Ecosystems

Ecosystems : 

Ecosystems Community of all species of organisms and the local nonliving environment in which matter cycles and energy flows Forest ecosystem, tallgrass prairie ecosystem, desert shrubland ecosystem, pond ecosystem, ecosystem in a puddle Structure Abiotic: non-living part; physical and chemical environment; atmosphere, water, soil Biotic: living part; the ecological community; set of species interacting within ecosystem Processes Chemical cycling, flow of energy Change Dynamic system, not static

Ecosystem Management : 

Ecosystem Management The core of modern natural resources management Conservation of endangered species or management of natural resources in a sustainable manner depends on the ecosystem continuing to function Defining the ecosystem and then maintaining chemical cycling, energy flow, community-level interactions and thinking about the dynamics of the system Hubbard Brook Large experiment set up in 1960’s Replicated watersheds Log entire watersheds, measures inputs and outputs of chemicals, flows of energy, erosion, etc. Answers questions about effects of clearcutting on forested ecosystems

Slide 3: 

Nutrient Cycling vs. Energy Flows Energy flows through systems once - plants must continuously fix energy Nutrients may be recycled Different nutrients cycle in different ways

An Energy Transformation : 

An Energy Transformation Photosynthesis: plants transform solar energy (parts of visible energy spectrum) into energy-rich biochemical compounds Photosynthesis sustains (almost) all life on earth

Efficiency of Energy Transformation in Ecosystems : 

Efficiency of Energy Transformation in Ecosystems Respiration is the other major energy transformation by living organisms Energy transformation is 10% efficient, the rest is lost as heat

Slide 6: 

Flow of energy through a food chain 1st Trophic Level Producers (plants) 2nd Trophic Level 1o Consumers (herbivores) 3rd Trophic Level 2o Consumers (carnivores) 4th Trophic Level 3o Consumers (top carnivores) Detritivores (decomposers and detritus feeders)

How many trophic levels are possible? : 

How many trophic levels are possible? Because the transfer of energy is only ~ 10% efficient, the number of organisms at the top of the food web and the number of trophic levels is limited.

Hot Spring Ecosystems In Yellowstone : 

Hot Spring Ecosystems In Yellowstone Primary producers: Herbivores: Carnivores: Top-level carnivores

A Simplified Terrestrial Food Web : 

A Simplified Terrestrial Food Web

A Simplified Oceanic Food Web : 

A Simplified Oceanic Food Web

In reality, food webs are complex… : 

In reality, food webs are complex…

Direct and Indirect Effects : 

Direct and Indirect Effects Organisms can interact directly through food chains Predation (+ , -) Competition (- , -) Symbiosis (+ , +) Can also interact indirectly by affecting a species which will affect another species “Community-level interactions” B1 A B2

Keystone Species : 

Keystone Species Sea otters feed on shellfish (sea urchins and abalone) Overhunted in 1700’s and 1800’s Populations have rebounded Fishermen say recovered and overpopulated now Conservationists say necessary for persistence of many species How is it a Keystone species? Otters eat sea urchins  urchins eat kelp  kelp provides habitat for many species  otters   sea urchins   kelp   biodiversity Otters indirectly affect kelp abundance Keystone species: One which has a unexpectedly large effect on a community or ecosystem Its removal changes the community drastically

Slide 14: 

Gopher tortoise Keystone species of longleaf pine forest

Biogeochemical Cycles : 

Biogeochemical Cycles the continuous movement of materials through the 4 “spheres” Atmosphere: _______ layer Biosphere: _______ layer Hydrosphere: _______ layer Lithosphere: _______ layer Six Principle Element Cycles (the “macronutrients”) What are they?

Elements in Organisms are in Different Amounts than in Earth : 

Elements in Organisms are in Different Amounts than in Earth Biogeochemical cycles are necessary to transport and temporarily store nutrients until taken up by organisms

Pools and Flows : 

Pools and Flows Pools = Sources and sinks Flows = Both important in understanding nutrient availability Humans have effects on both as well

Residence Time : 

Residence Time Amount of time it takes to turn over the whole pool Sizes of pools and rates of flows determine residence time Small for CO2, higher for O2 and H2O, very high for Phosphorus (P)

Nitrogen Cycle : 

Nitrogen Cycle

Slide 20: 

Phosphorus Cycle

Carbon Cycle : 

Carbon Cycle Major pools? Two major flow cycles: 1) Biosphere  Atmosphere Withdrawal of CO2 from atmosphere from photosynthesis Carbon dioxide + water with sunlight produces sugars and oxygen What is the chemical equation for photosynthesis? Returns to atmosphere from respiration and combustion 2) Atmosphere  Hydrosphere (ocean) ocean sediments from organisms burning of fossil fuels

Pool Sizes : 

Pool Sizes Most of the carbon in the world resides in the oceans Missing carbon sink? Calculations suggest CO2 in atmosphere has not increased as much as scientists think it should have Many scientists think “missing” C has: a) been dissolved into ocean, b) is present as roots of organisms which are very difficult to measure, or c) has led to increases in boreal forest plant growth

How humans can change biogeochemical cycles : 

How humans can change biogeochemical cycles Accelerate cycles Extraction and redeposition Leads to depletion of resources and pollution Example: Carbon Extraction and burning of fossil fuels Redistributed to atmosphere where may lead to global warming Example: Phosphorus Use in soaps