Geography Reference
In-Depth Information
accumulate very deep. The tropical rainforests are lush with broad-
leaf evergreen tree cover. The tallest trees tend to be narrow with
few branches or leaves below the top of the canopy. These areas
produce around 40 per cent of the world's land-based
primary pro-
duction and contain half of the world's faunal and floral species. The
lack of strong seasonality means that fruit production and growth can
continue across the forest all year and there is a dense leaf canopy as
the plants compete for every last bit of light. Climbers and epiphytes
(plants which grow above the ground surface using other plants for
support and that are not rooted in the soil) are common. Lianas (a
type of climbing vine) climb rapidly and will not usually form leaves
until sufficient light is available. The rainforests contain a huge diver-
sity of animals with many adaptations for climbing such as monkeys
with strong tails, snakes and lizards. There is relatively little vegeta-
tion on the forest floor as it is so dark (only around 1 per cent of the
light at the top of the canopy) but this provides room for ground-
based large animals such as pigs, leopards and jaguars.
Savanna temperatures tend to be similar to those in rainforests
but the long dry season (rainfall less than 250 millimetres per month
for more than five months) means that the vegetation is seasonal in
nature and is often adapted to be drought tolerant. The high rates of
evaporation and transpiration mean that rainfall needs to be plentiful
at these temperatures to achieve high productivity. A sparse tree
cover allows the growth of grass and other ground flora. The struc-
ture varies across the landscape representing local differences in
water and nutrient availability. Savanna plants are adapted to with-
stand fire and drought, such as the baobab which has thick bark, a
short leaf season and a trunk that stores a lot of water from wet
periods. Deep roots to capture water and thorns and spines to deter
grazers mean that plants only need a few leaves. Fruiting of trees
and other plants tends to be dominated by fire which can occur
every few years. Fruits are dropped at the end of the fire into the
soil. This soil is temporarily rich in nutrients from the deposited
material left after the fire. Large animals are often found in the
savanna, particularly in Africa, such as wildebeest, antelope, zebra,
buffalo and elephant. Nocturnal animals have adapted to reduce
water loss and hide from predators (e.g. aardvark).
Hot deserts do contain plants and animals. The soils are gener-
ally poor and lack cohesion though since the plant cover is
