scholarly journals Seed shadow, seedling recruitment, and spatial distribution of Buchenavia capitata (Combretaceae) in a fragment of the Brazilian Atlantic Forest

2006 ◽  
Vol 66 (3) ◽  
pp. 883-890 ◽  
Author(s):  
B. A. Santos ◽  
F. P. L. Melo ◽  
M. Tabarelli
Keyword(s):  
Spatial Distribution ◽  
Atlantic Forest ◽  
Seedling Recruitment ◽  
Local Population ◽  
Forest Understory ◽  
Seedling Mortality ◽  
Long Distance ◽  
Seed Shadow ◽  
Treefall Gaps ◽  
Suitable Habitats

Here we describe the seed shadow, seedling recruitment, ontogenetic structure and spatial distribution of Buchenavia capitata (an emergent canopy tree) in a 380-ha fragment of the Atlantic forest in northeast Brazil. In particular, we examine seed distribution around 10 parental trees and both seedling recruitment and mortality, during an 18 month period beneath and around parental trees. Moreover, we describe: (1) B. capitata occurrence within treefall gaps; (2) population structure in terms of ontogenetic stages for the whole site; and (3) spatial distribution of adults within an area of 51 hectares. 99% of seeds were found beneath parent crowns (n = 4,236) and seed density reached 14.6 ± 29.9 seeds/m² (0-140 seeds/m²). 49% of all seeds germinated but seedling mortality reached 100% after an 18 month period. In addition, saplings of B. capitata were not found in forest understory and within 30 treefall gaps (94-2,350 m²). The adults showed an average DBH of 69.3 ± 22.1 cm, were 19.2 ± 2.9 m tall and presented a clumped spatial distribution. B. capitata matched some of the features presented by shade intolerant trees or large-gap specialists, and we hypothesize that low rates or even lack of long distance seed dispersal events may be reducing the probability of B. capitata seeds reaching suitable habitats for successful seedling recruitment and growth. Because of that (1) seedlings face high levels of early mortality; (2) there is no sapling recruitment at the study site; and (3) local population faces senility and it is threatened by local extinction.

scholarly journals The influence of two wildfires and biological control agents on the population dynamics of Melaleuca quinquenervia in a seasonally inundated wetland

2021 ◽  
Vol 14 (1) ◽  
pp. 3-8
Author(s):  
Philip W. Tipping ◽  
Melissa R. Martin ◽  
Jeremiah R. Foley ◽  
Ryan M. Pierce ◽  
Lyn A. Gettys
Keyword(s):  
Biological Control ◽  
Population Dynamics ◽  
Seedling Recruitment ◽  
Additional Treatment ◽  
Seed Rain ◽  
The Other ◽  
Melaleuca Quinquenervia ◽  
Biological Control Agents ◽  
Seedling Mortality ◽  
Sapling Growth

AbstractThe potential of Melaleuca quinquenervia (Cav.) S.T. Blake to reinvade cleared areas was evaluated over a 13-yr period that included two wildfires and the introduction of biological control agents. The first wildfire occurred in 1998 and was followed by a mean of 591.5 recruited seedlings m−2. Recruits from that fire were cleared 7 yr later in July 2005 for a second experiment to evaluate seedling recruitment into cleared areas. Seed rain, seedling recruitment and mortality, and sapling growth rates were measured in four plots located around individual large reproductive trees. A second natural wildfire in 2007 burned through those plots, leading to increases in seed rain followed by a pulse in recruitment of 21.04 seedlings m−2, 96.5% fewer than after the 1998 fire. Recruits in half of the plots around each tree were then treated with regular applications of an insecticide to restrict herbivory by biological control agents, while herbivory was not restricted in the other half. There was no difference in seedling mortality between treatments 1,083 d post-fire (2007) with 96.6% seedling mortality in the unrestricted herbivory treatment and 89.4% mortality in the restricted herbivory treatment. Recruits subjected to the restricted herbivory treatment grew taller than those in the unrestricted herbivory treatment, 101.3 cm versus 37.4 cm. Many of the recruits were attacked by the biological control agents, which slowed their growth. Although solitary M. quinquenervia trees retain some capacity to reinvade areas under specific circumstances, there was a downward trend in their overall invasiveness at this site, with progressively smaller recruitment cohorts due to biological control agents. Land managers should prioritize removing large reproductive trees over treating recently recruited populations, which can be left for many years for the biological control agents to suppress before any additional treatment would be needed.

scholarly journals Great flights by great snipes: long and fast non-stop migration over benign habitats

2011 ◽  
Vol 7 (6) ◽  
pp. 833-835 ◽  
Author(s):  
Raymond H. G. Klaassen ◽  
Thomas Alerstam ◽  
Peter Carlsson ◽  
James W. Fox ◽  
Åke Lindström
Keyword(s):  
Migratory Birds ◽  
Strenuous Exercise ◽  
Migration Route ◽  
Long Distance ◽  
Migration Strategy ◽  
Ice Caps ◽  
Fuel Loads ◽  
Stopover Sites ◽  
Ecological Barriers ◽  
Suitable Habitats

Migratory land birds perform extreme endurance flights when crossing ecological barriers, such as deserts, oceans and ice-caps. When travelling over benign areas, birds are expected to migrate by shorter flight steps, since carrying the heavy fuel loads needed for long non-stop flights comes at considerable cost. Here, we show that great snipes Gallinago media made long and fast non-stop flights (4300–6800 km in 48–96 h), not only over deserts and seas but also over wide areas of suitable habitats, which represents a previously unknown migration strategy among land birds. Furthermore, the great snipes achieved very high ground speeds (15–27 m s −1 ), which was not an effect of strong tailwind support, and we know of no other animal that travels this rapidly over such a long distance. Our results demonstrate that some migratory birds are prepared to accept extreme costs of strenuous exercise and large fuel loads, even when stopover sites are available along the route and there is little tailwind assistance. A strategy of storing a lot of energy before departure, even if migration is over benign habitats, may be advantageous owing to differential conditions of fuel deposition, predation or infection risk along the migration route.

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.

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.

Seed dispersal, spatial distribution and population structure of Brazilnut trees (Bertholletia excelsa) in southeastern Amazonia

1997 ◽  
Vol 13 (4) ◽  
pp. 595-616 ◽  
Author(s):  
Carlos A. Peres ◽  
Claudia Baider
Keyword(s):  
Spatial Distribution ◽  
Seed Dispersal ◽  
Average Distance ◽  
Climatic Conditions ◽  
Long Distance ◽  
Neotropical Forests ◽  
Bertholletia Excelsa ◽  
Entire Study ◽  
Natural Stands ◽  
Seed Shadows

ABSTRACTSeeds of the Brazilnut tree (Bertholletia excelsa Humb. & Bonpl., Lecythidaceae) sustain one of the most important extractive industries in neotropical forests. Yet little is known about the demography and seed dispersal ecology of Bertholletia, particularly in natural stands which have not been previously harvested. This study presents data on the population density, spatial distribution, and seed dispersal ecology of Brazilnut trees at a pristine stand located within the Kayapó Indian Area of southeastern Amazonia, Pará, Brazil. Brazilnut trees were primarily found within groves (castanhais) of 75 to 149 trees, with a few isolated trees in between. Although the density of trees ≥ 10 cm in diameter at breast height (hereafter, dbh) at two groves was 4.8 to 5.1 trees ha–1, the overall density for the entire study area of c. 950 ha was estimated at 1.3 tree ha–1. Within-grove nearest neighbour distances averaged 21 m and were markedly skewed towards even shorter distances. Seed dispersal experiments using 709 marked seeds indicated that this pattern can be largely explained by the highly restricted seed shadows imparted by the main seed dispersal agents of Bertholletia at this site, the red-rumped agouti (Dasyprocta leporina). Agoutis on average scatterhoard Bertholletia seeds to an average distance of 5 m, and rarely beyond 20 m, from seed stations. We suggest that, once edaphic and climatic conditions are suitable, the highly contagious spatial distribution of Bertholletia trees at the landscape level can be largely accounted for by the quantitatively dominant effect of short-distance dispersal by caviomorph rodents, and rare events of long-distance dispersal provided by other vectors. This mechanism of grove formation need not resort to untested conjectures of human dispersal and intentional planting in prehistoric and historic times as it has often been suggested in the literature.

Spatial distribution and morphology of shoots in the variant crown form of Rhododendron reticulatum

Botany ◽  
2010 ◽  
Vol 88 (11) ◽  
pp. 995-1005 ◽  
Author(s):  
Kenichi Yoshimura
Keyword(s):  
Spatial Distribution ◽  
Functional Differentiation ◽  
Forest Understory ◽  
Width Ratio ◽  
Crown Architecture ◽  
Western Japan ◽  
Long Shoots ◽  
Short Shoots ◽  
Lower Depth ◽  
Crown Form

Rhododendron reticulatum D. Don ex G.Don is a common understory shrub in western Japan that exhibits highly plastic crown architecture and occurs in various light environments. I investigated how functional differentiation and spatial distribution of long and short shoots contribute to the plasticity of crown architecture of R. reticulatum. Crown form was derived from the crown depth/width ratio. Crown depth/width ratio was higher in sun-lit crowns. In crowns with higher depth/width ratio, long shoots were distributed in upper positions of the crown. Long shoots grew vertically and horizontally. In crowns with lower depth/width ratio, long shoots were arranged in the outer position of the crown and grew outward. Within neighboring shoots, long shoots had less mass than their paired short shoots. Results suggest that long shoots of R. reticulatum function to expand the crown and to reduce leaf overlap in multilayer crowns, which are found in high-light environments, while both long and short shoots function to minimize leaf overlap in monolayer crowns, which are found in shaded environments. Plasticity of crown architecture by altering shoot position and shoot morphology allows growth under various light environments in the forest understory.

scholarly journals Spatial Distribution of Aboveground Carbon Stock of the Arboreal Vegetation in Brazilian Biomes of Savanna, Atlantic Forest and Semi-Arid Woodland

PLoS ONE ◽  
2015 ◽  
Vol 10 (6) ◽  
pp. e0128781 ◽  
Author(s):  
Henrique Ferraco Scolforo ◽  
Jose Roberto Soares Scolforo ◽  
Carlos Rogerio Mello ◽  
Jose Marcio Mello ◽  
Antonio Carlos Ferraz Filho
Keyword(s):  
Spatial Distribution ◽  
Atlantic Forest ◽  
Carbon Stock ◽  
Aboveground Carbon ◽  
Semi Arid

Environmental filters and seedling recruitment on a coastal dune in subarctic Quebec (Canada)

1996 ◽  
Vol 74 (9) ◽  
pp. 1507-1513 ◽  
Author(s):  
Gilles Houle
Keyword(s):  
Seed Germination ◽  
Spatial Pattern ◽  
Seedling Establishment ◽  
Seedling Recruitment ◽  
Salt Spray ◽  
Spatial Segregation ◽  
Coastal Dune ◽  
Seedling Mortality ◽  
Environmental Filters ◽  
Dune System

One important factor that often determines the presence of a plant species on a site is propagule availability. Afterwards, abiotic and biotic factors act as a series of filters operating sequentially from the seed to the adult stage, determining the pattern of recruitment. By comparing the spatial pattern of emerging seedlings to those of seed availability and of surviving seedlings, one can determine the relative importance of the environmental filters acting on the seed germination and the seedling establishment phases. On a coastal dune system in subarctic Quebec (Canada), sand accumulation, salt spray, and substrate physicochemistry, all affecting microsite quality for seeds and seedlings, vary along a short topographical gradient. My goal was to determine whether or not conditions changing along this gradient differentially affect the initial stages of population recruitment of two perennial herbaceous species for which adults are segregated along the gradient: Honckenya peploides and Elymus mollis. The spatial pattern of seeds in the seed bank and that of emerging seedlings were not related to one another for either Honckenya or Elymus. However, patterns of surviving seedlings were spatially correlated with those of emerging seedlings. Seed and seedling mortality were not density dependent; they were both spatially variable, although not clinal. These results suggest that the environmental filters acting on the germination stage are those that determine the spatial patterns of recruitment. Spatial segregation along the flank of the foredune between adults of the two species studied thus seems to be maintained in part (and maybe reinforced) by low seed mobility, or low seed retention, and the availability of suitable microsites for seed germination. Population progression towards the upper beach seems to depend mostly on seedling establishment for Honckenya but on clonal growth for Elymus. Keywords: Elymus mollis, Honckenya peploides, Hudson Bay, partial Mantel test, spatial segregation, Whapmagoostui-Kuujjuaraapik.

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