Nitrogen interactions with medusahead (Taeniatherum caput-medusaessp.asperum) seedbanks

Weed Science ◽  
1998 ◽  
Vol 46 (2) ◽  
pp. 191-195 ◽  
Author(s):  
James A. Young ◽  
James D. Trent ◽  
Robert R. Blank ◽  
Debra E. Palmquist
Keyword(s):  
Seedling Establishment ◽  
Surface Soil ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Nitrogen Enrichment ◽  
Land Productivity ◽  
Nitrogen Levels ◽  
Field Samples ◽  
Low Nitrogen

Medusahead is an invasive annual grass that, once established, severely affects range-land productivity and stability. Medusahead builds large seedbanks in the litter and on the soil surface. Effective weed control of medusahead involves either inhibiting germination from the seedbank, eliminating the seedbank, or enhancing germination so that plants are available for control. The purpose of this study was to determine the influence of nitrogen enrichment, immobilization, and nitrification inhibition treatments in the field on the size and germination status of medusahead seedbanks. The germination status of medusahead seeds in seedbanks was determined by periodically collecting field samples of surface soil and litter and bioassaying them in greenhouse emergence tests. Control seedbanks had increased seedling emergence with KNO3or GA3enrichment of the bioassay substrate. The combination of these two materials increased emergence. Nitrogen enrichment increased seedling establishment in the field. Carbon enrichment in the field decreased seedling establishment and increased medusahead seeds in seedbanks. Nitrapyrin treatment decreased medusahead in the field similar to carbon enrichment. In comparison to the control or other treatments, GA3enrichment was not as effective in increasing emergence from nitrapyrin-treated bioassay samples. The combination of carbon and nitrapyrin treatments was very effective in eliminating medusahead emergence in the field, but in wetter years, it never completely eliminated medusahead seedling recruitment and subsequent reproduction. These treatments have promise for influencing succession in medusahead infestations if an adapted perennial species, capable of competing under low nitrogen levels, becomes available.

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.

The effects of passage through the gut of goats and cattle, and the application of dung as a fertiliser on seedling establishment of Dichrostachys cinerea and Acacia nilotica

2015 ◽  
Vol 37 (2) ◽  
pp. 147 ◽  
Author(s):  
T. J. Tjelele ◽  
D. Ward ◽  
L. E. Dziba
Keyword(s):  
Seedling Establishment ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Recovery Period ◽  
Recruitment Rate ◽  
Acacia Nilotica ◽  
Dichrostachys Cinerea ◽  
Dry Seasons ◽  
And Control ◽  
Wet And Dry Seasons

Seed pods of Dichrostachys cinerea and Acacia nilotica have higher nutritive value than grasses and other browse plants during the dry season and form an important part of the diet of livestock. Seeds of Acacia may be destroyed during passage through the digestive tract of herbivores whereas seeds of other browse species can remain viable even after mechanical (chewing) and chemical (digestive) scarification. The seedling emergence, seedling establishment and recruitment of D. cinerea and A. nilotica seeds, dispersed by cattle and goats, were measured under natural conditions in the wet and dry seasons following sowing in the dry season. Seeds retrieved from goats and cattle, during the first 3 days and the last 4 days of the recovery period, and control seeds were subjected to the following planting methods: (1) seeds placed on top of the soil with no dung, (2) seeds buried to a depth of 2 cm in the soil with no dung, and (3) seeds buried to a depth of 2 cm in the soil with dung, in the wet and dry seasons. Significantly more A. nilotica and D. cinerea seeds were retrieved from cattle (40.0 ± 3.6% and 25.7 ± 3.9%, respectively), than goats (11.7 ± 3.1% and 13.2 ± 3.8%, respectively). There were significant interactions among animal species, seed-recovery day, planting and season for percentage seedling recruitment. Seedlings from seeds retrieved from goats (12.0 ± 0.06%) had a significantly higher recruitment rate than from seeds retrieved from cattle (7.6 ± 0.05%) and control seeds (i.e. no passage through the gut) (4.1 ± 0.02%). Seedling recruitment rate was higher from seeds recovered from animals in the last 4 days of the recovery period and from D. cinerea than A. nilotica. The planting method of seeds buried to a depth of 2 cm in the soil with no dung had the highest seedling recruitment rate. We conclude that both goats and cattle may facilitate woody plant encroachment by enhancing seedling emergence.

Patterns of willow seed dispersal, seed entrapment, and seedling establishment in a heavily browsed montane riparian ecosystem

2005 ◽  
Vol 83 (6) ◽  
pp. 678-687 ◽  
Author(s):  
Edward A Gage ◽  
David J Cooper
Keyword(s):  
Seed Dispersal ◽  
Spatial Patterns ◽  
Cervus Elaphus ◽  
Seedling Establishment ◽  
Surface Relief ◽  
Seedling Emergence ◽  
Rocky Mountain ◽  
Soil Surface ◽  
Seed Rain ◽  
Seed Sources

Declines in riparian willow (Salix spp.) communities in Rocky Mountain National Park, Colorado, USA , coincident with a large increase in elk (Cervus elaphus L.) populations, has raised concerns about the future of willow communities. To identify possible constraints on willow establishment in two heavily browsed riparian areas, in 2000 and 2001, we examined seed dispersal phenology, germinability, and the spatial patterns of aerial seed rain, quantified the effects of soil surface relief, texture, and moisture on seed entrapment, and examined natural patterns of seedling emergence in relation to seed source proximity. All species dispersed seeds following peak streamflow and exhibited high germination rates (85%–99%). Total seed rain differed between years, although broad spatial patterns were similar. Seed rain density as high as 7650 seeds/m2 occurred in reference areas but declined by over two orders of magnitude in heavily disturbed areas and by >90% within 200 m of seed sources. Seed entrapment rates varied significantly with soil moisture and surface relief, but not with texture, and were low (<30%) regardless of treatment. Seedling density declined with distance from seed sources, suggesting that propagule availability may limit initial seedling establishment. Without a change in elk population or behavior, or intervention by park managers, degradation of willow communities will likely continue.Key words: Salix, riparian, dispersal, ungulates, elk.

Factors Affecting Seed Germination of Perennial Wall Rocket (Diplotaxis tenuifolia) in Southern Australia

Weed Science ◽  
2007 ◽  
Vol 55 (5) ◽  
pp. 481-485 ◽  
Author(s):  
Samuel G. L. Kleemann ◽  
Bhagirath S. Chauhan ◽  
Gurjeet S. Gill
Keyword(s):  
Osmotic Potential ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
South Australia ◽  
Soil Surface ◽  
Burial Depth ◽  
Optimal Conditions ◽  
Factors Affecting ◽  
Depth Of Burial ◽  
Osmotic Potentials

Germination response of perennial wall rocket to temperature, light, osmotic potential, and depth of burial emergence was evaluated under controlled environmental conditions. The effect of seed burial depth on seedling recruitment in the field was also investigated at Roseworthy, South Australia. Under optimal conditions (30 C, light/dark) germination of perennial wall rocket was rapid, with 90% of seeds germinating within 48 h of imbibition. Germination was reduced (20%) at lower, suboptimal temperatures (10 to 20 C) when seeds of perennial wall rocket were exposed to light. Germination declined with increasing osmotic potential and was completely inhibited at osmotic potentials of −1.5 MPa. Perennial wall rocket emergence was greatest from seeds placed on the soil surface, but some seedlings (< 10%) emerged from a depth of 0.5 to 2 cm. Under both field and growth-cabinet conditions, the greatest seedling emergence of perennial wall rocket occurred from seed present on the soil surface; however, the level of absolute recruitment from the seed bank was much lower (< 5%). Information gained from this study will further improve our understanding of the germination behavior of perennial wall rocket and contribute to developing sustainable strategies for its control.

Seed Germination and Seedling Recruitment Behavior of Winged Sea Lavender (Limonium lobatum) in Southern Australia

Weed Science ◽  
2018 ◽  
Vol 66 (4) ◽  
pp. 485-493 ◽  
Author(s):  
Samuel G. L. Kleemann ◽  
Gurjeet Gill
Keyword(s):  
Seed Germination ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Base Temperature ◽  
Weed Species ◽  
Factors Affecting ◽  
Weed Seeds ◽  
Sea Lavender ◽  
C 50

AbstractWinged sea lavender [Limonium lobatum(L.f. Chaz)] is emerging as a significant weed of field crops in southern Australia. Several environmental factors affecting germination and seedling recruitment were examined to provide a better understanding of the behavior of its seedbank. At maturity, weed seeds were dormant for a period of around 2 mo, but dormancy was easily broken with scarification or by pretreatment with 564 mM NaOCL for 30 min, which confirms the role of the seed coat in regulating seed germination. Exposure to light significantly increased germination. Seeds were able to germinate over a broad range of temperatures (5 to 30 C), with maximum germination (~92%) at temperatures between 10 and 30 C. At 20 to 25 C, 50% germination was reached within 1.3 to 2 d, and the predicted base temperature for germination of the two populations ranged from 1.4 to 3.9 C. The NaCl concentration required to inhibit germination by 50% was 230 mM, with some seeds capable of germination at salinity levels as high as 480 mM. These results indicated greater tolerance to salinity inL. lobatumthan many other Australian agricultural weed species previously investigated. Seedling emergence was the highest (51% to 57%) for seeds present on the soil surface and was significantly reduced by burial at 1 cm (≤11%) and 2 cm (≤2%), with no emergence at 5 cm. Under field conditions, seedling recruitment varied considerably among the three experimental sites. The level of seedling recruitment was negatively associated with rainfall received at the site, organic carbon (OC) level, and microbial biomass of the soil. Rapid decay of weed seeds in high-OC soils appears to be an important determinant of seedling recruitment in this species and could explain greater occurrence ofL. lobatumon soils with low OC and low microbial activity in low-rainfall areas of southern Australia. Furthermore, many such soils in southern Australia are affected by salinity, which would enableL. lobatumto be more competitive with crops and other weeds present at a site.

Biology and control of Reseda lutea L. 2. Life cycle: seedling emergence, recruitment, and vegetative reproduction

1997 ◽  
Vol 48 (4) ◽  
pp. 517 ◽  
Author(s):  
J. W. Heap
Keyword(s):  
Life Cycle ◽  
Seedling Recruitment ◽  
Vegetative Reproduction ◽  
Seedling Emergence ◽  
Soil Surface ◽  
First Year ◽  
Shoot Production ◽  
Tap Root ◽  
And Control ◽  
Fluctuating Temperatures

The reproductive biology of Reseda lutea L. was studied in the laboratory and field in southern Australia. Seedling emergence was greatest from 5 mm depth (57%) to 10 mm (53%) but also occurred from 80 mm. Seeds on the soil surface did not germinate. Following cultivation of a field population, seedling emergence was high (144/m2) in the first winter and recruitment to the perennial population was estimated at 10·2%. Seedling emergence in subsequent winters was low. Perennial shoot numbers increased gradually in the first year after cultivation, from seedling recruitment and daughter shoots, and then stabilised at around 28/m2. Shoots formed on root fragments at a range of constant and fluctuating temperatures between 10° and 35°C, with a maximum of 17·3 shoots per 50-mm fragment at 15°C. Shoot production increased with root fragment length and diameter. Shoots were produced on root fragments as short as 10 mm and as thin as 1 mm. Fragments from the upper tap root produced more shoots than those from further down the tap root, or from laterals. An illustrated model of the life cycle of R. lutea in Australia is presented.

"Windows of opportunity" for recruitment in long-lived clonal plants: experimental studies of seedling establishment in Vaccinium shrubs

1996 ◽  
Vol 74 (9) ◽  
pp. 1369-1374 ◽  
Author(s):  
Ove Eriksson ◽  
Heléne Fröborg
Keyword(s):  
Seedling Establishment ◽  
Life Histories ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Experimental Studies ◽  
Organic Soil ◽  
Clonal Plants ◽  
Distinct Pattern ◽  
High Fecundity ◽  
Windows Of Opportunity

Two experiments were performed to analyse seedling recruitment in Vaccinium myrtillus, Vaccinium vitis-idaea, Vaccinium uliginosum, and Vaccinium oxycoccos. The purpose was to examine the probability of recruitment at "windows of opportunity," i.e., spatially or temporally unpredictable conditions in which seedling recruitment is possible within stands of established conspecific adults. Seedling emergence in all four investigated species depended on a combination of seed and microsite (disturbance) availability. In V. myrtillus, which was studied in more detail than the other species, emergence and survivorship were similar on non wood substrate and on decaying wood, but seedling growth was favored on the latter substrate. An experiment along an environmental gradient with all four species showed that recruitment required approximately similar conditions even though the adults of the species exhibited a clear zonation along the gradient. For all species except V. oxycoccos, recruitment was confined to only a part of the adults' range. Vaccinium species are generally good seed dispersers and have a high fecundity but usually lack developed seed banks. This behavior is interpreted as a response to occurring windows of opportunity for recruitment, i.e., small disturbances with high moisture and organic soil content. Recruitment at windows of opportunity is suggested as one distinct pattern of recruitment among clonal plants, along with previously suggested repeated and initial seedling recruitment patterns, and some implications of this distinction are briefly discussed. Keywords: clonal plants, genets, life histories, population dynamics, seedling establishment, Vaccinium.

Seasonal cycles in germination and seedling emergence of summer and winter populations of catchweed bedstraw (Galium aparine) and wild mustard (Brassica kaber)

Weed Science ◽  
2006 ◽  
Vol 54 (1) ◽  
pp. 114-120 ◽  
Author(s):  
Husrev Mennan ◽  
Mathieu Ngouajio
Keyword(s):  
Soil Depth ◽  
Cropping Systems ◽  
Seedling Emergence ◽  
Seed Mass ◽  
Soil Surface ◽  
Burial Depth ◽  
Galium Aparine ◽  
Wild Mustard ◽  
Seed Population ◽  
Brassica Kaber

Catchweed bedstraw and wild mustard each produce two populations per year: a winter population (WP) in June, and a summer population (SP) in September. Experiments were conducted to determine whether the WP and SP differ in seed mass and seasonal germination. Seeds of both weeds were buried at 0, 5, 10, and 20 cm in cultivated fields, and retrieved at monthly intervals for 24 mo for germination tests in the laboratory. Additionally, seedling emergence from seeds buried at 0, 5, and 10 cm in the field was evaluated for 1 yr. Seeds from the WP were heavier than those from the SP for both species. Germination of exhumed seeds was affected by burial depth and by seed population. It was highest for seeds that remained on the soil surface and declined with increasing depth of burial. The WP of catchweed bedstraw produced two germination peaks per year, whereas the SP and all populations of wild mustard had only one peak. The WP of both weeds germinated earlier than the SP. Seedling emergence for both species in the field was greater for the WP than for the SP. Increasing soil depth reduced seedling emergence of both the WP and SP of wild mustard and affected only the WP of catchweed bedstraw. We conclude that the WP and SP of catchweed bedstraw and wild mustard seeds used in this study differed in seed mass, seasonal germination, and seedling emergence. The ability of a WP to produce large seeds that germinate early and have two germination peaks per year could make these populations a serious problem in cropping systems.

Direct seeding of black spruce in northwestern Ontario: Seedbed relationships

1994 ◽  
Vol 70 (2) ◽  
pp. 151-158 ◽  
Author(s):  
R. L. Fleming ◽  
D. S. Mossa
Keyword(s):  
Seedling Establishment ◽  
Black Spruce ◽  
Mineral Soil ◽  
Soil Surface ◽  
Direct Seeding ◽  
First Year ◽  
Strongly Correlated ◽  
Seedling Mortality ◽  
Northwestern Ontario ◽  
Seedbed Preparation

A series of spot seeding experiments was set out on coarse-textured upland sites in northwestern Ontario to investigate how black spruce (Picea mariana [Mill.] B.S.P.) seedling establishment and growth could be improved by site selection and seedbed preparation. Virtually all germination occurred within the first growing season. Annual seedling mortality rates were greatest during the first year, then declined steadily and stabilized at low levels (<10%) after the third year. The highest fifth-year establishment ratios (seedlings/viable seed sown) were found on seedbeds derived from materials near the mineral soil/humus interface. On wetter sites (i.e., higher Soil Moisture Regimes) the best seedbeds occurred closer to the soil surface. Mean fifth year establishment ratios for the best seedbeds were 0.032 on moderately fresh to fresh sites, 0.146 on very fresh to moderately moist sites, and 0.082 on moist to very moist sites. On adjacent lowland sites, slow-growing, compact Sphagnum mosses had a mean establishment ratio of 0.179. Mean fifth-year seedling heights on upland sites ranged from 12 to 14 cm, and were not strongly correlated with site or seedbed type. Key words: direct seeding, black spruce, seedbed, seedling establishment, site type and germination

scholarly journals Factors affecting Cyperus difformis seed germination and seedling emergence

2013 ◽  
Vol 31 (4) ◽  
pp. 823-832 ◽  
Author(s):  
A. Derakhshan ◽  
J. Gherekhloo
Keyword(s):  
Seed Germination ◽  
Integrated Management ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Soil Surface ◽  
Weed Species ◽  
Factors Affecting ◽  
Cyperus Difformis ◽  
Emergence Patterns

Specific knowledge about the dormancy, germination, and emergence patterns of weed species aids the development of integrated management strategies. Laboratory studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of Cyperus difformis. Germination of freshly harvested seeds was inhibited by darkness; however, when seeds were subsequently transferred to complete light they germinated readily. Our results showed that 2 wk of cold stratification overcome the light requirement for germination. Seeds of C. difformis were able to germinate over a broad range of temperatures (25/15, 30/20, 35/25, and 40/30 ºC day/night). The response of germination rate to temperature was described as a non-linear function. Based on model outputs, the base, the optimum and the ceiling temperatures were estimated as 14.81, 37.72 and 45 ºC, respectively. A temperature of 120 ºC for a 5 min was required to inhibit 50% of maximum germination. The osmotic potential and salinity required for 50% inhibition of maximum germination were -0.47 MPa and 135.57 mM, respectively. High percentage of seed germination (89%) was observed at pH=6 and decreased to 12% at alkaline medium (pH 9) pH. Seeds sown on the soil surface gave the greatest percentage of seedling emergence, and no seedlings emerged from seeds buried in soil at depths of 1 cm.

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