Postfire Demography of the Wet-Mallee Eucalyptus luehmanniana F Muell (Myrtaceae)

1991 ◽  
Vol 39 (5) ◽  
pp. 459 ◽  
Author(s):  
SJ Davies ◽  
PJ Myerscough
Keyword(s):  
Water Availability ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Seed Viability ◽  
Experimental Methods ◽  
Low Levels ◽  
Seed Fall ◽  
Experimental Plots ◽  
Mature Population ◽  
Growth And Reproduction

The post-fire demography of Eucalyptus luehmanniana, a wet-mallee eucalypt restricted to the Sydney region, was studied by descriptive and experimental methods. Patterns of growth and reproduction were related to time since the last fire for 15 populations burned from 2 to 24 years previously. After fire, mature individuals (clumps) resprout from subterranean lignotuberous buds producing numerous narrow stems. Resprouted clumps flower within 2-4 years and fruit within 5-6 years of the last fire. Fruits accumulate in the canopy with increasing time, up to at least 24 years since fire. Measurements from one reproductively mature population showed that there is a low level of seed-fall below the canopy (0.98 seeds m-2 day-1) in the absence of fire. Recruitment without fire appears unlikely due to a combination of factors: low seed viability (34.9%, s.e. = 5.3), low levels of field emergence, no soil-stored seed, and a high proportion (86.9%, s.e. = 3.4) of seed failing enclosed in capsules. Canopy-stored seed is released en masse following fire. Three factors potentially influencing the recruitment of E. luehmanniana seedlings, fire-related effects, water availability and protection of developing seedlings from animals, were investigated experimentally in the field. Seedling emergence was uniformly low (2.2-2.6%), and not significantly increased on burned plots, caged plots, or water-added plots alone. In one experiment, plots both burned and caged had significantly higher emergence. Mortality in all experimental plots was 100% within 6 months. Seedling recruitment of E. luehmanniana will not occur following all fires, and will depend on the coincidence of fire with suitable post-fire conditions.

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.

Influence of Canopy Removal by Burning or Clipping on Emergence of Eragrostis lehmanniana Seedlings

1991 ◽  
Vol 1 (1) ◽  
pp. 35 ◽  
Author(s):  
LB Sumrall ◽  
BA Roundy ◽  
JR Cox ◽  
VK Winkel
Keyword(s):  
Water Availability ◽  
Prescribed Burning ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Red Light ◽  
Warm Season ◽  
Desert Grassland ◽  
Soil Temperatures ◽  
Canopy Removal ◽  
Seeding Emergence

Abstract Eragrostis lehmmniana (Lehrnann lovegrass) is a warm-season bunchgrass native to South Africa which dominates many desert grassland sites in southern Arizona. To determine why fire results in high seedling recruitment of this species, we measured germination of seeds in the seedbank and field seedling emergence following 1) no treatment, 2) burning, 3) clipping and herbicide and 4) herbicide d y . Treatments were designed to compare the effects of initial fire heat treatment with those of canopy removal, as affecting seedbed temperatwe, light and water availability, on seedling emergence. Treatments were replicated over 2 years on a stand of Lehrnann lovegrass at the Santa Rita Experimental Range. Canopy removal, by either clipping or burning, increased seedling emergence in seedbank samples taken prior to summer rains and greatly increased field seeding emergence. High seedling emer- gence after canopy removal was not the result of greater seedbed water availability but probably the result of a greater range in diurnal soil temperatures and increases in red light reaching the seedbed, both of which stimulate germination. The ability of E. lehmanniana to persist after fire indicates that prescribed burning could be used to control associated woody plants and improve forage palat- ability of E. lehmanniana dominated grasslands.

Influence of Late-Season Herbicide Applications on Control, Fecundity, and Progeny Fitness of Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Biotypes from Arkansas

2012 ◽  
Vol 26 (4) ◽  
pp. 807-812 ◽  
Author(s):  
Prashant Jha ◽  
Jason K. Norsworthy
Keyword(s):  
Seed Weight ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Seed Viability ◽  
Palmer Amaranth ◽  
Late Season ◽  
Control Seed ◽  
Seedling Biomass ◽  
Lincoln County ◽  
100 Seed Weight

Experiments were conducted in 2008 and 2009 in Fayetteville, AR, to determine the influence of late-season herbicide applications on control, seed reduction, seed viability, and seedling fitness of two glyphosate-resistant (GR) Palmer amaranth biotypes, one from Mississippi County (MC) and the other from Lincoln County (LC) in Arkansas. Glyphosate (870 g ae ha−1), glufosinate (820 g ai ha−1), 2,4-D amine (1,060 g ae ha−1), dicamba (280 g ae ha−1), and pyrithiobac (70 g ai ha−1) were each applied at the first visible sign of inflorescence of GR Palmer amaranth plants. Glufosinate, 2,4-D, and dicamba provided 52 to 74% control of MC GR Palmer amaranth plants 28 d after treatment (DAT). The LC biotype was larger (94 cm tall) than the MC biotype was (64 cm tall) at application and was more difficult to control. Although control of GR Palmer amaranth was inadequate, late-season applications of glufosinate, 2,4-D, and dicamba reduced seed production of the LC biotype by 75 to 87% and production of the MC biotype by 94 to 95% compared with nontreated plants. Irrespective of biotypes, glufosinate, 2,4-D, and glyphosate reduced 100-seed weight by 22% compared with the nontreated control, and viability of seeds produced by treated plants was only 45 to 61% compared with 97% seed viability in nontreated plants. Glyphosate, glufosinate, 2,4-D, or dicamba reduced cumulative seedling emergence by an average of 84% compared with the nontreated check. Seedling biomass was four times greater for the LC than for the MC biotype, suggesting greater vigor and fitness for the LC progeny. This research demonstrates that a single, late-season (early inflorescence stage) application of glufosinate, 2,4-D, or dicamba could potentially reduce seedbank replenishment of GR Palmer amaranth. Additionally, reduction in seed weight, viability, and seedling recruitment would impair the success of GR Palmer amaranth progeny in the following season.

Seed-dispersal and seedling recruitment patterns by the last Neotropical megafaunal element in Amazonia, the tapir

2000 ◽  
Vol 16 (3) ◽  
pp. 369-385 ◽  
Author(s):  
José M. V. Fragoso ◽  
Jean M. Huffman
Keyword(s):  
Seedling Recruitment ◽  
Germination Rate ◽  
Seed Viability ◽  
Seed Rain ◽  
Dry Land ◽  
Forest Sites ◽  
Seed Dispersion ◽  
Tapirus Terrestris ◽  
Spatio Temporal ◽  
Seed Shadows

Tapirs (Tapiridae) are the last representatives of the Pleistocene megafauna of South and Central America. How they affect the ecology of plants was examined by studying the diversity, abundance, and condition of seeds defecated by the lowland tapir (Tapirus terrestris) in Amazonian Brazil. Additionally, the spatio-temporal pattern of the seed-rain and seed-shadows generated by tapirs was recorded. Three hundred and fifty-six tapir faeces were examined. Eleven per cent were found in water (n = 41), while 88% were located on dry land (n = 315). Of those found on dry land, 84% were located at sites that flood seasonally, while 14% of the total were encountered at forest sites that do not flood. In 127 faeces checked in the laboratory over 12 906 seeds of at least 39 species were found. Seed viability ranged from 65% for Maximiliana maripa to 98% for Enterolobium schomburgkii. Of nine seed species planted in the laboratory, seven germinated within 4 wk, with one species achieving an 89% germination rate. For many species recruitment to the seedling stage was also high under natural conditions, with 13 plant species occurring as seedlings in older faeces. Tapir generated seed-rain occurred throughout the year, with seeds defecated in all months. Two temporal patterns in species seed rain occurred: (1) contiguous monthly occurrence with peaks in abundance, and (2) discontinuous occurrence (time clumped) with small (a few months) to large (many months to more than a year) temporal gaps. The highest diversity of seeds appeared in April, at the end of the dry season. As the last of the Pleistocene megafauna of the region, tapirs may have particular importance as dispersers of large seeds and generators of unique seed dispersion patterns.

scholarly journals Seedling recruitment in subalpine grassland forbs: Predicting field regeneration behaviour from lab germination responses

Botany ◽  
2017 ◽  
Vol 95 (1) ◽  
pp. 73-88 ◽  
Author(s):  
Vigdis Vandvik ◽  
Reidar Elven ◽  
Joachim Töpper
Keyword(s):  
Predictive Power ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Selective Advantage ◽  
Dormancy Breaking ◽  
Bare Ground ◽  
Seasonal Timing ◽  
Moist Chilling ◽  
Germination Behaviour ◽  
Carry Over

Environmental cueing that restricts seed germination to times and places where mortality risk is relatively low may have considerable selective advantage. The predictive power of lab germination responses for field regeneration behaviour is rarely tested. We screened 11 alpine grassland forbs for germination behaviour predictive of microsite and seasonal selectivity, and seed carry-over across years. The predictions were tested in a field experiment. Germination in the lab ranged from 0.05% to 67.9%, and was affected by light (5 species), temperature (6 species), fluctuating temperatures (4 species), moist chilling prior to germination (cold-stratification) (6 species), and dormancy-breaking by means of gibberellic acid (8 species). Seedling emergence in the field varied from 0.1% to 14.1%, and increased in low-competition microsites (bare-ground gaps and cut vegetation; 7 species), and showed seasonal timing (1 species in autumn and 1 species in spring), and seed carry-over across years (7 species). Lab germination responses successfully predicted microsite selectivity in the field and to some extent seed carry-over across years but not seasonal timing of germination. Gap-detecting species were generally small-seeded, low-growing, and found in unproductive habitats. Larger-seeded species germinated in all of the microsites but experienced increased mortality in high-competition microsites. Seed carry-over across years was lower for alpine specialists than for more widely-distributed species.

Effects of disturbance and rabbit grazing on seedling recruitment of six mesic grassland species

1999 ◽  
Vol 9 (2) ◽  
pp. 145-156 ◽  
Author(s):  
Grant R. Edwards ◽  
Michael J. Crawley
Keyword(s):  
Seedling Recruitment ◽  
Plantago Lanceolata ◽  
Plant Cover ◽  
Seedling Emergence ◽  
Soil Disturbance ◽  
Seedling Mortality ◽  
Grassland Species ◽  
Rabbit Grazing ◽  
Plant Densities ◽  
Seed Sowing

AbstractSeeds of two grass (Arrhenatherum elatius and Festuca rubra), two herb (Plantago lanceolata and Rumex acetosa) and two legume (Lotus corniculatus and Trifolium repens) species were sown in summer 1995 at four densities (no seed, 1000, 10 000 and 50 000 seeds m−2) into an established rabbit-grazed grassland given factorial combinations of rabbit fencing (with and without fences) and soil disturbance (with and without cultivation). On plots where no seeds were sown, only the species with persistent seed banks (P. lanceolata, L. corniculatus and T. repens) showed enhanced seedling emergence in response to disturbance. In disturbed soil, seedling densities of all species increased with increasing density of sown seeds, the effects of which were still evident for plant cover 2 years after seed sowing. In undisturbed vegetation, A. elatius, F. rubra, P. lanceolata and R. acetosa showed increased seedling densities following seed sowing; but in each case, there was an upper asymptote to seedling recruitment, presumably due to microsite limitation. Rabbit grazing reduced seedling densities, with this reduction being more pronounced with disturbance than without. However, the effect of rabbit grazing did not persist for some species; seedling mortality of R. acetosa, P. lanceolata, L. corniculatus and T. repens was higher on plots without rabbit grazing, so that plant densities of these species in summer 1996 and plant cover in summer 1997 were greater on grazed plots. The results indicate interactions between soil disturbance, propagule availability and herbivory, rather than disturbance alone, will play an important role in controlling seedling recruitment and species habitat distributions in grasslands.

scholarly journals The value of trophic interactions for ecosystem function: dung beetle communities influence seed burial and seedling recruitment in tropical forests

2016 ◽  
Vol 283 (1844) ◽  
pp. 20161634 ◽  
Author(s):  
Hannah M. Griffiths ◽  
Richard D. Bardgett ◽  
Julio Louzada ◽  
Jos Barlow
Keyword(s):  
Tropical Forests ◽  
Seedling Recruitment ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Seedling Emergence ◽  
Negative Relationship ◽  
Dung Beetle ◽  
Burial Depth ◽  
Seed Burial ◽  
Emergence Success

Anthropogenic activities are causing species extinctions, raising concerns about the consequences of changing biological communities for ecosystem functioning. To address this, we investigated how dung beetle communities influence seed burial and seedling recruitment in the Brazilian Amazon. First, we conducted a burial and retrieval experiment using seed mimics. We found that dung beetle biomass had a stronger positive effect on the burial of large than small beads, suggesting that anthropogenic reductions in large-bodied beetles will have the greatest effect on the secondary dispersal of large-seeded plant species. Second, we established mesocosm experiments in which dung beetle communities buried Myrciaria dubia seeds to examine plant emergence and survival. Contrary to expectations, we found that beetle diversity and biomass negatively influenced seedling emergence, but positively affected the survival of seedlings that emerged. Finally, we conducted germination trials to establish the optimum burial depth of experimental seeds, revealing a negative relationship between burial depth and seedling emergence success. Our results provide novel evidence that seed burial by dung beetles may be detrimental for the emergence of some seed species. However, we also detected positive impacts of beetle activity on seedling recruitment, which are probably because of their influence on soil properties. Overall, this study provides new evidence that anthropogenic impacts on dung beetle communities could influence the structure of tropical forests; in particular, their capacity to regenerate and continue to provide valuable functions and services.

Secondary seed dormancy prolongs persistence of volunteer canola in western Canada

Weed Science ◽  
2003 ◽  
Vol 51 (6) ◽  
pp. 904-913 ◽  
Author(s):  
Robert H. Gulden ◽  
Steven J. Shirtliffe ◽  
A. Gordon Thomas
Keyword(s):  
Seed Dormancy ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Conventional Tillage ◽  
Western Canada ◽  
Tillage Systems ◽  
Spring Canola ◽  
Typical Summer ◽  
Different Soils

In western Canada, little is known about the seedbank ecology of volunteer canola. Therefore, integrated recommendations for the management of this weed are limited. In this study, we investigated the seedbank persistence and seedling recruitment of two spring canola genotype groups with different secondary seed dormancy potentials under contrasting tillage systems. The study was conducted at two locations with different soils in the Mixed Moist Grassland ecoregion of Saskatchewan. A single cohort seedbank was established in 1999 and was followed for 3 yr in successive wheat crops. In a separate laboratory study, the six canola genotypes examined were classified as those with high and those with medium potentials for the development of secondary seed dormancy (HD and MD, respectively). After one, two, and three winters, maximum persistence of 44, 1.4, and 0.2% of the original seedbank was observed among the treatments, respectively. In 2001, HD canola genotypes tended to exhibit 6- to 12-fold greater persistence than MD canola genotypes, indicating lower seedbank mortality in HD canola. Seedling recruitment of HD canola also was higher than MD canola when differences were observed between these genotype groups. Therefore, long-term seedbank persistence of canola can be reduced by growing genotypes with low inherent potential for the development of secondary seed dormancy. The proportion of persisting seeds tended to be higher under conventional tillage than under zero tillage because of lower seedbank mortality, but no clear distinction in seedbank persistence in terms of absolute time could be made between these two tillage systems. Volunteer canola seedling recruitment followed the pattern of a typical summer-annual weed, where seedling emergence was observed only during May and June.

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