Tom's Blog

Wednesday, April 19, 2017

Spring 2017 burn of the oak woodland at Pleasant Valley Conservancy

Oak woodlands need fire, and at Pleasant Valley Conservancy we try to burn our major oak woodland (Units 15 and 16) at least biennially.

The big burn in November 2016 was fairly successful, but some areas did not burn well, and the County F road cut, which has a lot of good savanna forb species, did not burn at all. Yesterday, since all of the surrounding units at PVC had been burned, we had no need for fire breaks, and simply lighted from the bottom of the hill along County F. The fire easily moved up from County F into the woods, and in most areas burned through the woods until it reached some barrier. In several areas, the fire line moved all the way to the top of the hill, where it reached the North Fire Break and stopped.

This was a two-person burn (Amanda and Susan), with two drip torches and no water at all. (We had water backcans as back up, but they were not needed.) There was a strong wind out of the south, but on this north-facing hill everything was fairly quiet. The temperature was 70 F and the R.H. about 45%. There had been several sunny, windy days, so oak leaves, the principal fuel, were dry and crackly. All that was required is to light along the bottom of the County F road cut and watch the fire move.


Fire line moving through the woods from lighting at the bottom of the County F road cut.


Looking down from the top of the hill (along the North Fire Break).
In this area the fire had moved all the way from the bottom to the top of the hill in about an hour.


Zig-zag goldenrod, a woodland species, is an early starter. In this area, the fire went around the patch on the left, but burned the other two patches. Because this is a low-intensity fire (around 200 C), root buds of the burned patches will soon replace the damaged plants.






See more photos on the PVC Facebook page.


Friday, April 14, 2017

Genetic (DNA) taxonomy of three species of oaks at Pleasant Valley Conservancy

It is easy to identify a tree as a member of the genus Quercus (“oak”), yet often difficult to distinguish a specimen at the species level. This is especially true for oaks of the section Lobatae, which includes red, black, and Hill’s oak, three species that are prolific at Pleasant Valley Conservancy. To keep things simple, I will call this the “red oak group”.

Key taxonomic characteristics of oaks include bud and leaf morphology, acorn shape (including the cap), and bark thickness and structure. If the specimen is a “good species”, the characteristics fit well, and a species name can be attached. But confusion often arises, and this is often due to hybridization.

It has been known for some years that hybridization is common in the red oak group, which explains why these species are hard to pin down taxonomically. It seems reasonable that if two or more of these species are growing in the same general area, hybridization might occur.

Present day plant taxonomy makes extensive use of DNA analyses, which provide “ground truth” for traditional morphological taxonomy.

We have been fortunate that botanist Andrew Hipp, Senior Researcher at the Morton Arboretum, has taken an interest in the oaks at Pleasant Valley Conservancy. (Andrew worked as a naturalist at the UW-Madison Arboretum, and received his Ph.D. working on sedges. He wrote an outstanding book on the Sedges of Wisconsin.)

Since Andrew took up his post at the Morton Arboretum, he has been working on the taxonomy of oaks, using DNA techniques.

Later he returned with a research team and sampled a number of oak specimens for DNA analysis.

The details of the DNA studies are too complicated to present here, but can be found at the following link: 
Owusu, Sandra A., Sullivan, Alexis R., Weber, Jaime A., Hipp, Andrew L. and Gailing, Oliver. 2015. Taxonomic relationships and gene flow in four North America Quercus species (Quercus section Lobatae). “Systematic Botany”, Vol. 40(2): 510-521.


Andrew’s group studied red oak-group specimens from 17 separate geographic sites in the Midwest. My post here deals just with the oaks he sampled from PVC.

The map here is from Andrew’s paper, with a few labels added to indicate the approximate locations where the samples were taken. It shows the distribution of genetically pure, hybrid, and misclassified individuals. Each specimen is shown with the classification originally made based on traditional taxonomic criteria. Symbols with open centers indicate that the DNA data agreed with the taxonomy. If the symbol has a black circle, it means that the DNA indicated that specimen was a black oak but had been misclassified. Those with a black star indicate black X red oak hybrids. Those with a white plus sign are black X Hill’s oak hybrids.

Figure showing distribution of members of the red oak group from the research paper,
with labels added to show the approximate location at Pleasant Valley Conservancy.

The table below summarizes the data from this figure.

Analysis of hybridization in the red oak group, based on an analysis of 64 specimens from the north and east side of Toby’s Prairie.
Tree identity
How many?
Hill’s oak (Q. ellipsoidalis)
5
Red oak (Q. rubra)
20
Black oak (Q. velutina)
23
Hills X Black
2
Red X Black
5
Black misclassified as Hill’s
8
Black misclassified as Red
1

In sites such as PVC, where all three species are living close together, it is perhaps not surprising that hybrids (based on DNA) are common. A significant number of specimens of Hill’s and black oak had been misclassified (based on DNA). However, the DNA analysis indicated that quite a few tree specimens at PVC were not misclassified.

Andrew has now moved on to a study of the bur oak/white oak group, and will be back this summer to do DNA sampling from some of these trees.


Sunday, April 9, 2017

Early prairie flower blooms in fall-burned sites

Generally prairie burns in the fall are not too successful because grass, the principal fuel, has not yet fully cured. However, last fall was especially favorable for curing and prairie burns were quite successful.

The advantage of a fall burn? You don’t have to burn in the following spring. Depending on the weather, a spring burn might have to occur late enough so that species that flower early, such as pasque flowers, take a major “hit”. (I once watched a whole hillside of stunning pasque flowers at Koltes Prairie get burned up!)

Last fall two outstanding prairies were burned in the fall, thus giving them a “head-start” for this spring: Walking Iron and Black EarthRettenmund.

Yesterday, Kathie and I visited these prairies to see how they had responded. Although this has been a cold March and early April, lots of early prairie species were above ground. Pasque Flower Hill at Walking Iron Prairie indeed had quite a few pasque flowers (Anemone patens) in flower, although the major bloom will probably be next week.

Pasque Flower Hill at Walking Iron County Park in April 8, 2017. This prairie was burned the previous fall.
Lots of new growth scattered across the site, and a few dozen pasque flowers.


Pasque flower in bloom at Walking Iron. Pascha is Latin for Easter, which is often the time this species is in bloom.

Prairie smoke, a species that is especially prolific at Walking Iron.
 
Early buttercup (Ranunculus fascicularis). This species is the earliest bloomer in the Upper Midwest, but
generally found only in mowed lanes or other areas where the vegetation is short.
Because of the burn at Walking Iron, all the vegetation is short, so early buttercup is thriving.

At Rettenmund, where pasque flowers are fairly uncommon, shooting star shoots were all over the South Unit. Also, wood betony was in bud everywhere, prairie smoke was in the vegetative state but flourishing, and there were lots of rattlesnake master shoots.

Wood betony with a few buds already showing, and a vigorous rosette of shooting star;
the South Unit (burned Fall 2016) at Black Earth Rettenmund Prairie


From now until the end of October, there should be something new to see each week at these two nice prairies in western Dane County.

Monday, April 3, 2017

Pattern formation in little bluestem prairie

The little bluestem in our tallgrass prairie is so lush that the underlying growth pattern can’t be seen until it is burned. A close look at the burned half of this photo will reveal the individual clumps, which are shown in more detail in the second photo.

Fire moving across the South Slope little bluestem prairie. The bluestem clumps are visible in the burned portion.

Close up of the burned little bluestem clumps. The distance between clumps is about 12 inches (~30 cm).
 Little bluestem (Schizachyrium scoparium) is a classic bunchgrass and is widespread in North America. Each individual “bunch” is a complex of tightly joined tillers that arise from buds just below the soil surface. Little bluestem evolved where the fire regime constitutes frequent, generally annual, burns. In the absence of frequent burns, little bluestem grows poorly.

On dry sites such as ours, little bluestem grows in separate, erect clumps, with bare ground between plants. Each bunch is a clone, derived originally from a seed. The bluestem clone can have several hundred stems crowded into a patch of 5-10 inches in diameter.

Research in Texas has shown that the individual stems (called ramets) of the clone are integrated physiologically, with transfer of resources from older to juvenile ramets.

The mature root system consists of a huge network of roots, which spread out from the clump. Although most clones flower, seed production is not prolific, and is not too important in a mature stand.

The individual ramets in a bluestem clone are fairly short lived (mostly 2-3 years or less), and new ramets are produced to offset mortality. As new ramets are formed, older ones die and decompose. Long-lived clones often have hollow crowns due to death and decomposition of older ramets in the center. The age of a single clone may be as long as 50 years, but eventually the clone dies.

A lot of research has been carried out on the physiological processes by which the bluestem clone grows and maintains itself. Even if seeds of little bluestem are planted in a uniform manner across a field, regular patches develop. It seems evident that clones in a prairie compete with each other for one or more essential resources: water, light, nitrogen, etc. Those clones that get started earlier will have more roots and above-ground plant material to draw on vital resources and will hence win out. The end result is a pattern of clones with bare ground between them.

Although each bunch of little blue keeps other bunches away, the bare spaces between bunches are not barren, as other species can grow there. Here are two photos showing prolific growth of prairie forbs in the bare spaces between the little bluestem.

Violet wood sorrel in flower (with other species) among the little bluestem clumps in mid-May, 2014.
Butterfly milkweed and other forbs growing profusely in the bare patches between little bluestem clumps, July 1, 2014

Wednesday, March 29, 2017

Oak savannas: unburned patches in an otherwise complete burn

Given the right fuel and weather, oak savanna burns can be as complete as prairie burns. However, there are times when unburned patches remain after burning is otherwise complete. Although these unburned patches could be "touched off", the drip torch operator(s) have often moved on and don't have time to go back.

The oak savanna burn at Pleasant Valley Conservancy on March 21, 2017 was mostly successful, but distinct unburned patches were left in the white oak savannas on the lower slopes (Units 11D and 12A).

Yesterday I had time to go back and try to figure out why these areas did not burn.

Unburned patch on the lower slope of Unit 12A (White Oak Savanna)

There is plenty of fuel in this patch (oak leaves and prairie grass), and if "touched off" it should burn completely.

Since this unit faces south and has substantial steepness, it was backburned from the top of the hill to protect the large open-grown white oaks (over 150-years old). Because the wind was variable, it might have been blowing uphill at the time the fire line reached this point. Also, this patch is almost level, which could have influenced the fire line. Although the fire went out here, it burned around the edges and continued downhill.

This patch constitutes what is called a "refuge", where fire-sensitive organisms survive. My estimate is that about 85% of Unit 12A burned completely, leaving about 15% as refugia. In the adjacent Unit 11D the unburned areas were even more, amounting to about 50%.


Monday, March 27, 2017

Pleasant Valley Conservancy burn summary 2017

The year 2017 was without a doubt the most successful burn year that we have had at Pleasant Valley Conservancy. If we include the North Woods burn that was done in November 2016 (part of the same dormant season), we burned 132 acres: 34 acres (November) + 98 acres (February/March).

Also: For the first time we were able to burn virtually all of the PVC-owned wetland (15 acres).

The GIS-based map shown here provides the details.


Several factors contributed to the success of the burns.

  • The simplification of the DNR permitting system made it possible for us to make our plans the day before a burn.
  • The NOAA weather predictions have been detailed and accurate. The graphical version especially provides hour-by-hour predictions of the four key weather elements we use: temperature; dew point; relative humidity; and wind (speed and direction).
  • The availability of a very capable burn crew from Integrated Restorations, plus experienced supplementary people; all available at the ready when conditions are right.
  • Our own experience. We have been doing these burns for 20 years and have learned how to do them. Among other things, we are doing larger burns, getting as much fire on the ground as possible when the weather permits.
  • Amanda's great work as burn boss, supervising the crew, getting all burn breaks ready ahead of time and ensuring that we have enough water and drip torch fuel.
  • The success of our restoration efforts, which has meant that the vegetation of the burn units is "fire-ready". Although some internal lighting is still necessary, once the black line has been burned in, most units burn themselves with very little work on our part.
Flanking fire line moving through the bur oak savanna and tallgrass prairie; burn of Feb 2017

Burn crew lighting along a tricky spot at the edge between prairie and savanna; burn of Feb 2017

Kathie and Denny monitoring the edge of the savanna burn; Feb 2017.
The unit to the right was burned with the rest of the savannas on March 21, 2017
Later stage of the savanna burn; Feb 2017. The fire line carried all the way through the unit.
The savanna burn of March 21, 2017. Kathie, Amanda, Chris
Protecting the boardwalk while burning the wetland; burn of March 23, 2017.
The Kawasaki Mule with pumper unit was backed up to the edge of the boardwalk.


Wednesday, March 22, 2017

What to do with dead trees during oak savanna burns?

Scattered dead trees are characteristic of oak savannas. Some of these trees are fire-sensitive species such as birch and cherry, whereas others are oaks that die as part of the standard mortality process that occurs in forests.

Standing dead trees, often called “snags”, are an important part of the savanna ecosystem and are left for wildlife. Dozens of animal species depend on snags, including numerous cavity-nesting birds, some mammals, and a vast array of insects and other invertebrates.

In addition to snags, logs and other woody debris that fall to the ground, generally called “coarse woody debris”, play additional important roles in the savanna system.

However, the dead wood in a savanna becomes a special problem during savanna burns. As part of the rotting process, dead wood becomes fire sensitive, and can cause problems during the burn mop-up process.

Dead wood is subject to decay by wood-rotting fungi, which break down the lignin and cellulose that confer rigidity on the tree. Decay results in formation of wood that is soft and spongy, generally called “punky”.

Punky wood catches on fire unusually well. (Another name for punky wood is “tinder”.) A few sparks from a strike by flint and steel is often all that is needed to start a small fire. The radiant heat of a fire passing near a tree with punky wood may all it takes to start a small fire. Although these fires generally go out quickly, there is always the possibility of a larger scale conflagration.

Why is punky wood more flammable than intact wood? In intact wood, heat is conducted into the interior and dissipated. Punky wood has an open structure surrounded by air, so heat is retained, and the oxygen necessary for ignition encourages the flame. Everyone knows that if you want to start a fire in the woods to cook your dinner or stay warm, you first find some tinder (punky wood) and use it at the base of the campfire. According to U.S. Forest Service data, punky wood will ignite and create a flame at a lower temperature than grass (~230 C instead of > 300 C).

At Pleasant Valley Conservancy we work hard to protect snags from fire by clearing a fuel-free zone around the base of each snag. This generally works well, but occasionally we get fire in a snag and have to put it out. The photo here shows how we deal with this.

A dead white oak in the East Basin savanna. Although it had been cleared around (see base of tree), some of the punky wood still caught fire. Kathie is using the high-pressure water from the pumper unit in the Kawasaki Mule. It took only a few minutes to put out the fire.
If a snag smoker is well within the burn unit we generally leave it, as the fire usually goes out, and getting rid of the punky wood is actually beneficial. However, the tree shown in this photo is fairly near the edge of the burn unit, and there is about 40 acres of grassland nearby that belongs to someone else. Given those conditions, we put the fire out.

Sometimes the fire is not near the base, like this, but high in the tree. Putting out such a fire is nearly impossible, so the tree is cut down and broken up into pieces. (A chain saw is standard equipment for a savanna burn!)

The photo below shows a large fallen log that fell, next to a live bur oak. We did not bother to put this fire out, because the tree is well inside the burn unit so that there is no danger of a spot fire. Letting logs like this burn helps recycle nutrients into the ecosystem.

This log is a good example of large coarse woody debris. It is in Unit 19D, well inside the burn unit.