Friday, March 23, 2012

Lecture 21

Plant Physiology
• Leaf has cholorphyll which absorbs sunlight and carbon dioxide
• Transforms into oxygen which is released into atmosphere, and carbohydrites for energy
• Water is lost through transpiration (from the leaf while it is photosynthesiszing or perspring)
• During the day: major process which interacts with/affects climate
• At night: gives off heat and transpires water

Photosynthesis
• Stomata: CO2 is absorbed, O2 is released
• While it is open, this is where water flows out
• Holds rigidity up through turgor pressure
• Very dry, pressure goes down, stomata closes, no photosynthesis happens
• Must have enough chlorophyll (made of nitrogen) for photosynthesis to occur

C3 vs C4
• How plants function differently
• Leaf Temp vs Photosynthesis: C3: normal around 25 C, C4: max at 40C
• CO2 vs Photosynthesis: C3: CO2 increase as CO2 increase, C4: wide range of CO2 levels can be used for photosynthesis
• C3: rice, wheat, barley, potatoes (almost every plant in Canada)
• C4: tropical grasses, corn, sugar cane, LOTS of weeds, tolerates very high temperatures
• CAM: desert plants, don’t have leaves, have photosynthesizing flesh in stems, cactus, pineapple family, process photosynthesis in a different way (specialized), very efficient water use

Atmospheric Carbon Dioxide
• Annual oscillations
• Increasing over time
• A lot more in the Northern Hemisphere than the Southern Hemispehre
• Because the ocean absorbs CO2 – EXAM QUESTION: What is the biggest CO2 exchange? SURFACE-OCEAN

How Will Climate Change Affect Plants?
• Extreme weather, precipitation, land use, disturbances, storm intensity/frequency, temperature, water vapour (amounts of clouds and how that affects solar radiation), sea level change

Climate Impacts on Trees
• Up Sides:
• More CO2 fertilization (only works if there are no other limiting factors ex: water, nitrogen for chlorophyll), C4 plants grow more as temperature increases, longer growing season (more productivity)
• Down Sides:
• More disturbance (fires), precipitation change affects plant limitation, too hot for C3 plants (limiting factor), increased breeding of insects which feed on trees, cascading affects because shift in niche

Food Webs and Cascading Effects
• Herbivore: eats plants
• Carnivore: eats other animals
• Heterotrophs: mushrooms, worms
• Autotrophs: plants make their own food

Ecological Niche
• The climatic envelope in which an organism exists
• Fundamental niche: without organisms interacting
• Realized niche: two organisms live in same place and compete
• Species live and overlap, compete, think about where its food lives
Ecosystem States
• Not resilient, pertibation and going back to old state is hard
• Fisheries: it will take a very long time to overcome the huge obstacle of overfishing to get back to where it was before
• Can get pushed over threshold and cannot get back to original state without a very big push

Global Change and Tropical Forests
• Dense vegetation that has about 40% of Earth’s carbon, a large percentage of the Earth’s animals
• One of the biggest sources of oxygen (next to oceans) CO2 going in
• Trees are C3 plants
• Increased temperature: increased stress which reduces producticity
• Increase in variability in rainfall: more flooding, more droughts
• Feedbacks:

Global Change and Boreal Forests
• Change in fire dynamics; warmer, more variability in precipitation (better conditions for fire)
• Change in temperature/precipitation that could favour insects: more insect infestations
• Could favour or hinder productivitiy in plants depending where you are

Global Change in the North
• Trees anchored to permafrost, lost support and tip over
• Permafrost – Wet – Dry
• Changes composition of plants, cascading affect to plants and animals which interact with these plants

Species Invasion
• Correlation in temperature and more exotic species (increases)
• More exotic species with climate change?

Climate Change Affecting the Ocean
• Increase in CO2 absorbed by ocean (biggest flux between atmosphere is with ocean)
• When CO2 is in water, it acidifies water, decreases pH of ocean, problem with organisms with calcium shells or coral with calcium skeletons
• Increase in water temperature
• Increase in storm frequency
• Upwelling: brings nutrients from colder ocean water to the surface for organisms to use
• Organisms get pushed around by ocean current
• Adults can control where they are, transport processes determine where they end up
• A lot of breeding, where they are, how they get around depends on ocean currents

Mangrove
• Group of species that are not related genetically but adapted to same conditions
• Grow in inter-tidal zone; wet by the ocean daily; high disturbance
• Foundation species: form ecosystem for other organisms and plants that grow there
• Links terrestrial with marine; roots are in marine and leaves are in terrestrial; leaf litter falls into ocean
• Provide ecological sources: absorb a lot of carbon, productivity as high as rainforest, provide refuge for small fish from predators and nutrients, grow on coast so protect against storms and tsunamis
• Climate Impact of Mangroves: increase in CO2 increases mangroves growth rate in places where there is very low stress, grow in high salinity areas so usually doesn’t increase productivity (too stressful of an environment)
• Temperature: optium level of photosynthesis is at 32C, maxes out at 38C (over 38C is detrimental)
• Precipitation: salt/salinity is stressful to the plant, increase in precipitation will decrease salinity and increase productivity
• Storm Frequency and Intensity: when it increases, will change species composition, because the faster-growing species will dominate over slower-growing when there is a disturbance
• Sea-Level Rise: mangroves grow in places where sea level change (high tide vs low tide) is 2m
• 1. No sea-level change: no change in mangrove position
• 2. Sea level-drop: mangroves will move seaward
• 3. Sea level-rise: mangroves either move landward, or have peat accumulation (leaf litter from trees) anerobic respiration so organic material can accumulate and relative elevation of mangrove forest can rise because of organic matter that is settling
• 4. Human development and sea-level rise: want to move landward but there is a hotel in the way, ones near ocean die, detrimental loss to mangrove forest

Demise of the Corals?
• Create environment that all the organisms live in
• Very deep food chains
• High productivity for coral reefs where it is usually low productivity because of no nutrients
• Only lots of productivity where coral is… more interesting and more species
• Symbiotic with alge: filters out plankton from water and alge grows inside structure; trades nutrients alge
• Relationship with alge is delicate; when it gets warm alge doesn’t photosynthesize as much and this is detrimental to coral to have alge there; kick them out and then the coral turns white; animals go dormant – survival mechanism for sudden shocks of heat
• Coral will eventually die off, can only go dormant for a little bit of time
• More acidification in oceans dissolves calcium skeleton of coral, harder to grow after a disturbance
• Above 36C in ocean: bleaching happens with coral (# of days that it occurs)

Climate and Phenology
• Phenology: repeated (seasonal) lifecycle phases
• Mating, flowering, migration, ect