Dendro Midterm

Calibration

use of known environmental data to identify the tree growth response to changes in that variable

Verification

assessment of the accuracy of an environmental reconstruction

Reconstruction

use of tree-ring (or other) data to infer past environmental variability

The principle of Cross Dating

Matching patterns in ring widths or other ring characteristics among several tree-ring series, which allows the identification of the exact year in which each tree ring was formed. This ensures we have assigned the correct calendar year to each ring and helps account for problems, such as false or absent rings. This is accurate because trees within a region will respond similarly to the overall conditions

The principle of limiting factor

A basic principle of science that there is some resource that limits the amount of product that can be made. It is adapted for dendrochronology, since tree growth can proceed only as fast as allowed by the primary environmental and physiological mechanisms that restrict growth. When growth is limited fewer cells are produced making narrower rings when growth isn’t rings are larger, this variability allows us to distinguish when conditions have changed in the environment.

Principle of ecological amplitude

The idea that a tree species will be more responsive and sensitive to changes in environmental conditions in the outer limit of its range. This range can be latitudinally, longitudinally, and even changes with altitude. Trees will be less stressed at the center of its range and more stressed at the edge, where the climate might be harsher. These edge areas are where changes in tree growth is more likely to occur when climates are changing.

Principle of Uniformity

The idea that the present is the key to the past. This means that the processes that occur in the present are the same that occurred in the past. By looking at current environmental records (meteorological, insect outbreak, etc.) and seeing how it affects the growth of trees in the present a model can be built. When this model is inverted past conditions can be analyzed this is only accurate, because of the principle.

Field techniques

Increment borer

Field form

Paper straw

Chopstick

Sharpie

Pen

Container for cores

What to fill out the field form with

Height estimate, dbh, crown condition, slope, vegetation, location

How to assemble the borer

Unscrew extractor

Remove extractor

Remove the auger

Place the extractor next to the tree

Open the latch on the middle of the handle

Place the extractor through the hole and close the hatch

How to core

Find a tree that has very little vegetation or competition

Mark its height, dbh, location, slope, crown condition

Assemble the borer

If there is a slope do not core up or down it

Place the borer at chest height against the tree

With one hand on the handle and the other on auger, while pushing into the bark turn the handle clockwise

Once the bit bites into the tree continue turning using both hands

Listen for odd sounds and feel if the turning gets too easy, if it does stop and remove borer

Check periodically for jams

Check distance in the tree

Extract core when done

examine the core and mark on the field form if it is pith, near pith, or no pith

How to check for jams

Insert extractor till it hits the core

Mark with your thumb

Pull the extractor out

Place the tip against the bark

The distance should be the same if not it is jamming

How to extract the core

Insert the extractor under the core

Gently push the extractor the full length of the auger

The teeth will bite into the core

Ture one or two turns counter clockwise

Pull the extractor gently to not break the core

Cradel the core as it exists in case piece fall off

Insert the core immediately into the paper straw

Labe the straw with the proper id

Lab stuff

Let the straw dry for a couple of days

Remove core from straw

glue into a holder

saw the excess from the holder

sand the core down until it is smooth

Skeleton plotting why

Is extremely time consuming and old fashion

Reduces bulky sample amount to a concise record that can be compared between samples

Useful when you don’t know the most recent date of a sample

Prevents personal biasis, since another scientist or program is used to confirm the plots.

Skeleton plotting how

Uses graph paper were there are 10 cells within 1 inch of paper each line represents 1 year typically 110 years can be marked additional sheets are used for years past.

x is the year or ring number

y is the inverse scale of narrowness ranging from 0 for average or larger width and 10 for absent rings

Begin by marking the plot with a flag at the starting year and work to the right

You look at a small number of neighboring typically 3 on either side where the center ring is the one being examined against its neighbors.

If it is narrower than its neighbors mark it to its severity and if its the same do not mark it.

This is done for every ring in a core sample.

When one sample is done a new skeleton plot is made for the next.

When all plots are made for all the samples they are sent to another dendrochronologists for them to create there own if it comes back the same then you have a chronology if not you have to go back and check for mistakes and fix them.

List dating why

It cannot be used when the last known date is unknown, meaning preserved or dead wood cannot be used.

Quicker than skeleton plotting.

Also utilizes self standardization

Creates a master list verified from reanalysis and comparison of samples which can be used to quickly date the rest of the samples

List dating how

From the outside in (bark to pith) the rings are counted and dated.

Uses the neighboring rings for comparison.

When a narrow ring is noted, the date is written in a vertical list under the sample ID.

When 5 to 10 cores are done go back to the list and determine which rings are consistently narrow among the samples.

If the samples are consistently off you must go back and look for corrections or throw out the samples.

Sensitivity

How variable the tree ring growth is in a sample