Tom's Blog

Thursday, September 18, 2014

Buckthorn eradication: results of a five year study

Because of buckthorn's importance, there have been many earlier posts from Tom's Blog. A list of these posts, with URLs, can be found at this link.
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Buckthorn is probably the most difficult shrub to get rid of in prairie and savanna restoration (it’s at the top of IPAW’s list). Because of its strong allelopathic nature, if unchecked it can form extensive monocultures.

Removal of buckthorn requires the use of an herbicide, either as a basal bark or cut stem application. Although these treatments are very effective, they do not eradicate an infestation for two reasons:
  •  There is almost always an extensive seed bank. This is fairly easy to control, and only persists for several years.
  • There are numerous dormant root masses capable of sending up new shoots, and these are a much more difficult problem. Experience has shown that these viable structures can remain alive for at least 15 years, perhaps longer, even if any new shoots they form are mowed or top-killed by annual fire.

What I am reporting here are the results of a long-term study I carried out at Pleasant Valley Conservancy. The area used was a small part of a much larger bur oak savanna which was first cleared of buckthorn in the 1999-2000 period. The initial fairly large-diameter shrubs were killed by basal bark treatment with Garlon 4 in oil. After the shrubs had died (which took about two years) they were removed when the savanna was restored. Since then, the site has been burned annually.


Despite annual burns, new buckthorn shoots kept appearing every year. Each shoot was part of an extensive underground root mass. Five years ago I decided to see how long it would take to get rid of them. I think I have finally succeeded.


Starting in 2010 I canvassed the site carefully and sprayed with Garlon each buckthorn shoot, counting as I proceeded. In the three early years, when there were lots of shoots, I returned over and over again at 2-3 week intervals. At the end of the season, I made sure that there were no live buckthorn shoots left.

The table shows the results. I should emphasize that the effectiveness of my spraying is not in question. Thus, a shoot found in 2012 is not one that had been sprayed in 2011 and not killed. My conclusion is that in this small area there were many dormant root masses, but not all of them left dormancy the same year.

Year
Buckthorn shoots sprayed in study area
Year total
2010
not recorded
>300
2011
12+30+71+35+27
175
2012
17+18+55+5+44+20+82
241
2013
6+7+8
21
2014
0
0

Another conclusion is that it is possible to eradicate a site of buckthorn, but the site must be revisited in multiple years.

One might ask what effect this multiple spraying might have on the natural flora. That’s a lot of Garlon! I should emphasize that I was careful with my spraying, making sure that nearby “good” plants were not treated.  The table below is the species check list I made this year, when no spraying had been done. The diversity is satisfyingly high! Note the presence of Gentiana alba, a State Threatened species. There are actually two separate patches of this species, one of which has numerous stems, and both patches flowered.

Latin name
Common name
Actaea rubra
Red baneberry
Agrimonia gryposepala
Tall agrimony
Allium cernuum
Nodding wild onion
Amorpha canescens
Lead-plant
Andropogon gerardii
Big bluestem
Anemone virginiana
Woodland thimbleweed
Asclepias syriaca
Common milkweed
Asclepias verticillata
Whorled milkweed
Aster ericoides
Heath aster
Aster novae-angliae
New England aster
Aster sagittifolius
Arrow-leaved aster
Campanula americana
Tall bellflower
Desmodium glutinosum
Pointed tick-trefoil
Desmodium illinoense
Illinois tick-trefoil
Elymus hystrix
Bottlebrush grass
Eupatorium altissimum
Tall boneset
Eupatorium purpureum
Purple joe-pye weed
Gentiana alba
Cream gentian
Gentianella quinquefolia
Stiff gentian
Heliopsis helianthoides
Ox-eye sunflower
Hieracium kalmii
Canada hawkweed
Lactuca canadensis
Tall lettuce
Monarda fistulosa
Wild bergamot
Ratibida pinnata
Yellow coneflower
Rudbeckia hirta
Black-eyed Susan
Schizachyrium scoparium
Little bluestem
Silphium integrifolium
Rosinweed
Silphium terebinthinaceum
Prairie dock
Solidago rigida
Stiff goldenrod
Solidago speciosa
Showy goldenrod
Sorghastrum nutans
Indian grass
Sporobolus heterolepis
Prairie dropseed
Toxicodendron radicans
Poison ivy
Tradescantia ohiensis
Common spiderwort
Verbena stricta
Hoary vervain
Zizia aurea
Golden Alexander

Sunday, September 14, 2014

Baltimore oriole nest

We've been having Baltimore orioles nesting near our cabin for quite a few years. They build their characteristic nest in a nearby decrepit elm. We ought to fell this tree but won't as long as the orioles  use it.

Several days ago during a stiff wind the oriole nest, now no longer used, came down and Kathie found it. The structure is impressively complex, as the photo shows.


How do they make it?

According to the Cornell bird web site, the female weaves the nest from various types of fibers: grass, strips of grapevine bark, and wool, as well as artificial fibers such as twine or fishing line. They may also use fibers from an old nest to build a new one. Males may occasionally bring nesting material but don't help with the weaving.

The nest is built in three stages:

  1. Construction of an outer bowl of flexible fibers for support
  2. Springy fibers are woven into an inner bowl, which maintains the bag shape
  3. Addition of downy fibers and feathers to provide a soft lining which cushions the eggs and young.
They do one brood a year and the clutch size is 3-7 eggs.

At lunch we spent some time looking at the structure. Under a hand lens the fibers of this nest looked mostly like bits of cloth, although it was also possible to see strands of plant material. According to Cornell, no knots are tied, but some do arise due to random poking of fibers.

It's hard to imagine how someone without hands can make such a structure!


Friday, September 12, 2014

Story of a small prairie parcel

When we started restoration about 15 years ago, the parcel under discussion here consisted of a small clone of quaking aspen, about 0.2 acres. The trees were girdled in 1998 and the dead logs were removed 2 years later. Two medium-sized Hill's oaks were left standing and are thriving.

 Because this small area was an orphan trapped between our gravel service road and a small CRP parcel (the Ridge Prairie), we more or less ignored it. Although we don't have any specific records, we may have planted it once or twice with a dry-mesic seed mix. However, beginning about 2007 or 2008 it had become mostly a solid patch of Canada goldenrod (Solidago canadensis). In mid-summer 2008 the whole patch was mowed with a brush cutter to try to get a handle on the goldenrod. After that, all we have done is burn it when we burn the adjacent Ridge Prairie. It has been burned annually since then (7 or 8 burns) and otherwise it has been ignored.

I never paid any attention to it since I assumed that it was still predominantly Canada goldenrod. Last week I looked more carefully and realized that most of the Canada goldenrod had been replaced with a surprising diversity of forbs and graminoids, including some relatively uncommon species.

The photo shows one part of this parcel, with the Ridge Prairie in the background. (The nearest tree is probably a Hill's oak.)


The table below shows the results of my quick survey.

Latin name
Common name
Aster ericoides
Heath aster
Aster lateriflorus
Calico aster
Aster novae-angliae
New England aster
Aster pilosus
Hairy aster
Aster sagittifolius
Arrow-leaved aster
Baptisia alba
White wild indigo
Carex pensylvanica
Pennsylvania sedge
Cirsium discolor
Pasture thistle
Corylus americana
American hazelnut
Desmodium canadense
Showy tick-trefoil
Desmodium illinoense
Illinois tick-trefoil
Elymus riparius
Woodland wild rye
Eupatorium perfoliatum
Common boneset
Gentianella quinquefolia
Stiff gentian
Monarda fistulosa
Wild bergamot
Prenanthes alba
Lion's foot
Ratibida pinnata
Yellow coneflower
Rudbeckia hirta
Black-eyed Susan
Silphium integrifolium
Rosinweed
Silphium perfoliatum
Cup plant
Smilacina racemosa
False Solomon's seal
Solidago canadensis
Common goldenrod
Solidago nemoralis
Gray goldenrod
Solidago rigida
Stiff goldenrod
Solidago speciosa
Showy goldenrod
Sorghastrum nutans
Indian grass

Some of these species probably moved in on their own, since it is unlikely we would have had them in a seed mix. Noteworthy are Lion's foot and stiff gentian, which are hardly "weedy" species.

I'm convinced that the frequent (annual) burns played an important role in transforming this parcel from a monoculture to a diverse prairie.

It is encouraging to see what burns and patience can bring!

Friday, September 5, 2014

Mysterious Silphium dieback summer 2014

Have other prairie restorationists observed this?

At Black Earth Rettenmund Prairie a major dieback of Silphium species is occurring. Strikingly, at Rettenmund this has only occurred in the areas that were not burned in the spring of 2014.

This die-back was most dramatically revealed with compass plant (Silphium laciniatum), one of the signature species of the prairie, but rosin weed (Silphium integrifolium) is exhibiting the same phenomenon. In other sites (also unburned) in southern Wisconsin, the two other Silphium species, cup plant and prairie dock (not present at Rettenmund), are also suffering from this die-back. 

 As often happens in restoration ecology, this dieback creeped  up on me. The leaves of compass plants grew normally in late spring/early summer. Most plants had a lush complement of typical leaves. But in mid-June, no flower stalks developed at the time they normally would appear. Since the compass plants in the areas that had been burned were flowering normally, I knew something was wrong. But what?

By mid August all the compass plant leaves had turned brown. A survey of compass plants at Rettenmund indicated 100% dieback. 

Because of its structure, the situation with rosin weed was somewhat different. All the rosin plants grew normally but at the time they would be flowering they began to turn brown. The flowers on any plants that had already started developing aborted. Again, 100% effect.

Since we did not have the other Silphiums at Rettenmund, I visited a few other sites in Dane County. Both cup plant and prairie dock also showed the same phenomenon. 

The end result? Unless the site was burned, there may be no Silphium seeds to collect!

I am trying to document the extent of this dieback and would welcome reports from others who have experienced it.

One more thing. All of the other species at Rettenmund are growing and flowering normally except flowering spurge (Euphorbia corollata), which has also shown 100% dieback.

Let me emphasize that sites that had been burned this spring are not exhibiting this dieback. 


Wednesday, September 3, 2014

Fringed gentian; new to the site

As the photo here attests, fringed gentian (Gentianopsis crinita) is an extremely handsome plant. It was first discovered for us by a participant on our Labor Day 2014 field trip, although Peter Gorman had beat us by a day with his photo on Facebook.

Fringed gentian is a characteristic species of wet prairies, and we found it in a newly restored area of our marsh (details below).
Fringed gentian

Restoring a wet prairie: Our wet prairie is part of a much larger wetland that is present in the valley of Elvers Creek and East Blue Mounds Creek. Our part of the watershed is a side branch that runs up Pleasant Valley. In addition to a cold-water stream, we have a number of substantial springs that feed the area. The photo below provides an overview of the area where the gentian is present.

Sedge meadow where fringed gentian grows
Originally, this area was a monoculture of Carex trichocarpa, a rhizomatous sedge which forms thick, dense patches through which nothing else can grow. About five years ago, I discovered a relationship between this sedge and lousewort (Pedicularis lanceolata), a hemiparasitic plant (related to wood betony). Although lousewort does not kill the sedge outright, it sets back its growth significantly, making it possible for many other wetland species to grow. We have a good lousewort seed source here and spread the seed into the Carex areas. The link given above and those links it refers to describe the work. 

Once the sedge was under control, lots of other wetland species got started. But this was only part of the story. We needed fire to complete it.

Originally our wetland was burned only as part of a large burn of the whole area. Although this was very beneficial, the space between burns was 3-5 years. This year we decided to introduce annual burns in our piece of the wetland, focusing primarily on the long strip of C. trichocarpa that borders the Valley and Barn Prairies. This was a successful burn, and there has been a great response by the vegetation, as the photo above shows.

One of the outcomes of controlling the Carex was this first appearance of fringed gentian. (The seed came from a wet-mesic site elsewhere in Dane County.)

Since fringed gentian is an annual/biennial, its continued presence will depend upon good seed production and subsequent germination and growth. Unfortunately, we won't have a lot of control of that.

Friday, August 29, 2014

Baltimore checkerspot butterflies and turtlehead plants

Baltimore checkerspot at Pleasant Valley Conservancy
Turtlehead (Chelone glabra) in the Valley Prairie
The primary larval host of the Baltimore checkerspot (Euphydryas phaeton) is the White Turtlehead (Chelone glabra), a species of marshes, sedge meadows, and wet prairies. Turtlehead is native to Pleasant Valley Conservancy. It seems to be favored by wetland burns and flourished extensively in the sedge meadows after our first wetland burn in 2005. It was shortly after this burn that butterfly aficionados reported the presence of Baltimore checkerspots along the lane separating the Crane Prairie from the wet sedge meadow.


Although Baltimore checkerspots are not common in Wisconsin, they were very prolific at Pleasant Valley Conservancy during the last two trips (2013, 2014) led by the Southern Wisconsin Butterfly Association. They were especially common this year in the Valley Prairie area.

In past years we had not seen turtlehead in the Valley Prairie, but because of the checkerspot findings we anticipated finding them. Also, both the Valley Prairie and the marsh near it had good burns this past spring. 

Indeed, Amanda and Susan have been successful in finding quite a few flowering stems of this attractive plant in both locations.

Note added: according to the Illinois flower web site, checkerspot larvae in their later instars may move to and feed on swamp lousewort, a species that is prolific in our wetland. This may help explain the extensive populations at Pleasant Valley Conservancy.

Sunday, August 24, 2014

Bur oak grub growing on hard rock

Bur oaks are amazing trees! Long-lived, powerful, fire-resistant, and providing great ecological support for a wide range of creatures. In fact, many long-lived bur oaks are not giant trees, but small ones called grubs, only a few feet tall, but with quite large root systems.

Yesterday we were in the middle of an extensive woodland sunflower survey when Kathie discovered this small but powerful bur oak with two good-sized acorns. It is growing right out of the dolomite on the East Overlook. It's hard to know how old this tree is, and it is interesting to speculate how it survives. Its root system should be quite interesting.

Bur oak grub growing out of the dolomite, with two acorns.



The East Overlook has always been one of my favorite spots at Pleasant Valley Conservancy because it gives great views out over the valley, the prairies and savannas, has a lot of interesting rock formations, and is surrounded by a very nice grove of open-grown bur oaks.

The Short Loop Trail (reached by this link) goes right by the East Overlook in either direction.