407_TREERING

ESCI 407/507: Forest Ecology

Spring 2024

Last updated: 4/1/2024

Lab #2: Climatic, Edaphic and Biological Controls on Tree Growth

Readings:

Agee, J.K. and M.H. Huff. 1986. The care and feeding of increment borers. National Park Service Cooperativ Park Studiies Unit, College of Fores Resources, Univ. of Washington. CPSU/UW 86-3 (Click for pdf version)

Fritts, H.C. 1971. Dendroclimatology and Denroecology. Quaternary Research 1:419-449. (Click here to access)

Here are some cool links with useful info on Dendroclimatology:

1. http://www.ncdc.noaa.gov/paleo/slides/slideset/18/18_357_slide.html

2. http://www.ncdc.noaa.gov/paleo/slides/slideset/18/18_355_slide.html

3. http://www.ncdc.noaa.gov/paleo/slides/slideset/18/18_369_slide.html

4. http://www.ncdc.noaa.gov/paleo/treering.html

In this exercise, we will examine the relationship between climatic, edaphic and biological controls on tree growth. The paper by Fritts (1971; link above) provides and excellent introduction to this topic. As described in this review, interannual variation in ring widths can be used to reconstruct past variation in climate. In this exercise, we will reverse this relationship and use the historic record of climate as a predictor variable and we will view ring width as the response variable. Our general objective is to determine the strength of this relationship. Is tree growth tightly linked to variations in climate in PNW forests? Does the strength of this relationship vary among species? Is the strength of this linkage influenced by edaphic factors (soils and hydrology) or competitive interactions between trees?

Climate Data: We will be using the climate data that we downloaded from the National Climate Data Center last week.

Study Area: Our work will be conducted adjacent to the Mt. Baker Ski area on US Forest Service lands. The site is located in the Mt. Hemlock (Tsuga mertensiana) zone (Franklin and Dyrness 1988) at an elevation of about 1200 meter (about 4000 feet). The area where we will be working is very close to tree line. It contains widely scattered solitary trees and small clusters of perhaps 3 -10 trees. In addition to Mt. Hemlock, we will also encounter Pacific Silver Fir (Abies amabalis) and perhaps a few other tree species. We will be working in gently undulating terrain. The snowpack in this area quite variable from year to year. In some years, the snowpack can be well over twenty feet deep at this time of year. This is a very harsh environment with a short growing season and severe winters. Many trees show evidence of damage from winter storms and probable lightning strikes. I am anticipating that year-to-year variability in the growth of these trees will be strongly controlled by climate. Ideally, we want to select trees that are growing by themselves to minimize the chances that the growth of the tree may be influenced by competitive interactions with other trees. This may not always be possible. Another very important thing to avoid is any tree that has a broken top. This broken top is mostly likely caused by a lightning strike but it may be cause by a winter storm. In either case, the trauma caused by this injury is likely to have influenced the growth of the tree for many years. Including data from trees like this would introduce substantial "noise" in our analysis. We want to avoid this. Ideally, we would be taking our cores from near the base of each tree. Because of the deep snowpack, this will not be possible.

The Mountain Environment: DRESS PROPERLY! We are going into an environment that is harsh for us as well as for the trees. It is absolutely essential that you dress properly. We will be working from snowshoes that I will provide for you. We will only be out on the snow for about 1 - 1.5 hours. Nevertheless, proper dress is critical. Cotton clothing can be deadly in an environment like this. Cotton gets wet and stays wet and it sucks heat from your body. Don't wear it! You should be wearing a layer of "polypro" (or similar) adjacent to your skin. "Polypro" wicks moisture away from your skin and it will keep you warm even when it is wet. Over your polypro, you should wear one or more layers of "fleece" (Polartec or similar). Finally, you will need an outer layer that is water resistant and breathable (Goretex or similar). You will also need warm boots and a hat and gloves. If it is snowing and blowing, ski goggles might also be nice. Anyone who shows up for lab wearing blue jeans and tennis shoes will not be permitted to go along.

Safety: The area where we will be sampling is quite safe. We will not be more than a few hundred yards from the parking lot. The terrain is gently undulating. Nevertheless, it is very important that we all stick together. Under no circumstances should anyone go wandering off alone. There is some very steep terrain not far from where we will be working. The avalanche danger now is extreme and if you wander out onto this steep terrain, you could put yourself, and others, in great danger. Stay away from all steep slopes!

Tree Sampling: We will be taking increment cores from a number of trees throughout the stand.

PRIOR TO LAB, IT IS ABSOLUTELY POSITIVELY ESSENTIAL THAT YOU READ THE PAPER ON THE CARE AND FEEDING OF INCREMENT BORERS (By Jim Agee and Mark Huff; On reserve in the Huxley Library)! ANYONE WHO SHOWS UP FOR LAB WITHOUT READING BURIED UP TO THEIR NECKS IN A TREE WELL!!!!!!!!!!!!

The reason for being such a fanatic on this point is that, despite appearances, these increment borers are very delicate items and they are surprisingly expensive. The cost of the increment borers we will be using ranges from $200 to over $600. Improper use of these borers by people who did not receive proper training has cost Huxley quite a bit of money in the past. READ THE HANDOUT! We will discuss this handout in the field before anyone takes a core. One of the real dangers in using an increment borer is getting it stuck in the tree. In some cases, it is impossible to remove the borer and it must be abandoned. The chances of getting stuck can be reduced by careful selection of trees and by careful selection of the point in the tree where the core is taken. For this reason EVERY SINGLE TREE THAT WE SAMPLE WILL BE SELECTED EITHER BY MYSELF OR ONE OF THE TAs.

As a minimum goal, I would like everyone to take one core. If we have time, we may take some additional cores. Next week, we will be processing these cores back in the lab and measuring the width of the last 10 to 20 rings in the core. We will discuss this lab work and the subsequent data analysis next week.

For those trees that we choose to sample, I want you to record the following information:

1) Tree species.

2) Diameter at Core Height

3) Canopy position -- This is a subjective assessment of the position of the tree in the canopy. If the tree is in a clump with other trees, is it a canopy-dominant, sub-dominant or understory tree?

4) Other trees. Is this a solitary tree or one that is growing as part of a clump of trees? This is to give us a sense of whether the growth of this tree may have been influenced by competitive interactions. As a way of quantifying the “neighborhood” for each tree that we core, we will record the distance (in meters) and diameter (in centimeters)

a.) to it’s nearest neighbor and;

b.) it’s next nearest neighbor.

5.) Finally, I want you to determine the height of each tree that you core. To do this, you back away from the tree until you have a clear view of the top of the tree. Getting farther away will enable you to get a more accurate reading. You then measure the angle to the base of the tree and also to the top of the tree (record downslope angles as a negative value) using a clinometer. We will demonstrate the use of the clinometers in the field. You then dust off your middle school trigonometry to calculate the height of the tree. You also need to record the distance to the base of the tree. The calculation goes like this:

A diagram of a triangle with a tree

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We will give each tree a unique ID#. Your first, middle and last initials, plus a number would make a good ID#. Cores will be extracted from each tree and placed in drinking straws for transport to the lab. Each straw will be sealed with tape and carefully labeled (with the tree ID#). For big trees, you may need to break the core into pieces and put it in separate straws. You may find that it is difficult to avoid breaking the core during extraction. If the core does break, be sure to carefully label each straw and note the order in which the pieces need to get put back together. Be VERY VERY careful about this or it will create major problems in the lab!!!!! As soon as we get back to campus, and before you can go home, you will need to glue your cores to small wooden sticks (about 2cm X 2cm X 50cm). These sticks will stabilize and protect your cores. After the glue dries, the TAs and I will sand these down so they will be ready for processing next week.

Additional Information About Tree Rings: For additional information, you might take a look at these web pages:

Laboratory of Tree Ring Research at the University of Arizona (Take a look at their searchable bibliographic database!)

References:

Franklin, J.F. and Dyrness, C.T. 1988. Natural vegetation of Oregon and Washington. USDA Forest Service General Technical Report PNW-GTR-8, Portland, Oregon. (Go here for a link to this document)

Fritts, H.C.. 1971. Dendroclimatology and dendroecology. Quaternary Research 1:419-449.

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