Lecture 2: Atmospheric CO2

Question 1

Anthropocene:

Answer 1

humans have created a new era due to their change on climate

Question 2

climate change and global warming =

Answer 2

NOT always warming!

- not globally uniform, colder in some places, warmer in other

Question 3

modelling climate change:

Answer 3

V V complex,

- CO2 effect on future of planet predicted by looking at the past

Question 4

CO2 conc= last 800 thousand years

Answer 4

pretty steady, never above 300 ppm until last 50 years or so
- humans never had to deal w higher then 300ppm

Question 5

CO2 conc = last 500 mill years

Answer 5

• Much more range
• has been much higher
• BUT HUMANS HAVE NO EXPERIENCE AT THESE HIGH CONC, ANIMALS AND PLANTS W SURIVE, HUMANS WONT

Question 6

The inorganic Geochemical carbon cycle: would occur =

Answer 6

happen EVEN if everything on the planet died

- geochemical = long term

Question 7

The inorganic Geochemical carbon cycle:

Answer 7

• Carbon cycle between atmosphere & Lithosphere
• rainfall & silicate rocks (weathering of silicate rocks)
• Run off from rocks, limestone & HCO3- ions and are buried (long term storage)
• metamorphism of carbonate rocks = CO2 pressure
• volcanic (degassing) activity and CO2 is released
  AND REPEAT

Question 8

The inorganic Geochemical carbon cycle: Atmosphere and lithosphere carbon

Answer 8

Atmosphere = 700-800gt 
lithosphere = 75 million gt

Question 9

lithosphere =

Answer 9

earth crust & earth soil

Question 10

carbon leaves the atmosphere in 2 ways

Answer 10

• rainfall, dissolved in rainwater to form carbonic acid (I precip, D C in atmos)
• direct removal by silicate rocks
• -> Both lead to weather if silicate rocks == formation of limestone (28% of earths crust = silicate rocks)

Question 11

Organic carbon cycle =

Answer 11

• CO2 taken up by plants
• photosynthesis & respiration (&decomposition)
• CO2 + H2O <==> CO2 + H2O
• ## short term-photosynthesis takes up 120gt,
  -respiration releases 60gt, biomass absorbs 60gt
• agricultural farming removes 3gt
• microbial respiration & decomposition releases 60gt
  SO BALANCED, W US REMOVING EXTRA 3GT BUT

industrial processes, concrete production and land use change by humans adds 9gt

= loss of 6gt / year into atmosphere

Question 12

carbon store in soil

Answer 12

2300gt

Question 13

plant biomass carbon

Answer 13

550gt

Question 14

human activity effect ___ & ___ carbon

Answer 14

natural flux (deforestation) 
long term storage (degrading wetlands, soils etc)

Question 15

global CO2 atmospheric conc throughout the year

Answer 15

more in winter, less in summer due to photosynthesis ESP in upper latitudes (where most boreal forests are)

Question 16

transpiration =

Answer 16

• Water is a ghg

- as temp increases, more water can be stored in atmosphere

Question 17

evolution of plants impact on inorganic carbon cycle

Answer 17

increases weathering (more carbon taken up by plants and by rocks of earths crust) 
- more important role they play in carbon cycle

Question 18

5 effects of plants on weathering:

Answer 18

• respiration and evapotranspiration increases global rainfall
• plant roots, break into soil and hold it together, stabilising soil particles whilst rain washes past it
• mycorrhiza interactions & plant roots secrete organic acids into soil, decreasing pH
• roots respire = CO2, dissolves in water = carbonic acid, lowers pH
• plants die & are decomposed by fungi & microbes = organic acids released

ALL INCREASE WEATHERING

Question 19

ATMOSPHERE & PLANT INTERACTION: The evolution of leaves: megaphyll vs microphyll leaves

Answer 19

microphyll = simple, single vein, no leaf gap, limited size (simple vasculature)

megaphyll = leaf gap, branching veins, often larger (complex vasculature)

Question 20

ATMOSPHERE & PLANT INTERACTION: The evolution of leaves. Earliest land plants =

Answer 20

• 415Mya Cooksonia
• similar to mosses or liverworts today
• single, simple upright stems

Question 21

when did woody shrubs evolve =

Answer 21

385 Mya

STILL NO LEAVES, tiny tiny microphyll leaves

Question 22

megaphyll leaves evolution?

Answer 22

365 Mya in Late Devonian
(50Mya of evolution of plants)
– very very long time? WHY

Question 23

why did microphyll –> megaphyll take so long?

Answer 23

lost of theories debunked,
—> Hao et al 2002

SUN (light)? probably!!

• • plant evolution in late Palaeozoic = HUGE CO2 decline (no fungi /microbes able to decompose dead plants, = coal today we burn)
• • drop in CO2 relate to increase stomatal density as plants having to work hard to get CO2 in
• • DEVELOPED TO BIGGER LEAVES

Question 24

limited CO2 leading to leaf evolution: Erect axis vs laminate leaf

Answer 24

• flat leaf (laminate) can absorb more solar energy throughout the day
• BUT if they have small stomata, then energy/heat cannot escape and they overheat
• early devonian (HIGH CO2) erect axis leaves benefit as low stomata and don’t want leaves to over heat
• late devoniana (LOW CO2) megaphyll leaves benefit as more stomata due to lacking CO2, allowing heat energy to leave

Question 25

Recent increases in CO2 led to _____ in number of stomata

Answer 25

DECREASES

Gray et al 2000

Question 26

megaphyll leaves evolved __

Answer 26

separately in FOUR groups

– such an advantage, so evolved separately across multiple groups

Question 27

leaves evolved because of ___

Answer 27

the atmospheric carbon levels

Question 28

leaf evolution had huge effects ON the long-term carbon cycle

Answer 28

1) increased photosynthesis (led to huge diversity)
2) root and shoot co-evolution (big leaves, more roots required)
3) carbon burial (more microbes, more fungi so increased decomposition and burial)