Showing papers on "Seed dispersal published in 1970"

Herbivores and the Number of Tree Species in Tropical Forests

Abstract: A high number of tree species, low density of adults of each species, and long distances between conspecific adults are characteristic of many low-land tropical forest habitats. I propose that these three traits, in large part, are the result of the action of predators on seeds and seedlings. A model is presented that allows detailed examination of the effect of different predators, dispersal agents, seed-crop sizes, etc. on these three traits. In short, any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents. Either event will lead to more space in the habitat for other species of trees, and therefore higher total number of tree species, provided seed sources are available over evolutionary time. As one moves from the wet lowland tropics to the dry tropics or temperate zones, the seed and seedling predators in ...

Flowering plants; origin and dispersal

Abstract: Flowering plants; origin and dispersal , Flowering plants; origin and dispersal , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Relationships between Fruiting Seasons and Seed Dispersal Methods in a Neotropical Forest

Abstract: The weight of fruits and seeds that fell into 75 polyethylene sheets, each 152 x 152 cm, totalling 175 m2 in area, was measured over a period of 17 months in the humid forest of Barro Colorado Island, in the Panama Canal Zone. A total of 72 species of fruits and seeds fell into the traps, and the number falling into any individual trap varied from three to 14. The number of fruiting species per month varied from 11 to 26, while the combined weight of fruits and seeds varied from a monthly average of 0.61-1.930 gm/square meter per day. Small-seeded fruits ripened rather evenly throughout the year, whereas large-seeded fruits tended to be seasonal. Although the primary determinants of fruiting times may be physical, small fruits the seeds of which pass unharmed through the guts of animals tend to be nonseasonal and thus avoid competition for dispersal. Fruits with large seeds that are destroyed by the animals eating them fruit synchronously. The agouti (Dasyprocta punctata), being unable to devour the entir...

Natural seed fall in white pine (Pinus strobus L.) stands of varying density

Abstract: Seed fall was observed in three stands of mature white pines at stand basal-area densities of 80, 120, and 187 square feet per acre. It was found that the intermediate-density stand produced nearly 50 percent more seed than the stands of other densities. During a good seed year this stand produced 59 pounds of dry sound seed per acre. Most of the seeds were dispersed during a 7-week period beginning about the middle of September. The seed crop was reduced by action of birds, animals, and insects.

Decline Of The Negev's Acacias - A SpatiallyExplicit Simulation Model As An Aid ForSustainable Management

Abstract: In the Negev desert there is high concern about the high mortality and low recruitment of Acacia trees, a major source of livestock feed and firewood for the native Bedouins. The Acacias are mostly restricted to ephemeral riverbeds and areas with high ground water levels near oases. As the only trees in much of this desert, the Acacias constitute a major ecological concern in southern Israel. To develop sustainable conservation and management strategies it is necessary to understand the population dynamics of the trees. A spatially explicit, object-oriented computer simulation model is presented which is based on demographic data gained by field studies. As an example, we show first results of an application of the model to the ephemeral riverbed Nahal Saif which is cross-cut by a road. The road alters the flood regime. This leads to modifications in seed dispersal and reduces the water availability to the Acacia trees. It is shown that both factors have a negative impact on the population dynamics of A. raddiana. Culverts under the road would reduce the severity of this impact although this should be done in conjunction with the reintroduction of herbivorous mammals in order to facilitate seed dispersal and germination.

The role of frugivorous birds in the dispersal of shrubs in submontane zone of tropical forest, West Java, Indonesia

Abstract: . Partasasmita R. 2015. The role of frugivorous birds in the dispersal of shrubs in submontane tropical forest, West Java, Indonesia. Nusantara Bioscience 7: 144-148. Shrubs are widely distributed, from lowland to mountainous area. Submontane forest zone is one of many ecosystem types rich in many species of shrub. The success of plant growth and establishment depends on the role of the seed dispersal agents. This study of shrub seed dispersal by frugivorous birds has been conducted in tea plantation area of Panaruban, Subang, West Java. To get seeds trapped in feces, samples of feces were collected from birds trapped in mist nets and from fecal dropped count method. The study sites were tea plantation which had been neglected for five years and bush in a secondary forest nearby. The results showed that seeds of 7 species of shrub were found in the feces of six species of frugivorous birds trapped in mist nets and one species of bird from fecal dropped count method. Based on feces analysis, of the seven shrub species, Clidemia hirta was dispersed mostly by Dicaeum trigonostigma, and then by Pycnonotus aurigaster. Sambucus javanica was mostly dispersed by Pycnonotus goiavier and Scissirostrum dubium. The germination rate of seeds collected from feces was 1.43-5.71% higher than that of seeds which had not passed through the bird’s digestive tract.