Seedling recruitment of the exotic grass Andropogon gayanus (Poaceae) in northern Australia

2005 ◽  
Vol 53 (3) ◽  
pp. 243 ◽  
Author(s):  
Trish A. Flores ◽  
Samantha A. Setterfield ◽  
Michael M. Douglas
Keyword(s):  
Seed Production ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Perennial Grass ◽  
Effective Control ◽  
Northern Australia ◽  
Wet Season ◽  
Soil Cultivation ◽  
Andropogon Gayanus

Andropogon gayanus Kunth. (Gamba grass), a tall perennial grass from Africa, is invading savanna ecosystems in northern Australia. This study investigated A. gayanus recruitment to determine the habitats at risk of invasion and to provide recommendations for its management. A. gayanus is able to establish and spread into new areas because of its high seed production (averaging 70 000 seeds m–2) and ability to establish across a range of habitats: from open woodlands on relatively dry lateritic soils to the more closed forests on black soil of the floodplain margins. Seedling emergence occurred in the absence of soil cultivation, although soil cultivation did increase emergence in the wetter habitats (Melaleuca uplands and floodplain margins). Seedling survival was high in the savanna (~90%) but low in the wetter habitats owing to wet-season inundation. A seed longevity trial based on burying seed in the field and retrieving between 1 and 12 months after burial showed that less than 1% of seeds survived in the seedbank after 12 months. Effective control programs are needed immediately because of the vast area and range of habitats in northern Australia that could potentially be invaded by A. gayanus. Management that can limit site disturbance and seed production, and can incorporate follow-up control for one to two years, should be an important part of an A. gayanus control strategy.

Ecology of Nassella neesiana, Chilean needle grass, in pastures on the Northern Tablelands of New South Wales. II. Seedbank dynamics, seed germination, and seedling recruitment

2003 ◽  
Vol 54 (6) ◽  
pp. 621 ◽  
Author(s):  
M. R. Gardener ◽  
R. D. B. Whalley ◽  
B. M. Sindel
Keyword(s):  
Seed Production ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
New South ◽  
Seedling Emergence ◽  
New South Wales ◽  
Separate Experiment ◽  
Bare Ground ◽  
Total Percentage ◽  
South Wales

This is the second in a series of papers investigating the ecology of Nassella neesiana (Trin. & Rupr.) Barkworth (Chilean needle grass) in pastures on the Northern Tablelands of New South Wales. The reasons for its success as a pasture weed are discussed. Nassella neesiana has a large and persistent soil seedbank. After 3 years without seed input, the seedbank declined from 4676 to 1323 seeds/m2. When an exponential decay curve was fitted to the data it was predicted that the seedbank would reach 10 seeds/m2 after 12.4 years. When seed production was large in 1996, 41.6% of seeds produced were incorporated into the seedbank, whereas in 1995 and 1997 the smaller seed production was only sufficient to maintain seedbank numbers. Furthermore, it is likely that the seedbank numbers were underestimated because they did not include basal cleistogenes. In a separate experiment, basal cleistogenes were found to contribute a further 20% to the seedbank.A small proportion of the viable seeds in a natural seedbank emerged from bare ground over 2 years. Seedling survival was high, with 78% of those germinating from bare ground surviving for at least 20 months. Several experiments were designed to investigate the mechanisms of this germination and survival. It appears that the seeds of N. neesiana have an after-ripening requirement of between 3 months and 1 year for maximum germination. Lemma removal from seeds stored for 8 months increased germination from 49 to 82%. The rate of germination and the total percentage of seeds germinating also increased with time of burial in the ground. Of seeds that had been buried for 2 years, 90% germinated after laboratory incubation compared with 48% of seeds stored in the laboratory as controls. Depth of seed burial appears to affect seedling emergence and survival. A smaller number of seedlings emerged from 0–10 mm and they had lower survival than those from seed buried at 10–20 mm.

Ecological Studies of the Endangered Rutidosis Leptorrhynchoides .I. Seed Production, Soil Seed Bank Dynamics, Population Density and Their Effects on Recruitment

1995 ◽  
Vol 43 (1) ◽  
pp. 1 ◽  
Author(s):  
JW Morgan
Keyword(s):  
Population Density ◽  
Seed Production ◽  
Seed Bank ◽  
Seedling Recruitment ◽  
Fire Regime ◽  
Seedling Survival ◽  
Soil Seed Bank ◽  
Seedling Emergence ◽  
Seed Bank Dynamics ◽  
The Impact

The seasonal dynamics of the soil seed bank of Rutidosis leptorrhynchoides F.Muell. were studied by the seedling emergence technique. Seed longevity in soil was quantified in a seed burial and retrieval experiment. The importance of annual seed production to recruitment was also determined over a 2-year-period, as was the impact of conspecific neighbour density on seed production per inflorescence. Rutidosis leptorrhynchoides appears to form a transient seed bank with little capacity to store germinable seeds in the soil from year to year. No seedlings were observed in soil sampled after the autumn germination pulse and no viable seed was present in the soil within 16 weeks of burial. The rate of seed loss was similar when seed was buried under all intact grassland canopy and in 0.25m2 canopy gaps. It appears that most seeds simply rot in moist soil or are predated by soil invertebrates. Seedling recruitment was at least 15 times greater in plots where natural seed input occurred than where it was curtailed. Less than 10% of seed shed resulted in seedling emergence. It is suggested that recruitment in the large populations studied was limited by germination rather than by microsite availability for seedling survival. Population density had an impact on seed production with sparsely distributed individuals producing fewer seeds per inflorescence than plants from denser colonies, although there was much variation. Sparse plants produced significantly fewer seeds per inflorescence than hand crosspollinated heads suggesting reduced pollinator efficacy in these colonies relative to larger colonies where there was no such difference. Rutidosis leptorrhynchoides is dependent on the maintenance of the standing population for recruitment. Any factors that influence flowering and subsequent seed production will limit the ability of the species to regenerate. Over sufficient time, this could lead to the localised extinction of the species and may explain why R. leptorrhynchoides has failed to reappear in remnants where a suitable fire regime has been re-implemented after a period of management unfavourable to the survival, flowering and regeneration of this species.

scholarly journals Potential Role of Sequential Glufosinate and Foramsulfuron Applications for Management of Fescues (Festucaspp.) in Wild Blueberry

2017 ◽  
Vol 31 (1) ◽  
pp. 100-110 ◽  
Author(s):  
Scott N. White ◽  
Shanthanu Krishna Kumar
Keyword(s):  
Field Study ◽  
Seed Production ◽  
Potential Role ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Seed Viability ◽  
Early Spring ◽  
Seedling Mortality ◽  
Wild Blueberry

Sheep and hair fescue are perennial, tuft forming grasses that spread by seed and form dense sods in wild blueberry fields. These sods compete with the crop for resources and hinder harvest. Field and greenhouse studies were conducted in 2015 to evaluate 1) the effect of sequential glufosinate and foramsulfuron applications on suppression of fescues in the greenhouse and field, and 2) efficacy of glufosinate and foramsulfuron on fescue seedlings when applied at 2, 4, 6, and 8 wk after seedling emergence in the greenhouse. Glufosinate applications at 750 and 1,005 g ai ha−1followed by foramsulfuron application at 35 g ai ha−1reduced fescue leaf number and biomass relative to foramsulfuron application alone in the greenhouse. In the field study, fescue flowering tuft density, tuft inflorescence height, seed production, and seed viability were reduced by foramsulfuron alone, but there was a trend towards lower seed production and tuft height when fescues were treated with glufosinate at 1,005 g ha−1followed by foramsulfuron. Foramsulfuron caused low seedling mortality at all application timings evaluated, but glufosinate caused >90% mortality in seedlings when applied at 2, 4, 6, or 8 wk after seedling emergence. Our results suggest that sequential applications of these herbicides are less effective under field conditions relative to results obtained in the greenhouse, though burndown glufosinate applications may have a role in reducing fescue seedling recruitment. Additional research should be conducted to determine the effect of early spring and autumn glufosinate applications on fescue seedling recruitment and suppression of established fescue tufts with subsequent foramsulfuron applications.

Growth, seed production and effect of defoliation in an early flowering perennial grass, Alloteropsis semialata (Poaceae), on Cape York Peninsula, Australia

2001 ◽  
Vol 49 (6) ◽  
pp. 735 ◽  
Author(s):  
Gabriel M. Crowley ◽  
Stephen T. Garnett
Keyword(s):  
Plant Growth ◽  
Seed Production ◽  
Perennial Grass ◽  
Soil Surface ◽  
Plant Size ◽  
Perennial Grasses ◽  
Wet Season ◽  
Cape York ◽  
Seed Dynamics

Alloteropsis semialata (R.Br.) A.Hitchc. is one of the first perennial grasses in monsoonal Australia to produce seed at the start of the wet season. Patterns of growth and seed production and seed dynamics of Alloteropsis semialata were examined in this study, along with the effects of partial defoliation. Growth of Alloteropsis semialata tussocks started with the first pre-wet-season rains, and was then interrupted during a period with little rain. Growth ceased before the end of the wet season, indicating that factors other than moisture availability were limiting. Seeds of Alloteropsis semialata were germinable on production, but did not remain viable or persist on the soil surface through the dry season. Most seeds and young seedlings were harvested and no seedlings were recruited. Inflorescence production increased with plant size. Moderate defoliation in the early wet season had no impact on plant growth, but reduced inflorescence and seed production for at least 2 years. Absence of a seed bank and early wet-season flowering mean that Alloteropsis semialata is likely to be sensitive to long-term over-grazing.

Seed and seedling studies of three Trifolium subterraneum var. brachycalycinum lines, in a predominantly summer rainfall environment

1995 ◽  
Vol 35 (8) ◽  
pp. 1101
Author(s):  
GM Lodge
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Trifolium Subterraneum ◽  
Summer Rainfall ◽  
Sowing Time ◽  
Buried Seeds ◽  
Initial Seed ◽  
Total Seed

Field experiments were conducted in a predominantly summer rainfall environment to investigate burr burial, seed production, seed characteristics, seedling emergence and survival, and the effects of time of sowing on 3 Trifolium subterraneum var. brachycalycinum lines (cv. Clare and 2 local lines). Each line produced more surface than buried burrs; surface burrs were 59% (range 56-62%) of the total number of burrs recovered and produced 59% of the total seed number. Numbers of seeds per burr were similar for surface and buried burrs, however, buried seeds were 0.97 mg heavier (P<0.05) than surface seeds. Storage for 5 months at 25/60�C decreased hardseed content of surface seed by 50% and buried seed by 70%. Surface and buried seeds stored at 25/25�C for 3 months prior to sowing in trays had a total emergence of <10%, compared with 70% emergence for seeds stored at 25/60�C before sowing. These emergence differences reflected their levels of hardseededness. Numbers of seeds recovered from the soil were not significantly different among lines, declining from about 4200 seeds/m2 after initial seed set to 150 seeds/m2 by the following winter, a 97% decrease. Seed production in the second year increased seed reserves to about 8730 seeds/m2. With no further seed production, levels had declined by 93% in June 1990 and by 99% in May 1991. These data confirm the importance of annual seed production for persistence. Total seedling emergence in summer-autumn accounted for only 10% of the estimated seed production in each year. Seedling survival in summer-autumn 1988-89 was 92.7%, more than double the survival in 1989-90. The effect of sowing time on flowering was always significant, with time to first flower being highest (196 days) for the earliest sowing in March (P<0.05), progressively decreasing (P<0.05) to 108 days for the latest sowing in July. In March, April and May sowings, inflorescence numbers on the first day of flowering were similar at about 120/m2, but increased markedly (P<0.05) for sowing in June or July. However, for the March and July sowings, number of inflorescences at the 9 November 1990 count, were lowest (P<0.05). May or June sowings had the highest number of burrs and seeds (P<0.05), indicating that these may be the best sowing times for maximum seed production in these Trifolium subterraneum var. brachycalycinum lines.

Soil seals in tropical tall grass pastures of northern Australia

Soil Research ◽  
1979 ◽  
Vol 17 (3) ◽  
pp. 483 ◽  
Author(s):  
J Mott ◽  
BJ Bridge ◽  
W Arndt
Keyword(s):  
Surface Soil ◽  
Seedling Emergence ◽  
Perennial Grass ◽  
Soil Surface ◽  
Mechanical Impedance ◽  
Organic Carbon Content ◽  
Grass Cover ◽  
Northern Australia ◽  
Tall Grass ◽  
Pastoral Management

Stable bare degraded areas exist in the lightly grazed perennial grass understorey existing in the eucalypt woodlands of northern Australia. Examination of these areas showed large differences in infiltration which led to increased runoff from the bare sites. However, there was little difference in soil composition between grass-covered and degraded sites apart from a higher organic carbon content in surface soil under grass. Micromorphological examination showed that soil without grass cover had lost its original open structure in the surface layers, developing a surface seal. The surface soil of the bare sealed area was shown to slake readily under quick wetting in contrast to soil surface under grass cover which did not slake. Heavy grazing of the grass understorey destroyed grass clumps within two wet seasons. Once the clumps were killed the soil surface quickly collapsed to form sealed areas, with the same properties as those occurring in ungrazed sites. The persistence of the bare sealed areas is attributed to seed removal during runoff, high temperatures and low moisture content in the sealed layer, as well as mechanical impedance preventing seedling emergence. As re-establishment of native grasses is difficult in this region, care must be taken in pastoral management to prevent the formation of degraded sites, which may take many years to re-vegetate.

Modeling Population Dynamics of Kochia (Bassia scoparia) in Response to Diverse Weed Control Options

Weed Science ◽  
2019 ◽  
Vol 67 (1) ◽  
pp. 57-67 ◽  
Author(s):  
O. Adewale Osipitan ◽  
J. Anita Dille ◽  
Muthukumar V. Bagavathiannan ◽  
Stevan Z. Knezevic
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Weed Control ◽  
Seed Production ◽  
Seedling Recruitment ◽  
Control Strategies ◽  
Effective Control ◽  
Parameter Estimates ◽  
Herbicide Resistant

AbstractKochia [Bassia scoparia(L.) A. J. Scott] is a problematic weed species across the Great Plains, as it is spreading fast and has developed herbicide-resistant biotypes. It is imperative to understand key life-history stages that promote population expansion ofB. scopariaand control strategies that would provide effective control of these key stages, thereby reducing population growth. Diversifying weed control strategies has been widely recommended for the management of herbicide-resistant weeds. Therefore, the objectives of this study were to develop a simulation model to assess the population dynamics ofB. scopariaand to evaluate the effectiveness of diverse weed control strategies on long-term growth rates ofB. scopariapopulations. The model assumed the existence of a glyphosate-resistant (GR) biotype in theB. scopariapopulation, but at a very low proportion in a crop rotation that included glyphosate-tolerant corn (Zea maysL.) and soybean [Glycine max(L.) Merr.]. The parameter estimates used in the model were obtained from various ecological and management studies onB. scoparia. Model simulations indicated that seedling recruitment and survival to seed production were more important than seedbank persistence forB. scopariapopulation growth rate. Results showed that a diversified management program, including glyphosate, could provide excellent control ofB. scopariapopulations and potentially eliminate already evolved GRB. scopariabiotypes within a given location. The most successful scenario was a diverse control strategy that included one or two preplant tillage operations followed by preplant or PRE application of herbicides with residual activities and POST application of glyphosate; this strategy reduced seedling recruitment, survival, and seed production during the growing season, with tremendous negative impacts on long-term population growth and resistance risk inB. scoparia.

Ecological Studies of the Endangered Rutidosis leptorrhynchoides. II. Patterns of Seedling Emergence and Survival in a Native Grassland

1995 ◽  
Vol 43 (1) ◽  
pp. 13 ◽  
Author(s):  
JW Morgan
Keyword(s):  
Soil Moisture ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Moisture Stress ◽  
Seedling Mortality ◽  
Themeda Triandra ◽  
Established Plant ◽  
Survival And Growth ◽  
Growth Of Seedlings

The emergence, survival and growth of seedlings of the endangered Rutidosis leptorrhynchoides F.Muell. were followed in a Themeda triandra grassland during 1991 and 1992. The effect of summer irrigation on seedling survival was also investigated. Seedling emergence occurred in both years within 2 weeks of the 'autumn break' when soil moisture rose above 20%. Ninety percent of emergence was observed within 4 weeks of the onset of germination and 87% of seedlings were within 20 cm of an established plant. No emergence was observed after 8 weeks. Thirteen percent of the 1991 cohort survived for 14 months. Mortality of most seedlings (63%) was attributed to soil moisture stress in summer. Small seedlings (Ͱ4 3 leaves) were no more susceptible to drought than larger seedlings. Seventy two percent of the 1991 cohort produced four leaves before subsequently dying. In 1992, however, most early seedling mortality was amongst cotyledonary seedlings. No seedlings flowered in their first year. Above-ground growth was slow and by 14 months, 60% of surviving seedlings had seven or fewer live leaves. Irrigation in a year of below-average rainfall had no significant effect on the survival and growth of seedlings. This suggests that seedling recruitment is not restricted to climatically favourable years (i.e. is not episodic) but rather, is potentially on-going provided suitable microsites are available for seedling survival.

scholarly journals SEED DISPERSAL, SEEDBANK, SEEDLING SURVIVAL, AND INITIAL GROWTH OF THREE CAATINGA TREES

2020 ◽  
Vol 33 (4) ◽  
pp. 1007-1016
Author(s):  
IVONETE ALVES BAKKE ◽  
JOSÉ EVANALDO RANGEL DA SILVA ◽  
OLAF ANDREAS BAKKE ◽  
ANTONIO LUCINEUDO DE OLIVEIRA FREIRE
Keyword(s):  
Seed Dispersal ◽  
Rainy Season ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Tree Height ◽  
Initial Growth ◽  
Forest Density ◽  
Before And After ◽  
Viable Seeds

ABSTRACT Myracrodruon urundeuva, Handroanthus impetiginosus and Amburana cearensis are Caatinga tree species that produce valuable timber, but little is known about their ecology. The objective of this study was to evaluate the seed distribution of these species on the forest floor before and after seed dispersal; and seedling emergence, survival, and growth during the rainy season after dispersal of seeds. There were no remaining viable seeds of these species in the seedbank before seed dispersal. The average numbers of seeds after seed dispersal were 188 seed m-2 in a 30 m radius around M. urundeuva, 9 seed m-2 in a 10 m radius around H. impetiginosus, and 5 seed m-2 in a 20 m radius around A. cearensis. The distance of seed dispersal reached 30, 20, and 10 m for M. urundeuva, H. impetiginosus, and A. cearensis trees, respectively, due to differences in tree height, seed weight, forest density, and wind intensity. Seedling emergence was observed during 4 (M. urundeuva) and 9 (H. impetiginosus and A. cearensis) weeks. High mortality predominated at the beginning and end of the rainy season for M. urundeuva and A. cearensis, respectively, while practically all H. impetiginosus seedlings survived. M. urundeuva showed the highest mortality but had higher number of established seedlings than the other species. Seedling survival peaked around 5 m from the tree base. Seedling recruitment and natural regeneration of these trees are assured in the Caatinga site evaluated.

scholarly journals Fall-bearing Year Herbicides and Spring-nonbearing Year Foramsulfuron Applications for Hair Fescue Management in Lowbush Blueberry

2020 ◽  
Vol 30 (6) ◽  
pp. 670-676
Author(s):  
Scott Neil White ◽  
Linshan Zhang
Keyword(s):  
Seed Production ◽  
Seedling Recruitment ◽  
Block Design ◽  
Perennial Grass ◽  
Interactive Effects ◽  
Production Cycle ◽  
Seedling Density ◽  
Vaccinium Angustifolium ◽  
Lowbush Blueberry ◽  
Randomized Complete Block Design

Hair fescue (Festuca filiformis) is a tuft-forming perennial grass that reduces yields in lowbush blueberry (Vaccinium angustifolium) fields. Nonbearing year foramsulfuron applications suppress hair fescue, but there is interest in increasing suppression through foramsulfuron use in conjunction with fall-applied herbicides. The objective of this research was to determine the main and interactive effects of fall-bearing year herbicide applications and spring-nonbearing year foramsulfuron applications on hair fescue. The experiment was a 5 × 2 factorial arrangement of fall-bearing year herbicide (none, terbacil, pronamide, glufosinate, dichlobenil) and spring-nonbearing year foramsulfuron application (0, 35 g·ha−1) arranged in a randomized complete block design at lowbush blueberry fields in Portapique and Stewiacke, Nova Scotia, Canada. Spring-nonbearing year foramsulfuron applications did not reduce total tuft density or consistently reduce flowering tuft density, flowering tuft inflorescence number, or flowering tuft seed production. Fall-bearing year pronamide applications reduced hair fescue density for the 2-year production cycle, although additional bearing year density reductions occurred when pronamide was followed by spring-nonbearing year foramsulfuron applications at Stewiacke. Fall-bearing year dichlobenil applications reduced total and flowering tuft density at each site, although reductions in flowering tuft inflorescence number and seed production were most consistent when followed by spring-nonbearing year foramsulfuron applications at Stewiacke. Suppression extended into the bearing year at each site, and dichlobenil should be examined further for hair fescue control. Fall-bearing year glufosinate applications reduced hair fescue total tuft density at each site and flowering tuft density and flowering tuft seed production at Stewiacke. Fall-bearing year glufosinate applications followed by spring-nonbearing year foramsulfuron applications also reduced nonbearing year flowering tuft inflorescence number and bearing year hair fescue seedling density at Stewiacke, indicating that this treatment may reduce hair fescue seedling recruitment at some sites. Fall-bearing year terbacil applications did not suppress hair fescue and are not recommended for hair fescue management in lowbush blueberry.

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