Cofrin Memorial Arboretum Mapping Project

This project was a semester-long independent study in collaboration with the staff of the Cofrin Center for Biodiversity. Three main tree groups were identified as "genera of interest", and were determined subjectively, those being oaks, birch, and jack pine. These groups were mapped with ArcGIS Field Maps and Desktop Pro. And various attributes were collected across all three generas, such as DBH (breast diameter height), presence of storm and insect damage, and canopy loss.

There are also several long term objectives identified that go beyond the scope of a single semester's worth of work:

1. Inform management decisions related to the Arboretum
2. Serve as the foundation for future academic work and research projects
3. Increase student and local interest in the Arboretum
4. Build the foundation for the eventual completion of all mapping

Below gives a brief overview of the three groups of trees (oaks, birch, and jack pine), giving information on distribution, habitat requirements, and the species for each genera that are likely to be encountered in the Wisconsin area.

Jack pine (Pinus banksiana) is described as being fire-tolerant, early successional, and requiring full sun  ^1,4,8  . It tends to favor dry, acidic conditions, but can also grow in sandy and gravelly environments as well  ^2,7 . Jack pine is known for being short-lived (60-80 years depending on conditions), and undergoing "self-thinning" after reaching maturity  ⁴ . Which becomes a larger component of mortality with increasing age  ⁴ . And seedlings tend to favor disturbed, semi-barren to barren ground for optimal germination  ⁸ .

Birch (Betula) trees can be found across a wide span of geographic space, such as Asia, North America, and the artic regions of Europe  ² . Around 12-18 species of birch that can be found in North America, four of which can be found in the Wisconsin area  ² .

1. Yellow birch (Betula alleghaniensis)
2. White birch (Betula papyrifera)
3. Silver birch (Betula pendula)
4. River birch (Betula nigra)

Below are pictures of white, silver, and yellow birch.

Another important thing to point out while on the topic of birches is the differentiation between long and short shoots. Shoots are a characteristic feature of woody plants, and are how the plant expands its framework into new areas with more sunlight  ¹ . Short shoots are, as the name would suggest, smaller compared to long shoots, and grow much slower  ¹ . Barnes (2004) gives the example of how a 28-year-old short shoot of a yellow birch could be less than 2cm long. While a long shoot could grow anywhere from 1in to 10ft annually. Aside from the stark differences in growth rates, short shoots tend to persist for multiple seasons and are only characteristic of a few genera of trees, such as birch, beech, and maple  ¹ . Whereas long shoots can be found in all tree generas, and hold the greatest potential for expanding the canopy of a tree  ¹ .

As a genus, there are around 280-300 species, with around 90 being found in North America  ² . Oaks (Quercus) can be found in Mexico, North America, Central, and South America, Europe, the West Indies, Asia, and North Africa  ² . And can be divided into two main groups, white and red oaks  ² . With one of the main diagnostic traits being leaf morphology, white oaks typically have rounded leaf lobes, while red oaks have bristle tipped lobes  ² .

There are a total of 12 oak species that can be found in the Wisconsin area:

1. White oak (Quercus alba)
2. Swamp white oak (Quercus bicolor)
3. Bur oak (Quercus macrocarpa)
4. Chinkapin oak (Quercus muehlenbergii)
5. Dwarf chinkapin oak (Quercus prinoides)
6. Northern red oak (Quercus rubra)
7. Shumard oak (Quercus shumardii)
8. Black oak (Quercus veltina)
9. Scarlet oak (Quercus coccinea)
10. Northern pin oak (Quercus ellipoidalis)
11. Pin oak (Quercus palustris)
12. Shingle oak (Quercus imbricaria)

Oaks are generally wind-pollinated and poorly adapted to prolonged freezing winters  ² . They can be grouped into various subgroups based on their adaptations to their environment, which range from dry, periodically flooded, to swamps  ² . They are have varying leaf morphology and pubescence based on where the leaves are in the canopy (image below)  ² . Leaves near the edges or in the upper portions of the canopy are called sun leaves, while leaves found in the middle or interior of the canopy are shade leaves, which have much shallower lobes  ² .

Oaks are also known for their extensive hybridization, and can easily confuse scientists and field identification  ^1,6 . The most common method of identification for hybridization is intermediate characteristics in leaf morphology (first image below)  ⁶ . This can be taken a step further by using various leaf measurments to quantitativly show the various in leaf morphology (second image below)  ⁶ .

Another method of identifying hybrids is through winter bud and twig identification. An oak is likely to be a hybrid when there is a conflict between a sample's characteristics and the description when keying it out. Such as a discrepancy in the presence or type of pubescence. The sample could be densly pubescent, when the key describes the bud as being glabrous or mostly glabrous. To increase the confidence in ensuring an oak is a hybrid, the sample should be identified through more than one key. If the same issue persists, this increases the probability of it being a hybrid.

Within the boundaries of this project, the only confirmed oak hybrid is Quercus xdeamii. Which was determined based on the discrepancy between the described and observed pubescence (pubescent vs. glabrous). Based on the few oaks there were successfully identified in the white and red oak groups, the extent of their hybridization cannot be determined definitively due to time constraints. But one can extrapolate the potential amount of hybrids from Quercus alba and Quercus coccinea (which were the select few to be correctly identified). Q. alba tends to hybridize with almost the entire white oak group, compared to Q. coccinea (11 vs. 3 possible hybrid combinations)  ^1,6,9,10 . Quercus muehlenbergii like Q. coccinea, has 3 possible hybrid combinations based on available literature on the subject  ^1,6,9,10 . Below is a more detailed extrapolation of the amount of possible hybrids for white and red oaks.

Between the red and white oak groups, there are some notable differences in the winter buds, twig morphology, canopy structure, and bark appearance. Some differentiation in characteristics can be less reliable and depend more on the species, such as patterns in new twig growth, and branching being alternate or opposite.

White Oaks:

1. Canopy grows more up instead of out
2. Branching is mostly alternate
3. Bark is fissured to flaky fissured, which can be more apparent higher up in the tree
4. Winter buds are closer to the axis of the twig
5. Can be acute to ovide conical
6. New twig growth can be more clustered together

Red Oaks

1. Canopy grows more out instead of up
2. Branching is mostly opposite
3. Bark has deep fissures, and becomes smooth higher up
4. Winter buds are more divergent (grow away from axis of twig)
5. New twig growth can be more spread out

*oaks are incomplete due to time constraints

• Total: 177
  • Alive: 169
  • Dead: 8

• White birch:
  • Total: 188
  • Alive: 144
  • Dead: 44
• Yellow birch:
  • Total: 1
  • Alive: 1
  • Dead: 0
• Silver birch:
  • Total: 2
  • Alive: 2
  • Dead: 0

• Total: 22
• Alive: 22
• Dead: 0

A total of 18 birch samples exhibited various levels of odd growths on both long and short shoots, with there being no obvious pattern in where these growths appear. It seems to be more prevalent among white birches, as silver and white showed no to minimal signs. Yet silver and yellow birches have a smaller sample size and are not fairly represented. As the only yellow birch in the project area also exhibited odd growths, but appeared to be very minimal, or this was starting to occur at the time of this project.

White birch:

• Affected: 15
• Total: 15

Silver birch:

• Affected: 2
• Total: 2

Yellow birch:

• Affected: 1
• Total: 1

1. Gained valuable field experience
   1. DBH tape
   2. Handheld GPS and limitations
   3. ArcGIS Online, FieldMaps, Desktop Pro
   4. Dichotomous keys
2. Learned more about each genera of intrest
   1. Oaks and complexity of hybridization, unique characteristics of oaks and their classifications
   2. Jack pines and prefered environmental conditions, life expectancy and unique traits
   3. Birchs and main diagnostic traits between groups
3. Oak hybrid identification
   1. To confidently identify a hybrid, multuple keys must be used
   2. Hybrid literature was suprizingly limited and lacked comprehensive reviews that were were recent

1. Bud length was not a reliable indicator for keying out oaks in general
   1. Identification became more time consuming because of this
2. Shape, color, level of branch corkyness all could be unreliable or inconistent depending on level of maturity for twigs and buds
3. Handheld GPS units proved too inaccurate for needed sub-meter accuracy

1. Aldrich, P.R., Cavender-Bares, J. (2011). Quercus. In: Kole, C. (eds) Wild Crop Relatives: Genomic and Breeding Resources. Springer, Berlin, Heidelberg.  https://doi.org/10.1007/978-3-642-21250-5_6 
2. Barnes, B.V., Warren, W.H. Jr. (2004). Michigan Trees: A Guide to the Trees of the Great Lakes Region. (3rd ed.). The University of Michigan Press.
3. Burns, R.M., Honkala, B.H. (1990). Silvics of North America Volume 1: Conifers. United States Department of Agriculture. https://www.srs.fs.usda.gov/pubs/misc/ag_654_vol1.pdf 
4. Conkey, L.E., Keifer, Mary Beth, Lloyd, A.H. (1995). Disjunct jack pine (Pinus banksiana Lamb.) structure and dynamics, Acadia National Park, Maine.  https://doi.org/10.1080/11956860.1995.11682281 
5. Gailing, O. (2008). QTL analysis of leaf morphological characters in a Quercus robur full-sib family (Q. robur × Q. robur ssp. slavonica).  https://doi.org/10.1111/j.1438-8677.2008.00063.x 
6. Hardin, J. W. (1975). Hybridization and Introgression in Quercus Alba. Journal of the Arnold Arboretum, 56(3), 336–363.  http://www.jstor.org/stable/43781979 
7. Michigan.gov. (2022). Jack Pine.  https://www.michigan.gov/dnr/education/michigan-species/plants-trees/jackpine 
8. OCEC. (2010). Section 2 - Jack Pine (Pinus banksiana). OECD Publishing.  https://doi.org/10.1787/9789264095434-6-en 
9. Swink, F., & Wilhelm, G. (1994). Plants of the Chicago Region. Indiana Academy of Science.
10. Voss, E. G. (1985). Michigan flora. Part II. Dicots. University of Michigan. Ann Arbor, Michigan, USA.