Major Ecosystems and Environmental Concepts

Grasslands

In general terms, a grassland ecosystem is characterized by huge open lands where the vegetation includes different types of grasses with very few trees. There are six main types: tropical grasslands, temperate grasslands, flooded grasslands, tundra grasslands, montane grasslands, and xeric grasslands. Tropical grasslands receive 50-130 cm of rainfall, while temperate grasslands receive 25-75 cm.

Key Characteristics of Grasslands

• Limited annual rainfall
• Dry climate
• Lack of nutrients in the soil
• Frequent droughts and uncertain precipitation
• Frequent forest fires due to semi-arid climate and flash lightning
• Poor vegetation dominated by grasses
• Home to a variety of animal species

Deserts

Most hot deserts occur in high air pressure areas where air descends. As the air sinks, it warms up. The moisture in warmer air is less likely to undergo condensation and produce precipitation, which is why there is less precipitation in high-pressure areas. Air descends between 15 and 30 degrees north and south of the equator, forming high air pressure cells where deserts tend to form. However, deserts can extend far beyond these high-pressure zones. Deserts can form for other reasons, such as topographical features. For example, areas on the leeward side of mountains can create rain shadows. Rain shadows receive little precipitation because mountains block wind and moisture. Types of deserts include subtropical, coastal, interior, polar, and rain shadow.

Tundra

Almost no trees grow in the tundra due to poor soil, permafrost, and weather. Vegetation is adapted to the cold weather and short growing seasons. Key characteristics include:

• Extremely cold climate
• Low biotic diversity
• Simple vegetation structure
• Limited drainage
• Short season of growth and reproduction
• Energy and nutrients in the form of dead organic material
• Large population oscillations

Rainforest

There are two types of rainforests: tropical and temperate. A rainforest is a hot, moist biome where it rains all year long. The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter. This material decomposes rapidly in the wet, warm conditions (like a compost pile), sending nutrients back into the soil. Few plants are found on the floor of the forest due to the lack of sunlight. However, the hot, moist atmosphere and all the dead plant material create the perfect conditions in which bacteria and other microorganisms can thrive.

Taiga

The boreal forest, or taiga, covers about 11% of Earth's land mass, making it the world's largest terrestrial biome. It is located in the Northern Hemisphere, extending from around 50° North latitude to 65° North latitude. The soil is extremely acidic due to the high numbers of needles that fall from the trees.

Life History Theory

Life History Theory is an analytical framework designed to study the diversity of life history strategies. It helps to explain aspects of an organism's anatomy and behavior. All organisms follow a specific sequence in development: birth, childhood, maturation, reproduction, and senescence. Every species has its own pattern of this. Traits looked at include:

• Size at birth
• Growth pattern
• Age and size at maturity
• Number, size, and sex ratio of offspring
• Age- and size-specific reproductive investments
• Age- and size-specific mortality schedules
• Length of life

RV = current reproduction + residual reproductive value

Traditional Ecological Knowledge (TEK)

Traditional Ecological Knowledge (TEK) refers to the evolving knowledge acquired by indigenous and local peoples over thousands of years. It is specific to a location and includes the relationships between plants, animals, natural phenomena, landscapes, and the timing of events that are used for lifeways. Methods for documenting TEK include ethnography and literature.

Renewable Resources

• Wind: Found in the US and UK, wind power uses wind to spin a turbine and converts kinetic energy into electricity.
• Solar: Solar power captures sunlight on solar panels by use of the photovoltaic effect.
• Hydroelectric: Hydroelectric power uses flowing and falling water to turn a turbine.
• BioEnergy: BioEnergy is generated when organic matter is burned. It releases CO2 but can be regrown.