A positive effect of the drought?

Bluegrass (Poa pratensis), an undesirable component of prairies, is much more sensitive to drought than prairie grasses. Black Earth Rettenmund Prairie has areas where bluegrass is still prominent, a legacy of former times. A brief survey showed that the drought has killed most of this bluegrass, leaving prominent bare areas.

Former bluegrass area (between the forbs), now bare ground.

Hopefully, prairie grasses will be able to take over these bare areas.

Amazing what a little bit of rain will do!

At Pleasant Valley Conservancy we missed some of the rains that passed through southern Wisconsin but we did get about 1.5" total spread out over about a week. This helped a lot and the prairie grasses have snapped back.

Our most critical area was the south-facing slope, which not only receives the full blazing sun, but is very rocky and has very thin soils. The principal grass is little blue stem, which with the thin soils is quite shallowly rooted. Before the rain, many of the bunches were completely dry and brown.

During the later stages of the drought I marked some of these seemingly "dead" bunches with flags and yesterday I checked them again to see how they had responded to the rain. Several of the larger bunches were now completely green! The brown leaves, of course, are still there, but completely crowded out by all the new growth.

Little blue stem also looks quite good now in the savanna areas. Also, Indian grass has bounced back. In fact, I saw several Indian grass plants that had started to flower.

Considering that southern Wisconsin is still in serious drought conditions (at least as far as agriculture is concerned), it is gratifying to see how quickly the prairies have responded to a little rain.

Spotted knapweed

Spotted knapweed (Centaurea biebersteinii) is a nasty invasive weed that competes well in sandy areas. Although we have not generally been plagued with it at Pleasant Valley Conservancy, it has turned up at a few locations along our gravel road. Its presence there was not accidental, as it was brought in with the gravel.

When we did a major overhaul of our gravel road in 2007 the contractor brought in lots of loads of gravel, and we were careful to ensure that it was weed-free. However, after the major rainstorms in June 2008 one part of our road suffered a serious wash-out. The contractor was able to repair it, but was unable to get gravel from the same source. It was from this new gravel that spotted knapweed is coming from.

Our general procedure is to walk along the gravel road in early June, when the knapweed is just getting started, and spray it with 2,4-D or Garlon 3A (aqueous). However, the plant shown here was hidden along the edge of the gravel and was missed. Fortunately, knapweed is quite easy to recognize when it is in flower and at this stage it is ideal for my Garlon 4 (in oil) basal stem technique. It took less than a minute to spray the bases of the five or six stems of the plant seen here. Two other plants at different locations along the road were also found and sprayed.

This is not our only fight with spotted knapweed. About five years ago the Town of Vermont rebuilt the whole two miles of Pleasant Valley Road. As part of that project, many loads of gravel were brought in for the shoulders. This gravel had some spotted knapweed mixed in with other weeds. It took us about four years to eradicate this infestation, using the foliar spray technique.

The lesson learned here is to catch an infestation when it is still small.

The Bradley Method: An interesting approach for control of invasive plants

Back in 2002 I published a short article on the "Bradley Method" for invasive plant control in Plants out of Place (PooP), the newsletter of the Invasive Plants Association of Wisconsin (IPAW). In those years, circulation of PooP was fairly limited and although my article has been picked up by quite a few internet sites, these are mostly outside the Midwest.Therefore I am republishing it here.

The Bradley Method for the Control of Invasive Plants

 An interesting approach to the control of invasive plants in natural habitats is the Bradley method, first developed in Australia by the late Joan Bradley and her sister Eileen. Outside of Australia it has apparently only been used in California, but it should be applicable to most parts of the world.

The Bradley method is first of all a “philosophy” of weed control.

There are three basic principles:

1) Always work away from undisturbed natural areas toward the weedy areas.

            According to the Bradleys, if native plants are given a chance they will recover the ground that has been taken from them by weeds. The principal here is to start in areas where the native plants are thriving and gradually clear into the weedy areas. Weeds do not invade readily into areas where the native plants are already well established.

           

            If one clears weeds in the worst areas first, this may not only be ineffective, it may be harmful. Removing weeds in such areas exposes bare ground, tipping the balance in favor of the weeds. On the other hand, weeding a little at a time within and adjacent to good stands of native plants, moving toward the worst weed areas, gives the natives a chance to move in and thrive.

2) While weeding, try to keep from disturbing the environment any more than necessary.

            Large numbers of weed seeds rain down on natural areas. If the ground is opened, these weed seeds can thrive. Undisturbed native soil, with its natural mulch, is resistant to weed invasion.

3) Do not overclear

            Leave the natural area as undisturbed as possible. If a large team of workers is available, people should spread out and weed small amounts in many places, rather than having everybody weed in one place. The total area weeded will be as large, but regeneration by native plants will be greater.

The Bradley method emphasizes that removing weeds from a natural area involves two different kinds of time, working time and waiting time. Patience is not only a virtue, it is essential.

The Bradley plan of approach

1) Start with areas where native plants are dominant. Weeds may be scattered throughout, singly or in small groups. The risk of overclearing here is nil, so this is the place to start. After clearing all the weeds, return once or twice a year and remove any weeds that were missed, or which have just grown.

2) Then move into areas of heavier weeds, where there is some native undergrowth. Choose an area of substantial growth where native plants are pushing up against a mixture of weeds and natives. Remove weeds in a strip about 10 feet across, then stop and give the natives time to move into the weeded areas. As the natives take hold, extend the strip along the boundary.

3) Maintain the advantage already gained. It is important to resist the temptation to clear deeper into the weeds before regenerating natives have become established. Weed seeds will continue to germinate in newly cleared areas, so they should be removed as soon as possible. This is more important than starting to clear new areas.

4) Be very cautious in moving into the worst areas. However ugly an area of solid weeds may look, do not start clearing it until the native vegetation has been brought right up to it.

Although Joan and Eileen Bradley were trained as chemists, their method makes very little use of herbicides. “We regenerate [native vegetation] by using methods that give us the most effective kill of weeds and the most bountiful growth of natives; that is, by skilful manual weeding. This can be laborious, and we are often asked, especially when we are having to spend a long time extracting a big weed ‘Why don’t you poison it?’ We prefer not to use poisons if we can avoid it, and we certainly condemn their indiscriminate use.”

I think the point here is to use herbicides in selective ways, rather than by broadcast spraying. Their reasoning is that herbicides are not truly selective, may have detrimental effects on the environment, and do not always work. However, they do admit that for some weeds, or for some areas, herbicides may be necessary. However, their hand weeding technique is perfectly safe, highly effective, and reliable. It does require one trait that we do not always have or want to use: staying power.

 

Although I have generally approached a restoration area with the Bradley method in mind, I have not always used it. The "waiting time" that the Bradley method requires is not always available. However, we have always tried to start with the "good" areas first and then move into the "bad" ones. This is the most important part of the Bradley method.

 

Details of the Bradley method, including many practical suggestions for weeding, have been published in a book called “Bringing back the bush: The Bradley method of bush regeneration.” Lansdown Publishing Company, The Rocks, New South Wales, Australia.

I obtained my copy from Books of Nature, P.O. Box 345, Lindfield NSW 2070, Australia. http://www.booksofnature.com

An internet search for "Bradley Method" AND "Invasive Plants" will bring up quite a few "hits", including some further details under a Wikipedia page called "Bush regeneration". 

Finally, those interested in the broader scope of restoration ecology should look into the Australian literature. Of all the countries outside of North America, Australia is probably the most advanced. In some ways they are ahead of us.

Precipitation history of Madison

In my last post I published a graph of the Palmer Drought Index for southcentral Wisconsin. This index reflects precipitation but includes other factors as well.

The graph in the present post presents precipitation data only.

Although the average annual precipitation for Madison is around 30 inches it varies widely from year to year. In recent  years the highest total has been the 44 inches  in 2008 and the lowest have been the 21 inches in 1976 and the 23 inches in 1988. The average in the so-called drought year of 2005 was about 25 inches.

However, annual averages do not show the time in the year when a precipitation deficit may have occurred. In 2005, for instance, the dry period was in late summer, whereas this year it was in June, the time when prairie plants are making their most growth. Thus, this year's drought is more serious, even if the annual average (which we won't know for another six months) is higher.

Thanks to the Wisconsin State Climatology Office, and its director John Young, for providing all this historical data!

Drought history of our area

We are now "officially" in a serious drought and who knows how long it will last. I find it useful to look at an overview of the drought history of our area, since it helps to put this current situation in perspective.

There are a number of different ways of expressing drought, and one index used by climatologists and agriculturalists is the Palmer Drought Severity Index. The Wisconsin Climatology Office has a nice graph that gives Palmer data from 1895 until today, and this graph is interesting to look at.

The period that we have been restoring Pleasant Valley Conservancy (1995 to the present) has been primarily a "wet" period. Only 2003 and 2005 have been on the negative side, and these have been not very severe. The major periods of the most serious drought were the early 1930s (the "dust bowl" period) and 1955-1967. There was a sharp peak in  1976-1977 and a less serious one in the late 1980s (the famous Yellowstone fires were in 1988).

Is the current drought a brief "blip" or does it represent the first stage in a new major drought period? We'll have to wait and see.

Obviously, those years when we were planting new prairies and savannas (1998-2005) were very favorable (that is, wet) years. Fortunately, most of our planted prairies and savannas are now well established and will hopefully be able to struggle through the current drought. Only the East Basin, planted in 2009,  is at a critical stage (its third growing season) and is hence potentially at risk.We were obviously just lucky that we did our major restoration work during a wet period.

Those thinking of planting new prairies now might want to think about the Palmer Drought Index data.

More on the drought

I had a conversation at the Farmer's Market today with a distinguished meteorologist whose explanation of the drought led me to conclude that it might be September before the weather pattern will change. The best we can do is try to cut our losses and just observe how various species respond to this onslaught.

The lush green photo below was taken yesterday at the Barn Prairie, one of the wet-mesic prairies at Pleasant Valley Conservancy. The Silphiums, yellow cone flower, ironweed, mountain mint, and others are doing very well, which is understandable, since they are not suffering any drought at all. There is a broken tile field within 100 feet of this prairie that I use to monitor ground water and its water level has not even dropped an inch. In fact, the extensive springs and pools in this area have continued to flow through all the droughts we have had over the last 15 years.

However, the upland sites at Pleasant Valley are a different story. The north-facing oak woodlands have some species that have remained green, but all of the ferns have turned completely crisp. (The photo here is of maidenhair fern, but all the other fern species have dried up also.)

The savanna areas are quite variable, and how they have responded depends on the openness of the canopy. The photo below shows false solomon's seal (completely crisp) and carrion flower (lush green). Woodland sunflower is also completely wilted, and woodland Joe Pye is starting to wilt. Woodland thistle will end up with stunted growth.

The most severe areas are the south-facing slopes. However, prairie dropseed looks as lush and green as ever (photo below), whereas little bluestem is mostly crisp and dead. Obviously, dropseed has a deep root system.

Finally, Black Earth Rettenmund Prairie is a disaster. Just a few weeks ago this dry to dry-mesic prairie was a riot of color and now it looks really bad. Only compass plant, one of the most deep-rooted species, remains in flower, and it is not certain how long it will continue to thrive. However, some patches of big bluestem were flowering.

Anyone planning to collect seeds for a fall planting might as well forget it. It seems unlikely that any of the species flowering from mid-summer through fall will make any seeds at all. Seed companies that have irrigation should be able to make a killing this year!

Savanna/prairie drought effects

This may be a year for the ages as far as drought effects are concerned. However, I keep thinking back to the "dust bowl" period of the 1930s, and John Weaver's important work (summarized in North American Prairie, 1954, Johnsen Publishing Co., Lincoln, Nebraska) on how prairies responded to what was really the worst drought of the ages. "Little bluestem suffered the greatest losses....In numerous prairies not a trace remained, at least above ground....Big bluestem, although suffering great losses, withstood the ravages of drought in a most remarkable manner. It frequently persisted, even if in small amounts..." (For a detailed analysis, see Weaver and Albertson, 1936, "Effects of the great drought on the prairies of Iowa, Nebraska, and Kansas." Ecology 17: 567-639)

Not surprisingly, our little bluestem is in awful shape. The whole south-facing slope is suffering the worst from dryness and the blazing sun. Many stands of little blue have died, although there are still areas where it is hanging in there. I am assuming ground water is better in areas where it is still green. What the conditions of the roots of these plants is uncertain. We'll just have to wait until it rains, to see whether the roots are still alive. However, the response, if it comes, may not be seen until next year.

 The response of forbs is highly variable, presumably determined by the specific location, the species, and the depth of their root systems.

I was especially interested in purple milkweed. Unfortunately, it is showing signs of severe wilting. Although I haven't checked all of our stands, those I have checked are in extremely bad shape. The photo here is typical.

However, other species seem to be thriving. For instance, right next to this purple milkweed stand is a large population of a Special Concern species, upland boneset (Eupatorium sessilifolium), which is in great shape. These two are growing in the same soil under the same canopy and are getting the same moisture. The root system must be making all the difference.

Aureolaria grandiflora in full bloom

Aureolaria grandiflora, the large-flowered yellow false foxglove, is now in full bloom. This species (C value of 8) is parasitic on roots of oaks and is a characteristic species of rich oak savannas. We introduced this about 10 years ago and it became readily established where planted and has now spread widely. The photo shows a rather large patch at the edge of an open savanna.

Although Aureolaria grandiflora is an obligate parasite on oaks, it does not do any harm to the tree. It primarily "infects" the tiny roots that are present under the drip line of the canopy.  

 It may seem odd to see this species in an area full of birches. Where are the oaks? However, if you start to look around you will probably see an oak grub or two. These small grubs are often years old, being burned back each year by our annual savanna fires, and readily support A. grandiflora.

According to greenhouse research by Musselman from UW-Milwaukee, seedlings never get past the cotyledon stage unless they infect oak roots. Although this species is often called a "hemiparasite", it looks like an obligate parasite to me. It is an interesting "obligate" however, since it does not destroy its host.

This is one of the showiest species in flower right now, and well worth seeking out in our ridge-top savannas.

Culver's root in full bloom

Despite the prolonged drought, some prairie plants are doing very well and seem to be flourishing. For instance, Culver's root (Veronicastrum virginicum).

This is a species that grows well in savannas and wet-mesic prairies. However, this year the drought has suppressed it in our savannas, but it is doing better than ever in the wet-mesic prairies.

Although reasonably common (it has a C value of 6), we seem to have hit the right conditions in the Valley Prairie, as the photo shows. The soil in this prairie ranges from dry to dry mesic at one side to wet mesic and almost wet at the other side. It is near the wet end that Culver's root is flourishing, growing in a relatively narrow strip.

Turning a lawn into open oak woodland

Our backyard is fairly small, which is good because we spend most of our time working on a 140 acre natural area. However, in her "spare" time Kathie has done a great job of "restoring" it.

Our backyard is best called an open oak woodland, because it has some reasonably mature white oaks. Because of the shade, lawn never did well, and after years of mowing, I finally convinced Kathie to convert it into a "forest floor". We had already planted woodland species around the edge of the lawn, so the logical step was to get rid of the lawn and extend the forest understory. The lawn fell easy prey to glyphosate, and by last November the ground was bare. A good mix of open oak woodland species was planted, and a narrow path was delineated with judicious use of wood chips.

Despite the June drought, everything has grown well, and we now have quite a colorful backyard. In addition to the bergamot and black-eyed Susans seen in the photo, other species include American bellflower, white and red baneberry, yellow and purple hyssop, purple milkweed, bottle brush grass, and a lot of other species.

A major attraction here is that there is no lawn to mow. Another feature is that there will be a continual progression of native species throughout the year.

This represented a lot of work for Kathie, but hopefully all that will be needed now is judicious hand weeding, and occasional planting of new species.

I was quite impressed by how effective glyphosate was in turning the lawn into bare soil. With the good shade that the herbaceous species create, we should have no problem in keeping grass from coming back.