sapwood, and increasing height of log above ground. For the same diameter of log, base logs decayed less rapidly than second logs, possibly because of their lower proportion of sapwood in relation to heartwood.Decay expressed as a percentage of total log volume (Y) may be estimated (R2 = 0.71) with the following equation: Y = 13.2 + 10.7X1 − 3.2X2, where X1 = years elapsed and X2 = d.i.b. (diameter inside bark) top of log.Of 30 wood-decay fungi isolated, Naematoloma sp. (N. capnoides or N. fasciculare), which causes a white rot, was associated with the most decay. Fomes pinicola was mainly responsible for brown cubical sap rot, while Poria monticola and P. carbonica caused a brown cubical heart rot at the ends of logs.The significance of variations in deterioration rate and fungal associates is discussed in relation to log durability and salvability.

Freshwater Cyanobacteria of North-Eastern Australia: 2. Chroococcales

Phytotaxa ◽  
2013 ◽  
Vol 133 (1) ◽  
pp. 1 ◽  
Author(s):  
GLENN B. MCGREGOR
Keyword(s):  
Light Microscopy ◽  
Natural Populations ◽  
Northern Territory ◽  
Detailed Account ◽  
Ecological Data ◽  
Eastern Australia ◽  
North Eastern ◽  
Rivers And Streams ◽  
Original Illustrations ◽  
Freshwater Habitats

This volume provides the first detailed account of the Chroococcales of north-eastern Australia. It provides keys, morphological and ecological data for 6 families, 33 genera and 112 species, and photomicrographs and original illustrations to enable the identification of natural populations based on stable and recognizable characters observable with the aid of light microscopy. Distributional data are based on extensive surveys at 270 sites representing the major freshwater habitats including rivers and streams, palustrine and lacustrine wetlands, thermal springs, and man-made reservoirs in Queensland and the Northern Territory as well as a review of the Australian phycological literature. 

An ecological explanation for hyperallometric scaling of reproduction

2021 ◽  
Author(s):  
Tomos Potter ◽  
Anja Felmy
Keyword(s):  
Body Size ◽  
Reproductive Output ◽  
Resource Competition ◽  
Natural Populations ◽  
Scaling Exponent ◽  
Wild Populations ◽  
Wet Season ◽  
Size Dependent ◽  
In The Wild ◽  
The Relationship

AbstractIn wild populations, large individuals have disproportionately higher reproductive output than smaller individuals. We suggest an ecological explanation for this observation: asymmetry within populations in rates of resource assimilation, where greater assimilation causes both increased reproduction and body size. We assessed how the relationship between size and reproduction differs between wild and lab-reared Trinidadian guppies. We show that (i) reproduction increased disproportionately with body size in the wild but not in the lab, where effects of resource competition were eliminated; (ii) in the wild, the scaling exponent was greatest during the wet season, when resource competition is strongest; and (iii) detection of hyperallometric scaling of reproduction is inevitable if individual differences in assimilation are ignored. We propose that variation among individuals in assimilation – caused by size-dependent resource competition, niche expansion, and chance – can explain patterns of hyperallometric scaling of reproduction in natural populations.

Environmental and Genetic Control of Reproduction in Danthonia caespitosa Populations

1978 ◽  
Vol 26 (3) ◽  
pp. 351 ◽  
Author(s):  
KC Hodgkinson ◽  
JA Quinn
Keyword(s):  
Floral Induction ◽  
Flag Leaf ◽  
Day Length ◽  
Herbarium Specimens ◽  
Floral Initiation ◽  
Inflorescence Development ◽  
Southern Limit ◽  
The North ◽  
Eastern Australia ◽  
Controlled Environments

Seedlings and older plants of five populations of Danthonia caespitosa from south-eastern Australia were grown in controlled environments and in a transplant garden to determine the effect of day length, temperature, and vernalization of floral initiation and inflorescence development. The populations were selected from widely separated sites which spanned the latitudinal range (31-42°S.) for the species and extended from a hot, semiarid environment in the north to a relatively cool and moist temperature environment in the south. Examination of herbarium specimens indicated that seed set could occur as early as mid September at the northern limit for the species and not before mid January at the southern limit (Tasmania). In a uniform transplant garden located at Deniliquin (latitude 35° 23′S.) plants from the northern site reached anthesis 4 weeks earlier than plants from southern sites. Controlled environment experiments revealed that D. caespitosa is a long-day plant. Northern populations required a 9 . 5 hr day length or longer for floral induction compared with 11 hr or longer for southern populations. The number of days in inductive conditions (outside, day length 13.5 hr) required for floral initiation was 5-7 for the three most northern populations and 21-25 days for the two southern populations. Inflorescence development (initiation to flag leaf stage) was considerably slower in southern populations. All but the most northern population responded to vernalization. Flowering was earlier in temperatures that were optimal for plant growth. At high temperatures (36/31°C day/night) flowering was not significantly delayed for the three most northern populations, but was for the two southern populations, and florets contained caryopses in only the three northern populations. These results suggest that in cool and moist temperate habitats reproduction of this species is programmed by day length and temperature effects on floral initiation and development to coincide with a predictable growing season, whereas in hot semiarid habitats this control is relaxed, which permits opportunistic reproduction whenever soil moisture and temperature permit growth.

scholarly journals Measurements of optical properties of atmospheric aerosols in Northern Finland

2005 ◽  
Vol 5 (6) ◽  
pp. 11703-11728 ◽  
Author(s):  
V. Aaltonen ◽  
H. Lihavainen ◽  
V.-M. Kerminen ◽  
M. Komppula ◽  
J. Hatakka ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Seasonal Pattern ◽  
Late Summer ◽  
Aerosol Optical Properties ◽  
Air Masses ◽  
Angstrom Exponent ◽  
Northern Border ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. Three years of continuous measurements of aerosol optical properties and simultaneous aerosol number size distribution measurements at Pallas GAW station, a remote subarctic site in the northern border of the boreal forest zone, have been analysed. The scattering coefficient at 550 nm varied from 0.2 to 94.4 Mm−1 with an average of 7.1±8.6 Mm−1. Both the scattering and backscattering coefficients had a clear seasonal cycle with an autumn minimum and a 4–5 times higher summer maximum. The scattering was dominated by submicron aerosols and especially so during late summer and autumn. The Ångström exponent had a clear seasonal pattern with maximum values in late summer and minimum values during wintertime. The highest hemispheric backscattering fraction values were observed in autumn, indicating clean air with few scattering particles and a particle size distribution strongly dominated by ultrafine particles. To analyse the influence of air mass origin on the aerosol optical properties a trajectory climatology was applied to the Pallas aerosol data. The most polluted trajectory patterns represented air masses from the Kola Peninsula, Scandinavia and Russia as well as long-range transport from Britain and Eastern Europe. These air masses had the largest average scattering and backscattering coefficients for all seasons. Higher than average values of the Ångström exponent were also observed in connection with transport from these areas.

scholarly journals Laboratory-based surveillance for Cryptosporidium in France, 2006–2009

2010 ◽  
Vol 15 (33) ◽  
Author(s):  
Collective The ANOFEL Cryptosporidium National Network
Keyword(s):  
Seasonal Pattern ◽  
Late Summer ◽  
Epidemiological Data ◽  
University Hospitals ◽  
National Network ◽  
Lack Of Information ◽  
Health Authorities ◽  
Public Health Authorities ◽  
Set Up ◽  
Voluntary Basis

In 2002, the French Food Safety Agency drew attention to the lack of information on the prevalence of human cryptosporidiosis in the country. Two years later, the ANOFEL Cryptosporidium National Network (ACNN) was set up to provide public health authorities with data on the incidence and epidemiology of human cryptosporidiosis in France. Constituted on a voluntary basis, ACNN includes 38 hospital parasitology laboratories (mainly in university hospitals). Each laboratory is engaged to notify new cases of confirmed human cryptosporidiosis, store specimens (e.g. stools, duodenal aspirates or biopsies) and related clinical and epidemiological data, using datasheet forms. From January 2006 to December 2009, 407 cryptosporidiosis cases were notified in France and 364 specimens were collected. Of the notified cases, 74 were children under four years of age, accounting for 18.2%. HIV-infected and immunocompetent patients represented 38.6% (n=157) and 28% (n=114) of cases, respectively. A marked seasonal pattern was observed each year, with increased number of cases in mid to late summer and the beginning of autumn. Genotyping of 345 isolates from 310 patients identified C. parvum in 168 (54.2%) cases, C. hominis in 113 (36.4%) and other species in 29 (9.4%), including C. felis (n=15), C. meleagridis (n=4), C. canis (n=4), Cryptosporidium chipmunk genotype (n=1), Cryptosporidium rabbit genotype (n=1) and new Cryptosporidium genotypes (n=4). These data represent the first multisite report of laboratory-confirmed cases of cryptosporidiosis in France.

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