Environmental Engineering Reference
In-Depth Information
2a
Dry deciduous forest and savanna
III
Subtropical dry
3
Subtropical desert and semi-desert
IV
Transitional and winter rain
4
Sclerophyllous forests of winter rain regions
V
Warm temperate
5
Temperate wet - evergreen forest
VI
Typical temperate
6
Deciduous forest
VII
Arid temperate
7
Steppe
7a
Semi-desert and deserts with cold winters
VIII
Boreal cold temperate
8
Boreal coniferous
IX
Arctic
9
Tundra
X
Montane
10
Mountain
Source: After Walter (1976).
deciduous forests and savannas
(2a) occur here. The
Subtropical Dry Zone
(III) is the hot
desert zone and is located poleward of 30° N and 30° S. Rainfall is very low, daytime
temperatures are very high, and at night in the winter months the temperatures may drop
to zero. The main tracts of these
subtropical deserts and semi-deserts
(3) occur in the
Sahara and Libyan deserts of northern Africa, the Arabian desert in Asia and the Middle
East, interior Australia, south-western parts of North America, southwestern Africa,
northern Chile and Pakistan.
The
Transitional Zone with Winter Rain
(IV) is located at latitudes approximately 40°
N and 40° S. In this Mediter-
CLIMATIC DIAGRAMS OF VEGETATION REGIONS
key concepts
The correlation between vegetation and climate has formed the basis of many
classifications of both climate and vegetation in the past. Climatic elements of
temperature and precipitation determine the type of plant species that can grow and
survive in any climatic zone, because of the effects of these climatic elements on plant
physiology. These climatic elements also influence nutrient cycling and nutrient
availability, and they also influence plants indirectly through weathering and soil
formation.
There is a close correspondence between climate and vegetation, but it is a complex
relationship, as plants are affected by the combined effect of many climatic elements such
as temperature, precipitation, frost and wind. The seasonal variations of these are crucial
to plant survival. In order to consider climate as a whole, and to represent seasonal
changes, Heinrich Walter, a German biogeographer, introduced climatic diagrams. These
are used to accompany atlases of vegetation, or indeed any maps of vegetation regions.
Figure 1(a) shows the climatic diagram for Karachi, Pakistan, a subtropical desert region
in Zone III, and Figure 1(b) that for Colombo, Sri Lanka, a tropical rain forest region in
Zone I. The months of the year are shown on the horizontal axis, and the graphs show
mean monthly temperature and mean monthly precipitation One division on the vertical
