Total Number Of Seedlings Research Articles

Potency of Ramin (Gonystylus bancanus Kurtz.) and Other Commercial Species in Peat Swamp Forest Managed with TPTI Silvicultural System in Bagan, Riau

Ramin ( Gonystylus bancanus Kurtz.) is one of the tree species in peat-swamp forest that is endangered due to excessive exploitation. The objective of this research was to assess the potency of rarnin and other commercial tree species in primary and logged over peat-swamp forests at Bagan, Riau. The tree stands were inventoried in primary forest of the 2004 and 2006 Annual Work Plan (RKTs) and in the 1997 and 2001 RKTs managed with Indonesian Selective Cutting and Planting (TPTI) silvicultural system. The result showed that rarnin in Bagan peat-swamp forest was not evenly distributed. The total number of ramin in tree stage in primary forests was fewer than that in logged over forests. The total number of ramin species at tree stage in primary forest was between 4.5 and 5 trees ha·' with the important value index (IVI) of 10.3 to 12.0%, whereas the one at logged over forest were between 2.5 and 15 trees ha·' with theM indices of 7.9 to 20.4%. Commercial species of swamp meranti (Sho r ea ul ig i n os a and S . t e y s m a n iana) and balam/ suntai or (Palaq qium spp.) were dominant at tree stage both in the primary and the logged over forests. Enrichment in logged over forests is not needed since the total number of seedlings and saplings is enough. The total number of potential core trees in logged over forests was enough for the next cutting cycle. The effort that must be done in logged over forests is to protect them from illegal logging.

Effects of water level and phosphorus enrichment on seedling emergence from marsh seed banks collected from northern Belize

The effects of water level and nutrient additions on seed germination from the seed banks of phosphorus-limited freshwater herbaceous wetlands in Northern Belize, Central America, were tested in a greenhouse study. Seed bank soil was exposed to both draw-down and flooded conditions with and without added phosphorus (P) in a replicated germination assay. The seed banks of herbaceous species, as assessed by seedling emergence, in 7 marshes of the study area ranged in size from 55 to 1556 seeds m −2 and from 4 to 15 species. The dominant species in the standing vegetation, Typha domingensis Pers., Eleocharis cellulosa Torr., and Cladium jamaicense Crantz, were almost completely absent in the seed banks. The addition of phosphorus and flooding each reduced the number of species germinating from the seed banks by 50%, although the effect of water level varied by marsh. Phosphorus had a greater effect on the total number of seedlings emerging in flooded than draw-down treatments, reducing emergence by 75 and 20%, respectively. Overall, flooding reduced seedling emergence by 50%. The emergence of Typha from the seed banks, a competitive dominant in the marshes, was not increased by the addition of P.

Inter-annual variation in the soil seed bank of flood-meadows over two years with different flooding patterns

Persistent soil seed banks are presumed to play a significant role in bridging and exploiting the effects of major flood disturbances in riparian systems. However, presently there is little empirical data on the correlation between flooding and seed bank dynamics. The objective of this study was to assess the impact of inter-annual flooding variation on soil seed bank dynamics in flood-meadows. We analysed seed bank composition at 46 plots along the northern Upper Rhine River, Germany, after two periods with contrasting flooding conditions (1996–1997: low and rare flooding; 1998–1999 high and very frequent flooding). Between both sampling occasions the total number of seedlings emerging from the seed bank decreased by 50% and average species-richness per sample by 30%, irrespective of the sampling depth. Similar decline occurred in mesophytes and wetland species as well as over different functional groups, with the exception of legumes. Considerable compositional changes in the seed bank were also indicated by shifts in DCA ordination and by the comparison of similarity matrices from both years with the Mantel test. The Mantel test also confirmed that compositional changes were more pronounced in the seed bank than in aboveground vegetation. There was poor correlation between the decline in total seed densities and species in the soil seed bank and environmental variables such as flooding duration and ecological groupings such as floodplain compartment and seed bank community types. Further distinct patterns of decline and persistence were evident only at the species level. While 21 species displayed a significant decline, only two species increased. Annual arable weeds and perennial ruderals with high temperature or nutrient requirements to break dark dormancy were amongst the most significantly declining species. In contrast, there was no decline in typical winter annuals and certain perennials that preferably germinate in autumn and fall into dormancy at the beginning of the warm period. Generally, differences in germination requirements and dormancy cycles of species gave the best explanation for the patterns of decline and persistence after intense flooding. Given these findings, the heavy depletion of the persistent soil seed bank we observed is most likely attributed to a post-flood germination flush due to very favourable recruitment conditions prevailing during the draw-down period after early summer flooding in 1999. The results of our study suggest that persistent soil seed banks are of outstanding importance to bridge and exploit the highly variable hydrological conditions that are typical of flood-meadows. Thus, they play a significant role in maintaining the floristic diversity of this habitat type over time and space.

Variability of seedling recruitment under dominant, moss, and litter removal over four years

In a four-year removal experiment we investigated the effect of removing a dominant species (Nardus stricta), the litter layer and moss layer on species composition of established vegetation and on numbers and species composition of seedlings. The experiment was conducted in an oligotrophic wet meadow (Molinion with some features ofViolion caninae according to phytosociological classification). After four years of the experiment, the redundancy analysis (RDA) did not reveal any changes in the composition of the established plant community. Seedling numbers and their species composition, however, varied significantly both among treatments and over years. Whereas the differences between treatments were mainly in total seedling numbers, the years differed in both seedling numbers and relative representation of individual species. In particular,Myosotis nemorosa seedlings highly increased their abundance in a favourable year 1995 constituting one third of all the seedlings found, whereas in other years their abundance was between 4% and 10%. The effects of year and treatment were not additive (significant year × treatment interaction). This means that plots under different treatments are differently affected by climatic conditions of individual years. The greatest increase of seedling recruitment was observed in the plots with the moss layer removed. Microsites with high seedling recruitment persisted in the plots for no more than two years. Why the established vegetation composition does not differ among treatments even after four years, despite the relatively pronounced and immediate response of seedlings? The number of species with regular seedling recruitment is limited. They are mostly perennials, and consequently, it might take even longer than four years before recruitment limitation affects the population size of established plants.

RECENT ISSUES ON VEGETABLE GRAFTING

RECENT ISSUES ON VEGETABLE GRAFTING

Seedling herbivory and the influence of plant species richness in seedling neighbourhoods

The aim of this experiment was to determine how increasing species richness within artificially created grassland gaps affected the overall magnitude of seedling losses to, and the selectivity of, seedling herbivores. Using chemical exclusion methods, the influence of molluscs the principal invertebrate herbivores in temperate grasslands, was assessed at three levels of plant species diversity (3, 6, and 12 species per gap). In comparison with ungrazed controls, mollusc herbivory significantly reduced seedling numbers. However, the total number of seedlings killed by molluscs was unrelated to the number of seedling species present in the gap. Furthermore, there was no evidence to suggest that seedling species diversity influenced rates of mollusc selection of the three individual species (Agrostis capillaris, Senecio jacobaeae, and Taraxacum officinale) present in each diversity treatment. This work highlights the preferential selection by molluscs of broad-leaved herb species over neighbouring grass seedlings. However the results also suggest that when presented with an increasing choice of different seedling species, the overall magnitude and selectivity of seedling removal by molluscs remains unchanged.

Effect of the Presence or Absence of Corn on Common Lambsquarters (Chenopodium album L.) and Barnyardgrass [Echinochloa crus-galli (L.) Beauv.] Emergence1

A 3-yr study was conducted to establish if the presence of corn had an effect on the emergence patterns and total weed seedling density under growing conditions in southwestern Québec. Weed seedling emergence was monitored in permanent quadrats throughout the growing season in the presence and absence of growing corn. Common lambsquarters and barnyardgrass were prevalent in most site-years. The presence of corn did not affect the patterns of common lambsquarters and barnyardgrass emergence nor their total weed seedling density except in 1994. Corn canopy was probably not sufficiently developed to affect light levels or soil temperature needed for weed germination and, consequently, seedling emergence. In 1994, in the absence of corn, some soil crusting was observed on a fine-textured soil, and the total number of seedlings was reduced. The results of these weed emergence studies in corn can be extended to other crops growing with wide row spacing and relatively slow canopy closure similar to those of grain corn.Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; common lambsquarters, Chenopodium album L. # CHEAL; corn, Zea mays L. ‘Pioneer 3921’.Additional index words: Amaranthus retroflexus L., AMARE, crop competition, redroot pigweed, weed density, weed seedling emergence.Abbreviations: CHU, corn heat units; PAR, photosynthetically active radiation.

Effect of Natural Ageing on Germination and Seedling Vigour of Teak (Tectona grandis Linn.f.) Drupes

A study was conducted to find the effect of natural ageing on the germination and seedling vigour of fresh, one and two years-old teak drupes (Fruit with seed). The fresh, one and two year-old drupes were allowed for germination under open and mist chamber conditions following soaking and drying of drupes for 6 days at an interval of 12 hrs recorded 8, 37 and 51 per cent and 3, 40 and 50 per cent germination respectively. The total number of seedlings also reflected the same trend as that of germination. Seedlings from one and two year’s old-drupes emerged early in mist chamber (10 days) than in open condition (12 days). Seedlings from one and two year-old drupes also exhibited better seedling vigour than fresh drupes.

Field tests with a molluscicide containing iron phosphate

The effect of slug pellets containing iron phosphate was evaluated in field trials. In comparison with untreated controls, iron phosphate reduced leaf loss of lettuce, increased the number of marketable lettuce heads and reduced numbers of the slug Arion lusitanicus. The reference treatment metaldehyde was more effective in preventing slug damage and reduced numbers of all slug species present ( A. lusitanicus, A. hortensis and Deroceras reticulatum). In rape, iron phosphate reduced the percentage of seedlings with slug damage, but did not affect the total number of seedlings per unit area. Iron phosphate seems promising for organic agriculture, where other chemical molluscicides cannot be used.

Comparative effects of different smoke treatments on germination of Australian native plants

Abstract This study consists of a series of investigations designed to determine the potential of concentrated smoke products to stimulate seed germination and assist in the rehabilitation of degraded landscapes. Aerosol smoke and conventional smoke water products are not practical for use in broad‐scale seed bank regeneration programmes due to infrastructure limitations and the high rate of application required for their use. Concentrated smoke products have been found to be effective in stimulating soil seed banks and are suitable for broad‐scale use due to the lower rate of application required to elicit germination within smoke‐responsive species. The use of concentrated smoke products on undisturbed soil seed banks at 50 and 100 mL m‐2 increased total seedling numbers 10‐fold, while species richness more than doubled over untreated controls. Although aerosol smoke applied directly to soil promoted 10 times more seedlings compared to concentrated smoke products, species richness levels in each treatment were similar. Concentrated smoke products cause leaf scorch when applied directly over plants in active growth, with limited to nil damage when plants are not actively growing. The affected plants generally recovered following application of concentrated smoke products as a foliar spray.

Monitoring of natural regeneration in a mixed deciduous forest

Monitoring of natural regeneration in a dense semi-natural mixed hardwood forest on the base of ash, beech, oak and sycamore occurred over 3 years in the Aelmoeseneie experimental forest, Belgium. 40 permanent plots (4 m x 5 m) were selected in three various humus types, located in an ash stand and in an oak - beech stand. In all plots abundance and top height of all broad leaved regenerated species were determined at the end of the growing seasons 1995 and 1998. In addition, the seedlings which appeared in the plots during 1996 and 1997 were identified and followed up. This study proves that in the investigated sites natural regeneration is drastically poor and diversity is low, in particular where the humus layer is more acidic (mull moder) and the litter layer is thick. No regeneration phase older than the seedling stage (h < 40 cm) is developed on the different humus types. On average, total number of seedlings in 1995 amounts to 38 units/are in the ash stand and to 63 units/are in the oak - beech stand. Survival rate over a 3- year period is 37% and 42% respectively in the ash and oak - beech stands. Total ingrowth during the growing seasons 1996 and 1997 is virtually poor, indicating 16 and 8 units/are respectively in above mentioned stands. Survival rate of occurring seedlings, as well as the ingrowth of new seedlings are notably different (P < 0.05) according to the soil conditions of the ash stand. Generally, the low presence of seedlings and the lack of regeneration older than the seedling stage reveal that the regeneration development encounters with a critical problem. The continuation of this process would likely result in a progressive succession by the invasive and the unwanted tree species.

The relationship between pellet size and the quantity of imidacloprid applied to sugar beet pellets and the consequences for seedling emergence

When imidacloprid was applied to sugar beet pellets at 90 g a.i. per unit of 100,000 seeds, the quantity of imidacloprid applied to individual sugar beet pellets was directly proportional to the size of pellet, resulting in lower dosing of some pellets and high dosing of others. This variability in application resulted in a slowing of germination in a laboratory experiment but had no effect on the rate of emergence in a field trial of young seedlings produced from large pellets compared with that from smaller pellets. However, there was a significant reduction in total number of seedlings emerging from large imidacloprid-treated pellets in a spring-sown field trial suggesting that additional phytotoxicity had occurred. Uptake of imidacloprid in leaf tissue was also greater in plants produced from large pellets. In a field trial at Broom's Barn, sown in the autumn, imidacloprid at 30, 60, 90 and 120 g a.i. per unit significantly slowed the rate of emergence of three varieties of sugar beet but there was no effect on pellet size. However, in contrast to the earlier trial, small pellets of two of the three varieties produced significantly fewer seedlings than large pellets, irrespective of the rate of imidacloprid applied, and there were no interactions between pellet size and rate of imidacloprid applied. Similar results were observed in another field trial in Norfolk where small pellets of one of the varieties, untreated, or treated with 30, 60 and 90 g a.i. of imidacloprid, but not 120 g a.i., produced significantly fewer seedlings. Small pellets of another variety produced the highest number of seedlings. Thus the variability in application of imidacloprid to sugar beet pellets can sometimes cause increased phytotoxicity to plants produced from large pellets, but this effect was not consistent with different varieties and different batches of the same variety.

Observations on the maintenance and measurement of soil water in simple pot experiments and its effects on seed‐borne Fusarium culmorum seedling blight of winter wheat

Summary.A simple method for maintaining and measuring soil water and the relationship between soil water and seed‐borne Fusarium culmorum seedling blight of wheat was investigated under controlled environmental conditions to develop reproducible assay conditions for epidemiological studies and the testing of fungicide seed treatments. For reproducibility, soil matric potential (ψm) was used to define soil water, and a range of watering regimes were tested. Treatments were watered to either a maximum ψm or to maintain a mean ψm in order to establish which parameter best described the effect that soil water had on the incidence of disease symptoms. The severity of disease symptoms was closely related to the mean soil water status and not the maximum ψm value. Watering intervals, ranging from three times a day to once every three days, did not affect this relationship. The percentage of seedlings showing symptoms after emergence (i.e. localised or extensive necrotic lesions) was inversely related to the mean ψm. With increasing soil dryness (mean ψm from ‐0.14 MPa to ‐0.17 MPa) the percentage of seedlings with post‐emergence symptoms decreased from 50% to 20%. However, as the mean ψm changed from ‐0.14 MPa to ‐0.17 MPa the percentage of seedlings dying before emergence increased from 25% to 55% in direct proportion to ψm. Overall the incidence of infection as indicated by the total number of seedlings showing symptoms either before or after emergence remained relatively constant, and was not significantly related to mean ψm.

Germination and early establishment of lower salt‐marsh species in grazed and mown salt marsh

Abstract. Lower salt‐marsh species occur more in the grazed than in the mown sites of a salt marsh in Schiermonnikoog in the Netherlands. This was demonstrated by a sowing experiment which determined which characteristic of the stand structure, height of the canopy or percentage of bare soil, is responsible for this difference. The total number of seedlings which emerged was negatively related to the height of the canopy and positively to the percentage of bare soil. The survival of seedlings of Suaeda maritima and Plantago maritima could be explained by the height of the canopy and for the latter species also by the percentage of bare soil. The survival of Aster tripolium and Plantago maritima was higher in grazed than in mown sites. Since the amount of bare soil was higher than seemed necessary for germination and survival, it was concluded that the taller canopy was responsible for the absence of lower salt‐marsh species in the mown sites.

Naturally established seedlings on an artificially regenerated area in Northern Sweden

A field experiment in northern Sweden was established to compare different regeneration methods. Pinus sylvestris (L.) seeds of various origins were used. On the plots on the clear‐felled area where local seed had been sown, the naturally established conifer regeneration was recorded. Eleven growing seasons after sowing, the total number of seedlings increased by 335% giving a total of 4 754 seedlings ha‐1 when the number of naturally established conifers was added to the number of seedlings from the artificial regeneration. The number of main crop plants almost doubled. The number of naturally established seedlings decreased with increasing distance from the neighboring seed‐tree stand. Up to 110 m from the seed‐tree stand 50% of the sowed 2 × 2 m quadrats had at least one naturally regenerated seedling. The extent of natural regeneration found in this study suggest that it could contribute to a significant increase in stand density under appropriate management on suitable sites. Moreover, naturally esta...

Improvement of Seedling Emergence of Lupinus texensis Hook. Following Seed Scarification Treatments

Abstract Seeds from four commercial seedlots of Lupinus texensis Hook. (Texas bluebonnet) were placed in concentrated sulfuric acid for 0 to 120 minutes and then sown. Emergence was promoted by acid scarification in three of the four seedlots. For the lots that responded to acid scarification, the optimal scarification time was 30–60 minutes which resulted in 85–95% emergence one month after planting. In addition to increasing the total number of seedlings that emerged, acid scarification hastened emergence. The same aliquot of sulfuric acid was used for five 60-minute scarification periods before its efficacy was reduced. Acid scarification did not reduce seed coat thickness or strength but created several small pores in the seed coat which likely facilitated imbibition. Cutting, filing, or piercing the seed coat promoted emergence to a similar extent. Placement of seeds in 85%C (185%F) water and then cooling for 24 hrs promoted emergence relative to the non-treated controls, but was not as effective as other scarification techniques. Freezing and thawing of seeds had no effect on emergence. Results indicate that acid scarification functions by removing a mechanical rather than a chemical barrier to gennination of L. texensis.

Density‐dependent interactions between seedlings of Dactylorhiza majalis (Orchidaceae) in symbiotic in vitro culture

Growth of the heterotrophic seedlings of Dactylorhiza majalis (Rchb.f.) Hunt & Summerh. (Orchidaceae) in vitro with a symbiotic fungus (Rhizoctonia sp.) is density‐dependent, even at densities that are not high enough to exploit the growth medium fully. Competition was two‐sided; increasing density among seedlings did not increase size inequality between them. The slowly growing and smaller seedlings are normally more likely to die than the bigger ones, but mortality was not increased by higher density within the studied range. Growth depression by neighbouring seedlings is independent of their physical distance but varies with the total number of seedlings sharing the same culture dish and the same mycelium.Therefore, if the growth‐promoting effects of different fungi or treatments are to be compared in future work, the density of planting in the culture dishes should be comparable.

Evaluation of the emergence method in estimating seed bank composition of prairie wetlands

Bottom samples were collected in each of two semi-permanent prairie marshes in Stutsman County, North Dakota, to determine the accuracy of the seedling emergence method in assessing seed-bank composition. Samples were divided into two equal portions and placed under moist and submerged soil conditions in the greenhouse. Emerged seedlings were identified and counted. To check the results of this technique, a portion of the field samples were sieved and seeds were isolated and identified. The seedling emergence method was generally accurate in determining wetland seed bank composition. The same five species ( Scirpus spp., Chenopodium rubrum L., Typha spp., Rumex maritimus L., and Ranunculus sceleratus L.) accounted for 92.6% and 93.4% of the total number of seedlings and seeds, respectively. The rank-order of all species was also significantly correlated between methods. Only Utricularia vulgaris L. failed to germinate well in the emergence flats (0.13% emerged seedlings versus 3.19% isolated seeds). Providing conditions in the submerged-soil treatment that are more conducive to the germination of open water species would improve the method. A modification of the flotation method used for separating seeds in recommended in wetlands with relatively large seeds.

The Effects of Seed Burial and Soil Disturbance on Emergence and Survival of Arable Weeds in Relation to Minimal Cultivation

(1) Seeds of sixteen weed species (six grasses and ten herbs) were collected from arable field margins during 1977. Species included were Agrostis gigantea, Alopecurus myosuroides, Arrhenatherum elatius, Avena fatua, Bromus sterilis, Poa trivialis, Capsella bursa-pastoris, Galium aparine, Papaver rhoeas, Plantago major, Polygonum aviculare, Stellaria media, Tripleurospermum inodorum, Veronica arvensis, Veronica persica, and Viola arvensis. Seeds were sown in soil in pots or boxes at various depths, and either disturbed periodically or left undisturbed. Periodicity of emergence was recorded for each species. (2) Four patterns of emergence were recorded: (i) emergence in spring alone; (ii) predominantly in autumn; (iii) in both spring and autumn; (iv) emergence indifferent to season. Most of the grasses emerged predominantly in autumn whereas the main period of emergence for many of the dicotyledonous species was in spring. (3) Burial of small-seeded species both delayed and reduced seedling emergence as compared to surface-sown seed. In contrast germination and emergence of the larger-seeded species was increased by burial. Soil disturbance increased the total number of seedlings which emerged, but in general it did not alter the relative periodicity of germination, nor was emergence promoted by cultivation at times outside the period of natural emergence. (4) The number of viable but ungerminated seeds which remained after 2 years varied between species. It was least for surface sown seed and greatest for buried undisturbed seed. Most frequent were A. myosuroides, Viola arvensis, P. rhoeas and P. aviculare. No seeds of A. elatius, B. sterilis or G. aparine remained after 12 months. (5) Relatively few species emerged from below 50 mm with the exception of several large-seeded species. These species generally failed to establish from seed on the soil surface. (6) The results are discussed in relation to the use of minimal cultivations for cereal production. It is concluded that the majority of annual grass-weeds, despite having little innate dormancy, will continue to be encouraged by current agronomic practices. In contrast, many annual dicotyledonous species will decline in importance, partly as a result of their susceptibility to herbicides and partly because their periodicity of germination does not coincide with the establishment phase of autumn-sown cereals.

Dwarf mistletoe on white spruce in Sprucewoods Provincial Park, Manitoba

Pure stands of white spruce (Piceaglauca (Moench) Voss) have been decimated by dwarf mistletoe (Arceuthobiumpusillum Peck) in Sprucewoods Provincial Park. Infection ranged from 100% in some stands to 25% in stands invaded more recently. Large trees may live 40 years or longer after being infected. Trees with brooms, which previously had annual radial increments of 0.67 cm at 1.4 m, had annual increments in the last 5 years of 0.04 to 0.14 cm. White spruce less than 2 m tall were absent on all but one of the plots where the total number of seedlings decreased 20% in 2 years, and 24–27% of the surviving seedlings were infected. Dwarf mistletoe infection reduced annual height growth of infected seedlings 40% in 1977.