Lecture 3 CM Flashcards
1
Q
Secondary succession: peatlands
A
- vegetation in Ireland has developed since the end of the Pleistocene glaciation c.15000 ya
- bogs began forming around 9000 ya, once initial forest/scrub has become established
- vegetation developed along different pathways in different areas
2
Q
What happened approx 15000 ya in Ireland?
A
- Ireland had a mosaic of deep glacial sediment and shallow lakes. slow formation of soil by bacteria, lichen, mosses and artic herbs.
- it looked like present-day Iceland
3
Q
What happened approx 10000 ya in Ireland?
A
- Ireland had a mosaic of shallow lakes and sparse forests on poor soils. Peatlands became extensive after this point
- it looked like present-day Finland
4
Q
What methods are used to date sites?
A
- Deglaciation events
- Volcanic eruptions
5
Q
Deglaciation events
A
time point where ice recedes from landscapes
6
Q
volcanic eruptions
A
- time point where ash is deposited
- they disperse airborne particles across the globe
- each eruption creates a unique array of rock particles and crystals
- these deposits uniformly across the surface of the Earth and are used to calibrate dates between sites
7
Q
What are the 3 Irish peatland types?
A
- raised bogs
- atlantic/lowland blanket bogs
- mountain blanket bogs
8
Q
What are peatlands characterised by?
A
- very acid soils
- mor type soils
- permanently waterlogged
- anoxic
- acidic
- very low biological activity
9
Q
Poor degradation of organic material leads to peat accumulation…
A
- 5 m deep (blanket bogs)
- 10 m deep (raised bogs)
10
Q
What plants dominate peatlands?
A
- Sphagnum mosses (acidifiers)
- Ericaceae (heathers)
- Cyperaceae (sedges)
- some Poaceae (grasses)
11
Q
Blanket bogs
A
- approx 10000 ya before present, forest became established on the shallow soils that had formed over glacial mineral gravel
- approx 4500 ya, climate became wetter and cooler, rainfall began to leech nutrients from topsoil
- gradually all highly soluble nutrients were washed away completely
- soluble elements, especially iron came out of the solution in the subsoil and bound with anoxic clays to form iron pan
12
Q
What is iron pan impermeable to?
A
water and plant roots
13
Q
What did waterlogging in blanket bogs lead to?
A
- waterlogging ensued and combined with acidic surface soil conditions providing an ideal habitat for colonisation by acid loving plants
- this lead to a successional sequence where Sphagnum moss began to colonise the soils in place of tree seedlings, especially in poorly draining areas
- heathers, sedges, grasses and Sphagnum moss take over the habitat and peat begins to form
14
Q
Sphagnum moss
A
- K selected dominant species that controls growth of bogs
- high water retention : wet weight = 95%
- cell differentiation is evident but no vascular system
- secretion of the antibiotic Sphagnol impedes microbial degradation of dead plant tissue
15
Q
What are Sphagnum moss specialised structures?
A
- hyaline cells, non-photosynthetic with large open pores
- hanging branches that draw water upwards
- hydrogen ion pumps are present in the cell wall
–> exchange free hydrogen ions (H+) for CA++, Mg++, K+ etc
–> facilitates efficient nutrient foraging in mor soil conditions
–> acidification of soil and water
