A Case For Planting Conservative Species - A Love Story

In 1980, as part of my field ecology internship with the International Crane Foundation's (ICF) prairie restoration project, my supervisor Konrad Liegel and I divided our seed collection between an “experimental” fall plot of one acre and a much larger planting the following spring. This was the second planting on the newly purchased farm before any infrastructure was built, and at a time few practitioners saw fall plantings as a good alternative to the traditional spring ones. We didn't know then how pivotal this experiment would be.

This story begins and ends with my love of one species: the downy gentian (Gentiana puberulenta). The downy gentian is not the easiest gentian species to grow, but much of its difficulty is a result of the limits humans have imposed on it, not necessarily a fault of the gentian's ecology or life cycle. 

I saw my first downy gentian growing among bands of prairie dropseed at Avoca Prairie in Iowa County, Wis., while collecting and scouting seed sources for ICF. With ample rain in the fall of 1980, the dropseed and gentian harvest was great. Flowers with such deep blue color are rare, and the gentian immediately became my favorite prairie species. From that moment, I wanted to recreate the dropseed/gentian community. These species are not mutually dependent on each other, but they coexist quite well together.

We hand broadcast seed for the ICF planting in mid-November after soybean harvest on semi-frozen ground. In May 1981, the remaining seeds were hand broadcast on four adjacent acres. Both fall and spring seed mixes were identical. After 38 years, the boundary between the two is still visible.

The fall planting is much more diverse - with dropseed and a few gentians plus many other “conservative” species (most associated with virgin or undisturbed prairie as opposed to a planting) while the spring planting is dominated by big bluestem and low diversity.

Ironically, because of sampling methods (percentage native cover) and definitions of success (highest percentage native cover), the spring planting was rated better until the fifth year when the slower maturing species in the fall plot bloomed. So, either those species were too small to identify or the sampling method missed them entirely. After that, definitions of success changed, and fall plantings at ICF become the norm, not the exception, as they now have for many organizations.

The first planting my wife, Muffy, and I did on our farm in Sauk County, Wis., in 1988 was a small section of former pasture that we tilled twice and fall planted to dropseed and gentians, leaving out tall grass, cover crops and most everything else common in conventional seed mixes. The dropseed came in as thick as bluegrass and took a few years for the seedlings to thin out. But in five years, we had blooming dropseed and gentians.

Fear of failure is a great incentive to sow too many seeds per square foot, as I learned with the dropseed. A high seeding rate, coupled with the weeds already in the soil seed bank, results in the most aggressive, first-germinating species dominating at the expense of others. Fortunately, in this case, the gentians probably germinated before the dropseed and, because of different root systems and nutrient requirements, they formed a fairly stable community. But it certainly was not immune to some change over time.

We then planted a diverse seed mix, both clean seed and chaff, on subsoil exposed by bulldozer work along our driveway and near our house. The first downy gentian that bloomed was so small I barely noticed it, but over the years it grew into a nice, healthy specimen, and we have several individuals that are established and reproducing.
 
Challenging assumptions

In 1999, I read an article about “underground mysteries,”1 which claimed gentians and other “prairie obligates” need healed or virgin prairie soil, and yet here was contrary evidence right outside my window. Three gentian species – downy, bottle and fringed - grow within a few feet of each other in places. We also have wood lilies, leadplant, hoary puccoon, goat's rue, cream and white wild indigo, lupine, pale-spike lobelia, downy phlox, wood betony, and two orchids: Case's ladys'-tresses and the tubercled orchid. Except for the orchids, which arrived on their own, we used mostly seeds and a few plugs. 
 

These plantings and many others contradict the theory that a dropseed/gentian-type community can only be achieved after decades of linear plant succession to a “climax” community.2 In fact, since the original community at Avoca Prairie was destroyed by the flood of 1993 and replaced by big bluestem, the very idea of a climax is debatable. There are no guarantees that the dropseed will return, even in that “wild” system. Based on what we know about seed germination, these species germinate the first growing season in spring after breaking dormancy, some as soon as the ground thaws. The notion that they “fail to show up”3 is primarily a function of sampling method, seed mix design and planting date, assuming no catastrophic weather event.

The goals of quick native cover and diversity are mutually exclusive because the former works against the latter by favoring the fastest, most aggressive species planted at rates that far exceed the norm for wild prairie. Also, one fall versus spring comparison is one replicate. To average out differences in soil type, weather, seed supply, weed pressure and post planting management, we need several replicates over many years, and this is where published research has mostly failed us.

ICF, like TPE and Madison Audubon, have plantings that span several decades. Each has excellent examples of better early diversity as seed mixes and methods improve, but publishing and presenting is expensive and not the primary goal of these organizations.

Most prairie species, regardless of their longevity, are essentially pioneer species and able to colonize either bare soil or disturbance in existing vegetation, native or otherwise, by seeding followed by either mowing or burning. If given a choice, I would rather start with bare soil or old field than established tall grass, like big bluestem. Our data from seed and plant production shows that many species thrive on low fertility as a function of their biochemistry, and this gives our natives a competitive advantage on poor soil over many weed species.

Even many orchid species do not wait for “healed” soil. Muffy and I found prairie white fringed orchids, which escaped the nearby virgin prairie and colonized the drainage ditch of the adjacent corn field where herbicide killed the competition. In fact, that was where the majority of individuals were for a year or so until the use of glyphosate-resistant crops killed everything in and adjacent to the ditch.4 

We also have more than 40 years of experience planting thousands of acres with the WI-DNR, private landowners and non-profits using no inoculants of any kind under all sorts of planting conditions and soil types, including a reclaimed parking lot.5             

We greatly underestimate the ability of fungi and bacteria to infect new soil; perhaps spores travel with the seeds because many pollinators and seed predators spend a good part of their life cycle in contact with soil. Absence of proof is not proof of absence. We often don't appreciate the ability of many species to utilize both organic and inorganic sources of nutrients; a mix of both is probably the most accurate model for our field conditions.

The great problem in restoration ecology theory is assumptions aren't tested thoroughly. Just because one study “proves” that one method works, it doesn't prove that others don't. And in some circumstances, no methods work because these are natural systems with many variables. Unfortunately, science is rife with examples of methodology designed to prove pre-existing assumptions.6
  
As we learned, simply changing the planting season challenged the assumptions about the fitness of conservative species. Many of our breakthroughs have been accidents resulting from the inability or reluctance to follow the standard procedures. The first gentian blooming on our subsoil, for instance, came from seed cleaning chaff thrown out a nearby window.

The limiting factor for plant colonization, based on our experience, is a function of a species' seed dispersal from an isolated remnant to new habitat managed for its survival. So instead of an ecological problem, it's an economic problem; how do we boost seed supplies of the rarest or most-difficult-to-harvest species if their commercial production is unprofitable or unaffordable, and local populations are scarce? How do we deal with human impatience?
 
Economics & profit affect production  
                       
If a species' production cannot be mechanized and accelerated, it can never be more than a footnote in a seed mix or research project. Throw in the issue of local genotype, and you have a very limited market. Growing downy gentian for any market isn't profitable, but it's essential to its survival. 

In the past, I greatly underestimated the economic and social factors that limit seed mix design.7 Our data collection may be as objective as possible, but all seed mix designs are highly subjective; no mix for any situation is independent of cost and human bias. The DNR, for example, buys few species (about 3% of the total seed count) that cost more than $100 per pound.8 Gentian, shooting star, phlox, prairie smoke, and many others, are well outside of the price range unless collected on public lands by limited-term labor. Most public and private land managers cannot control their budget or the number of acres to be planted in a given year.         

When crop fields are taken out of production, the vast majority are enrolled immediately in Natural Resource Conservation Service programs for cost sharing, and in that sector the gentian and other expensive species are excluded. 

This is why I'm volunteering to grow downy gentians for the TPE nursery. I must have faith in seeds and disregard the negative literature. There are many challenges for production, including highly variable seedling vigor, which may be a function of inbreeding depression9, and lack of good commercial growing media of the correct drainage and pH. The inclusion of downy gentian is a seed supply problem that must be subsidized by non-profits and volunteers, or they will continue to be lacking in restoration plantings.

Footnotes
1.  Kleine, Adele. Underground Mysteries, Mycorrhizal Fungi and the Healing of Prairyerth, The Prairie Reader, Fall 1999.
2.  Schramm, P. Prairie Restoration, A 25-year perspective on establishment and management, The Proceedings of the Twelfth North American Prairie Conference, University of Northern Iowa, 1992.
3.  Diboll, N., page 137, Designing Seed Mixes, The Tallgrass Restoration Handbook, edited by Packard and Mutel. Island Press, 1997.
4.  2000-2008 survey of Wiowash (formerly Oshkosh-Larsen) trail and State Natural Area for Platanthera leucophaea.
5.  DNR seed production plots at the former Badger Army Ammunition Plant. Look for the stand of prairie dock along highway 12 north of the main gate.
6.  See De Waal, Frans. Are We Smart Enough to Know How Smart Animals Are? W.W. Norton, 2016. Examples of bias methodology to “prove” how smart humans are compared to other animals.
7.  Weber, S. Designing Seed Mixes for Restorations: Revisiting the Formula, Ecological Restoration. Vol. 17, No. 4, 1999. UW Press.
8.  Analysis of 2012 DNR seed purchases.
9.  Based on author's unpublished data on Cypripedium seedling survival comparing results from crosses with parents of same and different populations. Both gentians and lady slipper orchids are insect pollinated, primarily by bee species.

 


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