future of forests 4 Flashcards
a palaeontological and evolutionary plant biology perspective (29 cards)
tree evolution
trees have evolved separately many times: convergent evolution
molecular schematics (excludes fossils) show 3 or more separate origins
fossil evidence uses morphology and anatomy
earliest forest
- giant ferns in SW England and Gilboa in NY state
- limited diversity, trees from a single genus with small species diversity
- ecologically simple ecosystem
- lasted about 10Ma before other plant groups evolved trees
earliest complex forest
carboniferous lowland equatorial forests (approx. 340-300 Ma)
- ecologically diverse: 100s plant species at any one time
- extended over vast tracts of low and mid paleo-latitudes for approx. 40 Ma
- massive carbon burial in water logged conditions forming coal resources (classical coal swamp)
- died out due to regional warming and climatic during at the end of carboniferous associated with Pangea supercontinent
atmospheric consequence of trees and forests
- massive drop in CO2 and rise in O2 through territorialisation
- middle Devonian evolution and spread of trees and forests a major contributor
- CO2 taken into due to increased plant biomass through photosynthesis
- large drop in atmospheric CO2 due to evolution of seed increasing plant biomass
- high O2 from plants supported animal respiration and wildfire: evidenced through charcoal
impact of the roots of trees and forests
greater roots In upper Devonian period (360 Ma) compared to lower Devonian period (420 Ma)
- inc water uptake
- increase plant size inc root depth
- inc biological weathering: rooks to mud
- increased biomass in geosphere – carbons storage
- roots hold soil together reducing physical erosion
Coevolution of plant and sedimentary environments
- sediment finer due to bio weathering
- braided rivers become meandering due to vegetation
- trees cause carbon burial as coal and charcoal
earliest rainforest
- fossil evidence of seed from fern Medullosa
- high evaporation rates: inc humidity, cloud cover and precipitation
- supports first rainforest in Paleozoic
Upland: Munros
- carboniferous (330-320 Ma) evolution of gymnosperm dominant forest
- drought tolerant plants, lowland plants live in wetland environment
Hyperthermal events:
sudden warming of the planet on a global scale
many hyperthermal events shown in sediment archives
- largest hyperthermal events coincide with mass extinctions e.g. end of Permian and Triassic period
- extinction from natural causes and processes pre-date humans
Primary causes of hyperthermal events
- Large igneous provinces – large scale volcanism
- ground heating including burning of carbon rich sediment (e.g. coals)
- release GHG
- LIP volcanism often cause mass extinction
Permian Triassic mass extinction
PMTE had the highest extinction rates of history of life on land and in the oceans
dramatic deforestation
loss of biodiversity
extinctions on land predate extinctions in the oceans
species adapted to wetter environments lost first
upland with seasonal dryland conifer and gymnosperm dominated vegetation less affected
loss of ozone in PTME causes UV exposure to pollen which causes malformation and sterility
role of vegitation of PTME
Vegetation is showed by models to have had the ability to increase recovery from PTME
super-greenhouse (8-10 degrees hotter) climate in early Triassic period is caused by loss of vegetation
hyperthermal event examples (historic and present)
- storms
- sea level rise
- climate zone change
- extinction
- ecological change
- pollution
- wildfire
- etc
recovery from PTME
Took 10 million years post PTME to see coal and biomass re-enter biosphere
fossil records repeatedly show how trees and forest have co-evolved with climate and environment in a bidirectional relationship (climate changes plants, plants change climate)
animals are more resilient due to faster migration than plants
Different drivers between ancient and modern hyperthermal
but similarities inc role of CO2 and GHG
faster than ancient analogue inc PTME
10 x faster ghg emission than any deep-time hyperthermal event
look to the past to understand the future
effect of inc emissions of CO2 on carbon sinks: stats
26% ocean carbon sink
30% land carbon sink
44% atmosphere
effect of inc CO2 emissions on carbon sinks: explanation
majority of natural carbon movement between carbon sinks and sources is natural
there is no increase in plant biomass that can make up for increased emissions (terrestrial biosphere)
it is very slow to take carbon from atmosphere to ocean: takes tens of thousands of years but is more efficient than land carbon sink
land carbon sink absorbs CO2 due to large quantity of energy for the sun
storing carbon as plant biomass is only temporary: what then happens to the plants? If burnt on deforest they then return to atmosphere
focus on geological net zero
Carbon response (land carbon sink) to temperature and precipitation
- carbon response to climate is large
- carbon response to climate is about 10x more certain over land than ocean
- increasing temperature and decreasing precipitation decreases land carbon sink much more on land than in the ocean
land -45.1 (uncertainty 50.6) PgC per degrees Celsius
ocean -17.2 (uncertainty 5.0) PcG per degrees Celsius
Carbon response to atmospheric CO2
0.2-1.4 kg C m-2 [100ppm]-1 (kilograms of carbon per meter squatter of land per 100ppm of co2 change) in northern hemisphere extratropic
other important effects on climate, biodiversity and human health
e.g. albedo (how much sun is reflected, forest have low albedo)
modelling transfer
wind movement, ocean currents and ocean modelling
land modelled as series of tiles under the atmosphere and interact with atmosphere above: one direction connection. Not much lateral connection with land except with freshwater through land
Why do we need Earth system models
- cannot measure everything everywhere all at once, need an estimate of what is not being measured
- can provide estimate of model future
- estimating the impact of climate change enables adaptation: informs policies e.g. transport, housing an industry
- understanding which processes control climate in some place (or globally)
- test new elements of our understanding of climate chemistry or physics
role of AI in earth system models
role of AI in earth system models
- AI is used for modelling
- patterns in earth system models may not be processes and AI is pattern based
- is a tool but not a replacement for mechanism models
evaluating earth system models: comparing models against data
models ranked on how well they match observed pattern
- identifies “best” model for a given data set
rarely leads to model improvement because it does not identify the reasons for bad or good model performance
- overlooks problems of equifinality (bad method but good outcome) and parameter tuning: makes model perform well for the wrong reasons
evaluating earth system models: assumption testing
- using hypothesis and assumption centred approach to turn hypothesis to testing
- use to refine model and measurements: two-way communication from model to experiment to improve understanding of the system
