Wind dispersed seeds and plant recovery on the Mount St. Helens debris avalanche

1989 ◽  
Vol 67 (5) ◽  
pp. 1434-1441 ◽  
Author(s):  
Virginia H. Dale
Keyword(s):  
Plant Density ◽  
Plant Cover ◽  
Debris Avalanche ◽  
Long Distance ◽  
Spider Webs ◽  
Climate Conditions ◽  
Disturbed Areas ◽  
Successional Species ◽  
Average Plant ◽  
Mount St Helens

Seed dispersal and plant establishment were monitored for 4 years on the debris avalanche created by the 1980 eruption of Mount St. Helens. The number of plants on the deposit increased over time to a high of almost 2 plants/m2 by 1983. The number of species per 250-m2 plot has increased to a mean of 10.3 in 1983 with 76 species being present over the entire deposit. Four years after the eruption only 30% of the species present before the eruption had reestablished themselves, and average plant cover was less than 1%. The debris avalanche has been invaded primarily via wind-dispersed seed of early successional species that survived or have become established in adjacent disturbed areas. Most of the early successional species on the avalanche have plumed seeds that are adapted not only for long distance dispersal, but also for being trapped in wet areas or by spider webs. Fluctuations in the density of seeds dispersed to the deposit were related to variation in precipitation. Neither seed abundance nor plant density correlated with absolute distance to a seed source or soil texture conditions. Colonization patterns are more influenced by the available biota and prevailing climate conditions than by substrate alterations resulting from the eruption.

Melinis repens (natal redtop).

2021 ◽  
Author(s):  
Sylvan Kaufman
Keyword(s):  
Arabian Peninsula ◽  
Perennial Grass ◽  
Ornamental Plant ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Pasture Grass ◽  
Disturbed Areas ◽  
Natural Grasslands ◽  
Successional Species ◽  
In Fire

Abstract Melinis repens, commonly known as Natal grass, is a short-lived perennial grass native to South Africa, the Arabian peninsula, India, the Seychelles island and Canary Islands. It is already widely distributed in tropical and subtropical regions due to its long use as a pasture grass and ornamental plant. Although considered a weed in many countries, it is not currently regulated. Wind disperses the seeds locally and long distance dispersal happens through the plant and seed trade. It mainly occurs in disturbed areas such as along roadsides and railway lines, but it can spread into natural areas interfering with early successional processes. It is mainly considered invasive in natural grasslands and shrublands. Holm et al. (1979) list it as a 'serious' weed in Australia, Brazil and Ghana, and 'principal' in Malaysia and Zambia. The dry biomass of the plant leads to an increase in fire frequencies and its dense growth crowds out native early successional species. Currently the main uses promoted for the plant are for reclaiming mined sites and planting as an ornamental plant.

Nitrogen Demand of Cut Chrysanthemums in Relation to Shoot Height and Planting Date

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 523c-523
Author(s):  
Siegfried Zerche
Keyword(s):  
Dry Matter ◽  
Plant Density ◽  
Plant Biomass ◽  
N Uptake ◽  
Planting Date ◽  
Dry Matter Accumulation ◽  
Planting Dates ◽  
Shoot Height ◽  
Climate Conditions ◽  
Growing Period

Refined nutrient delivery systems are important for environmentally friendly production of cut flowers in both soil and hydroponic culture. They have to be closely orientated at the actual nutrient demand. To solve current problems, express analysis and nutrient uptake models have been developed in horticulture. However, the necessity of relatively laborious analysis or estimation of model input parameters have prevented their commercial use up to now. For this reason, we studied relationships between easily determinable parameters of plant biomass structure as shoot height, plant density and dry matter production as well as amount of nitrogen removal of hydroponically grown year-round cut chrysanthemums. In four experiments (planting dates 5.11.91; 25.3.92; 4.1.93; 1.7.93) with cultivar `Puma white' and a fixed plant density of 64 m2, shoots were harvested every 14 days from planting until flowering, with dry matter, internal N concentration and shoot height being measured. For each planting date, N uptake (y) was closely (r2 = 0.94; 0.93; 0.84; 0.93, respectively) related to shoot height (x) at the time of cutting and could be characterized by the equation y = a * × b. In the soilless cultivation system, dry matter concentrations of N remained constant over the whole growing period, indicating non-limiting nitrogen supply. In agreement with constant internal N concentrations, N uptake was linearly related (r2 = 0.94 to 0.99) to dry matter accumulation. It is concluded that shoot height is a useful parameter to include in a simple model of N uptake. However, in consideration of fluctuating greenhouse climate conditions needs more sophisticated approaches including processes such as water uptake and photosynthetically active radiation.

scholarly journals The Effects of Management (Tillage, Fertilization, Plant Density) on Soybean Yield and Quality in a Three-Year Experiment under Transylvanian Plain Climate Conditions

Land ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 200
Author(s):  
Felicia Chețan ◽  
Cornel Chețan ◽  
Ileana Bogdan ◽  
Adrian Ioan Pop ◽  
Paula Ioana Moraru ◽  
...  
Keyword(s):  
Plant Density ◽  
Conventional Tillage ◽  
Quality Parameters ◽  
Soil Tillage ◽  
Reduced Tillage ◽  
Seeding Rate ◽  
Soybean Yield ◽  
Climate Conditions ◽  
Yield And Quality ◽  
Tillage System

The regional agroecological conditions, specific to the Transylvanian Plain, are favorable to soybean crops, but microclimate changes related to global warming have imposed the need for agrotechnical adaptive measures in order to maintain the level of soybean yield. In this study, we consider the effect of two soil tillage systems, the seeding rate, as well as the fertilizer dosage and time of application on the yield and quality of soybean crops. A multifactorial experiment was carried out through the A × B × C × D − R: 3 × 2 × 3 × 3 − 2 formula, where A represents the year (a1, 2017; a2, 2018; and a3, 2019); B represents the soil tillage system (b1, conventional tillage with mouldboard plough; b2, reduced tillage with chisel cultivator); C represents the fertilizer variants (c1, unfertilized; c2, one single rate of fertilization: 40 kg ha−1 of nitrogen + 40 kg ha−1 of phosphorus; and c3, two rates of fertilization: 40 kg ha−1 of nitrogen + 40 kg ha−1 of phosphorus (at sowing) + 46 kg ha−1 of nitrogen at V3 stage); D represents the seeding rate (1 = 45 germinating grains (gg) m−2; d2 = 55 gg m−2; and d3 = 65 gg m−2); and R represents the replicates (r1 = the first and r2 = the second). Tillage had no effect, the climate specific of the years and fertilization affected the yield and the quality parameters. Regarding the soybean yield, it reacted favorably to a higher seeding rate (55–65 gg m−2) and two rates of fertilization. The qualitative characteristics of soybeans are affected by the fertilization rates applied to the crop, which influence the protein and fiber content in the soybean grains. Higher values of protein content were recorded with a reduced tillage system, i.e., 38.90 g kg−1 DM in the variant with one single rate of fertilization at a seeding rate of 45 gg per m−2 and 38.72 g kg−1 DM in the variant with two fertilizations at a seeding rate of 65 gg m−2.

Survival of Endocronartium harknessii teliospores in a simulated airborne state

1989 ◽  
Vol 67 (3) ◽  
pp. 928-932 ◽  
Author(s):  
Kan-Fa Chang ◽  
P. V. Blenis
Keyword(s):  
Relative Humidity ◽  
Liquid Nitrogen ◽  
Long Distance ◽  
Spider Webs ◽  
Considerable Potential ◽  
Good Ability ◽  
Endocronartium Harknessii ◽  
Spore Longevity ◽  
Effects Of Temperature ◽  
Increasing Temperature

The effects of temperature and relative humidity (RH) on the survival of Endocronartium harknessii teliospores and the longevity of these spores out of doors during daylight hours were studied. In one experiment, fresh and liquid-nitrogen-stored spores of E. harknessii were impacted onto spider webs or plastic threads and incubated in darkness at temperatures of 6, 15, and 24 °C and RHs of 39 and 98%. Survival was measured after 1, 2, 4, 8, and 16 days. Spore longevity decreased with increasing temperature and was lower at 98 than at 39% RH. In a second experiment, spores were impacted onto spider webs and placed out of doors on clear days. Viability decreased linearly with time and averaged 33% after 12 h. The data suggest that E. harknessii has relatively good ability to survive in an airborne state and thus would have considerable potential for long distance spread.

Vesicular – arbuscular mycorrhizae in disturbed and revegetated sites from La Gran Sabana, Venezuela

1992 ◽  
Vol 70 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Gisela Cuenca ◽  
Milagros Lovera
Keyword(s):  
Arbuscular Mycorrhizae ◽  
Plant Cover ◽  
Ground Cover ◽  
Arbuscular Mycorrhizal ◽  
Most Probable Number ◽  
Probable Number ◽  
Organic Layers ◽  
Vesicular Arbuscular Mycorrhizae ◽  
Disturbed Areas ◽  
Vesicular Arbuscular

Savannas growing on stony, old and nutrient-poor soils of southern Venezuela were severely disturbed by removal of the soil organic layers with bulldozers for road building. Introduced species Brachiaria decumbens, Brachiaria humidicola, Pueraria phaseoloides, and Calopogonium sp. were sown. The substrate was fertilized and limed. Plant cover, vesicular – arbuscular mycorrhizae colonization, spore number, and most probable number of propagulels in undisturbed savanna, disturbed nonrevegetated savanna, and six revegetated savannas were assessed. The perturbation reduced the mycorrhizal propagule number in comparison with the undisturbed savanna. In the nonrevegetated areas the mean percent ground cover 2 years after disturbance was low (0.04%). In revegetated areas an increase in mycorrhizal propagule number occurred and the mycorrhizal colonization of the sown species was high. In restored areas there was an increase in species of nonmycotrophic Amaranthaceae. The results support other predictions on the mycorrhizae in successional biomes, because in the extremely nutrient-poor soils studied the colonizing species were mainly mycotrophic. The reclamation program applied in disturbed areas was useful because it has allowed the recovery of vesicular – arbuscular mycorrhizal inoculum and there was an increase in the recolonization of native plants. Key words: disturbance, endomycorrhizae, revegetation, savanna, vesicular – arbuscular mycorrhizae.

Natural plant recolonization of surficial disturbances, Tuktoyaktuk Peninsula Region, Northwest Territories

1973 ◽  
Vol 51 (11) ◽  
pp. 2177-2196 ◽  
Author(s):  
Helios Hernandez
Keyword(s):  
Plant Cover ◽  
Mineral Soil ◽  
Energy Budgets ◽  
Mackenzie Delta ◽  
Calamagrostis Canadensis ◽  
Disturbed Areas ◽  
Sedge Meadows ◽  
Tall Shrub ◽  
Seismic Lines ◽  
Plant Recolonization

Seismic lines or winter roads were sampled where they passed through three different plant communities in the Mackenzie Delta and through four of the major tundra communities in the Tuktoyaktuk Peninsula. Winter seismic lines have been less detrimental than summer lines for all communities examined. Although winter roads through upland areas remove most of the vegetation cover, the peat layer usually remains intact and soil energy budgets are relatively little affected. Wetland sedge meadows are highly susceptible to summer disturbance but least affected by winter operations. Winter-disturbed forested and tall shrub communities recover faster initially than similarly disturbed upland tundra communities.Eriophorum vaginatum and Carex bigelowii appeared to be stimulated by disturbances which did not eliminate them, with Eriophorum often flowering more abundantly in disturbed areas. This probably results from warmer soils and greater nutrient uptake.Summer seismic lines (1965), originally bladed to permafrost, resulted in exposure of mineral soil and thus led to secondary succession in tundra communities. Arctagrostis latifolia, Calamagrostis canadensis, Poa arctica, and Luzula confusa are the most typical and abundant pioneers of upland mesic sites. Wet sites are colonized predominantly by Arctophila fulva and Carex aquatilis. Once established, these species expanded rhizomatously. Six years after exposure of mineral soil, plant cover was usually 30 to 50%.Thaw was generally increased 80 to 100% where mineral soil was exposed, 30 to 50% if the peat remained intact, and 10% if plant cover was little altered. Subsurface ice has occasionally been exposed, resulting in thermokarst subsidence. Water erosion has not been a factor, probably because of the low precipitation in the region.

scholarly journals Allelic diversity in populations of Solanum lycocarpum A. St.-Hil (Solanaceae) in a protected area and a disturbed environment

2011 ◽  
Vol 25 (4) ◽  
pp. 937-940 ◽  
Author(s):  
Tânia Maria de Moura ◽  
Alexandre Magno Sebbenn ◽  
Karina Martins ◽  
Maria Andreia Moreno ◽  
Giancarlo Conde Xavier Oliveira ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Protected Areas ◽  
Allelic Diversity ◽  
Rare Allele ◽  
Conservation Unit ◽  
Long Distance ◽  
Disturbed Area ◽  
Disturbed Areas ◽  
Pasture Area ◽  
Two Populations

This study aimed to compare the genetic diversity of populations of Solanum lycocarpum A.St.-Hil between natural and human disturbed environments, with the assumption that protected areas have greater genetic diversity than disturbed areas. For this study, two populations were sampled in Goiás State, Brazil. One was located in a conservation unit, Serra de Caldas Novas State Park, in the Caldas Novas municipality. The other was located in a pasture area in the municipality of Morrinhos. The two populations are 41 km apart. We sampled 60 individuals from each population, which were genotyped with five microsatellite loci (SSR). The highest number of alleles was recorded in the population of the conservation unit, where we found 11 exclusive and five rare alleles. In the disturbed area, we recorded only three exclusive alleles and one rare allele. Although we did not observe significant inbreeding in these populations, genetic divergence between them was high (G ST (Hedrick)=0.147 =0.147) for a species with long distance seed dispersal. The results corroborate the hypothesis that the population in the less disturbed area harbors greater allelic diversity. They also confirm the effectiveness of using protected areas to preserve the genetic diversity of the species.

The influence of floral morph ratios and low plant density on mating and fertility in a tristylous colonizing species

Botany ◽  
2018 ◽  
Vol 96 (8) ◽  
pp. 533-545 ◽  
Author(s):  
Christopher M. Balogh ◽  
Spencer C.H. Barrett
Keyword(s):  
Field Experiment ◽  
Seed Set ◽  
Plant Density ◽  
Pollen Limitation ◽  
Lythrum Salicaria ◽  
Long Distance ◽  
Experimental Conditions ◽  
Wide Range ◽  
Morph Ratios ◽  
Floral Morph

Sexual reproduction in heterostylous populations may be vulnerable to demographic conditions because of the small number of mating types in populations. Here, we investigate mating and fertility under natural and experimental conditions in tristylous Lythrum salicaria L., an invasive species that exhibits a wide range of floral morph ratios and demographic contexts. We grew 147 open-pollinated seed families from six populations with different morph structures to estimate intermorph mating (d). In a field experiment, we used progeny ratios from 47 spatially isolated individuals to estimate d, and measured the intensity of pollen limitation experienced by the morphs. The M- and S-morphs experienced high rates of d, regardless of population size or morph ratio. Estimates for the L-morph revealed low levels of intramorph mating in three dimorphic and two trimorphic populations, but near complete intramorph mating in a monomorphic population. Despite high levels of intermorph mating in the field experiment, the morphs experienced significant pollen limitation of fruit and seed set, but this did not differ in intensity among the morphs. Our field experiment demonstrates that although plant isolation was associated with pollen limitation of seed set, “long-distance” bee-mediated pollen flow served to maintain intermorph mating. Tristyly in L. salicaria is remarkably robust to the demographic variation associated with colonization.

Seed-setting in subterranean clover (Trifolium subterranean L.). III. The effect of plant density

1961 ◽  
Vol 12 (1) ◽  
pp. 10 ◽  
Author(s):  
JJ Yates
Keyword(s):  
Seed Production ◽  
Seed Weight ◽  
Plant Density ◽  
Plant Cover ◽  
General Pattern ◽  
Strain Differences ◽  
Subterranean Clover ◽  
Seed Setting ◽  
Below Ground ◽  
Australian Wheat

Various aspects of seed production in a number of strains of subterranean clover sown at fire seeding rates at two sites in the Western Australian wheat-belt were investigated. Dry matter yields and percentage leaf in the foliage were also recorded. Percentage leaf increased with plant density in the earlier-maturing, stemmy strains, so that differences amongst strains diminished as density increased. The differences amongst strains in number of inflorescences when grown as single plants were largely eliminated under dense sward conditions, so that the two main factors in seed production were number of seeds per inflorescence and mean seed weight. The proportion of burrs above and below ground varied widely amongst strains, and was influenced by plant density in some strains. It is postulated that the extent of burr burial depends on the interaction between strain, environment, and condition of the surface soil. Burr burial improved the efficiency of seed-setting, particularly in the more severe environment. Strain differences in seeds per inflorescence below ground were relatively small, but within each strain, values were higher in the more favorable environment. The efficiency of seed-setting above ground differed considerably amongst strains and between the two environments, and tended to increase with plant density particularly in the earlier-maturing strains. Correlations were established between seeds per inflorescence above ground and the amount of plant cover in these strains. An artificial covering of wood-wool also improved seed-setting above ground. Mean seed weight followed the same general pattern as seeds per inflorescence.

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