Observations on survival and early growth of natural regeneration in floodplain coolibah Eucalyptus victrix (Myrtaceae) in the Pilbara, Western Australia
- Authors: Fox, John , Florentine, Singarayer , Westbrooke, Martin , Hurst, Cameron
- Date: 2004
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 26, no. 2 (2004), p. 150-160
- Full Text: false
- Reviewed:
- Description: Observations are presented on the natural regeneration of Eucalyptus victrix L. Johnson and K. Hill (coolibah), the dominant tree species of grassy woodlands on the floodplain of the Fortescue River, north of Newman in the Pilbara district of Western Australia. The main objectives of this study were to examine: (i) survival of newly recruited E. victrix seedlings on flooded and burnt sites, and (ii) growth and survival of established plants in a gilgaied landscape. Populations of newly-recruited seedlings following flooding or fire were monitored opportunistically at 'Marillana' and 'Ethel Creek' stations, for up to two years from tagging. A population of saplings at 'Roy Hill' station was observed over eight years. Seedling densities of E. victrix in flooded sites were 0.32 and 1.03 plants/m2 in 1995 and 1997 respectively. Locally high densities reached from 1.2 to 17.7 plants/m2 on areas of 28 and 6 m2 respectively. At the burnt site at 'Ethel Creek', 1.30 plants/m2 were observed where 58 seedlings were recorded on an area of 445 m2 a year after a natural fire. Many of these persisted well into their second year, whereas seedlings recruited in the flooded sites generally lasted less than a year (250-376 days). In contrast, persistence of a cohort of 100 established saplings <2 m tall in a gilgaied landscape at 'Roy Hill' was high. During 8 years of observations, only one sapling was lost. Those found at the edges of gilgais had attained greater heights (3.91 ± 1.14 m) than saplings located inside (3.16 ± 0.95 m) or on top (3.12 ± 0.93 m) of the gilgais. This study demonstrates that the seedling stage in E. victrix is critical, in that once newly recruited individuals reach the sapling stage (0.6-1 m), mortality rates are much reduced. Unfortunately, it was not possible during the course of this study to locate a cohort of young seedlings that did survive and so any consideration of the conditions necessary for their survival is speculative.
- Description: C1
- Description: 2003000725
The germinable soil seedbank of Eucalyptus victrix grassy woodlands at Roy Hill Station, Pilbara District, Western Australia
- Authors: Graham, R.A. , Florentine, Singarayer , Fox, John , Luong, T. M.
- Date: 2004
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 26, no. 1 (2004), p. 17-33
- Full Text: false
- Reviewed:
- Description: The paper reports soil seedbank species composition, of Eucalyptus victrix grassy woodlands, of the upper Fortescue River in the Pilbara District, Western Australia. In this study, our objectives were to investigate germinable soil seedbanks and species composition in response to three simulated seasons, using emergence. Variation in seed density from three depths was tested. Four field sites were sampled. Thirty samples were collected in late spring, after seed rain and prior to summer rainfall. From each sample spot, three soil depths (surface, 1-5, and 6-10 cm) were segregated from beneath surface areas of 100 cm(2). Samples were later incubated in a glasshouse to simulate three different seasonal conditions (autumn, winter and spring). Germinating seedlings were recorded on emergence and grown until identified. Forty-one species germinated, comprising 11 grasses (7 annuals and 4 perennials), 25 annual herbs and 5 perennial herbs. Distribution patterns of germinable seed in both the important annual grass Eragrostis japonica and the perennial Eragrostis setifolia (a preferred cattle fodder species), suggest that seedbank accumulation differs among species and between sites. In part, this may be associated with the absence of grazing. Species with most total germinable seed were E. japonica (Poaceae; 603/m(2)), and the annual herbs Calotis multicaulis (Asteraceae; 346/m(2)), and Mimulus gracilis (Scrophulariaceae; 168/m(2)). Perennial grass seed was sparse. Spring simulation gave most germination (1059), followed by autumn (892) and winter (376) sets. Greatest species diversity was produced from the spring simulation (33 species), followed by autumn (26), and winter (22). Of the total germination, 92% came from 17 species that were represented in all three simulations. Of the 1227 grass seedlings counted, most were recruited from the surface soil (735), followed by the 5 (310) and 10 (182) cm depths. Marginally more grass seedlings germinated from the spring simulation (558) than the autumn set (523). Only 11.9% of grass germinants came from the winter simulation. All grass species recruited from the soil seedbanks had a C-4 photosynthetic pathway. Except for Cenchrus ciliaris all grass species are native to Australia. Of the four sites sampled, one fenced to exclude cattle five years earlier had significantly more germination than the three unfenced sites. Seedbank sampling produced several new records for plants in the areas sampled.
- Description: C1
- Description: 2003000711
Allelopathic effects of Eucalyptus victrix L. on Eucalyptus species and grasses
- Authors: Florentine, Singarayer , Fox, John
- Date: 2003
- Type: Text , Journal article
- Relation: Allelopathy Journal Vol. 11, no. 1 (2003), p. 77-83
- Full Text: false
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- Description: C1
- Description: 2003000583
Competition between Eucalyptus victrix seedlings and grass species
- Authors: Florentine, Singarayer , Fox, John
- Date: 2003
- Type: Text , Journal article
- Relation: Ecological Research Vol. 18, no. 1 (Jan 2003), p. 25-39
- Full Text: false
- Reviewed:
- Description: Competition in a natural system may be interspecific or intraspecific. In semiarid ecosystems, competition for resources between established neighboring grass species and newly recruited seedlings is very high. To examine the effects of grass species density, growing space and time of establishment on Eucalyptus victrix seedlings (interspecific competition), and the effect of density and growing space within E. victrix (intraspecific competition) we conducted an experiment under controlled conditions. We tested four hypotheses (i) E. victrix seedling growth is not affected by grass density; (ii) there is no difference in E. victrix survival and growth between early and later grass establishment; (iii) interspecific competition is not more intense than intraspecific competition in E. victrix ; and (iv) growth of E. victrix seedlings is not dependent on available growing space. In a monoculture of E. victrix , seedling mortality was higher (10%) in large pots. In mixed culture pots, where E. victrix seedlings and grass seedlings were planted on the same day, E. victrix seedlings survived for up to 4 weeks, but started to die after week five in the smallest pots. However, mortalities occurred in pots of all sizes when grass was established before E. victrix seedlings. Results also indicated that the resources necessary for the growth of individual E. victrix seedlings were more limiting under conditions of increased density of neighboring grass species rather than intraspecific competition. In particular, photosynthetic area of E. victrix seedlings was drastically reduced in mixed cultures. Although density, pot size and time of planting had impacts on E. victrix seedlings, the patterns of these impacts were variable.
- Description: C1
- Description: 2003000544
Heat requirement for germination of the grass, panicum laevinode
- Authors: Florentine, Singarayer , Graham, R.A. , Fox, John
- Date: 2002
- Type: Text , Journal article
- Relation: International Journal of Ecology and Environmental Sciences Vol. 28, no. (2002), p. 143-145
- Full Text: false
- Reviewed:
- Description: Annual grasses are important components of vegetation, especially where perennial grasses have declined from overgrazing. Panicum laevinode is an annual grass that occurs in large numbers in grassy Eucalyptus victrix L. Johnson and K. Hill coolibah woodland in Pilbara, Western Australia. Little is known about the seed germination pattern and requirements of this grass. Our aim was to examine the effect of heat pre-treatment on seed germination of P. laevinode. Only 12% germination was observed from seeds pre-treated at 60oC for periods ranging from 1 to 8 weeks. However seed viability study showed that 61.5% and 71.5% of seeds were viable from 3 and 17 months respectively. Germination study did not reflect results of the viability test.
- Description: 2003000151
Morphological and physiological adaptations to waterlogging by Eucalyptus seedlings from the semi-arid Pilbara, Western Australia
- Authors: Florentine, Singarayer , Fox, John
- Date: 2002
- Type: Text , Journal article
- Relation: The Journal of the Royal Society of Western Australia Vol. 85, no. (2002), p. 61-70
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- Description: This study was undertaken to investigate the adaptation to long term waterlogging of semi-arid eucalyptus species. Long-term waterlogging of Eucalyptus victrix seedlings significantly increases seedling stem diameter. Flooding reduces photosynthesis, transpiration and stomatal conductance. Flooding does not increase shoot fresh or dry weight of 4-, 8- or 17- week old seedlings. Leaf emergence may be stimulated for flooded seedlings compared with unflooded seedlings. Root dry weight is not significantly greater for 17- week old flooded plants than 13- week old seedlings. We suggest that maintenance of a high root/shoot ratio is a drought adaptation. Furthermore, a comparative study of flood tolerance in semi-arid eucalypt species suggests that those species intolerant of flooding seldom express morphological adaptations and fail to recover from physiological damage. Flooding significantly reduced the transpiration rate and stomatal conduct of all three species. Diurnal transpiration, stomatal conductance and leaf water potential of E. terminalis and E. leucophloia were significantly different between treatment (flooding) and control seedlings.
- Description: C1
- Description: 2003000132