Conditions and Resources: The World's Biomes - Lecture 4 Flashcards
What is a Biome?
Large scale biological communities shaped by the regional climate, soil, and disturbance patterns. Usually classified by the growth form of dominant plants.
How are biomes described and classified?
Different Biogeographers recognise different numbers of biomes. Most commonly biomes are classified as areas of land dominated by plants with characteristic shapes, forms and physiological processes.
What classifies a Tropical rain forest?
- Global peak of biodiversity.
- Most productive biome, hgith solar radiation and reliable rainfall.
- Production achieved high in dense canopy.
- High animal diversity.
- intense soil activity.
Trees include: Vines, Epiphytes, figs ect.
Why is animal diversity so high in tropical rain forests?
- Reliable food sources for specialists.
- High floral diversity and parallel specialized diversity of pollinating insects and birds.
What occurs in tropical rainforests that results in intense soil activity?
- Rapid decomposition of leaf litter (soil surface almost bare)
- Most nutrients in plants themselves (lost when cleared); poor regeneration.
What classifies a Savanna?
- Seasonal rainfall restricts plant and animal diversity.
- Plant growth limited for part of the year by drought: season gluts and shortages of food.
- Migration of large animals and birds.
What causes grassland and scattered trees that would typically be forested from achieving this in a savanna?
- Grazing herbivores
- Unfavourable conditions i.e. waterlogging, drought, poor soils
- Fire
What classified a Hot Desert?
- At most extreme, too arid for any vegetation.
- Animal diversity is correspondingly low.
What are the two strategies desert plants adopt to survive?
- Rapid growth set seeds in weeks (to coincide with rare rain events)
- Cacti and succulents: thick fleshy stems, small thick, hairy leaves, long periods of physiological inactivity.
What classifies a temperate grassland?
- Warm moist summers and cold dry winters.
- Fire and frequent grazing.
Invertebrate biomass can be > large vertebrate biomass. - Soils rich in organic matter.
What makes temperate grasslands well suited to agriculture?
Soils rich in organic matter. This has resulted in temperate grasslands being the biome most affected by man.
What classifies temperate shrublands and woodlands?
- Characteristics of Mediterranean climate.
- Asynchrony between favourable growth temperatures (summer) and available water (winter rainfall).
- Regular fire prevents succession to woodlands.
What classifies temperate deciduous forests?
- Deciduous leaves adaption to long periods of freezing.
- Fertile soils allow replacement of leaves annually.
- Vertical structure: tall tress, shrubs and forbs; diverse but less so than tropical rainforest.
What classifies temperate evergreen forests?
- Occur over a wide range of rainfall.
- Nutrient poor soils.
- Fire can promote persistence.
- Reduced diversity compared with deciduous counterparts.
- High quality timber and pulp-extensive logging.
What makes the soils in temperate evergreen forests nutrient poor?
The pH of leaves.
