Ecotypic variation for seed dormancy contributes to the success of capeweed (Arctotheca calendula) in Western Australia

1999 ◽  
Vol 50 (8) ◽  
pp. 1451 ◽  
Author(s):  
Matthew T. Dunbabin ◽  
P. S. Cocks
Keyword(s):  
Seed Dormancy ◽  
Western Australia ◽  
Late Summer ◽  
Soil Surface ◽  
Summer Rainfall ◽  
Early Summer ◽  
Effect Of Temperature ◽  
First Year ◽  
Buried Seed ◽  
Dormancy Pattern

The seed dormancy characteristics of 2 capeweed [Arctotheca calendula (L.) Levyns] ecotypes from Western Australia were studied to determine aspects of seed dormancy that contribute to the success of this species in southern Australia. Short- and long-term dormancy pattern of buried and soil surface seed, effect of summer temperatures on afterripening, and effect of temperature on seed germination were investigated using seed produced in a common environment. There were large differences in the seed dormancy pattern of the 2 ecotypes studied. On the soil surface, >95% of seed of the Mt Barker ecotype became non-dormant and germinated in the first year, the remainder germinating the following season. In contrast, only 5% of Mullewa seed germinated in the first year, with 75% germinating in the second year and 20% of seed remaining dormant after 2 years. Cycling of dormancy was observed for buried seed of both ecotypes, with periods of non-dormancy corresponding with the likely timing of the break of the season. Dormancy cycling was also apparent in seed stored under constant conditions in the laboratory. Burial prevented germination of both ecotypes; however, the ability to resist germination while buried was lost in 30% of the Mt Barker seed in the second season. Differences in the duration of dormancy of soil surface and buried capeweed seed have evolved as an adaptation to the different environments likely to be experienced by plants at their site of collection. All seeds possessed primary dormancy at maturity, with any afterripening during the first year occurring by the end of summer. Afterripening was enhanced by exposure to typical soil surface temperatures, providing some protection against germination during early summer rainfall. Protection from late summer rains is insured by the inability of seed to germinate at temperatures >30°C and a relatively slow rate of germination. These features of capeweed seed dormancy, combined with the ability to evolve genetically distinct populations suited to particular environments, help explain why capeweed is so widespread and abundant across southern Australia.

The biology of Barleeia unifasciata (Gastropoda:Prosobranchia) in red algal turfs in S.W. Ireland

1982 ◽  
Vol 62 (2) ◽  
pp. 461-468 ◽  
Author(s):  
T. Southgate
Keyword(s):  
Sexual Development ◽  
Algal Species ◽  
Late Summer ◽  
Early Summer ◽  
First Year ◽  
Maximum Life Span ◽  
Red Algal ◽  
Second Year ◽  
Recruitment Period ◽  
Length Frequency Data

Variation in the abundance of Barleeia unifasciata is compared in several red algal species between June 1978 and June 1980 at Cooskeen Cove, Bantry Bay, Ireland. Population abundance in all algae varied seasonally, exhibiting a cycle of late-summer to autumn maxima, with winter to early summer minima. Greatest abundance was recorded in those algae which formed compact turf-like growths suitable for the entrapment of diatoms and detrital material and provided greatest shelter from wave-crash. Length frequency data showed the main recruitment period to be late June-October with a peak in August with juveniles present in all months of the year. Maximum life span was shown to be 2 years or more with only 15 % of the population surviving into the second year. Sexual development and reproductive cycle was determined for 0 + and 1 + animals. Mature males produced sperm continuously throughout the year. Not all 0 + females spawned in their first year. Summer spawning 0 + females exhibited reduced sexual activity in October and spawned again in the following summer. Some 1 + females spawned in winter and spring. Delayed sexual development in some individuals of both sexes was related to late hatching.

scholarly journals Root and shoot attributes of indigenous perennial accessions of the wild mungbean (Vigna radiata ssp. sublobata)

2006 ◽  
Vol 57 (7) ◽  
pp. 791 ◽  
Author(s):  
G. J. Rebetzke ◽  
R. J. Lawn
Keyword(s):  
Vigna Radiata ◽  
Plant Biomass ◽  
Lateral Roots ◽  
Late Summer ◽  
Soil Surface ◽  
Sowing Date ◽  
Early Summer ◽  
Seed Biomass ◽  
Total Plant Biomass ◽  
Total Plant

Root and shoot attributes of 12 indigenous perennial accessions of the wild mungbean (Vigna radiata ssp. sublobata) were evaluated in early and late summer sowings in the field in SE Queensland. All but one of the accessions were obtained from the Townsville–Charters Towers region of NE Queensland. In both sowings, the accessions developed thickened tap and lateral roots, the taproot thickening extending to a depth of 0.20–0.30 m below the soil surface, depending on accession. The thickened lateral roots emerged from the taproot within 0.10 m of the soil surface, and extended laterally up to 1.10 m, remaining close to the soil surface. Differences among the accessions in gross root morphology and phenology were relatively small. There were differences among the accessions in the production of seed, tuberised root, and recovered total plant biomass. Depending on accession and sowing date, the tuberised roots accounted for up to 31% of recovered plant biomass and among accessions, the root biomass was positively correlated with total plant biomass. In contrast, seed biomass represented only a small proportion of recovered plant biomass, up to a maximum of 14%, depending on accession and sowing date. Among accessions, the proportion of seed biomass tended to be negatively correlated with that of tuber biomass. The perennial trait appears to be unique to Australian accessions of wild mungbean obtained from coastal-subcoastal, speargrass-dominant woodlands of NE Queensland. Although the ecological significance of the trait remains conjectural, field observation indicates that it facilitates rapid plant re-growth following early summer rainfall, especially where dry-season fire has removed previous-season above-ground growth.

Distinct Principal Modes of Early and Late Summer Rainfall Anomalies in East Asia*

2009 ◽  
Vol 22 (13) ◽  
pp. 3864-3875 ◽  
Author(s):  
Bin Wang ◽  
Jian Liu ◽  
Jing Yang ◽  
Tianjun Zhou ◽  
Zhiwei Wu
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
Land Surface ◽  
Southern Oscillation ◽  
Southern China ◽  
Late Summer ◽  
Summer Rainfall ◽  
Seasonal Prediction ◽  
Early Summer ◽  
Rainfall Anomalies

Abstract The current seasonal prediction of East Asia (EA) summer monsoon deals with June–July–August (JJA) mean anomalies. This study shows that the EA summer monsoon may be divided into early summer [May–June (MJ)] and late summer [July–August (JA)] and exhibits remarkable differences in mean state between MJ and JA. This study reveals that the principal modes of interannual precipitation variability have distinct spatial and temporal structures during the early and late summer. These principal modes can be categorized as either El Niño–Southern Oscillation (ENSO) related or non-ENSO related. During the period of 1979–2007, ENSO-related modes explain 35% of MJ variance and 45% of JA variance, and non-ENSO-related modes account for 25% of MJ variance and 20% of JA variance. For ENSO-related variance, about two-thirds are associated with ENSO decaying phases, and one-third is associated with ENSO developing phases. The ENSO-related MJ modes generally concur with rapid decay or early development of ENSO episodes, and the opposite tends to apply to ENSO-related JA modes. The non-ENSO MJ mode is preceded by anomalous land surface temperatures over southern China during the previous March and April. The non-ENSO JA mode is preceded by lasting equatorial western Pacific (the Niño-4 region) warming from the previous winter through late summer. The results suggest that 1) prediction of bimonthly (MJ) and (JA) anomalies may be useful, 2) accurate prediction of the detailed evolution of ENSO is critical for prediction of ENSO-related bimonthly rainfall anomalies over East Asia, and 3) non-ENSO-related modes are of paramount importance during ENSO neutral years. Further establishment of the physical linkages between the non-ENSO modes and their corresponding precursors may provide additional sources for EA summer monsoon prediction.

Subseasonal Variation in ENSO-Related East Asian Rainfall Anomalies during Summer and Its Role in Weakening the Relationship between the ENSO and Summer Rainfall in Eastern China since the Late 1970s

2011 ◽  
Vol 24 (9) ◽  
pp. 2271-2284 ◽  
Author(s):  
Hong Ye ◽  
Riyu Lu
Keyword(s):  
Eastern China ◽  
Late Summer ◽  
Summer Rainfall ◽  
Rainfall Anomaly ◽  
Precipitation Anomaly ◽  
Early Summer ◽  
Huai River ◽  
Rainfall Anomalies ◽  
Circulation Anomalies ◽  
The Relationship

Abstract The findings of the study reported in this paper show that, during ENSO decaying summers, rainfall and circulation anomalies exhibit clear subseasonal variation. Corresponding to a positive (negative) December–February (DJF) Niño-3.4 index, a positive (negative) subtropical rainfall anomaly, with a southwest–northeast tilt, appears in South China and the western North Pacific (WNP) in the subsequent early summer (from June to middle July) but advances northward into the Huai River Basin in China as well as Korea and central Japan in late summer (from late July to August). Concurrently, a lower-tropospheric anticyclonic anomaly over the WNP extends northward from early to late summer. The seasonal change in the basic flows, characterized by the northward shift of the upper-tropospheric westerly jet and the WNP subtropical high, is suggested to be responsible for the differences in the above rainfall and circulation anomalies between early and late summer by inducing distinct extratropical responses even under the almost identical tropical forcing of a precipitation anomaly in the Philippine Sea. A particular focus of the study is to investigate, using station rainfall data, the subseasonal variations in ENSO-related rainfall anomalies in eastern China since the 1950s, to attempt to examine their role in weakening the relationship between the ENSO and summer mean rainfall in eastern China since the late 1970s. It is found that the ENSO-related rainfall anomalies tend to be similar between early and late summer before the late 1970s, that is, the period characterized by a stronger ENSO–summer mean rainfall relationship. After the late 1970s, however, the anomalous rainfall pattern in eastern China is almost reversed between early and late summer, resulting accordingly in a weakened relationship between the ENSO and total summer rainfall in eastern China.

Changes with time in the germination of buried scentless chamomile (Matricaria perforata Mérat) seeds

1995 ◽  
Vol 75 (1) ◽  
pp. 277-281 ◽  
Author(s):  
G. G. Bowes ◽  
A. G. Thomas ◽  
L. P. Lefkovitch
Keyword(s):  
Seed Bank ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Growing Season ◽  
Early Spring ◽  
First Year ◽  
Temperature Regimes ◽  
Buried Seed ◽  
Second Year ◽  
Persistent Seed Bank

Change with time in the germination of scentless chamomile (Matricaria perforata Mérat) seeds was investigated. Seeds were placed in nylon net bags, buried 7 cm deep in soil, exhumed at monthly intervals for 2 yr and allowed to germinate in temperature regimes of 10/2 °C, 20/5 °C, 25/10 °C and 35/20 °C (16/8 h), simulating temperatures found during early spring or late fall, spring or fall, summer and mid-summer on the soil surface, respectively. Exhumed and refrigerator-stored (2 °C) check seeds exhibited no yearly dormancy/nondormancy germination cycle, but mortality of buried seed increased to 36%, after 10 mo in contrast with that of the check seeds which remained low for two years. Light was required for germination during the first year but was not required for a portion of the seed during the second year. The retention of viability in buried seed explains the persistent seed bank and seedling emergence throughout the growing season when moisture and temperature are nonlimiting. Key words: Seed burial, germination, Matricaria perforata Mérat

Terrestrial Breeding in the Australian Leptodactylid Frog Myobatrachus gouldii (Gray)

1981 ◽  
Vol 8 (2) ◽  
pp. 451 ◽  
Author(s):  
JD Roberts
Keyword(s):  
Surface Activity ◽  
Western Australia ◽  
Preliminary Data ◽  
Egg Size ◽  
Late Summer ◽  
Soil Surface ◽  
Direct Development ◽  
Egg Deposition ◽  
South West ◽  
Breeding Seasons

M. gouldii is widespread in south-west Western Australia. Males call on the soil surface after rain in spring and in early and late summer. Females orient to calling males but amplexus does not occur on the surface. Egg size and number, and egg deposition sites 1 m deep in sand, are described; the male call and the distribution of calling males are documented, with preliminary data on breeding seasons and surface activity. M. gouldii is a terrestrial breeder with probable intracapsular, direct development, as has long been suspected.

Seed production by skeleton weed (Chondrilla juncea L.) in Western Australia in relation to summer drought

1987 ◽  
Vol 38 (4) ◽  
pp. 689 ◽  
Author(s):  
J Dodd ◽  
FD Panetta
Keyword(s):  
Soil Water ◽  
Seed Production ◽  
Western Australia ◽  
Summer Rainfall ◽  
Soil Water Storage ◽  
First Year ◽  
Root Penetration ◽  
Summer Drought ◽  
Air Temperatures ◽  
Viable Seeds

Seed production in Forms A and C of C. juncea was measured at 11 wheatbelt sites in Western Australia and under glasshouse conditions. Most field-grown plants produced abundant viable seeds, even without substantial summer rainfall. Up to 27.6 x l03 seeds per plant were recorded, and their viability was frequently between 80 and 90%. Even in their first year, some plants produced more than 10000 seeds each. Through the summer, seed production often followed either a positively skewed, or a bimodal curve. Falls of rain in summer did not increase seed output or affect its quality in established plants. Exceptionally high air temperatures appeared to depress seed numbers and/or viability at several, but not all, sites. At the end of summer, when young plants were 9-12 months old, soil water extraction had occurred to 310 cm, indicating root penetration to this depth. Conservative water use by C. juncea during summer was indicated by low values of soil water depletion. In glasshouse-grown plants, simulated drought reduced seed numbers, viability, primary dormancy and seed weight, although the two forms responded differently. Given adequate winter rainfall to recharge soil water storage, C. juncea appears capable of producing large quantities of viable seeds throughout the Western Australian wheatbelt.

Comparisons of the productivity of sheep grazing natural pastures of the Riverine Plain

1970 ◽  
Vol 10 (46) ◽  
pp. 549 ◽  
Author(s):  
AD Wilson ◽  
JH Leigh
Keyword(s):  
Growth Rate ◽  
High Growth ◽  
Late Summer ◽  
Summer Rainfall ◽  
High Growth Rate ◽  
First Year ◽  
Sheep Grazing ◽  
Wool Growth ◽  
The Mean ◽  
Second Year

The productivity of Merino sheep grazing on the semi-arid natural shrub (Atriplex vesicaria) and grassland (Danthonia caespitosa-Stipa variabilis, D. caespitosa, S. variabilis) pastures of the Riverine Plain was measured over three years. At 0.5 sheep to an acre, the sheep on A. vesicaria (bladder saltbush) community at first grew more wool than those on the grasslands, but wool growth rate declined in autumn to the same degree as on the grassland. In the second year most of the A. vesicaria bushes did not recover from grazing and wool growth-rate fell to half that on the grasslands. The sheep on A. vesicaria had to be removed in the second year, but on the grasslands there was no evidence that sheep could not be maintained indefinitely at that stocking rate. At 1.0 sheep to an acre, both the A. vesicaria and the D. caespitosa-S. variabilis grassland were incapable of maintaining the sheep for the duration of the experiment. Wool growth of the sheep on the grasslands showed an annual rhythm, with high growth-rate in spring (14 g per day) followed by a gradual decline in rate to 6-8 g per day in late summer and autumn. However, the extent of this decline was dependent on summer rainfall, as in one summer when rainfall was high, wool growth-rate was maintained at near the spring rate. The mean annual rate of wool growth was found to be correlated (r = + 0.92, P<0.01) to summer rainfall (November-April). The weight gain of weaner sheep was best on E. caespitosa, and was equaiied by that on A. vesicara only in the first year. Growth was not influenced by the presence or absence of bushes of Kochia aphylla Growth on S. variabilis was less than on D. caespitosa.

scholarly journals Temperature and light effects on Trichobilharzia szidati cercariae with implications for a risk analysis

2020 ◽  
Vol 62 (1) ◽  
Author(s):  
Azmi Al-Jubury ◽  
Per Kania ◽  
Anette Bygum ◽  
Kurt Buchmann
Keyword(s):  
Risk Analysis ◽  
Life Span ◽  
Intermediate Host ◽  
Lymnaea Stagnalis ◽  
Late Summer ◽  
Early Spring ◽  
Early Summer ◽  
Effect Of Temperature ◽  
The Public ◽  
Cercarial Dermatitis

Abstract Background Cercarial dermatitis (swimmer’s itch) caused by bird schistosome cercariae, released from intermediate host snails, is a common disorder also at higher latitudes. Several cases were observed in the artificial Danish freshwater Ringen Lake frequently used by the public for recreational purposes. The lake may serve as a model system when establishing a risk analysis for this zoonotic disease. In order to explain high risk periods we determined infection levels of intermediate host snails from early spring to late summer (March, June and August) and elucidated the effect of temperature and light on parasite shedding, behavior and life span. Results Field studies revealed no shedding snails in March and June but in late summer the prevalence of Trichobilharzia szidati infection (in a sample of 226 pulmonate Lymnaea stagnalis snails) reached 10%. When investigated under laboratory conditions the cercarial shedding rate (number of cercariae shed per snail per day) was positively correlated to temperature raising from a mean of 3000 (SD 4000) at 7 °C to a mean of 44,000 (SD 30,000) at 27 °C). The cercarial life span was inversely correlated to temperature but the parasites remained active for up to 60 h at 20 °C indicating accumulation of cercariae in the lake during summer periods. Cercariae exhibited positive phototaxy suggesting a higher pathogen concentration in surface water of the lake during daytime when the public visits the lake. Conclusion The only causative agent of cercarial dermatitis in Ringen Lake detected was T. szidati. The infection risk associated with aquatic activities is low during spring and early summer (March-June). In late summer the risk of infection is high since the release, behavior and life span of the infective parasite larvae have optimal conditions.

Broad-scale coastal movements of white sharks off Western Australia described by passive acoustic telemetry data

2017 ◽  
Vol 68 (8) ◽  
pp. 1518 ◽  
Author(s):  
R. B. McAuley ◽  
B. D. Bruce ◽  
I. S. Keay ◽  
S. Mountford ◽  
T. Pinnell ◽  
...  
Keyword(s):  
Western Australia ◽  
Ecological Factors ◽  
Late Summer ◽  
Early Summer ◽  
Telemetry Data ◽  
Limited Evidence ◽  
The South ◽  
Seasonal Movement ◽  
Passive Acoustic ◽  
Broad Scale

Movements of 89 acoustically tagged subadult and adult white sharks (Carcharodon carcharias) were monitored off the south and west coasts of Western Australia (WA) between December 2008 and May 2016 by a network of up to 343 passive acoustic receivers. In all, 290 inter-regional movements, totalling 185092km were recorded for 73 of these sharks. Estimated rates of movement in excess of 3kmh–1 (mean 1.7kmh–1; maximum 5.6kmh–1) were common, even over distances of thousands of kilometres. Detections indicated that white sharks may be present off most of the south and lower west coasts of WA throughout the year, although they are more likely to be encountered during spring and early summer and are least likely to be present during late summer and autumn. There was limited evidence of predictable return behaviour, seasonal movement patterns or coordination of the direction and timing of individual shark’s movements. Nevertheless, the data suggest that further analyses of movements in relation to ecological factors may be useful predictors of shark activity at local scales. It is hoped that these data may be useful for informing public safety initiatives aimed at mitigating the risks associated with human encounters with white sharks off the WA coast.

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