Control of seedling density on disturbed ground: role of seedling establishment for some midsuccessional, old-field species

1991 ◽  
Vol 69 (4) ◽  
pp. 773-777 ◽  
Author(s):  
R. J. Reader ◽  
J. Buck
Keyword(s):  
Seedling Establishment ◽  
Seed Mass ◽  
Interspecific Variation ◽  
Frequency Of Occurrence ◽  
Seedling Density ◽  
Old Field ◽  
Species Frequency ◽  
Seed Availability ◽  
Natural Seedling

In midsuccessional old fields, seedlings are often concentrated in patches of disturbed ground, such as earth mounds created by burrowing mammals. An experiment was conducted to determine whether interspecific variation in seedling density on mounds reflected interspecific variation in potential seedling establishment (i.e., the number of seedlings established per 1000 seeds sown). Seeds of 13 old-field forbs were sown on experimentally created mounds in an abandoned pasture. Their potential seedling establishment ranged from 0 to 156 seedlings per 1000 seeds sown, and seedling establishment was directly related to seed mass. The number of seedlings becoming established naturally on mounds ranged from 0.1 to 41 seedlings per mound for the 13 species. Natural seedling establishment and potential seedling establishment were not directly related. Instead, natural seedling establishment on mounds was correlated with species' frequency of occurrence off mounds. This suggests that seed availability may be more important than seedling establishment in controlling seedling density on mounds. However, if seed availability is unlimited or equal among species, then seedling establishment could control seedling density on disturbed ground. Key words: disturbance, seedling density, old field.

Post-dispersal seed predation in Pinus halepensis and consequences on seedling establishment after fire

2008 ◽  
Vol 17 (3) ◽  
pp. 407 ◽  
Author(s):  
Maria José Broncano ◽  
Anselm Rodrigo ◽  
Javier Retana
Keyword(s):  
Seed Predation ◽  
Seedling Establishment ◽  
Pinus Halepensis ◽  
Spatiotemporal Patterns ◽  
Seedling Density ◽  
Burned Areas ◽  
One Year ◽  
Rodent Populations ◽  
Very High

In the present study, we analyse the spatiotemporal patterns of seed predation and the consequences of this predation in the establishment of new Pinus halepensis individuals. Rodents were the main predators of P. halepensis seeds in burned areas, while predation by ants was considerably lower. Concerning spatiotemporal patterns of seed predation, the results obtained indicate that, although there were some small differences among distances or among seasons, removal of P. halepensis seeds was consistently very high in all situations, whether close to or far from the unburned margins, in pine or mixed forests, in different sites and in all sampling periods throughout the year. We analysed the role of seed predation on the modulation of post-fire regeneration of P. halepensis. Just after fire, no differences in seedling density were found between plots with or without rodent exclusion, probably owing to the high density of seeds on the ground and the low density of rodents affected by fire. One year after fire, when rodent populations had recovered in burned areas and seeds were much less abundant, the combination of addition of seeds and rodent exclusion led to an increase in pine seedling establishment.

Post-dispersal losses to seed predators: an experimental comparison of native and exotic old field plants

2001 ◽  
Vol 79 (3) ◽  
pp. 284-292 ◽  
Author(s):  
C S Blaney ◽  
P M Kotanen
Keyword(s):  
Seed Predation ◽  
Seed Mass ◽  
Interspecific Variation ◽  
Experimental Comparison ◽  
Old Fields ◽  
Old Field ◽  
Seed Predators ◽  
Predator Exclusion ◽  
Reduced Rate ◽  
Insect Exclusion

Invasions by exotic plants may be more likely if exotics have low rates of attack by natural enemies, including post-dispersal seed predators (granivores). We investigated this idea with a field experiment conducted near Newmarket, Ontario, in which we experimentally excluded vertebrate and terrestrial insect seed predators from seeds of 43 native and exotic old-field plants. Protection from vertebrates significantly increased recovery of seeds; vertebrate exclusion produced higher recovery than controls for 30 of the experimental species, increasing overall seed recovery from 38.2 to 45.6%. Losses to vertebrates varied among species, significantly increasing with seed mass. In contrast, insect exclusion did not significantly improve seed recovery. There was no evidence that aliens benefitted from a reduced rate of post-dispersal seed predation. The impacts of seed predators did not differ significantly between natives and exotics, which instead showed very similar responses to predator exclusion treatments. These results indicate that while vertebrate granivores had important impacts, especially on large-seeded species, exotics did not generally benefit from reduced rates of seed predation. Instead, differences between natives and exotics were small compared with interspecific variation within these groups.Key words: aliens, exotics, granivores, invaders, old fields, seed predators.

Variation in the morphology and flowering time of cluster clover (Trifolium glomeratum L.) and its relationship to distribution in southern Australia

1995 ◽  
Vol 46 (5) ◽  
pp. 1027 ◽  
Author(s):  
FP Smith ◽  
PS Cocks ◽  
MA Ewing
Keyword(s):  
Genetic Variation ◽  
Flowering Time ◽  
Seed Mass ◽  
Annual Rainfall ◽  
Strongly Correlated ◽  
Summer Maximum ◽  
Maximum Temperatures ◽  
Pattern Of Variation ◽  
Growth Habits

Cluster clover is a widely distributed and ecologically successful introduced legume in southern Australia. In an attempt to understand the role of genetic variation in this success, morphological and physiological traits were measured in 94 accessions from southern Australia and 6 from the Mediterranean basin. Flowering time ranged from 105 to 185 days after sowing, but was not strongly correlated with annual rainfall or length of growing season at the site of collection. Variation in other traits partitioned the populations into two morphs which, apart from flowering time and leaf marker, were largely homogeneous. The morphs differed significantly in floret number per inflorescence (22 v. 32-37) and seed mass (379 8g v. 523 8g), had different growth habits and strong within-morph associations between leaf markers and stipule and petal coloration. The morphs differed in their distributions within southern Australia and the pattern of distribution was related to summer maximum temperatures, winter minimum temperatures and spring rainfall. These results demonstrate that genetic variation has been important to the success of cluster clover and suggests that the variation is organized. The pattern of variation observed and its relationship to ecogeography is consistent with findings for other highly inbreeding species. A map of the species distribution in Western Australia is presented.

scholarly journals Iridescent structural colour production in male blue-black grassquit feather barbules: the role of keratin and melanin

2009 ◽  
Vol 6 (suppl_2) ◽  
Author(s):  
Rafael Maia ◽  
João Victor O Caetano ◽  
Sônia N Báo ◽  
Regina H Macedo
Keyword(s):  
Thin Film ◽  
Natural Variation ◽  
Single Layer ◽  
Coherent Scattering ◽  
Interspecific Variation ◽  
Stray Light ◽  
Main Role ◽  
Minimum Number ◽  
Keratin Layer

Iridescent coloration plays an important role in the visual communication system of many animal taxa. It is known that iridescent structural colours result from layers of materials with different refractive indexes, which in feathers usually are keratin, melanin and air. However, the role of these materials in the production of structural iridescent coloration is still poorly documented. Despite the great interspecific variation in the organization of such structures in bird plumage, melanin layers are usually considered too opaque, suggesting its main role is to delineate the outermost keratin layer and absorb incoherently scattered stray light. We combined spectrometry, electron microscopy and thin-film optical modelling to describe the UV-reflecting iridescent colour of feather barbules of male blue-black grassquits ( Volatinia jacarina ), characterized by a keratin layer overlying a single melanin layer. Our models indicate that both the keratin and the melanin layers are essential for production of the observed colour, influencing the coherent scattering of light. The melanin layer in some barbules may be thin enough to allow interaction with the underlying keratin; however, individuals usually have, on an average, the minimum number of granules that optimizes absorbance by this layer. Also, we show that altering optical properties of the materials resulted in better-fitting models relative to the empirically measured spectra. These results add to previous findings concerning the influence of melanin in single-layer iridescence, and stress the importance of considering natural variation when characterizing such photonic structures.

Effect of forest floor disturbance on seedling establishment of Chamaecyparislawsoniana

1980 ◽  
Vol 10 (4) ◽  
pp. 441-446 ◽  
Author(s):  
Donald B. Zobel
Keyword(s):  
Seedling Establishment ◽  
Forest Floor ◽  
Soil Disturbance ◽  
Litter Removal ◽  
Growing Seasons ◽  
Percentage Survival ◽  
Natural Seedling ◽  
Forest Floor Disturbance ◽  
Natural Stands ◽  
Port Orford Cedar

Native seeds of Chamaecyparislawsoniana (A. Murr.) Parl. (Port-Orford-cedar) were sown on treated 1-m2 plots in four natural stands in southwestern Oregon, U.S.A. Treatments, replicated four times per stand, were (1) control, with natural litter undis-turbed, (2) litter removed, (3) litter removed and burned with ash replaced on plot, and (4) spaded after litter removal. Eighty-nine percent of germination occurred in early to mid-June. The spading treatment had the most germinants and the most survivors. Litter removal and burning treatments supported many fewer germinants, had the smallest seedlings, and had no survival after two growing seasons. Percentage survival of the few germinants in the control was as good as for the spading treatment, 5–6% after three summers. Although much natural seedling establishment may occur on natural litter, soil disturbance appears to greatly increase the rate of establishment. Litter removal alone does not increase establishment.

scholarly journals ENT trauma in children: causes, frequency and characteristics in different periods of childhood

2020 ◽  
Vol 19 (6) ◽  
pp. 94-101
Author(s):  
E. Yu. Radtsig ◽  
◽  
M. M. Evsikova ◽  
M. A. Varavina ◽  
◽  
...  
Keyword(s):  
Conservative Treatment ◽  
Soft Tissues ◽  
Traumatic Events ◽  
Frequency Of Occurrence ◽  
External Nose ◽  
Post Traumatic

Numerous injuries (and their treatment) have been encountered since the very beginning of the development of human civilization and remain one of the most significant problems in our time, since the frequency of injuries in general (and of ENT organs in particular) does not tend to decrease either in children or adults. ENT injuries are in fourth place in terms of emergency appeal rates. The most common injury to the maxillofacial area is a fracture of the skeleton of the nose. The article presents data on the frequency of occurrence of this pathology and describes the features of the causes that caused it in different periods of childhood, presents an algorithm for managing patients. The role of homeopathic arnica-containing remedies (Arnigel®) in the conservative treatment of reactive post-traumatic events from the soft tissues of the external nose is shown.

Pair-wise competition-trials amongst seedlings of ten dipterocarp species; the role of initial height, growth rate and leaf attributes

2005 ◽  
Vol 21 (3) ◽  
pp. 317-328 ◽  
Author(s):  
E. V. J. Tanner ◽  
V. K. Teo ◽  
D. A. Coomes ◽  
J. J. Midgley
Keyword(s):  
Leaf Nitrogen ◽  
Interspecific Comparison ◽  
Seedling Density ◽  
Height Difference ◽  
Initial Height ◽  
Sand Mixture ◽  
Hardwood Species ◽  
Nitrogen Concentrations ◽  
Equal Height

To investigate whether seedlings of ten dipterocarp species differed significantly in terms of growth and mortality or whether species were not significantly different and could be considered ecologically similar, seedlings were grown, two per pot, in two experiments: (1) where the two seedlings were of equal height (30 cm); and (2) where one seedling was 10 cm shorter than the other. Seedlings were grown in a shade house with 15% above-canopy light in a 50:50 forest soil–sand mixture and were watered frequently; pots were placed so that seedling density was 130 seedlings m−2 of ground. In the first experiment there were 45 pairwise combinations of species when seedlings were 30 cm tall (AB, AC, AD,…. BC, BD…IJ; where A, B, C…J signify different species); each combination was replicated 10 times so there were 450 pots with 900 seedlings. In the second experiment there were 100 pairwise combinations of species and size e.g. Aa (30 cm A with 20 cm a), Ab (30 cm A with 20 cm b), each combination was replicated 10 times hence there were 1000 pots with 2000 seedlings. After 22 mo 79% of the initial 2900 seedlings survived; on average they had grown 42 cm (i.e. to 72 cm tall from their initial 30 cm). The most frequent outcome of competition-trials between different sized individuals (784 of 1000 trials) was that the initially taller seedling of each pair ‘won’ (it was the taller or surviving seedling). When 900 of these trials (setting aside, Aa, Bb, Cc etc.) were analysed as 45 comparisons between species with different sized individuals (Ab and aB are one interspecific comparison for these purposes), initial height determined the outcome in 23 cases (even in some competitions between light hardwood species and heavy hardwood species); in 6 cases a species (mostly light hardwoods) behaved as a ‘dominant’ – they usually won even if they were smaller initially. We found few significant differences between species in: initial seedling heights; leaf nitrogen concentrations; and specific leaf areas when they were grown in similar conditions, and these attributes were not correlated with growth rates. The similarity of seedlings of different species meant that often a height difference of just 10 cm was enough to determine the outcome of a pairwise competition-trial in high seedling densities and light equivalent to that in forest gaps.

Species Size and Reproductive Economy in Herbaceous Vegetation

2016 ◽  
Author(s):  
Amanda Tracey
Keyword(s):  
Species Coexistence ◽  
Plant Size ◽  
Future Research ◽  
Traditional Theory ◽  
Old Field ◽  
Critical Question ◽  
Self Fertilization ◽  
Reproductive Economy ◽  
Competition For Resources

According to traditional theory, larger plants generaly have an advantage with respect to competition, especially for light. It seems a paradox then that most species that coexist within natural vegetation are relatively small; specis size distributions are right-skewed at virtually every scale. The critical question then becomes: if bigger is better in competition for resources, why then are there so many small plants? A potential explanation for this paradox is that smaller species may have greater reproductive economy-i.e. the ability to reproduce despite suppression from intense competition. Selection for greater reproductive economy may be associated with smaller seed sizes, increased rates of self-fertilization and/or clonality, and in the case of this study, smaller size at reproductive maturity. Random plots in an old field at Queen's University Biological Station were sampled and the largest and smallest reproductive individuals of each species were collected, dried and weighed - to test the hypothesis that smaller species can reproduce at a smaller proportion of their maximum potential plant sizes. The results did not support this, but the hypothesis that smaller plants have greater reproductive economy could not be rejected as it was not possible to record data for the largest possible plant size for each species (since even the largest plants were subjected to competition from neighbours). This provides a focus for future research. Understanding the role of plant size in affecting the process of species assembly has important implications for species coexistence and mechanisms of biodiversity preservation, and thus efforts involving conservation and ecosystem management.

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