Lecture 11 Flashcards
demand of timber is
increasing
- wood fuel, charcoal, pellets, paper and paper board, sawn wood, industrial roundwood
- global demand increased by over 300 million m3 from 2012-2016
ectomycorrhiza found in __ of plant species
in only 3%, but these plants are exceptionally important dominant around the globe
the total C pool in forest ecosystems is about ___ Gt, out of a global ___Gt of which __% is boreal forests
1190Gt
2110 Gt
58% in boreal forests
in boreal zone __% of C is in soil and plant litter
62%
what is the worlds largest vegetation system
Boreal forests
-over 35% of the global forest cover is provided by ectomycorrhizal trees in boreal forests (Ecto useful in storing carbon)
the ____ & __ are experiencing the greatest rates of warming and models suggest they will continue to do so
northern hemisphere boreal forest and tundra
threats to the boreal forest
logging, fire, pine beetle (normally ok as cold winters kill them off), global warming
burning of forests =
- common in north america, less fires but the first which do occur are much bigger
- British columbia, canned nearly 13,000 km2 burnt in 2018
bad outcomes from forest fires
often generate extra lightning storms from the upwelling heat, smoke and water vapour (create their own microclimates)
- file tornadoes reported in 2018 Californian forest fires
- pollution from particulate carbon
post fire soil erosion and degradation
- wash off of ash, and erosion
- takes a long time to recover, whole soil system gets reset 1000 of years
- soil loss and soil erosion a major problem often in areas where it is not normally
- BUT lots of charcoal, biochar may accumulate in soil and have beneficial effects (storing carbon)
logging: carbon loss
a lot of carbon originally stored in forest floor, this takes a long time to recover after logging
-even after 79 years post logging, a lot of carbon bad but in trees not in ground so risk of burning and its gone
ectomycorrhiza:
- 70-112 m2 hyphal absorptive area per m
- EM compromise 70% of the total soil microbial biomass
- from 2.5m2 of forest soil EM can wrap around the earth
ectomycorrhizal fungi =
- almost exclusively in basidiomycetes, a few ascomycetes
- over 95% of root times of pine, spruce and fir trees ar covered in fungus (Taylor et al 2001)
- roots not in contact w soil
- almost all organic carbon passes through fungus
ectomycorrhizal fungi produce a range of extracellular enzymes that are involved in
hydrolysis of organic C, N & P containing components of litter and C- containing structural components of plant litter
Perez-Moreno & Read 2000 Leaf litter
-beech tree litter & birch sapling tree , positive feedback between nutrient uptake by EM mycelia and increased lead area for C fixation .
EM uptake of N & P result in
left over high carbon , nutrient poor organic matter. other organisms cannot decay these
- increased C:N ratios
EM & Tannins
partly depolymerise the tannins
tree logging: cutting down Coastal Redwood
- live up to 3500 y
- stem biomass = 3500 tonnes /ha
- N content of 0.1% (3.5 tonnes per hectare)
- same amount of N you add to wheat field for ten years
- cutting down you lose the nutrients accumulated over 100 generations
much tropical deforestation does not involves timber extraction but
burning
- for clearance for grazing land etc
- lose 7.7% per year
most tropical trees are ___ mycorrhizal
arbuscular
majority of tropical forest changes are for
food production (mainly animal feed) at the cost of biodiversity and ecosystem carbon storage and soil
palm oil & forests
clear a lot of forest to grow it
- in a lot of products
- Tsujino et al 2015
- major source of vegetable oil
trees agroforestry
- Zomer et al 2016
(trees on agricultural land) - sequest a lot of carbon
- globally these trees increasing by 2% each year
- soil organic carbon is higher when you have trees at edge of fields (Pardon et al 2017)
soil water movement and hedgerows
water pulled out towards hedges (build up water capacity in soil)
- soil at the hedge can capture soil reducing risk of contaminated waters going into streams / rivers
-flood risk mitigation & pollution
Ghazavi et al 2011
train track trees
trees nearby are chipped an left, could we not use it for efficiently? fuel?
Draw power station largest in UK
to keep it burning for longer buning coal to –> burning wood pellets (which we import from the USA)
- marginally better, but where is it being cut down from?!
californian biomass ‘waste’
estimated 14 million dry tons of forestry residue could be sustainably processed each year for energy
- could help reach bioenergy targets
- should think carefully on how we are using such materials
sustainable forest ecosystems: issues to consider
1) climate change impacts and interactions
2) soil degradation on removal of forest cover
3) nutrients in wood ash quickly washed away
4) tree removal in high rainfall areas like the tropics causes extreme soil erosion and soil degradation
5) problems of nutrient export on logging
6) competition for fertilisers (NPK) between forest production and food production
7) competition for land biofuels /crops
8) biofuels temptation to use forestry waste but where is this coming from
9) increasing g demand for wood and paper
10) opportunities to make greater use of agro-forestry & tree legumes and tree food crops
ectomycorrhiza vs arbuscular mycorrhiza
arbuscular = penetrate cell membrane for nutrient exchange, greater surface area
ectomycorrhiza = can break down complex organic substrates
Both transfer N & P to plants in exchange for C
