Nick Ashton-Jones, with Oronto Douglas and Susi Arnott

“ However, the forest floor is protected from such fierce heat, as we notice when we enter its shade during the day. In fact the temperature can be as much as 4 degrees lower than at the canopy, and oligophotic plants have adapted accordingly. However, this does mean that when forest is damaged or disturbed it is less well able to withstand the temperature stress than the euphotic plants. Lianes and other climbing euphotic plants tend to take over the lower forest stories when this happens, and create a real 'jungle'—thereby restricting the development of more economically useful tree species. ”

“ Rarely is the natural tropical rainforest a nightmare 'jungle' of vines and thick undergrowth. More often the dense tree canopy above ensures that light intensity on the forest floor is limited, so that there is little undergrowth and passage is easy. ”

“ For example, the nature and location of soil itself is difficult to define because of the spatial confusion of the various soil and semi-soil components: litter, detritus, humus, inorganic particles, organic compounds, and the soil-water and soil-atmosphere interfaces. Apart from the parasitic plants, all plants need soil of some sort and since rainforest trees give physical support all sorts of other plants—in branch forks, in holes made by animals, on stems and branches, and in any nook or cranny—there is soil in places other than on the ground. ”

“ Where light does enter the forest, the high intensity of the tropical sun causes an explosion of growth: in the interior, regeneration of many plant species only occurs with the collapse of a dead mature tree, cutting a slash of light through the canopy to the forest floor. ”

“ Populations of micro-arthropods in Nigerian tropical rainforests have been estimated to exceed 38,000 per m2 of surface soil.
One of the most conspicuous Arthropods is the ant, exploiting every level of the ecosystem of the tropical rainforest as individuals and in multitudinous drives, found at every level from deep under ground to the very top of the Silk Cotton Tree. They are extraordinarily active; it has been estimated that ants are responsible for eating 1% of all leaves of the tropical rainforest each year. ”

“ A meaningful sample area must cover square kilometres; vertically, access must be gained to intermediate levels and to the canopy which may be over 30m high, then root systems must be followed as far as 5m down through a soil that is hard and crammed with vegetable life.
Secondly, the life span of the dominant life forms (mainly trees) makes for observation periods that exceed human life spans.
And thirdly, the high diversity of plants and animals is daunting; a square kilometre of natural Nigerian rainforest will contain thousands of plant species and countless more animal species. ”

“ Tap roots, grow vertically down into the soil. Tap root systems are less common in the tropical rainforest than in the temperate forest, partly because nutrients are concentrated in the surface layers of soil and partly because deep roots are also unnecessary as far as seeking for water is concerned. The physical work of anchoring the plant that is another function of deep taproots is often carried out by aerial or buttress roots to compensate. Lateral roots, which grow horizontally. Fibrous roots which form thick interwoven mats as in palm trees. Aerial roots, which grow in the air. ”

“ These inequalities create localised rainfall, when transpired vapour from one area condenses back to water in a cooler area or on a cooler surface. On a still day evapotranspiration may be limited by the build-up of a saturated layer of vapour above individual leaves and the forest canopy as a whole; on windy days evapotranspiration increases because the saturated layer is removed.
Rainforests effectively regulate their own humidity. When it is very high, less water can be transpired because the air is already so moist. So in turn the plants draw up less water from the soil. ”

“ Although the trunks of some tropical rainforest trees have special characteristics such as fluting, they tend to have very similar smooth, light-coloured cylindrical shaped trunks. As the crown and leaves of a mature emergent tree are well out of sight, species can often only be distinguished by making a slash through the outer and inner bark of the trunk with a machete. ”

“ It is often assumed that there is no soil erosion beneath tropical rainforest. However, under certain conditions where there is very little plant ground cover, soil protection is dependant on leaf litter and other fallen vegetation. ”

“ In tropical rainforests, 50 to 60% of N and P is found in the leaves, stems and roots of plants, and nearly 90% of the K. By the time the C horizon of the soil is reached, no N is found, only about 11% of the P and only minute amounts of K. Nitrogen is not found in mineral deposits, but must enter the system by being 'fixed' from the air into organic molecules. ”

“ Interactions between tropical rainforests and their environment are far more complex than those of temperate forests, and this also complicates their study. The most important interactions are between roots and soil, and between leaves and the atmosphere. ”

“ Because of the high rainfall there is a strong tendency for nutrients to leach out, resulting in poor sandy soils. This is balanced to some extent by the high rate of biomass addition to the soil, as vegetation dies and decays, rapidly re-cycling nutrients. ”

“ Many plants in the Oligophotic layer depend on sunflecks to set off flowering and seed formation.
5.5.2 MICRO-CLIMATE: TEMPERATURE
We have discussed the seasonal and diurnal (daily) temperature cycles within the macroclimate of the tropical rainforest biome as a whole. However, micro-climatic temperature changes also occur.
The surface temperature of any living thing affects its activity. In the direct midday sunlight of the tropics, surfaces of human skin, naked soil and leaves can reach temperatures in the high thirties Celsius. When this happens, we humans can move into the shade ”

“ The LEM natural rainforest ecosystem serves as a good introduction to the natural rainforest of the Niger Delta in general, because the LEM ecozone covers the greater part of the West African Tropical Rainforest biome. The LEM ecozone is different from the BAM and FAM ecozones because the soils are comparatively well drained and relatively uniform ”

“ The architecture of a tree is defined as much by its roots as by other body parts. However the more immediately visible characteristics of architectural variation are the shapes and branching habits of trunks and crowns. ”

“ There is great competition for the light that does reach the Oligophotic layer, and shade-tolerant plants, called the Sciophiles, grow here. As little as 1% of the available sunlight may reach the forest floor, which is therefore much less bioactive. ”

“ A host tree may be smothered by clinging roots or live to an old age, growing happily together with its parasite species for years. There is a good example in the ancient Ficus preserved as a sacred tree in the village square of Botam-Tai. ”

“ Patterns of inheritance are complicated by the fact that one set of genes for all traits are inherited from each parent, so that any given individual will normally have two complementary sets. This overall genetic context is also very important; many traits may only be seen where genes for alternative forms are absent. ”

“ Thick horizontal surface roots, and well-developed taproots and sinkers. Weak surface roots, but a rich system of many oblique roots and a prominent taproot. Numerous sizeable aerial roots, plus a network of weaker underground roots. #⁠roots of emergent trees
Emergent trees are those that rise to become part of the canopy and which therefore dominate the tropical rainforest. These trees all tend to have thick horizontal surface roots which frequently merging into large spurs or buttresses. However they may or may not have taproots, while the vertical 'sinkers' can be weak or well developed. ”

“ To give a simple example; a rat which can run faster than all the other rats will live longer than her sisters who are caught and eaten by the cats. Thus she will have more offspring and the trait allowing faster running will spread through the population. ”

“ They are so efficient at doing this that the natural rain forest ecosystem as a whole loses very small amounts of nutrients. Where deeper taproots are put out, they serve mainly as physical anchors and to access water from lower soil horizons. ”

“ It turns out that growth rates vary greatly from species to species, and even within species depending on the precise conditions. Armed with this knowledge, loggers could leave slower growing species behind to maintain the canopy, harvesting only the faster growing ones. ”