Lecture 17 - carbon stuff

Question 1

what is used as a source for phosphorus for fertilisers

Answer 1

rock phosphate
and this is finite

Question 2

what are face experiments

Answer 2

free air co2 enrichment
just a localised place where they artificially increase CO2 over plants to measure the processes

Question 3

what are common results of FACE experiments

Answer 3

• plants grow more (more photosynth)
  so increased NPP (biomass)
  increased root groeth
  more C released from soils

Question 4

what is gross primary production

Answer 4

The total amount of carbon compounds produced by photosynthesis of plants in an ecosystem

Question 5

what is net primary production

Answer 5

the difference between the amount of carbon produced through photosynthesis (GPP) and the amount of energy that is used for respiration (R)

Question 6

by what process is C produced from leaves and soil

Answer 6

autotrophic respiration

Question 7

how does heterotrophic resp occur from soil

Answer 7

soil organic matter being broken down by microbes (which respire)
free living ones, not the root associated ones

Question 8

what are the 2 mqin pathways of carbon into soil

Answer 8

litter (dead plant matter) - slow
exudates (via live roots and mycorrhizal soil) - fast

Question 9

what does girdling a tree prevent

Answer 9

used experimentally
stripping bark from outside
prevents C from moving from shoots to roots
then will measure effects of this on CO2 flux
to see how important the fast pathway is in soil respiration

Question 10

what were the effects on CO2 flux after gurdling a tree

Answer 10

decreased CO2 released from soil by ~50%

Question 11

what is priming

Answer 11

input of labile (new) carbon will cause degradation of native (old - recalcitrant) carbon
so little bit of carbon in cause lots of carbon out

Question 12

how does global warming link with priming

Answer 12

more CO2 in atmosphere
more new carbon intake
even more old carbon being released
overall lots of carbon loss from soils

Question 13

what does decomposition of plant biomass produce

Answer 13

CO2 and methane

Question 14

what are the 3 factors that affect decompo rates

Answer 14

• properties of material being decomposed
• temperate, moisture conten, UV
• diversity of organisms alongside the plants, e.g. invertabrates or microbes

Question 15

what is the first thing to decompose in littler decomp

Answer 15

soluble first
at end will be lignin

Question 16

what are the 2 types of wood rotting fungi and what do they each degrade

Answer 16

brown rot = cellulose
white rot = lignin

Question 17

what are the 3 cellulases

Answer 17

endoglucanase
exoglucanase
cellobiase

Question 18

3 monomers found in lignin

Answer 18

coumaryl
coniferyl
sinapyl
all alcohols

Question 19

what are the 3 key enzymes that white rot fungi uses to degrade lignin

Answer 19

• lignin peroxidase
• manganese peroxidase
  (these 2 use H2O2 to oxidise it)
• laccase = directly oxidises lignin