Ecosystems and Ecosystem Energetics Notes

Habitats and Ecosystems

Habitat Definition: The natural environment where a species lives, finding food, shelter, protection, mates, etc. Includes physical aspects like soil, water, temperature, wind, and wave action.
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: Grass eaters that also browse bushes and trees, consuming up to 60 kg per day. They significantly impact vegetation, creating mosaic landscapes through grazing, trampling, wallowing, and nutrient recycling via faeces.

Carbon Sequestration: A group of 170 European Bison in 48 sq. km of grasslands can help capture an additional 2 million tons of carbon per year by stimulating vegetation growth through nutrient recycling.

Ecosystem Impacts of Large Herbivores: Mammoths and other large herbivores could promote sub-arctic grasslands and slow the thawing of frozen soils.
Mammoth Steppe: Large herbivores trampled mosses and shrubs, encouraging grass growth over woody vegetation. Grasslands absorb less solar radiation, maintaining colder soils that keep carbon pools and greenhouse gases frozen longer. Trampling snow reduces its insulation, further cooling the ground.
Extinction Impact: Mammoth extinction may have led to the conversion of steppe grasslands to birch forests, increasing solar radiation absorption and regional warming.

Large animals uproot seedlings and shrubs, preventing woody vegetation expansion.
Trampling snow reduces its isolating effect, helping maintain permafrost by decreasing below-ground temperatures.

Methane Production: Large megaherbivore populations can significantly contribute to atmospheric methane through foregut fermentation.
Extinction Impact: The mass extinction of megafaunal herbivores may have caused a reduction in global atmospheric methane.
Examples: The extirpation of the North American bison caused a decrease of as much as 2.2 million tons of methane per year. The human-driven mass extinction of megafauna in the Americas decreased methane production by about 9.6 million tons per year.
Younger Dryas Cooling: The absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the Younger Dryas.

Biotic Components: Primary producers (autotrophs & chemotrophs), consumers (heterotrophs), and decomposers (saprotrophs).
Abiotic Components: Non-living physical factors of the environment.

Types: On land, green plants dominate. In open water, algae (phytoplankton) dominate. In shallow water, rooted plants dominate.
Function: Synthesize complex, high-energy organic matter from simple, low-energy molecules using an energy source.

Chemosynthesis: Produce complex organic matter from simple molecules using chemical energy.
Examples: Mostly bacteria found in extreme environments like deep oceans, hot springs, and volcanoes.
2 H2S + O2 \rightarrow 2 So + 2 H2O + Energy

Unique archaea that convert CO and H2O to CO2 and O_2, producing H as a by-product; found in deep mines and hot springs.

Consumers: Gain energy by feeding on other organisms (terrestrial and aquatic).
Decomposers: Gain energy by feeding on dead organisms, releasing simpler inorganic compounds that are taken up by primary producers; include bacteria and fungi.

Energy Transfer: All ecological processes involve energy transfer and are subject to thermodynamic laws.
Energy Loss: Energy is dissipated as heat and becomes unusable. Constant energy inputs from the sun counteract this loss.

Chemical elements are cycled among abiotic and biotic components.
Dynamics: Energy flow and chemical cycling.
Energy Flow: Light energy is converted to chemical energy by producers, passed to consumers as food, and dissipated as heat.
Recycling: Energy cannot be recycled and is constantly lost.
Continuous energy is needed in an ecosystem usually in the form of light.
Matter cycles within ecosystems.

Productivity: Rate at which organic matter is created by photosynthesis (gCm-2yr-1).
Standing Crop Biomass: Amount of accumulated organic matter in an area at a given time (gCm-2).
NPP = GPP - R

High Rainfall: More water available for transpiration, allowing stomata to remain open and photosynthesis to occur for longer.
Excessive Rainfall: May inhibit production due to low soil oxygen and mineral leaching.

High variation in productivity at high temperatures due to water stress.
Plant cell processes are slow at low temperatures and limited at high temperatures due to water stress.

The length of the photosynthetic period is the number of days with sufficient light to support growth.
Longer photosynthetic periods typically correspond to higher temperatures.

Primary production increases with a greater supply of nutrients, chiefly phosphorus and nitrogen.

There is a general trend of increasing net primary productivity with decreasing latitude (ie as we move from poles to the equator).

An ecosystem consists of all the organisms living in a community and all the abiotic factors with which they interact.
The dynamics of an ecosystem involve energy flow and chemical cycling.
Energy enters most ecosystems as sunlight.
Light is converted to chemical energy by autotrophs, passed to heterotrophs, and dissipated as heat.
Chemical elements are cycled among abiotic and biotic components.
Energy cannot be recycled.
Ecosystems must be powered by a continuous influx of energy from an external source, usually the sun.
Energy flows through ecosystems, while matter cycles within them.