Chapter 3 Ecosystem Ecology

The Deforestation of Haiti 1923-present

Haiti Floods from deforestation

What is an Ecosystem? A particular location on earth with a mix of interacting biotic and abiotic components. Example of biotic components: trees, birds, insects, bacteria etc. Example of interacting abiotic components: Sunlight, temperature, soil, water, pH, nutrients, climate (they determine which organisms can live in the ecosystem)

Ecosystems Boundaries The biotic and abiotic components of an ecosystem provide the boundaries that distinguish one ecosystem from another. Ex: A cave- has very clear boundaries and a well defined ecosystem

Ecosystems can vary in size. Boundaries sometimes are determined by people.

Small Ecosystem

Energy flows through ecosystems The sequence of consumption from producer through tertiary consumer is a food chain.

Photosynthesis and Respiration Photosynthesis: solar energy is used by producers to convert CO 2 and H 2 O into C 6 H 12 O 6 + O 2 (stored energy) Respiration: organisms convert C 6 H 12 O 6 + O 2 into H 2 O and CO 2 + energy

Trophic levels, food chains and webs Consumer= heterotrophs (consume other organisms to gain energy) Primary consumers = heterotrophs that eat producers; herbivores such as deer, zebras, grasshoppers Secondary consumers= heterotrophs that eat other primary consumers; carnivores such as lions, hawks, snakes Tertiary consumers= carnivores that eat secondary consumers; eagles Each successive levels of organisms consuming one another are called trophic levels

Food Web

Other Consumers Scavengers: carnivores that consume dead animals= vultures Detritivores= breakdown dead tissues and waste products into smaller particles to be decomposed= dung beetles Decomposers= complete the breakdown process and return nutrients back into the ecosystem= fungi and bacteria

Ecosystem Productivity Where does energy in an ecosystem come from? How does it move through the food web? What amount is available on each trophic level? Scientists use the GPP (gross primary productivity)of the ecosystem to find out. This is the total amount of solar energy that producers consume during photosynthesis in an ecosystem. Producers usually capture only about 1% of available solar energy via photosynthesis.

GPP and NPP 99% of solar energy is reflected or passes through producers w/o being absorbed. Of the 1%, captured, 60% is lost to respiration and 40% is used to support growth and reproduction of producers (Net primary productivity or NPP). Measurement of NPP lets us compare productivity of different ecosystems The highest productivity occurs where there is plenty of sunlight, water and nutrients, and warm temperatures= tropical rain forest and salt marshes. The lowest productivity occurs in the artic, dry deserts, and dark regions of the deep sea.

Ecological Efficiency The proportion of consumed energy that can be passed on from one trophic level to another. Range from 5-20 percent across ecosystems with 10 percent being the average Out of all of the biomass available at a given trophic level only 10% can be converted to energy at the next higher trophic level. This explains why the populations of herbivores are always so much larger than the populations of carnivores. It explains why there are more plants than everything else combined--the plant populations support all other populations in the ecosystem, either directly or indirectly.

Trophic Pyramid Most energy and biomass is found at the producer level and decreases as we move up the pyramid.

BIOGEOCHEMICAL CYCLES The movement of matter within and between ecosystems involve biological, geological, and chemical processes. These include: the water cycle (hydrologic), Carbon cycle, Nitrogen cycle, Phosphorus cycle, and the Ca, Mg, K, and S cycles. How can human activities can alter these cycles?

Hydrologic Cycle

Carbon Cycle

Nitrogen Cycle

Phosphorus Cycle

Sulfur Cycle

Ecosystem Disturbance An event that results in changes in population size or community composition Natural disturbances= hurricanes, tsunamis, volcanic eruptions, forest fires Anthropogenic disturbances = human settlements, agriculture, air pollution, deforestation, mountain top removal for coal mining.

How does a disturbance change an ecosystem? Scientists study watersheds(all of the land in a given landscape that drains into a particular stream, river, lake or wetland)to determine the impact of a disturbance. Ex: Hubbard Brook Ecosystem

Resistance vs. Resilience The resistance of an ecosystem is a measure of how much a disturbance can affect the flows of energy and matter. When a disturbance influences populations and communities but has no effect on the overall flows the ecosystem has high resistance. Resilience refers to how quickly an ecosystem can recover its original condition after its flows of energy and matter are affected by a disturbance.

Intermediate Disturbance Hypothesis States that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels.

Instrumental Value of Ecosystems Instrumental value= when a species has a worth as an instrument or a tool that can be used to accomplish a goal; lumber, medicines, provide food, filter water, all impact our economy. 5 categories: Provisions, regulating services, support systems, resilience, and cultural services.

Instrumental value broken down: Provisions= goods that humans can use directly; lumber, food, crops, rubber, furs, most medicines Regulating Services= natural ecosystems help to regulate environmental conditions such as nutrients and water. Support Systems= ecosystems provide habitats that allow for pollination of food crops by native bees and insects, allows for the filtration of pathogens and chemicals from water

Resilience= specie diversity ensures that the ecosystem can continue to to exist even when there is a disturbance. Cultural Services= Ecosystems provide aesthetic benefits

Intrinsic values of Ecosystems Intrinsic value= when a species has worth independent of any benefit it may provide to humans; moral value of life, beauty, etc. We have a moral obligation to save our ecosystems and policies and protection should be driven by this.