Field Methods in Dendrochronology Sampling Design

Field Methods in Dendrochronology

Sampling Design • A procedure for selecting events from a population • Pilot sample (or pretest) • Simple random sample • random number generators are handy for x/y selection Y X

Sampling Design • Systematic random sample • • x select k-th individual from gridded population lay out a line = transect, sample individual nearest the preselected point x x x x x x x x x x x x x x x x x x x x

Sampling Design • Stratified random sample • population is layered into strata and then we conduct random or systematic sampling within each cell

Sampling Design • Stratified, systematic, unaligned = point sampling • 8 1 9 5 2 Hybrid technique, favored among geographers 4 5 1 8

Sampling Design • Stratified, systematic, unaligned = point sampling • 8 1 9 5 2 Hybrid technique, favored among geographers 4 5 1 8

Sampling Design • Transect = line sampling, but lay-out must have a random component! (How can this be accomplished? ) • Many variations: • Sample all individuals along the transect (row 1) • Sample quadrats along the transect (row 2) • Sample all individuals within a belt (row 3) x x x xx x x

Sampling Design • Targeted sampling = non-random sampling • Is this a legitimate technique? • It is often necessary because of: • Time constraints • Budget constraints • Lack of field labor • Physical limitations of field labor • Topographic limitations • Advantages? • Maximize information with minimum resources • Target areas where samples are known to exist • Less time needed and less money wasted

Sampling Design • Targeted sampling = non-random sampling • Used in practically all types of dendro research: fire history, climate reconstruction, insect outbreak studies, …

Sampling Design • Specifically sample only trees that have best record of fire scars. (dots = trees, circles = trees collected with fire scars, X’s = fire scars, but not sampled = poor record. ) • What issues must we consider? Topography, slope, aspect, hydrology, tree density: all affect susceptibility to scarring by fire. X X X X Shallow slope area Valley bottom X Steep slope area

3. Sampling Design • Complete inventory is possible • Sample all trees that have fire scars, regardless of number of scars or quality of preservation, but … • Not very efficient (time, money, labor) • Benefits are considerable, though. Shallow slope area Valley bottom Steep slope area

Field Methods in Dendrochronology • So, you’ve selected your site and you can even see your trees. NOW WHAT? • Two primary means of collecting wood samples: • • • Increment borer Chain saw Forget the chain saw for this class …

The Increment Borer Pressler, M. R. 1866. Der forstliche Zuwachsbohrer neuester Construction. Tharandter forstliches Jahrbuch 17: 155 -223.

The Increment Borer (broken apart) Grissino-Mayer, H. D. 2003. A manual and tutorial for the proper use of an increment borer. Tree-Ring Research 59(2): 63 -79.

The Increment Borer (assembled) Grissino-Mayer, H. D. 2003. A manual and tutorial for the proper use of an increment borer. Tree-Ring Research 59(2): 63 -79.

Preparing the Increment Borer • Fasten auger onto the handle via the clip. • Spray inside and outside of auger with WD-40. • Place the extractor some place convenient (NOT on the ground). • Place the tip of the auger against the tree. • Breast height or ground level? • Are you coring on a slope? WHY does this matter? • Look for a furrow in the bark. Bark is GOOD. • Grasp the handle with one hand the auger with the other. • Push and turn simultaneously. • Keep the shaft steady. Why is this important?

Starting an Increment Borer (I)

Starting an Increment Borer (II)

Coring the Tree • Turn with both hands, even pressure on each handle. • Listen for “odd” sounds. If it sounds strange, stop immediately. • You do not want to “jam” the wood inside • • As you continue to turn, though, new wood is pushed against the jammed wood. • • This occurs when the inner portion of the core stops. This creates an awful mess inside your borer, and sometimes renders your borer useless for the rest of the trip. Jammed borers often must be cleared in a wood shop.

Coring the Tree • Every few turns, check to see if the wood is jamming inside: 1. Insert the extractor until it hits the core. Mark this location with your thumb.

Coring the Tree • Every few turns, check to see if the wood is jamming inside: 2. Pull the extractor out. Place the tip against the bark. Its distance should be the same as when it was inside the auger.

Coring the Tree • Every few turns, check to see if the wood is jamming inside: 3. If your thumb is away from the handle, your wood is jamming! Stop immediately.

Extracting the Core • Insert the extractor under the core. • Gently push the extractor the full length of the auger. • The teeth on the extractor will bite into the end of the core. • Turn one or two full turns out. • Pull the extractor gently to break the core from the tree. • Cradle the core as it exits the auger in case pieces fall off. • Insert the core immediately into a paper or plastic straw. • Label the straw with the proper ID.

Extracting the Core

Extracting the Core

Wrapping up … • Write down tree and site information on standard field forms, including: • Height estimate, dbh, crown condition, aspect, slope, topography, vegetation, location (relative and GPS). • Photo documentation: helps in crossdating and archiving • Ensure all samples and equipment are accounted for before heading back. • Clean all your equipment!

Field Methods in Dendrochronology