The effect of stocking rate on the population dynamics of siratro in siratro (Macroptilium atropurpureum)-setaria (Setaria sphacelata) pastures in south-east Queensland. II. Seed set, soil seed reserves, seedling recruitment and seedling survival

1988 ◽  
Vol 39 (2) ◽  
pp. 221 ◽  
Author(s):  
RM Jones ◽  
GA Bunch
Keyword(s):  
Seed Set ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Stocking Rate ◽  
Seedling Regeneration ◽  
Pasture Legumes ◽  
Setaria Sphacelata ◽  
Seed Reserves ◽  
Cattle Faeces

Measurements were made of the seed set, seed content in cattle faeces, soil seed reserves, seedling regeneration and seedling survival of Siratro (Macroptilurn atropurpureum) in south-east Queensland. Measurements were made from 1972 to 1985 in pastures of Siratro/setaria (Setaria sphacelata) sown in 1968 and stocked at 1.1, 1.7 and 2.3 and at 3.0 (1969-1973) reduced to 2.0 (1974-1985) heifers ha-1. Siratro seed set and seedling demography were markedly affected by stocking rate. At the highest stocking rate, Siratro yields were low and seed input ceased after 1972, yet appreciable seedling recruitment from the soil seed bank was maintained for a further 10 years. At the lightest stocking rate (1.1 heifers ha-1), seed set and soil seed reserves were highest, but seedling recruitment was of little importance as almost all seedlings died. Seedling recruitment and survival were best at an intermediate stocking rate (1.7 heifers ha-1), where they were the key to long-term persistence of Siratro. Soil seed reserves of Siratro ranged from 500 m-2 under light stocking to < 100 m-2 after several years of heavy stocking. Very little seed was recovered in cattle faeces. Likely factors responsible for seedling death (light, water, nutrients, grazing, frosting and insect damage) are discussed. The limitations of seed set and seedling regeneration in the persistence of Siratro are contrasted with some other perennial pasture legumes. Studies of this type can help in qualitatively predicting long-term persistence of pasture legumes under different conditions of management and climate.

Levels of germinable seed in topsoil and cattle faeces in legume-grass and nitrogen-fertilized pastures in south-east Queensland

1991 ◽  
Vol 42 (6) ◽  
pp. 953 ◽  
Author(s):  
RM Jones ◽  
M Noguchi ◽  
GA Bunch
Keyword(s):  
Perennial Grasses ◽  
Stocking Rate ◽  
Heavy Grazing ◽  
Seed Content ◽  
Setaria Sphacelata ◽  
Seed Reserves ◽  
Cattle Faeces ◽  
Autumn And Winter ◽  
Stocking Rates ◽  
Germinable Seed

Measurements were made of germinable seed of all species in the top 5 cm of soil beneath 9 paddocks in an 11-year-old pasture experiment in south-east Queensland. The experiment comprised two pasture types grazed by cattle: legume-grass (Macroptilium atropurpureum- Setaria sphacelata) pastures grazed at four stocking rates and nitrogen fertilized S. sphacelata pastures grazed at five stocking rates. Levels of germinable seed in the soil varied with pasture type and stocking rate and ranged from 6760 to 45480 seeds/m2. Seed reserves increased on the legume-grass pastures as stocking rate increased. Fifty-seven different plant species were identified from the seedlings grown from the soil seed reserve. For 11 of these species, which contributed 70% of the seed reserves, there were significant trends in relation to pasture type and/or stocking rate. The only species where seed reserves significantly decreased with increasing stocking rate were the two sown species. Cattle faeces were also collected from lightly and heavily stocked legume-grass and nitrogen-fertilized pastures in spring, summer, autumn and winter. Germinable seed contents of all species were measured. Seed content of faeces was higher in the summer and autumn than in the winter and spring samplings, and in the heavily stocked than in the lightly stocked pastures. The highest content recorded was 20.5 germinable seeds g-1 faecal dry matter. The species with the highest germinable seed content in faeces were Digitaria didactyla, Axonopus affinis and Eleusine indica, the latter being restricted to nitrogen-fertilized pastures. Seed dissemination in faeces is a factor contributing to the invasiveness of prostrate perennial grasses such as D. didactyla and A. affinis under heavy grazing.

Effect of companion perennial grasses and lucerne on seed yield and regeneration of subterranean clover in two wheatbelt environments

2001 ◽  
Vol 52 (10) ◽  
pp. 973 ◽  
Author(s):  
B. S. Dear ◽  
J. M. Virgona ◽  
G. A. Sandral ◽  
A. D. Swan ◽  
B. A. Orchard
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Seed Bank ◽  
Seed Set ◽  
Subterranean Clover ◽  
Seedling Regeneration ◽  
Early Autumn ◽  
Background Population ◽  
Seed Reserves ◽  
Clover Seed

Seed production of subterranean clover (Trifolium subterraneum L.) in mixtures with lovegrass (Eragrostis curvula (Schrader) Nees cv. Consol), cocksfoot (Dactylis glomerata L. cv. Currie), phalaris (Phalaris aquatica L. cv. Sirolan), danthonia (Austrodanthonia richardsonii (Cashm.) H.P. Linder, cv. Taranna), and lucerne (Medicago sativa L. cv. Aquarius) was compared with pure and degraded (invaded by annual volunteers) annual subterranean clover pasture at 2 sites (Junee and Kamarah) in the southern wheatbelt of New South Wales. Seed yields, clover seedlings in winter, and the change in the proportion of 3 subterranean clover cultivars (Dalkeith, Seaton Park, Goulburn) when grown with and without perennials were assessed. The effect of thinning the perennials to 10 plants/m2 on clover seed set was examined at the drier site. Seed production of subterranean clover in the mixtures was depressed by up to 50% compared with the pure and degraded annual swards. Initial clover seed poduction in the mixtures was at least 60 kg/ha even in the drought year at the wetter site (Junee), and >85 kg/ha at Kamarah, the drier site (seedling establishment at Kamarah failed in the drought year). Clover seed reserves in the following 2 years progressively increased to >300 kg/ha in the perennial swards at Junee but were <100 kg/ha by the end of the third year at Kamarah. In comparison, seed reserves in the pure clover and degraded annual swards were >650 kg/ha at Junee and >350 kg/ha at Kamarah. Reducing perennial density to 10 plants/m2 at the drier site increased clover seed yield about 3-fold in the first year compared with unthinned perennial swards. The increased seed yield was due to increased numbers of burrs set and increased seeds per burr and, in all perennial pasture treatments except lucerne, increased seed size. Clover seedling regeneration in 3rd and 4th year after sowing was substantially lower in the perennial-based mixtures than annual plots, with a significant (P < 0.05) positive correlation at both sites between clover seedling regeneration and seed bank size (1996, r2 = 0.46–0.64; 1997, r2 = 0.64–0.85). Following false breaks in early autumn, clover seedling populations were substantially higher in the pure and degraded clover treatments than in most perennial treatments. The proportion of the 3 cultivars present in the seed bank at the end of the pasture phase differed between sites but the sward type only influenced the proportion at the drier site. At the medium rainfall site, the later maturing cultivar Goulburn constituted 27–54% of the seed bank and the early flowering Dalkeith 25–46%, with unsown cultivars being insignificant ( <1%). At the low rainfall site, Dalkeith was the major component (33–52%) of the seed bank but the background population of unsown cultivars constituted 11–48%, the lowest proportion being in swards without a perennial component. The proportion of Goulburn was highest (23%) in the pure sward and lowest (10%) in lucerne and phalaris. It was concluded that subterranean clover could form relatively stable mixtures with perennials in medium rainfall environments, with clover populations increasing with time. In lower rainfall environments, clover seedling populations in perennial swards may be low due to reduced seed set and decreased seedling survival following early autumn rains. In these environments earlier maturing, hard-seeded cultivars are more likely to persist in mixtures and there is more potential for unsown cultivars to constitute a greater proportion of the sward. Decreasing perennial density offers scope for improving clover seed set and survival in these environments.

Effect of stocking rate and grazing frequency on a Siratro (Macroptilium atropurpureum)/Setaria anceps cv. Nandi pasture

1979 ◽  
Vol 19 (98) ◽  
pp. 318 ◽  
Author(s):  
RM Jones
Keyword(s):  
Total Yield ◽  
Rest Period ◽  
Residual Effect ◽  
Stocking Rate ◽  
Animal Performance ◽  
Good Recovery ◽  
Seedling Regeneration ◽  
Seed Reserves ◽  
Macroptilium Atropurpureum ◽  
Stocking Rates

Five stocking rates, ranging from 0.8 to 2.8 beasts ha-1, and three frequencies of grazing were imposed on a five-year-old Siratro (Macroptilium atropurpureum)/Setaria anceps cv. Nandi pasture at Samford, south-east Queensland. The three grazing frequencies involved grazing for four days every three, six or nine weeks. Plots were individually grazed from 1972 to 1976 and the residual effect of treatments was measured over a grazing-free period in 1977. Within the three week grazing frequency both Siratro yield and total yield declined markedly with increased stocking rate, with an increased invasion of prostrate species such as blue couch (Digitaria didactyla). The decline in Siratro yield at higher stocking rates was less marked in the nine week system where there was much less invasion of prostrate species. However, it is suggested that the value of rotational grazing with a long rest period as a means of maintaining Siratro productivity could be largely at stocking rates where the pasture is overgrazed in terms of animal performance. Siratro density and seedling regeneration were largely unaffected by treatment and there was a good recovery of Siratro in the heavily grazed treatments during the grazing-free period at the end of the experiment. However, Siratro soil seed reserves declined with increased stocking rate and there was a much greater decline in flowering and seeding. On this basis it is predicted that if grazing treatments had been continued the heavily grazed pastures would eventually have reached the stage where Siratro would not recover with spelling.

Comparison of the performance of subterranean clover cultivars in southern New South Wales. 2. Effects of Phytophthora clandestina and bromoxynil on seedling survival, growth, and seed set

1993 ◽  
Vol 33 (5) ◽  
pp. 591 ◽  
Author(s):  
BS Dear ◽  
GM Murray ◽  
PD Cregan ◽  
PA Taylor
Keyword(s):  
Seed Set ◽  
Seedling Survival ◽  
Severe Disease ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Leaf Damage ◽  
Wagga Wagga ◽  
Herbicide Application ◽  
South Wales

Effects of the root disease caused by Phytophthora claiidestina were assessed at Wagga Wagga on 14 cultivars of subterranean clover (Trifolium subterraneum) following application of the herbicide bromoxynil. Seedling death over autumn-winter ranged from 22% in Trikkala, the most resistant cultivar, to 96% in Woogenellup, the most susceptible. Compared with previous years (1984-85), herbage yields and seed set of the most susceptible cultivars were depressed. Cultivars with the most severe disease symptoms (Woogenellup, Nungarin, Northam) did not set seed. Later maturing cultivars (Karridale, Enfield) appeared to recover from the disease and set more seed than earlier maturing cultivars (Dalkeith, Daliak) with similar reactions to P. clandestina. Field susceptibility (determined by leaf damage scores, seedling losses, and dry matter yield depression) was similar to glasshouse phytophthora ratings for most cultivars; however, Trikkala, Karridale, and Enfield were more affected in the field following herbicide application than expected from the glasshouse reaction. Trikkala, Junee, and Dalkeith were the cultivars most tolerant in the field to root rot, while Woogenellup, Northam, and Nungarin were the most severely affected. Leaf damage following herbicide application was greatest in cultivars showing the most severe root lesions and having the highest susceptibility to P. clandestina in a glasshouse test. P. clandestina reduced the productivity of susceptible subterranean clover cultivars and has the potential to reduce long-term persistence by reducing seed set.

Persistence and growth of Lotononis bainesii–Digitaria decumbens pastures: 2. Sheep treading

1983 ◽  
Vol 101 (1) ◽  
pp. 9-15 ◽  
Author(s):  
A. Pott ◽  
L. R. Humphreys ◽  
J. W. Hales
Keyword(s):  
Seedling Survival ◽  
Late Summer ◽  
Management Systems ◽  
Sheep Grazing ◽  
Seedling Regeneration ◽  
Nodal Roots ◽  
Digitaria Decumbens ◽  
Cotton South ◽  
Seed Reserves ◽  
The Creation

SUMMARYA pasture of Lotononis bainesii and Digitaria decumbens cv. Pangola at Mt Cotton, south-east Queensland was mown on six occasions at intervals of ca. 3 months and after each mowing was subjected in 1 day to the treading intensity expected from sheep grazing at 0, 7, 14, 21 and 28/ha. A movable corridor and folds were employed to walk the sheep the required number of times on eight replicates of each treatment.Lotononis regrowth was negatively related to sheep treading intensity, whereas Pangola was highly resistant to treading and grew vigorously from underground buds on rhizomes and from persisting stolons. Young lotononis seedlings were more vulnerable than older seedlings which had branched; plants developed from autonomous nodal roots were more resistant than seedlings. Attention is drawn to the contractile growth of the hypocotyl following epigeal germination which leads to a buried crown.Lotononis plants were short-lived, and seedling regeneration of ca. 27 and 47 plants/m2 occurred in the late summer of the 2nd and 3rd year after sowing. Soil seed reserves averaged 16900/m2. Studies might be undertaken of management systems directed to favouring lotononis plant replacement through accretion to seed reserves, seedling regeneration through the creation of ‘gaps’, and seedling survival through judicious timing of grazing.

Tropical tree seedling dynamics: recruitment patterns and their population consequences for three canopy species in Panama

1994 ◽  
Vol 10 (3) ◽  
pp. 369-383 ◽  
Author(s):  
Diane de Steven
Keyword(s):  
Growth Rates ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Plant Size ◽  
Fruit Production ◽  
Barro Colorado Island ◽  
Maximum Height ◽  
Tree Seedling ◽  
Average Growth

ABSTRACTA study of seedling demography of three shade-tolerant canopy tree species (Quararibea asterolepis, Trichilia tuberculata, and Tetragastris panamensis) was initiated to integrate with long-term studies of tree fruit production and of tree population dynamics on Barro Colorado Island, Panama. Over a five-year period, all seedlings (height <50 cm) and small saplings (height ≥50 cm to dbh 1 cm) were measured and monitored in permanent tree-centred transects (N = 10–11 trees per species). Survival rates increased with plant size class and were similar among species. Maximum height growth rates increased with increasing plant size, but average growth rates did not; this disparity suggests the importance of release from understorey suppression for long-term recruitment success. Among the three species, Quararibea had the lowest standing seedling densities and almost no sapling recruitment, whereas Tetragastris had the highest densities of both seedlings and saplings; Trichilia seedling and sapling densities were intermediate. In all three species, a few trees produced very high seedling and sapling densities in comparison with the sample average. All three species exhibited a year of exceptionally high new seedling recruitment during the study period; these good years were not coincident among the species but instead reflected the species' phenological differences. Since seedling survival becomes relatively constant and high after the first few years of life (c. 80% y−1), such large new cohorts persist as a year-class effect in the seedling population and thus maintain seedling numbers over time. The interspecific differences in seedling and sapling dynamics were consistent with overall 10-year trends of a declining Quararibea population, a stable Trichilia population, and an increasing Tetragastris population.

Plant mortality and seedling recruitment responses to flupropanate in grassland populations of Nassella trichotoma

2017 ◽  
Vol 70 ◽  
pp. 160-164 ◽  
Author(s):  
G.W. Bourdôt ◽  
S. Jackman ◽  
D.J. Saville
Keyword(s):  
New Zealand ◽  
Dose Response ◽  
Sodium Salt ◽  
Seedling Recruitment ◽  
Residual Activity ◽  
Application Rate ◽  
Plant Mortality ◽  
Complete Control ◽  
Bio Synthesis

Flupropanate (sodium 2,2,3,3 tetrafluoropropanate), a slow-acting lipid bio- synthesis-inhibiting herbicide, was recently registered in New Zealand as Taskforce (745 g/L flupropanate as the sodium salt) for the selective and long-term control of Nassella trichotoma (nassella tussock) in pastures. In five dose-response experiments in permanent hill pastures in Canterbury, conducted between 2012 and 2016, we measured the efficacy of the herbicide against established plants of N. trichotoma and its residual activity against recruiting seedlings. Mortality, as an average across the five sites, was 93% 1.5 years after applying 1.49 kg flupropanate/ha (the label-recommended rate), and 100% at 2.98 kg/ha. This indicates that an application rate higher than the label rate will be necessary for complete control of a N. trichotoma infestation. The presence of 1,000 and 6,250 visible seedlings of N. trichotoma/ha in the autumn 3.2 and 2.1 years after applying 1.49 kg flupropanate/ha (at a Greta Valley and Scargill site respectively) indicates that the herbicide’s soil residues had decayed within 12 months to a concentration lower than necessary to kill the germinating seedlings of N. trichotoma.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

Persistence and growth of Lotononis bainesii–Digitaria decumbens pastures: 1. Sheep stocking rate

1983 ◽  
Vol 101 (1) ◽  
pp. 1-7 ◽  
Author(s):  
A. Pott ◽  
L. R. Humphreys
Keyword(s):  
Bulk Density ◽  
Soil Bulk Density ◽  
Grazing Pressure ◽  
Stocking Rate ◽  
Digitaria Decumbens ◽  
Heavy Grazing ◽  
Cotton South ◽  
Seed Reserves ◽  
Stocking Rates

SUMMARYSheep were grazed for 2 years at stocking rates of 7, 14, 21 and 28/ha on a pasture comprising Lotononis bainesii and Digitaria decumbens cv. Pangola at Mt Cotton, south–east Queensland. There were six replicates of each treatment grazed in rotation with 3 days' grazing followed by 15 days' rest.The initial dominance of lotononis was lost after 6 months of grazing and lotononis failed to persist satisfactorily at any stocking rate. Demographic studies showed that lotononis behaved as a short-lived plant, predominantly annual, with some vegetative perennation as stolon-rooted units under heavy grazing. Soil seed reserves varied from 5800 to 400 m2 at the lightest and heaviest stocking rates respectively. Lotononis failed to regenerate under Pangola shading or inopportune high grazing pressure. Soil bulk density (0–7 cm) increased from 1·2 to 1·4 g/cm3 according to stocking rate.

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