11, The future of forests

Question 1

What human activities have impacted forests in the uk? 5

Answer 1

1. coppicing
2. forestry commission plantations to get more wood
3. forest clearance for farming
4. urbanisation
5. will impact in the future

Question 2

What are some of the things that will impact forests in the future? 5

Answer 2

1. more co2 leads to climate change
2. increased population means more fuel/food demand so some deforestation, but not loads as not always good farmland
3. pollution - uncertain if there will be more or less
4. more conservation work has encouraged localised forest expansion
5. deforestation of any land for housing

Question 3

What are the effects of increased co2 on one leaf? 4

Answer 3

1. more carbon dioxide means more photosynthesis as co2 is substrate
2. the enzyme RuBisCo is used
3. more co2 means RuBisCo works faster
4. more growth and biomass

Question 4

What reactions occur in photosynthesis? 8

Answer 4

1. RuBisCo is ribulose biphosphate carboxylase oxygenase
2. most abundant protein on earth
3. 40-50% of leaf protein
4. RuBP + CO2 -> 2PGA, which is the desired reaction
5. RuBP + O2 -> PGA + phosphyclycolate - wasted energy
6. the second reaction is phosphorespiration and is pointless
7. photosynthesis is a very slow reaction
8. competition between these reactions exists

Question 5

What are some ways of measuring the impacts of co2 on forests? 3

Answer 5

1. growth chamber studies - very expensive
2. greenhouse - trees don’t behave as in wild, too artificial
3. open tip chambers - co2 pumped into chamber but chamber open so tree exposed to natural environment

Question 6

What is the effect of elevated co2 on pine saplings? 5

Answer 6

1. substantial increase in co2 leading to substantial increase in photosynthesis, more carbon fixed
2. capacity for photosynthesis reduced because plants optimize for conditions - acclimation
3. less investment in RuBisCo
4. same number of leaves produced but protein content changes
5. high levels of co2 mean reduced protein in leaves as less RuBiscCo and other photosynthesis enzymes

Question 7

What are FACE experiments? 6

Answer 7

1. free air co2 enrichment, whole ecosystem exposed to high co2 levels
2. began studying wheat fields
3. now study trees - rigs of pipes around area spray co2
4. co2 release direction changes with wind
5. co1 hotspots created within wider forest
6. changes to animals and plants studied

Question 8

Describe the POP-FACE experiment. 5

Answer 8

1. European artificial system - poplar trees are used often for wood etc as they grow quickly
2. with more co2, more carbon fixed by photosynthesis
3. in 2/3 species, stems increased in diameter with increase in photosynthesis
4. other species - making more sugars but not more above ground biomass
5. may be more roots and leaves

Question 9

Describe the effect of elevated co2 on the duke forst understory. 4

Answer 9

1. effects over 7 years of high co2
2. north american pine forest
3. did more photosynthesis at high co2 levels but no more growth
4. effect of co2 reduced due to light limitations

Question 10

Describe the effect of increased co2 on forest floor litter. 6

Answer 10

1. how much c and n compared
2. all increased over duration of experiment
3. more photosynthesis
4. produce more leaf material so more litter
5. provides food for organisms in and around soil
6. soil respiration only marginally increased

Question 11

What conclusions can we draw from FACE? 8

Answer 11

1. Fast growing trees maintain enhanced growth
2. mature trees show altered growth morphology with altered water relations
3. can close stomata more so water retained better
4. changes in lead phenology - stay green longer as profitable for longer
5. chanes in soil chemistry - more phosphorous
6. overlal changes are subtle and complex but lean towards more carbon sequestration
7. one study at duke showed 40-50% increase in net carbon sequestration in mature forests 3-5 years after co2 increased
8. forests basically resist this form of ultimate change

Question 12

What are the physiological effects on trees of increasing temperatures? 4

Answer 12

1. photosynthesis and respiration increase
2. overall growth increases
3. indirect effect on water relations (transpiration)
4. effects disease susceptibility

Question 13

What are the effects of temperature on soil processes? 4

Answer 13

1. respiration and growth of microbes
2. decay of organic matter
3. mineralisation/nitfrification/denitrification
4. increased soil turnover

Question 14

What are the ecosystem effects of temperature increase of the soil? 7

Answer 14

1. remember - temperature controls ecosystem type
2. a 5 degree c increase in soil temperature means growth rate increases
3. no direct effect on canopy
4. nutrients released faster from soil, so go into trees and they grow faster
5. a lot of variation, but carbon neutral overall
6. loss of carbon from soil and gain from trees is balanced out after 7 years
7. this is only considering temperature in isolation

Question 15

What effect could rainfall changes have on forests? 5

Answer 15

1. UK predicted warmer, wetter winters and hotter, drier summers, favouring evergreens
2. similar to Mediterranean climate
3. boreal forest will be reduced and replaced with deciduous forest eg. scotland and scandinavia
4. more dry grassland/shrubland
5. composition of american forest will change and there will be a knock on effect for animalss