La phénologie des arbres caducifoliés en forêt guyanaise (5° de latitude nord) : illustration d'un déterminisme à composantes endogène et exogène

1994 ◽  
Vol 72 (12) ◽  
pp. 1843-1857 ◽  
Author(s):  
Denis Loubry
Keyword(s):  
Key Words ◽  
Tree Species ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
French Guiana ◽  
Dry Season ◽  
Deciduous Tree ◽  
Leaf Fall

The French Guianan forest is an evergreen rain forest that contains approximately 100 deciduous tree species. The taxonomical distribution of the deciduous character is widely spread, and its presence or absence among some taxa, as well as its ancient origin, are arguments in favour of an endogenous origin. Leaf-fall periodicity was studied on a sample of 500 trees during a 2-year period. Periodicity is annual and seasonal. It is not correlated to rainfall and not linked to the occurrence of a dry season. It seems closely correlated to photoperiodical variations, even though those variations are weak (35 min at latitude 5°30′N). However, each tree has its own periodicity for leaves shedding. Therefore, there is a paradox between seasonality and individual periodicity of leaf fall. The existence of this paradox leads us to consider the hypothesis of an integration of endogenous and exogenous components in the determination of leaf-fall periodicity. Key words: deciduousness, French Guiana, phenology, photoperiodism, tree, tropical rain forest.

Change in leaf structure in relation to crown position and size class for tree species within a Sri Lankan tropical rain forest

Botany ◽  
2008 ◽  
Vol 86 (6) ◽  
pp. 633-640 ◽  
Author(s):  
P. A.K.A.K. Panditharathna ◽  
B. M.P. Singhakumara ◽  
H. P. Griscom ◽  
M. S. Ashton
Keyword(s):  
Tree Species ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
Size Class ◽  
Leaf Structure ◽  
Sri Lankan ◽  
Size Classes ◽  
Canopy Trees ◽  
Crown Position ◽  
Closed Canopy

The purpose of our study was to examine change in leaf structure (anatomy and morphology) through different phases of tree size and crown position within a Sri Lankan rain forest. We selected four late-successional canopy species that represented dominant genera ( Shorea , Mesua ) within an Asian tropical rain forest. All are considered shade-tolerant and capable of growing to maturity beneath closed-canopy late-successional forests. Species within each genus were either restricted to seepages and bottom slopes (valley species) or to upper slopes and ridges (ridge species). The size classes represented (i) seedlings, (ii) saplings, (iii) poles growing beneath closed-canopy conditions, and (iv) trees of the rain forest canopy. Between size classes, leaves were thicker and with higher stomatal densities for canopy trees than for seedling, sapling, and pole size classes. Plasticities for measures of leaf structure were greater for ridge species than valley species; except for cuticle thickness, which showed the opposite trend (valley > ridge). Area, length, and width of leaves attained maxima for the sapling size class for all species. Drip-tip lengths were greatest for seedlings of all species, and least for canopy trees. Trends in leaf structure and morphology dimensions across size classes for late-successional canopy tree species are the same as those trends reported between rain forest species of different habitat strata (e.g., understory shrubs versus upper canopy trees). Our results suggest leaf dimensions could provide robust measures of environment, irrespective of species, or size class of tree.

scholarly journals The Diversity of Tropical Orchids of South Papua

2018 ◽  
Vol 5 (1) ◽  
pp. 1-9
Author(s):  
Verena Agustini ◽  
Suharyanto Suharyanto ◽  
Suharno Suharno ◽  
Lisiard Dimara ◽  
Chris D. Sembay
Keyword(s):  
Key Words ◽  
Sea Level ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
World Wide ◽  
Mountain Forests ◽  
Threatened Plants ◽  
Highland Area ◽  
Wide Range ◽  
Lowland Area

Papua is an area with very wide range, from lowland with altitude 0 m to highland area with 4730 m above sea level. Orchids species constitute the greater part of orchids diversity, which can grow on the bare branches of tall trees, or embedded in moss dripping in wet and cool mountain forests, as well as in the eternal shade of tropical rain forest. Numerous plants world-wide are threatened with extinction because of degradation or destruction of their habitat. Orchids are among the most threatened plants of all, especially when pressure from dealers and collectors aggravales the problems. South Papua is a lowland area with the elevation around 0-7 m above sea level, temperature 23-300 C, and 1500 m rainfall per year. The aims of these investigations were to explore the diversity of tropical orchids in South Papua. The exploration and collection were done in Asmat, Boven Digul, Mappi, and Merauke. The study found 22 genera and 75 species, mostly are epiphytic. Key words: orchids, exploration, diversity, South Papua.  

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