Oak Woodlands at Pleasant Valley Conservancy

Most of the oak woodlands are burned biennially. The last burn of the north woods was Nov. 2016.

See this link for information on a very successful oak woodland burn

Oak woodlands at PVC include Units 13B, 15, 16, and 17 (link to map)


The contrast between the north-facing and the south-facing slopes at Pleasant Valley Conservancy is extreme. If one stands at the top of the ridge and looks south, one sees open oak savanna and prairie. Looking north, one sees a dense oak woods. The north-facing slope, which is almost always in the shade, is cool and moist, offering conditions favorable for dense growth of trees. Snow remains long on the north slope.

The air photo shown here illustrates the contrast well. The tree density on the north-facing slope is high; the canopy is mostly completely closed, whereas the savanna on the south side is partly open, with scattered open-grown oaks.

Air photo (from 2010) illustrating with GIS the north-facing woods.

Visiting the oak woodlands

Unit 13B

Unit 13B is a small, charming white oak woodland at the east end of the Conservancy. This is an interesting, even-age, stand of white oaks that are mostly about 80 years old. This stand has developed on a small outcropping of dolomite, with soils that are more alkaline than the surrounding land. It has been burned annually for the past ten years and has developed into a nice, brush-free, oak woodland.

Lush oak woodland
Big white oaks
Burning the woods
After the burn

 

North Woods

We maintain a modest trail through the middle of the north woods. This trail starts at the top of Unit 1 just above the quarry, and continues more or less along the middle of the north slope. About three-quarters of the way along, the trail forks. One fork goes steeply up and ends at the woods road in the savanna. The other fork continues east and eventually climbs to the west end of Toby's Prairie. This trail is shown as dashed blue lines on the map above.

Although this trail is interesting at any time of year, it is best taken in mid-May when the orchids are in bloom.

There are three ways then to view the north woods:

  1. A stroll along County F shows the woods from below. This walk is especially good from early summer to early fall when there are many forbs in bloom.
  2. A walk along the North Fire Break, which can be reached from a side trail at the west end of Toby's Prairie
  3. The North Woods Trail, which is especially nice in mid-May when the spring wildflowers are in bloom.

Because the north-facing woods is cool and moist, the plant understory is completely different from that of the south-facing slope. The predominant flowering plants here appear early, before the leaves are out. They flower, set seed, and senesce. In the dense shade of summer, the principal flora is ferns, of which maiden hair fern is the most frequent and attractive.

At Pleasant Valley Conservancy spring flowers start to appear in early to late April and flourish up to the time when the oak leaves appear, which is usually mid May. After leaf-out, there are very few flowering plants on the forest floor, due to insufficient sunlight. During the summer the predominant plants are ferns, which are able to grow with reduced sunlight.

The two most frequent members of the spring flora are trillium (Trillium grandiflora) and yellow ladyslipper orchid (Cypripedium pubscens). Some of our most showy wildflowers are among the spring ephemerals (see Photo Gallery and species list below).

The tree database

All trees larger than 10 inches in diameter have been tagged, ID'd, measured, and entered into our database. The photo below (prepared with GIS) shows the distributions of the three dominant oak species, Northern Red (Quercus rubra), Hill's (Q. ellipsoidalis), and White (Q. alba). On the north slope the most frequent species is red oak, although substantial numbers of white oaks are scattered about. Hill's oak is only found in a patch near the top of the ridge. (There are many Hill's oaks in another cluster at the east end of the Conservancy.)

GIS map showing distribution of red, white, and Hill's oaks on the north-facing slope.

The tree canopy of the north woods as measured with a fish-eye lens is 90% or higher, and the amount of light available on the forest floor is probably less than 10% of that found in savannas. The only places in oak woodlands where forbs are found in significant amounts during the summer are "canopy gaps", which are clear areas where trees have come down, either because of disease, or by windthrow.

In contrast to the savanna, the oaks in the north-facing woods are not open-grown. They are fairly close together, growing tall and reaching for the sunlight. Because the north-facing woods is heavily shaded, the forest floor is cool and damp. Because of this, these woods probably rarely if ever burned.

Although much of the woods remains as it would have been before settlement, there were two areas that had been cleared many years ago. These can be seen on the 1937 air photo. A large area at the far eastern end of the woods, near the property line, had been cleared some years before the 1937 photo, and had become a brush patch when this photo was taken. Presumably this area, easily reached, was cleared for firewood. Another area in the middle of the woods, across from where the Duhr driveway is today, had also been cleared. It is interesting that this formerly cleared area is now the site of a large population of Trillium grandiflora is .

Restoration Work in the Oak Woodlands

Although most of the emphasis of our restoration work has been on the oak savannas, work has being carried out on the oak woods as resources have permited.

Control of Woody Invasives There were lots of exotic honeysuckles and buckthorn in the north-facing woods. Although fire temporarily kills woody species, it does not eradicate them. Dormant buds in the soil are not affected, resprout, and the shrub continues to thrive. The most economical way of eradicating shrubs is with the use of herbicides.

In January 2006 we carried out an extensive herbicide project to control invasive shrubs in the oak woods. Although these shrubs were not as dense in the woods as in the savannas, there were quite a few large buckthorn and honeysuckle. The approach used was basal bark treatment with triclopyr (Garlon 4) in oil. This work was done by an outside contractor. Approximately 23 acres of the oak woods was treated. A series of swaths about 100 feet wide were marked, beginning at County Highway F and continuing straight up the hill to the upper ridge. A worker walked up each swath, moving back and forth and spraying the base of each undesirable shrub. The procedure took about 7 worker-hours per acre. Although costly, this approach was much less expensive than cutting and treating, and caused little damage to the woods.

The treated shrubs did not leaf out in the spring and gradually toppled over during the succeeding years.

Honeysuckle area at the west end There was one bad honeysuckle area, about 3 acres, at the west end of the north woods. This is an area that had been logged at one time, opening up the habitat and providing light for proliferation of shrubs. This area consisted of almost solid honeysuckles.

During the late fall/early winter of 2006, a contractor cut all these honeysuckles and treated the cut stems with glyphosate. Large piles were made of the cut slash, and most of these piles were burned during the following winter or the 2008 fall burn.

Although this work eliminated the large honeysuckles, it did not eliminate the seed bank. New honeysuckle growth developed over this whole area and had to be dealt with. Because the winters 2007-2009 were heavy snow years, work on this honeysuckle area could not be done until early spring 2010. At that time, Susan, Amanda, Marci, and Tom spent several days herbiciding (by basal bark with Garlon 4) all of this honeysuckle.

The area was then burned on 12 April 2010 (see photos below). This burn was moderately successful, but this area was burned again during the major fall burn in November 2010 (see below)..

Burning the west end of oak woodland (part of Unit 15) on 12 April 2010. The honeysuckles in this area had been herbicided (basal bark) before the burn.
The day after the burn in the oak woods, in an area where the burn was fairly successful. Getting an oak woods to burn requires a big burn crew and lots of drip torch fuel.

County Highway F

Pleasant Valley Conservancy owns about 2500 feet of Dane County Highwaty F. This roadside has significant prairie and savanna flora, and has been an area that we have been managing since 1999. This area was an important seed source in the early days of our restoration work. The importance of this roadside was first pointed out to us by Brian Pruka, and Paul West encouraged us to start collecting seed there. Although in the early years the Dane County road crew was somewhat uncooperative, since around 2005 we have had great cooperation following an agreement that we would cut and manage vegetation in this area.

There have been several management problems. Initially we had to deal with woody invasives such as honeysuckle and buckthorn ,, as well as aspen. When we began management the honeysuckle was especially bad on the upper slope where the county road mower did not reach. We continue to manage woody vegetation, although mostly now it is native species such as willow, elderberry, and viburnum. The goal here is to keep the roadside free of woody vegetation so that the prairie and savanna flora can flourish.

Wild parsnip was a major problem in the early years, but diligent hand pulling brought this under control and we have had no problems since the late 2000s. Although sweet clover was never a major problem, scattered patches were present and continue to require attention.

We were encouraged by the response to brush removal of prairie and savanna species, which seemed to have been living in a suppressed state. Those species which we have collected extensively on County F include Aster sagittifolius, Ceanothus americanus, Desmodium canadense, Euphorbia corollata, Gentianella quinquefolia, Hypericum pyramidatum, Krigia biflora, Pediculus canadensis, Polygala senega, Solidago nemoralis, Taenidia integerrima, Veronicastrum virginicum, and Zizia aurea. See this link for a detailed species list.

Further work on the County F roadside was initiated in 2011 under a LIP grant. See details at this link.

Controlled Burns

Since we started restoration work 15 years ago, we have done some large controlled burns in the oak woods (1999, 2007, 2008, 2010, 2012, and 2014).

The first controlled burn was done by the Prairie Enthusiasts in late October (Hallowe'en) 1999. Probably because of the unusually dry fall, this was a very successful burn. The spring ephemerals responded very well, and we had probably the largest display of large yellow lady slipper orchids we had ever seen. This was probably the first time that most of this woods had been burned since presettlement.

For years we waited for the right conditions to carry out another woodland burn. Finally, in spring 2007 everything was right and another burn was done. Again, the spring ephemerals responded well.

Encouraged by a new grant from the USDA Wildlife Habitat Incentives Program, we had a third fairly successful burn in October (Hallowe'en) 2008. The air photo below shows the results. About 25 acres burned.

North woods burn, Hallowe'en, 2008. The area that burned well is marked in red. The area in white shows the location of a large patch of Trillium grandiflorum.
View of the north woods after the Hallowe'en burn of 2008.

 

We had another successful burn on the north woods in November 2010. This was done during a spell of "Indian summer" that often occurs about this time of year.
Area of the north woods burned in November 2010 (shown in red), with the area burned in 2008 also shown (in white).
The most recent major burn was done on October 29, 2014. Details of this burn can be found in this link to Tom's Blog.
The final stage of the woodland burn is to light the roadcut above County F.

 

What have these burns accomplished?

They have helped keep the woods open and relatively free of invasive brush. They have definitely promoted the growth of spring ephemerals as well as the ferns. The maidenhair ferns, which do very well at Pleasant Valley Conservancy, really seem to thrive after a burn.

Time of year for the burns Four of the five burns were done in the fall and one in the spring. Fall burns aren't often done by prairie people, but this was when the Native Americans always burned. It makes sense to burn the woods in the fall. One important reason is that in the spring one always has snow to contend with on the north-facing slope. Our snow often lingers there until early April, and then it takes a while for the forest floor to dry out. In the fall, we burn before the snow comes. By late October, most of the bur oak leaves have fallen, providing fresh fuel for a burn.

The days we burned in fall 2008, 2010, 2012, and 2014 were especially good for a burn, with fairly low humidity.The oak leaves, the principal fuel, carried the fire fairly well.

Long-range burn plans for the north woods Since the successes of the last three burns, we are now planning to burn the north woods every other year (on the even years) in the fall of the year. This timing will depend upon weather conditions.

The importance of fire in eastern oak forests

Historical data have shown that throughout the 19th century, most eastern oak forests were burned at frequent intervals. With the advent of the U.S. Forest Service in the early 20th century there was a strong movement towards fire suppression. However, it was only since the early 1950s that fire suppression became the rule rather than the exception. In the absence of fire, oak forests in the eastern U.S. have seriously deteriorated.

In recent years the U.S. Forest Service has recognized the importance of fire for managing eastern oak forests and has conducted major conferences every three years. The latest one was the 4th, held in Springfield, Missouri in 2011 (earlier ones were held in Kentucky, Ohio, and Illinois in 2000, 2005, and 2008). The proceedings of these conferences are available through the Forest Service web site.

The work we are doing to introduce fire into our oak woodland will hopefully provide a model for what can be done by private landowners. Obviously, fire can be used to manage oak woodlands, and at a modest cost compared to other tools.

 

New Restoration Project 2011 (LIP grant)

In 2011 Pleasant Valley Conservancy received a new grant from the Landowner Incentive Program (LIP) for restoration work on the north woods. The work is focusing on the lower part of the woods, including County F and the wooded area just above.

Work on County F As mentioned above, the Conservancy owns about 2500 feet of County F. The restoration work that had been done in 1999-2000 was only on the 2000 feet east of Pleasant Valley Road. The last eastern-most 500 feet was in worse shape and time did not permit work there. With the LIP grant, this area could now be restored.

Work was initiated on this area in early November, after seed collecting had finished for the year. Fortunately, the weather over the month of November was favorable, permitting extensive work.

Work began at about the 2000 foot marker and continued to the end of the property line. This area of County F had extensive large honeysuckles plus smaller buckthorn and other woody vegetation. All of the woody vegetation was cut and the cut stems treated with Garlon 4 in oil. A lot of the cut vegetation was trucked to the burn pile on Pleasant Valley Road (see Tom's Blog for the elimination of this pile). Later, most of the cut woody vegetation was burned along the side of the road (with permission of the County Road Supervisor).

 

The final part of County F, now cleared. The cut vegetation on the lower part of the road cut was burned in the ditch. The brush cut in the woods itself was made into piles for later burning. The bare roadside will be seeded with prairie and savanna species collected earlier in the fall.

 

 
Some woodland species at Pleasant Valley Conservancy
Latin name Common name
Actaea rubra Red baneberry
Adiantum pedatum Maidenhair fern
Anemone quinquefolia Wood anemone
Aquilegia canadensis Wild columbine
Aralia nudicaulis Wild sarsaparilla
Arisaema triphyllum Jack-in-the-pulpit
Cypripedium calceolus pubescens Large yellow lady-slipper
Dicentra cucullaria Dutchman's breeches
Dodecatheon meadia Shooting star
Fragaria virginiana Wild strawberry
Galearis (Orchis) spectabilis Showy orchis
Galium tinctorium Stiff bedstraw
Geranium maculatum Wild geranium
Hackelia virginiana Stickseed
Goodyera pubescens Rattlesnake plantain
Hydrophyllum virginianum Virginia waterleaf
Maianthemum canadense Canada Mayflower
Osmorhiza longistylis Smooth sweet cicely
Podophyllum peltatum May-apple
Polemonium reptans Jacob's ladder
Polygonatum biflorum Smooth Solomon's seal
Ranunculus abortivus Small-flowered buttercup
Sanguinaria canadensis Bloodroot
Smilacina stellata Starry false Solomon's seal
Smilax illinoensis Green brier
Thalictrum dioicum Early meadow-rue
Trillium grandiflorum Large-flowered trillium
Uvularia grandiflora Bellwort
Viola spp Wood violet
 
Flora of County F (data from 2004)
Latin name Common name
Achillea millefolium Yarrow
Amorpha canescens Lead-plant
Anemone canadensis Meadow anemone
Anemone quinquefolia Wood anemone
Anemone virginiana Tall thimbleweed
Angelica atropurpurea Great angelica
Aquilegia canadensis Wild columbine
Aster laevis Smooth blue aster
Aster lanceolatus Panciled aster
Aster lateriflorus Side flowering aster
Aster novae-angliae New England aster
Aster pilosus Hairy aster
Aster prenanthoides Crooked aster
Aster puniceus Red-stemmed aster
Aster sagittifolius Arrow-leaved aster
Bromus kalmii Prairie brome
Caltha palustris Marsh marigold
Campanula rapunculoides European bellflower
Campanula rotundifolia Harebell
Carex hystericina Porcupine sedge
Ceanothus americanus New Jersey tea
Cicuta maculata Water-hemlock
Cornus racemosa Gray dogwood
Corylus americana American hazelnut
Cypripedium calceolus pubescens Large yellow lady-slipper
Desmodium canadense Showy tick-trefoil
Desmodium glutinosum Pointed tick-trefoil
Erigeron pulchellus Robin's plantain
Erigeron strigosus Daisy fleabane
Eupatorium maculatum Spotted joe-pye weed
Eupatorium perfoliatum Common boneset
Eupatorium purpureum Purple joe-pye weed  
Euphorbia corollata Flowering spurge  
Fragaria virginiana Wild strawberry  
Galium boreale Northern bedstraw  
Gentiana alba Cream gentian  
Gentianella quinquefolia Stiff gentian  
Geranium maculatum Wild geranium  
Hackelia virginiana Stickseed  
Helianthus divaricatus Woodland sunflower  
Heliopsis helianthoides False ox-eye sunflower
Heuchera richardsonii Prairie alum-root  
Hieracium longipilum Prairie hawkweed  
Hypericum perforatum Common St. John's-wort  
Hypericum pyramidatum Great St. John's wort  
Krigia biflora False dandelion  
Leucanthemum vulgare Ox-eye daisy  
Lithospermum canescens Hoary puccoon
Lysimachia ciliata Fringed loosestrife
Monarda fistulosa Wild bergamot
Oenothera biennis Common evening-primrose
Pedicularis canadensis Wood betony
Pedicularis lanceolata Lousewort
Podophyllum peltatum May-apple
Polemonium reptans Jacob's ladder
Polygala senega Seneca snakeroot
Polygonatum biflorum Smooth Solomon's seal
Prenanthes alba Lion's foot
Prunella sp. Self-heal
Ratibida pinnata Yellow coneflower
Rosa sp. Rose
Rudbeckia hirta Black-eyed Susan
Saponaria officinalis Bouncing bet
Scirpus cyperinus Wool-grass
Silphium perfoliatum Cup plant
Smilacina racemosa Solomon's plume
Smilax herbacea Carrion flower
Solidago canadensis Canada goldenrod
Solidago nemoralis Gray goldenrod
Solidago rigida Stiff goldenrod
Solidago ulmifolia Elm-leaved goldenrod
Sonchus spp Sow thistle
Taenidia integerrima Yellow pimpernel
Taraxacum officinale Common dandelion
Thalictrum dasycarpum Purple meadow-rue
Toxicodendron radicans Poison ivy
Trifolium pratense Red clover
Trillium grandiflorum Large-flowered trillium
Veronicastrum virginicum Culver's root
Viburnum acerifolium Maple-leaved viburnum
Viola soraria Door-yard violet
Zizia aurea Golden Alexander
Map