Methodology ~ Reconstructions

Question 1

What are pollen?

Answer 1

Male reproductive seed plants

Question 2

Vegetation reconstruction…

Answer 2

… is possible from pollen analysis

• Samples contain fossil pollen. By taking modern pollen and forming a calibration, the fossil pollen can be compared with modern times and vegetation can be reconstructed.
• However, species have a difference in pollen production, dispersal and deposition. Due to this the actual vegetation might differ from the reconstructed vegetation
• It is better to use the absolute pollen, as relative pollen counting may give wrong expectations

Question 3

Absolute pollen diagram

Answer 3

shows when which species were present and what the pollen concentration where.

Question 4

Give 3 arguments for the use of pollen diagrams instead of charcoal remains.

Answer 4

1. Small amount of species: Charcoal-based reconstructions can only take place for woody species; reconstruction based on pollen can take place on the basis of a much wider range of species
2. Probability: In order to reconstruct the vegetation based on charcoal, it is also a requirement that the woody plants present at the time have actually been burned and have led to charcoal residues in the sample analysed. That chance is not very great. The probability of the presence of pollen of (all) present species is much greater.
3. Transport: wood can also be imported and charcoal residues therefore need not to originate from locally present wood. The chance that somehow large quantities of pollen would have been imported is, of course, zero. Wood charcoal in itself is therefore a poor indicator for vegetation reconstruction

Question 5

What are 3 limitations of the use of pollen?

Answer 5

1. bias in what part of the past appears in an archive
2. Wind pollination (because of the wind direction there was no Holly found in the pollen)
3. Deposition, they are not all preserved in the same way

Question 6

What are the 4 states leading to the numerical data analysis of pollen according to Roberts (2014)?

Answer 6

1. life assemblage
2. Death assemblage
3. Fossil assemblage
4. Interpretation

Question 7

Life assemblage

Answer 7

pollen production
dispersal pollination
deposition

Question 8

death assemblage

Answer 8

sediment diagenesis
pollen preservation/destruction

Question 9

fossil assemblage

Answer 9

Coring and laboratory preparation.
Pollen identification and counting

Question 10

What are important aspects of pollen analysis that should be taken into account?

Answer 10

1. pollen productivity differs for species
2. Is is about a relative or absolute number? There can be relative changes, but the same amount
3. More herbs, means less trees due to agriculture
4. Tundra vegetation in late weichselien
5. Herbs increase on top, indicate open landscape due to humans.

Question 11

Diatom

Answer 11

a single-celled alga which has a cell wall of silica. Many kinds are planktonic, and extensive fossil deposits have been found.

Diatoms are unicellular algae and are used extensively in palaeoecological studies because they are excellent indicators of past environmental conditions. They are particularly useful palaeoecological proxies because they can be identified to the species level using light and scanning electron microscopy. Thus by inspection of assemblages in sedimentary records, we can make direct and indirect inferences about past environmental conditions.

-Can be well preserved due to skeletons.
-Skeletons have different conditions, good for reconstruction

-Have different optima in PH, so with the diatoms the differences in pH can be reconstructed.

Question 12

Climate reconstruction from ice cores

Answer 12

Ice cores are cylinders of ice drilled from ice sheets and glaciers. They are essentially frozen time capsules that allow scientists to reconstruct climate far into the past.

• By looking at past concentrations of greenhouse gasses in layers in ice cores, scientists can calculate how modern amounts of carbon dioxide and methane compare to those of the past, and, essentially, compare past concentrations of greenhouse gasses to temperature. Ice coring has been around since the 1950s.

Question 13

Tree ring

Answer 13

Tree ring width variation can also be used as an indicator for climate. Thick rings may indicate years of abundant growth due to for example a lot of rain.

Question 14

Pictorial evidence

Answer 14

Pictorial evidence: more recent, but pictures of a frozen Thames River indicate an extreme cold year

Question 15

Vegetation types

Answer 15

Cold temperatures have more tundra or boral forest.
Higher temperatures desert or tropical rainforest.

Question 16

Reconstruction of desertification

Answer 16

-The use of sediment core sampling
-increase surface water conductivity

-Conductivity is a measure of the ability of water to pass an electrical current. Because dissolved salts and other inorganic chemicals conduct electrical current, conductivity increases as salinity increases

Question 17

Ecological cascade (Salmon)

Answer 17

Allis shad fishery started with total collapse of Atlantic salmon stocks
* Twaite shad fisheries started with collapse of Allis shad stocks
* Twaite shad fisheries collapsed with closing of Haringdiep

Question 18

How can a declining number of Sturgeon and an increase in average weight of this specie occur?

Answer 18

Long-term data on sturgeon fisheries does not point towards early decline
- Seemed stable till the end of the 18th century
- Sturgeon stocks seem to be in free-fall decline at the end of the 19th century
* Smaller and lighter specimens seem to be disappearing in the 19th century
* The population is getting older on average
* No recruitment of younger specimens  failing reproduction in 19th century?
* Last large-scale successful reproduction around 1850s?

Question 19

Watch video

Answer 19

https://www.youtube.com/watch?v=CN83D-ra4_o