BAG 101: PHYSICAL ENVIRONMENTAL SYSTEM
Dr. K. Chatterjea
Lecture outline: Ecosystem Essentials and
Tropical Ecosystem
(This is the last topic I am going to teach!! The next one is your responsibility!!)
Concepts in Biogeography: Biogeography is a major field within Physical Geography. It is a study of distribution patterns of plants and animals on Earth.
Ecology: the study of the interactions between organisms and their environment.
Habitat: the place where an organism lives; it possesses various environmental conditions that affect the growth of plants.
Factors that control conditions in a habitat:
Edaphic: related to soil; nutrients, salinity, depth of soil, drainage etc.
Hydrologic: the most important factor: plants are classified according to their water requirements: hydrophytes, xerophytes, and mesophytes
Plants develop special characteristics to adapt to the prevailing conditions.
Geomorphic: controls exerted by the type of landform: steep slopes, valley bottoms etc.
Climatic: Temperature, light, wind
Terrestrial ecosystem: assemblages of land plants and animals
Biome: largest recognizable subdivision within terrestrial ecosystem, dominated by green plants.
Forest: ample soil water and heat
Savanna:transitional between forest and grassland
Grassland:moderate shortage of soil water, adequate heat
Desert:extreme shortage of soil water, adequate heat
Tundra:insufficient heat
Equatorial and Tropical Rain Forest
-continuous belt of green vegetation :
-provide capital asset to the developing countries
-total area: 12 m km2: 1/3 of world’s forests
-distribution not uniform: land/sea; mountains
-Latin America, Western Equatorial Africa, South-east Asia
-constant high temperatures: coldest month over 18 degrees C; a difference of less than 5 degrees C
-20 - 28 degrees C
-overhead sun: plenty of light
-no great variations in length of day: prolonged periods of photosynthesis
- diurnal range is greater than annual range: daily rhythm of change -- rather than a seasonal rhythm
Uniqueness of rain forests
-the great density of plant species:
1km2 of rain forest land can contain similar weight of wood as 200 - 300 km2 of temperate forests
-they are the most productive type of vegetation in the world
-2500 tonnes/km2/y compared to 700 tonnes/km2/y in temperate forests
Appearance of rain forests
has distinctive appearance and structure
RAIN FOREST TREES
-Average tree height: 50m, can be 90m
-often look very similar
-continuously shed leaves, grow new ones: foliage looks permanently green (evergreen)
-leaf-fall is critical for nutrient cycling
-large leaves - many are thick with waxy surface: to allow rainwater to run off easily
drip tips to allow water to drop on the ground
-thin, and straight trunk, few low branches (think what are implications!!)
- all branches grow towards the top: dense and compact vegetation
(there may be 400 - 600 trees with >10cm dia in .01km2 patch of rain forest)
-canopy is very closed: allowing less light to penetrate
-species diversity-- very imp.: no single species dominationCLIMBING
PLANTS
-lianas : can be up to 200 m long : form links between trees: could cause problems also
-epiphytes : grow on trees: not parasitic: could be heliophytes or sciophytes
ROOTS and BUTTRESSES
-have distinctive root structures
-generally limited root growth: even large trees
-95% of roots found in the top 130cm of the soil
- trees are supported by neighbouring plants (what are the implications??)
The rest you should get in:
1.Geosystems: Chapters 19 and 20
You may look into any other book on the subject: go and do some market study!!!