38:192 Environment & Society - Midterm II

Why Tropical Rainforests are so Diverse

1. Been around for a long time

2. Over long period of evolution, there is a positive feedback loop

3. High input of energy from the sun 

4. High moisture input

5. Coevolution and mutualism 

Ecological Weaknesses of Rainforests

• Soils are nutrient poor

• Nutrients are stored in the biomass

Endemic Species

• Are found in one area and nowhere else in the world 

• Are also often endangered species 

Percentage of Canada’s Endemic Species

• 1% - 5%

Percentage of North America’s Endemic Species

• ~2%

Percentage of Australia’s Endemic Species

• 68%

Canada’s Only Endemic Endangered Specie

• Vancouver Island Marmot

  • Marmota vancouverensis

• Live in alpine meadows on top of mountains

Surtsey Eruption

• A good example of ecological succession 

• New island on the southern coast of Iceland 

Ecological Succession

• The process where on assemblage of species is gradually replaced by another as conditions change over time

Primary Succession

• Colonization and occupation of a previously unvegetated surface

Ecological Succession - Lichen

• Example of primary colonizers

Ecological Succession Example

• Lichen →

  • Moss and grass →

    • Herbaceous plants →

      • Shrubs →

        • Trees →

          • Mixed forests →

            • Climax community

Ecological Succession - Herbaceous Plant

• E.g. Fireweed (from Mount Saint. Helens)

Ecological Succession - Shrubs

• Are secondary colonizers

• E.g. Willow species

• Build on past ecological steps (left by primary colonizers)

Ecological Succession - Trees

• Build on past ecological steps (left by secondary colonizers)

• E.g. White Spruce (Picea glauca) & Eastern Cottonwood (Populus deltoides monilifera)

Ecological Succession - Mixed Forest

• Is comprised of a multitude of species

Seral Stage

• A specific, intermediate stage in a series of communities that develop over time, leading to an ecosystem’s eventual stable climax community

Facilitation

• The setting of conditions for the next seral stage to start 

Climax Community

• All the species that can grow in an environment is already growing there

• The ceiling of how much a community/environment can sustain

Ecotone

• A region of transition between two biological communities 

  • Has greater biodiversity than any one of the communities it divides 

• Can be seen vertically and horizontally

• E.g. Area between wetlands and a forest

Example of an Ecotone

• Gros Morne National Park, Newfoundland, Canada 

Edaphic Climax

• Mature vegetation community determined by geology

  • More specifically, determined by the chemistry of the geology of the area

Edaphic Climax - Alpine Catchfly (Lychnis alpina)

• Survival and distribution of this species is tied to specific soil conditions 

  • Thrives in nutrient-poor soils

British Columbia 

• Most diverse province in Canada

• Biogeoclimatic Zones are named after dominant species of grasses or trees

Biogeoclimatic Zone Components

• Regional climate

• Specific climax vegetation

• Soils

• Animal life that result from the climate over time

Secondary Succession

• Same processes as primary succession but starts on a surface that has already been vegetated

• Rehabilitation of an environment but the process is quicker as the foundation is already set

Intermediate Disturbance Hypothesis

• Ecosystems subject to moderate disturbance generally maintain high levels of biodiversity 

  • Medium disturbance = highest amount of biodiversity

  • High & low disturbance = low amount of biodiversity

Ecosystem Characteristics 

• Food chains

• Net productivity 

• Species diversity 

• Niche specialisation 

• Nutrient cycles

• Nutrient conservation 

• Stability 

Ecosystem Characteristics - Food Chains

• Immature Ecosystem → Linear, predominantly grazer

• Mature Ecosystem → Web-like, predominantly detritus

Ecosystem Characteristics - Net Productivity 

• Immature Ecosystem → High

• Mature Ecosystem → Low

Ecosystem Characteristics - Species Diversity

• Immature Ecosystem → Low

• Mature Ecosystem → High

Ecosystem Characteristics - Niche Specialisation 

• Immature Ecosystem → Broad

• Mature Ecosystem → Narrow

Ecosystem Characteristics - Nutrient Cycles

• Immature Ecosystem → Open

• Mature Ecosystem → Closed 

Ecosystem Characteristics - Nutrient Conservation

• Immature Ecosystem → Poor

• Mature Ecosystem → Good

Ecosystem Characteristics - Stability 

• Immature Ecosystem → Low

• Mature Ecosystem → Higher 

Hot Fires

• Fires that are considered hazardous 

Cool Fires

• Natural fires that are beneficial and necessary for the ecosystem  

Duff

• Another word for dead matter

Implications of Maintaining an Early Succession Ecosystem 

1. Productivity is often higher

2. Nutrient cycling is more rapid 

3. Biodiversity reduced

4. Affects specialised species at high trophic levels 

5. Usually benefits pioneer species 

Insects

• Are a model animal when considering pioneer species (in relation to agriculture)

Dynamic Equilibrium 

• Multiple components working together to maintain balance

  • Abiotic and biotic components working together to maintain an overall neutrality

Gaia Hypothesis 

• The internal processes of an ecosystem adjust for changes in external conditions to produce a balanced state 

Inertia

• Ability to withstand change

Resilience

• Ability to recover following disturbance

  • E.g. Ecosystem with a high resilience is temperate forests

Alien Species

• A species found outside its normal range 

  • (Don’t usually stick around in the new environment)

Invasive Alien Species

• An alien species that multiplies rapidly and out-competes native species and change native habitats

• E.g. Purple loostrife ~ Lythrum salicaria

Characteristics of Alien Invasive Species

• Fast-growing

• Generalist

• Ability to alter growth form to local conditions

• Reproduce sexually and asexually

• Effective dispersal mechanism

• Associated with humans

  • E.g. moved by humans during transport

Invasive Species Examples 

• Eurasian Water Milfoil ~ Myriophyllum spicatum

• Knapweed ~ Centaurea sp.

Allelopathic 

• Plants that secrete chemicals into the soil that poison other plants, making other plants unable to grow 

• Cattle will not eat these type of plants 

Invasive Non-Native Plants in Canada

• Has continually increased since Europeans colonised Canada, among other places 

Ballast Water Dumping 

• Bringing water (usually with larvae, alien species, alien flora, etc.) to other waters around the world 

  • E.g. Lampreys

• Done to balance the weight of ships but has unfortunate affects 

• Greatest way for invasive species to arrive in the Great lakes

Trends in Non-Native Species in the Great Lakes 

1. Shipping

2. Planted/Stocked 

3. Unknown

4. Hitchhiker with organisms in trade

5. Aquariums 

Zebra Mussel ~ Dreissena polymorpha

• Came from eastern Europe, came in ballast water

• Introduced into the Great Lakes in the 1980s 

• Multiply very quickly 

• Use of potash can contain these animals (only viable in small, controlled waters) 

Species Removal Example

• Sea otter extirpation results in destruction of kelp forests because sea urchin populations were not under control without the otters

Positive Feedback

• Enhances change or exacerbates the problem 

Negative Feedback

• Works to suppress or moderate the change

  • Therefore works to maintain ecosystem stability by counteracting positive feedback loops

Reduction Factors for Population Growth 

• Biotic: predators, disease, parasites, competitors, etc.

• Abiotic: unfavourable weather, lack of water, alterations in chemical environment

Growth Factors for Population Growth

• Biotic: high reproductive rate, ability to adapt to environment change, ability to migrate to new habitats, ability to compete, etc.

• Abiotic: favourable light, favourable temperature, favourable chemical environment 

Reduction & Growth Factors 

• Work together to sustain population size 

Components of Carrying Capacity & Population Growth Rates

1. Initial carrying capacity

2. Population overshoots carrying capacity

3. Population crash or die-back

4. New carrying capacity

Density Dependence

• As population density increases, growth decreases

Density Independence 

• As population density increases, growth increases 

Biotic Potential 

• The maximum rate at which a species may increase if there is no environmental resistance 

• E.g. Fish flies

  • At small moments of time, they can reproduce at their biotic potential but can’t be maintained for long

Characteristics of K-Strategists

• Late reproductive age

• Few, larger young, with more care of young

• Slower development

• Greater competitive ability 

• Longer life, growing to be larger adults 

• Live in generally stable environments 

• Emphasis on efficiency 

• Stable population usually close to carrying capacity 

  • E.g. Killer Whales

Characteristics of R-Strategists

• Early reproductive age

• Many, small young, with little care of young

• Rapid development

• Limited competitive ability 

• Shorter life, growing to be smaller adults

• Live in variable or unpredictable environments 

• Emphasis on productivity 

• Large population fluctuations usually far below carrying capacity 

  • E.g Frogs, fish, etc.

Evolution

• Through time populations adapt to changing conditions through this process

• Mechanism of evolution is natural selection

• Variation predisposes a portion of the population to adapt to certain conditions 

Phyletic Evolution

• Occurs when a portion of the population has changed so much that it cannot interbreed with the rest

  • Which gives rise to speciation

Extinction 

• Elimination of a species that can no longer survive under current conditions 

• Can be a quick or slow process

• 99% of all species ever to exist are extinct

• Is the natural end of all species 

Background Extinction

• The natural extinction taking place in environments without the influence of humans

Extant

• Opposite of extinct

• Means that a species exists

Movement of Ecozones 

• Will be due to climate change 

Two Fundamental Processes for Life on Earth

• One-way flow of energy from the sun

• Recycling of matter required by living organisms

Matter Recyclers

• Are living organisms

• Living organisms take in matter and process it

Law of Conservation of Matter

• In any ordinary physical or chemical change, matter is neither created nor destroyed but merely changed from one form to another 

Major Macronutrients

• Carbon

• Hydrogen

• Nitrogen

• Oxygen

• Phosphorus

Nutrient

• Any element an organism needs to live, grow, and reproduce

Bioavailability (Amount)

• Often low in the ecosphere 

Biogeochemical Cycles

• Each nutrient is stored and released by components of the Earth’s systems

• Different nutrients follow slightly different path through the systems and are stored and released at different rates

Abiotic “Bins” in Biogeochemical Cycles 

• Atmosphere

• Lithosphere 

• Hydrosphere

• (Carbon cycle is found in these 3 spheres)

Biotic “Bin” in Biogeochemical Cycles

• Ecosphere

  • Ecosphere houses producers and consumers

Sedimentary Cycles 

• Are slow paced

• Come from the lithosphere 

Gaseous Cycles

• Are fast paced

• Include the nitrogen and oxygen cycles 

Human Impacts on the Phosphorus Cycle

1. Mining fertiliser and detergent → leads to excessive run-off

2. Removing biomass → leads to accelerated erosion

3. Concentrating number of domestic organisms → leads to increased waste

4. Removing P from oceans → returned as waste

Sulphur Cycle

• Is a sedimentary cycle 

• Important in 2 ways:

  • Has an atmospheric component and therefore better recycling potential. Seldom a limiting factor

  • Strong dependencies on microbial activity

• Must be transformed into sulphates before plants can take it up

Rhizobium Bacteria

• Uses nitrogen to create ammonia

• Mutualistic relationship with plants, live in the root nodules

Cyanobacteria

• Free-living bacteria 

• In water or soil 

• Use nitrogen for themselves 

Mineralisation

• Done by a lot of bacteria to break down matter to turn it back into its constituent parts

Human Impacts on the Nitrogen Cycle

1. Nitrates & ammonia as fertiliser → lead to eutrophication

2. High nitrate levels in water → blue-baby syndrome (methaemoglobinaemia)

3. Removal of nitrogen-rich crops → lead to soil nitrogen depletion

4. Nitric acid formation → acid rain

Carbon Cycle Features

• CO2 is the main reservoir for carbon 

• Incorporated into the biomass and passed along the food chain

• Respiration by organisms transforms some of the carbon back into CO2

• Increased atmospheric CO2 will have a positive feedback loop with carbon concentrations in the ocean 

Global Water Storage Types (Reservoirs)

• World oceans

• Ice sheets and glaciers

• Groundwater

• Lakes (freshwater)

• Inland seas, saline lakes

• Soil moisture

• Atmosphere

• Rivers and streams

Global Water Storage - World Oceans

• Average renewal rate - 3,100 years

• Percentage of global total - 97.2

Global Water Storage - Ice Sheets & Glaciers

• Average renewal rate - 16,000 years 

• Percentage of global total - 2.15

Global Water Storage - Groundwater

• Average Renewal Rate - 300 - 4,600 years

• Percentage of global total - 0.62

Global Water Storage - Lakes (Freshwater)

• Average Renewal Rate - 10 - 100 years

• Percentage of global total - 0.009

Global Water Storage - Inland Seas, Saline Lakes 

• Average renewal rate - 10 - 100 years 

• Percentage of global total - 0.008

Global Water Storage - Soil Moisture

• Average renewal rate - 280 days

• Percentage of global total - 0.005

Global Water Storage - Atmosphere

• Average renewal rate - 9 - 12 days

• Percentage of global rate - 0.001

Global Water Storage - Rivers & Streams 

• Average renewal rate - 12 - 20 days

• Percentage of global rate - 0.0001

Hydrological Cycle - Incoming Water 

• Precipitation on land → 24%

• Precipitation on oceans → 76%

Hydrological Cycle - Outgoing Water 

• Evaporation from vegetation and soil, Evaporation from lakes, ponds, and streams, Transpiration from vegetation → 14%

  • All three components are called evapotranspiration

• Evaporation from oceans → 86%