Sustainable forestry in a changing world Flashcards
37% of habitable land is forest
with 50% as agriculture (of which 77% livestock)
FAO 2017b Roser and Ritchie 2018
carbon dense forests are in the tropics (pan et al, 2013)
climate mitigation is most effective through reforestation, and avoided forest conversion and natural forest management (Griscom et al, natural climate solutions)
Bastin et al (2019)
Global tree restoration potential. Most effective strategies for climate change mitigation. They found an extra 0.9 billion hectares that could be potential canopy cover
Total global demand for wood has increased by over 300 million m3 from 2012-2016 (> 6%)
FAO 2016
If paper recycling rose to 66% globally this would save 153 million m3 of wood per year.
Many households rely on woodfuel for cooking
especially in africa and south-east asia
Ectomycorrhiza- found in only 3% of plant species, but these plants are exceptionally important dominant components of some forest ecosystems
Over 35% of the current global forest cover is provided by ectomycorrhizal trees in Boreal forests
> 16 M km2 - dominated by ectomycorrhizal pine, spruce and fir established on bare rock and glacial sands left after the last glaciation.
(Read et al., 2004)
The total C pool in forest ecosystems is about 1199 Gt, out of a global total of 2110 Gt of which 58% is in boreal forests. In the boreal zone 62% of C is in soil and plant litter. (Bhatti et al., 2002).
Ectomycorrhiza may be important assisting global soil C sequestration particularly in the boreal forest
(so are sphagnum mosses)
Roots and associated fungi drive long-term carbon sequestration in boreal forest
50%-70% of stored carbon in a chronosequence derives from roots and root-associated microorganisms (Clemmensen et al; Bodeker et al 2016)
Ectomycorrhiza: >95% of root tips of pine, spruce and fir trees are sheathed by fungus (Taylor et al., 2001)
These roots have no physical contact with soil
Virtually all plant nutrient and water uptake is through fungus
Almost all organic carbon released from living roots passes to the fungi
Ectomycorrhizal fungi
Almost exclusively basidiomycetes, a few ascomycetes
·Agaricales, Russulales, Boletales are the main groups
·Tuberales (ascomycetes) truffles- important as commercial product!
Ectomycorrhizal fungi produce a range of extracellular enzymes that are involved
in the hydrolysis of organic C, N and P containing components of litter, and C- containing structural components of plant litter.
(Read & Perez-Moreno, 2003)
EM mycelia- intensive, spatially precise, nutrient foraging
EM mycelia- intensive, spatially precise, nutrient foraging
Perez-Moreno & Read, 2000
Selective and highly effective mobilisation of organic nitrogen by ectomycorrhizas – but with limited decomposition of lignin and cellulose results in organic matter with very high C:N ratios and very low rates of decomposition by saprotrophs.
(Bending & Read, 1995)
Pollen has lots of DNA therefore lots of phosphorus
and nitrogen. EM can localise their efforts to maximise nutrient uptake
Selective depletion of labile N by etomycorrhiza restricts access to N by saprotrophs thereby inhibiting both N and C mineralisation- minimising N losses from these plant guilds.
(Leake et al. 2004)
The northern hemisphere boreal forest and tundra are experiencing the greatest rates of warming and models suggest they will to continue to do so.
Potential threats to soil C stocks and increased risks of forest fires
Burning accounts to up to 75% of forest loss in boreal areas.
Post-fire soil erosion and degradation
Sediment runs off and erosion is high due to rainfall
Biochar however may increase
carbon sequestration (Lehman et al 2006)
Burning or felling and removal depletes the ecosystem of nutrients accumulated over
>100 human generations
Coastal Redwood – Californian Sequoia sempervirens.
Live for up to 3500 y. Stem biomass up to 3500 tonnes ha-1.
N content of 0.1% = 3.5 tonnes N ha-1.
Same amount of N as added to wheat fields for 10 years production.
Much tropical deforesation does not involve timber extraction but burning
7.7% loss over 20 years
(105,000,000 ha)
Most tropical forest trees are arbuscular mycorrhizal
Food production (mainly animal feed) at the cost of biodiversity and ecosystem carbon storage and soil.
Agroforestry- a way of sustaining food production and soil ecosystem services?
Deep rooted plants lifting nutrients up from depth- where otherwise lost to leaching
Drax power station: from coal to biomass
Is it better to manage trees along roads and railways by felling and chipping them to leave as a mulch and soil carbon and nutrients for regrowth or should the wood be recovered and used as biomass fuel?
Energy from biomass ‘wastes’-
but we need to be careful not to increase deforestation
nor to deplete soil carbon or nutrient stocks or reduce soil carbon sequestration
Sustainable forest systems – issues to consider
Increasing global demand for wood and paper – the need to plant more forests and sustainably manage them
The potential to use trees to remove carbon from the atmosphere
Climate change impacts and interactions
Soil degradation on removal of forest cover- particularly severe effects of burning due to loss of soil organic matter and nutrients.
Nutrients in wood ash quickly washed away
Tree removal in high rainfall areas like the tropics causes extreme soil erosion and soil degradation.
Problems of nutrient export on logging
Competition for fertilizers (N, P, K) between forest production and food production
Competition for land for biofuels and crops
Biofuels- temptation to use forestry wastes (bark, and small branches)- but consequences for soil carbon, acidity, P supplies and N
Opportunities to make greater use of agro-forestry and tree legumes and tree food crops (fruits and nuts) – so trees provide food, capture carbon etc.
