Environment Archives - Peatlands

Initiation History

Paludification (creation of peatlands) started following the retreating ice margin 11 000 years ago

First peatlands originated in eastern finland as the Fennoscandian glaciers retreated

Peatlands are formed bu incomplete decomposition of in-situ plant material (unlike lakes) in anoxic conditions and usually in cool temperatures

They require high effective moisture level (precipiration > evapotranspiration)

Peatland initiation types

1. Primary paludification

In a meadow as the land uplifts (like in Finlands west coast) over 3000 years

2. Terrestrialisation (infilling)

Material is deposited at the bottom of a lake until it piles up into a peatland

3. Secondary paludification

Something blocks the waterway to initiate secondary paludification
- Beaver dams
- Forest fire

4. Lateral expansion

Peatlands expand from an initiation point

All of these processes are still ongoing. The oldest peatlands were formed by primary paludification, then terrestrialization, then secondary (as the most common factor)

Newly initiated carbon stock

Peatland lateral expansion and primary paludificationis occuring now in the Arctic due to climate change - this is storing carbon

Peatland Classification

Overall classification

Determined by vegetation - forested to open from 1 to 4
- These have Finnish names, what are they?

Morphologically and hydrologically

Bogs and fens, also permafrost peatlands (palsa) (thermokarst)

Bogs

Blanket bogs

Depth 1-3 m
Grasses on the surface

Fens

Palsa

Mixture of fens and bogs
Perennially frozen mounds up to 7m high and wet depressions

Southern hemisphere peatlands

These have been somewhat neglected by scientists
There are lots in Patagonia, Tasmania and NZ
1920 - 1930: Väinö Auer collected samples from Patagonia and measured Holocene climate change

Testate Amoeba

Biological response to warming on the Antarctic peninsula
- Not proper peatlands, but it is organic soil, so it could become a peatland
- Geological definition - needs 1m of peat, but biological definition is peat-forming plants
look into this

Tropical peatlands

These are usually forested and mostly composed of woody peat that is highly humified (everything else is very decomposed).
- So it's difficult to find plant macrofossils

Discovery and Applicability of peat archives

Layers in peat were first noticed in 1800s by Heinrich Dau (stratigraphic features)
Blytt and Sernander hypothesized that darker layers were deposited in dry ties and lighter layers in moist times
This resulted in this classification of Northern European climate periods called the Blytt-Sernander system , based on Danish peat bogs
- Later this concept was supplemented by palynologist Lennart von Post
In early 1900s WEber paid attentoin to sharp boundary horizons and matched these with Blytt-Sernander system.
Defined some climate phases (dry and warm)
- These were not radiocarbon dated and so they're not used so much anymore

Geological survey of Finland

Maintains a massive database of Finnish peat cores
There is a ton of data here that can be used for research questions

Soil scanning

Using radar techniques you can identify layers, but this cannot replace palaeoecological data analysis - no fossils or other pieces for radiocarbon dating can be used

Could these be used more in the GIS context?

Climate archives

Can be used for environmental reconstructions
But also the response of peatlands to climate and atmospheric feedback is studied

Destroyed archives

Many peatlands, especially in the Netherlands, ahve been destroyed by human impact (draining)

Peat and carbon accumulation

Plant composition determines the net primary productivity and decomposition process (peat accumulation rate)
- Sphagnum (bogs) has slower decomposition
- Sedges (fens) have dast decomposition
Warmer areas with more rain have higher accumulation rate
Since there are different accumulation rates, peatlands in Lapland still cover the whole Holocene but they are much thinner layers (in 2m of peat)

Fen-bog transition

All peatlands initiated as fens
Fens are more common further north
What causes the fen-bog transition? This is important since bogs accumulate more carbon and fens emit methane and CO2

Study methods

After taking cores:

Plant macrofossils: using a microscope to identify plant remains to different taxa to reconstruct water tables
Plant functional types and peat properties
Radiative forcing?
Testate amoeba - they have narrow niches in terms of hydrology so we can reconstruct water table from these
Pollen, isotopes, Cladocera, DNA can also be used
- Principal Component Analysis