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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: Desert: moderate shortage of soil water, adequate heat 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 domination CLIMBING 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!!!
