Ecosystems and Ecosystem Energetics Notes

Habitat Definition: The natural environment where a species lives, finding food, shelter, protection, and mates. It includes physical aspects like soil, water, temperature, wind, and currents.
Ecosystem Definition: All organisms (biotic factors) in an area functioning with non-living physical (abiotic) factors. These components are linked through nutrient cycles and energy flows.

European Bison Impact: Grazing affects vegetation, creating mosaic landscapes, trampling vegetation, wallowing in mud, and recycling nutrients.
Carbon Capture: Bison stimulate vegetation growth, recycling nutrients; a group of 170 bison can help capture approximately an additional 2 million tons of carbon per year in 48 sq. km of grasslands.
Mammoth Steppe: Large herbivores like mammoths trampled mosses/shrubs, uprooted trees, and promoted grass growth. Grasslands have colder soils, keep carbon pools frozen longer, and reduce solar radiation absorption compared to forests.
Methane Emissions: Extinction of megafaunal herbivores may have reduced global atmospheric methane; North American bison extirpation caused a decrease of as much as 2.2 million tons of methane per year.

Biotic Components: Primary producers (autotrophs & chemotrophs), consumers (heterotrophs), and decomposers (saprotrophs).
Primary Producers: Synthesize complex organic matter from simple molecules using an energy source; mostly green plants on land, algae in open water, and rooted plants in shallow water.
Chemotrophs: Produce complex organic matter using chemical energy, mostly bacteria in extreme environments. For example, $2 H<em>2S + O</em>2 \rightarrow 2 S^o + 2 H_2O + Energy$
Consumers: Gain energy by feeding on other organisms.
Decomposers: Break down dead organic matter, releasing simpler inorganic compounds.

Ecological processes involve energy transfer, subject to thermodynamic laws.
Energy flows through ecosystems; chemical elements cycle within them.
Productivity: Rate of organic matter creation by photosynthesis, e.g., gCm-2yr-1
Standing Crop Biomass: Amount of accumulated organic matter at a given time, e.g., gCm-2

Terrestrial Ecosystems: Limited by precipitation, temperature, light, and nutrients.
Precipitation: High rainfall increases water availability for transpiration and photosynthesis; excessive rainfall inhibits production due to low soil oxygen and mineral leaching.
Temperature: Plant cell processes are slow at low temperatures and can be limited at high temperatures due to water stress.
Nutrients: Primary production increases with nutrient supply, especially phosphorus and nitrogen.

Net primary productivity generally increases from poles to the equator.
Tropical rainforests and freshwater wetlands exhibit high net primary productivity.

Ecosystem dynamics involve energy flow and chemical cycling.
Energy enters as sunlight, converted to chemical energy by autotrophs, passed to heterotrophs, and dissipated as heat.
Chemical elements are cycled; energy is not recycled.
Ecosystems require a continuous energy influx, usually from the sun.