Adding Diversity to Existing Prairie

This spring I asked Ben, my partner in the quest for the “living seed bank”, to burn a couple areas for me, primarily two hills and adjacent valleys of about 10 acres.. I’ve written about it several times, but the idea was to burn, graze and generally beat up some existing prairie and then topdress with additional forb seed hoping to find some openings to let new seedlings thicken and diversify those 10 acres. We did all of that, grazing it both early and late after the burn; we topdressed seed this spring, and will spread more seed this fall. Though the 10 acres includes some very xeric hillsides and a couple swales of mesic soil, the majority of it is soils on the border between dry mesic and xeric. The grass cover is dominated by brome, but the soil isn’t good enough to allow the to brome eliminate competition, and there are over 50 species of forbs that occur there. Most of those forb species are widely scattered, though a few are common. Thus, in addition to the seed that we spread, there is certainly an existing contingent of seeds of all those species in the soil’s seed bank, hopefully still ready to grow up and be somebody. I have visited with several other practitioners of prairie management, notably Chris Helzer with The Nature Conservancy in Nebraska, and the consensus has been that topdressing additional seed works, but that it likely takes both luck and significant management to hold down the competition from the existing grasses. In most prairie restorations the grass competitor is big bluestem. In native pastures throughout eastern North and South Dakota and western Minnesota, however, it is smooth brome, an even tougher customer because of the incredible mass of rhizomes that criss-cross the ground beneath the surface. Big bluestem is a bunchgrass, theoretically leaving some potential space between bunches; brome leaves no space. Below is what a lot of the 10 acres looked like in September as the cows got their second shot at grazing. The only plants over six inches tall are common ragweed that used the biotic space I opened up earlier to have a party, though plenty of grass shoots are growing beneath the ragweed canopy. As one looks closer new possibilities emerge. The second picture is a close up of what a lot of it looks like now, a month later, after some September rains. I picked an area without the ragweed so you could see all the little forb seedlings.

There are several species in this picture, most of which I can’t confidently identify, but I was able to identify about 15-20 different species as I wandered around the two hills. I don’t know how many came from seed that Ben and I spread, and how many came from the seed that was already there, as most of the species are the same, but there are several new seedlings per square foot over much of the 10 acres, with the exception of the valleys with the thickest brome which we did not seed, and to which we will return later.

There is a severe funneling process that causes most species to make a great many seeds, of which very few will get to germinate, and very few of those that do will get to become mature plants making their own seed. If each plant replaces itself with one new child in the world we have a stable population. If that theoretical parent plant makes 100 seeds per year and lives 10 years we have a stable population if one in a thousand seeds grows and procreates. Every species has its own formula, of course, and many species “job” the system by also reproducing vegetatively, or clonally, usually through rhizomes spreading under the ground like my adversary the brome, but you get the idea. We have have tried to skew the numbers by the use of fire and cows to both open things up to allow more seeds the opportunity to germinate, and to decrease grass competition enough so some of the seedlings have a chance to continue their growth and become reproducing adults. That result is far from a sure thing, but I am hopeful. It helps to be an optimist sometimes. It can seem impossible for new seedlings to compete with an existing grass sod, but as I have stated in several other posts, it obviously happens. Else we would not see any of the forbs that we most assuredly do see. I have called this an experiment, but I will not be able to confidently evaluate results in a manner where one attempt, one site, can give a definitive answer. There is no replication of treatments and no careful data collection. In effect, we are giving up on the possibility of deductive reasoning. We are certainly not giving up on using inductive reasoning, the forming of conclusions from a group of observations which all indicate the same results. In other words, we need to do this several more times, and over the years hopefully come to conclusions regarding techniques and strategies. I am very wary of assuming my ability to continue to engage in these activities for very many more years, but I plan to make this a well documented trial and get started on the next one next year. Then, as time goes on, others can refine techniques, or just get the mass of observations that the process works or doesn’t work. We certainly plan to return to this with another post next spring or summer.

And below in the foreground of this picture we come to the mesic valleys which wind between the gravelly hills, this a picture from a year ago. And after that, a picture from this fall after the year’s grazing. Here there are far fewer forbs, but there are quite a few bunches of big bluestem fighting the brome for a place in the sun, and those are my focus. The same techniques that we hope allows the establishment of many more forbs should give an advantage to the big bluestem. There were no cattle in here from June15-September 15, the growing season for warm season grasses such as big bluestem. Thus, even though the cattle grazed some of the big bluestem this fall, it should have not regrown, meaning no root reserves were drained. Brome that was grazed in late September and early October will regrow in the cool conditions, but hopefully not so much that it gets to recharge its root reserves. If our sole goal this year was to reduce/get rid of brome the cattle should still be in there, so we aren’t getting the maximum damage from the grazing. Life always presents limitations, but we hope we used up some of the brome’s root reserves. The phrase that is used is “draining the bud bank”. We shall see how this looks next year, whether it appears the big blue clumps have expanded. I’m only a little optimistic here – brome is a very tough customer, and we didn’t graze it to nubs. Still, I hope to come out to the same place to take a picture a year from now and see more of the golden tones of the bluestem and less of the gray of the brome.

How to improve/rejuvenate/return degraded native pastures to some semblance of their former glory while bringing back some of the ecosystem services they once provided is a huge topic that is not commonly addressed. Most restoration work is centered around seeding down marginal cropped acres to diverse mixes of native plants, and then managing the restoration to keep the forb species around. This is what I’ve done on 230 acres of my farm. In places like Iowa, or even western Minnesota, where there is very little land that has escaped the plow, that is probably the best path. Establishing some restored prairie is getting the most prairie dependent ecosystem services out of the resources invested. Around me I see something different; in the half dozen counties in the northeast corner of South Dakota there are probably 2,000,000 acres of native grass. It may never have been plowed, but the great majority of those acres are a shell of their former selves after over a hundred years of overgrazing, herbicide and colonization by invasive weeds, and most of the native wildflowers are no longer there. Burning and enlightened grazing on those acres would be great, but cannot bring back species that are not already nearby providing seed. When I think of why I want to build my living seed bank, those are the acres that come to mind; providing seed for others engaged in activities like my experiment. I can’t believe that I am unique in my goals; there will be others – there already are others – who will want to turn their degraded pastures back to glorious prairies. I plan to build an ark filled with as many species as I can, so that there will be some truly adapted seed available for others to use, as well as some experience in how to best use that seed.

Thus, I have another experiment that I am conducting this fall. Green milkweed is a small, xeric adapted forb that is scattered through my native prairie hills. I have yet to see any in my restorations, though I have spread a little seed, and have transplanted 60-80 seedling plugs. However, green milkweed doesn’t transplant that well, which is true for most species on the gravel hills, where a couple dry hot weeks will eliminate the weak, and I have yet to find a living and reproducing plant from those plugs. This, though it was a poor seed year for green milkweed, I have gathered perhaps 25 pods from 15 green milkweed plants in my native prairies, and am in the process of trying to individually place all of those seeds into the soil across both the restorations and the native prairies. I have planted 650 seeds so far, and hope to break 1000. We will see if we can significantly increase what is probably an existing population of 50-100 plants. Because of how carefully I am placing the seeds, pushing them a bit into mineral soil where there are spaces, I hope to see a couple hundred grow, which would be a spectacular success. As I said earlier, it helps to be an optimist. With that I will close with a couple more pictures of new seedlings in last spring’s burn. The top picture has a couple flodman’s thistles towards the top and an alumroot seedling at the bottom. The middle picture shows a prairie smoke seedling. And the bottom picture has a pasqueflower seedling towards the right side. We did not seed any pasques, but they are quite common on these hills and there is likely lots of existing seed waiting for a chance. I’m excited to see what survives the winter and grows next spring! Life is so full of possibilities that are exciting and the list is different for every person. Tomorrow I go to New London, Minnesota where my friends, the Gustafsons, are visiting with a young woman who works for Minnesota Audubon about their Conservation Ranching program as they try to restore 250 acres of oak savanna. I will get to sit and listen to very sharp young people talk over the possibilities they might cooperate on, and they will be respectful and pretend that I have something to offer the conversation. What fun!

My 71st birthday is in a few days, and the day after my birthday will be 20 years since I was told I had a very serious, spreading cancer that would likely preclude ever seeing any grandchildren. My birthday present for myself this year is to drive to the Twin Cities to help trick or treat with the youngest of my three grandkids, Lily. There is nothing fair in this life; we play the cards we are dealt. My cards came up all aces and I am thankful; incredibly, overwhelmingly, transcendently thankful.