Some people think they're in a "restored prairie" when they stand among head-high big bluestem, Indiangrass, and little else. But true prairies are complex and relatively compact mixes of mostly rarer grasses and wildflowers, the grasses and most vegetation waist-high or lower. The common grasses in a high-quality prairie are little known to most people: prairie dropseed, Leiberg's panic grass, and porcupine grass. The dense tall grass stands are almost a delusion.
Dan Carter does a fine and important job (click here) summarizing the grass issues in a technical post.
He also does a good job of citing the literature, though most of it is little accessible to most interested people. In fact, much of the most significant conservation writing these days is not in journals; it comes from busy, dedicated people like Dan.
A real prairie in early summer looks like this:
And in mid summer, it looks like this:
Yes, the tall grasses will emerge here and there in August, but they'll be shorter and scattered, compared to a planted tall grass stand.
I looked in vain for a late August photo of the very high quality area at Somme Prairie, the one I know best. Somehow, this is all I found:
The only grass I can identify here easily is dropseed. I'll look for more photos and add them when I can. In high competition, many plants don't bloom every year. It's long been impressive to me that we rarely see even a single stem of big bluestem in the Somme high-quality area. In some years, there's lots of porcupine grass early and then much little bluestem mixed with the dropseed. In some years there'll be a lone stem of Indiangrass in every square yard or so - typically about four feet high, not six or seven.
So, today, September 24, I took more photos. A typical one is below. It's not all that great a photo, but it does show how tall the grasses are:
There's little grass that's more than knee-high, in this mesic prairie, this dry year.
In the above photo, starting at the top, there's a strip of sky, a strip of trees, and then a narrow strip of a tan color. That strip is Big Bluestem and Indiangrass, in a restored area, well away from the high-quality remnant. Many of the poorer-quality areas of the Somme preserves have vast stands of those head-high tall grasses. But, as Dan Carter makes clear, these stands of tall grass are not the goal of conservation and not true (or high-quality) tallgrass prairie.
So what shall we call it? Deep-Rooted Prairie? As we come to understand prairies as plant competitions rather than communities, perhaps we need to reconsider what "prairie" means altogether. As I read Dan's piece, I kept expecting him to discuss the role of fall burns, which he finally does, and only tangentially, at the very end. Our role as stewards is decidedly to put our thumb on the scale against invasives. As we become more active prescribed burners, the choice of burn season becomes yet another way we influence the character of the result.
ReplyDeleteTallgrass prairie is the right name. We just have to learn what "tall" means in this case. For "shortgrass prairie" the grasses are just a few inches to a foot high. For mixed grass prairie, most of the grasses are perhaps two feet tall. For tallgrass, the grasses in late summer are largely three or four feet tall - less in drier places - sometimes more in some areas after a burn. The problem that Dan writes about isn't really that the grasses are too tall; they are over-dominant in absence of diversity to compete with them. The solution is more species, especially the conservatives.
DeleteAnd though the explicit implication that fall burning or at least true dormant season burning is best isn't explicit until the end, the effects of seasonality (esp. mid to late spring burns) is discussed at length in terms of how grass phenology and growth form/habit respond.
DeleteAt what density (culms per square meter quadrat) are the tall-grass species considered to be “excessive?” When this level is exceeded in a restoration project what should be done to reduce those species to an acceptable level?: introduce a grass-parasitic species such as Pedicularis canadensis?; spritz some grass-specific herbicide here and there to thin out or at least weaken them?; do something else? What work is being done to achieve a resolution to this situation
ReplyDeleteEven in areas of excessively dense, tall-grass species, the grasses don’t reach 4 feet tall or so until late in the summer. Earlier than this, the shorter forbs and grasses predominate.
One solution to degraded or depauperate prairies is regular fire and the seed of missing species. Then diversity should increase over time, and the excessive dominance of any species should diminish.
DeleteUnfortunately, in many native grasslands conservative forbs and grasses do not. In remnants that is especially true at sites that have seen too little fire (dormant fire) such that the "understory" has been repeated smothered and eventually given up.
DeleteThe stories of the prairie grass being tall as a man on horseback were probably talking about prairie cordgrass and bluejoint grass which grow best in wetter areas and forms almost pure stands. When we were doing the Illinois Natural Areas Inventory it took us awhile to realize that most wet prairies were not very diverse and had to go back and look again at a lot of areas that we wrote off. The mesic black soil prairies found at Somme are just one type of prairie ecosystem in Illinois.
ReplyDeleteJerry – do cordgrass and bluejoint get that tall? I wonder how tall big bluestem could get in a wetter area? The only grass-like plants I can think of that get that tall are Phragmites and cattails. Or maybe people on horses were shorter back then?
DeleteThe Flora of North America website shows the maximum height of various prairie grasses to be:
DeleteBig bluestem (Andropogon gerardii): 3 m (9’ 10’’)
Switchgrass (Panicum virgatum): 300 cm (9’ 10”)
Cordgrass (Spartina pectinata): 250 cm (8’ 2”)
Indian (Sorghastrum nutans): 240 cm (7’ 10”)
Little bluestem (Schizachyrium scoparium): 210 cm (6’ 11”)
Bluejoint (Calamagrostis canadensis): 180 cm (5’ 11”)
At a height of over 9 feet, grass as tall as a man on a horseback may not have been so apocryphal.
I came across one account that was clearly the native subspecies of Phragmites. It does seem that tall big bluestem was also dominant in open parts of some of the big river alluvial bottomlands, and also some of the low prairies in old glacial lakebeds, but in the latter case, little bluestem is was only modestly less abundant than big bluestem, and sometimes prairie dock was much more dominant than any individual grass.
DeleteThe truth is, we don’t know why tall grasses dominate in one area and not another. The western part of the main prairie (PR01) at Poplar Creek Forest Preserve and the 160 at Spring Creek Forest Preserve both have patches that have almost none to no tall grasses. In these same preserves, there are areas where higher-quality prairie species were seeded and grew, but in between the high-quality prairie species tall grasses have since invaded. Why do some patches have no tall grasses and in other areas tall grasses have invaded? I have no idea. It is not from differences in where seed was sown. The main prairie at Poplar Creek Forest Preserve was seeded with tall grasses before they knew how much the tall grasses tended to dominate.
ReplyDeleteWood betony is a piece of the puzzle. It will weaken tall grasses. This allows conservative plants to establish that will not grow in areas of unrestrained tall grass domination. Allelopathic plants are also a piece of the puzzle.
In the patches without tall grass at Poplar Creek and Spring Creek, there is no wood betony. The plants in these patches without tall grass appear to be the same species that established in other areas that have since been invaded by tall grass. Something else is happening to eliminate tall grasses. As far as I know, no one knows the reason.
In the below blog post are two images of a large patch of prairie reconstruction that has not been invaded by tall grasses. These images were taken at Spring Creek Forest Preserve, but as I mentioned above there are similar patches on the western side of the main prairie reconstruction (Carl R. Hansen Woods) at Poplar Creek Forest Preserve. Scroll down past all the flower images to the heading “Drier Areas at the 160” and then the subheading “Patches With No Tallgrass.”
Deletehttps://stewardshipchronicles.blog/2023/09/27/spring-creek-the-160-8-16-2023-and-8-17-2023/
These prairie reconstructions are burned biennially during the dormant season (before reptiles become active). This is close to what Dr. Dan Carter has written is necessary to preserve high-quality prairie.
These patches of reconstruction are not high-quality prairie. The prairie plants were seeded thinly at the Spring Creek 160 with the result that they are spread out in the restoration and will be filling in gaps for many years. However, the similarities in vegetation to Mr. Packard’s image of high-quality prairie at Somme are apparent.
Is this only referencing mesic prairie in IL or the Upper Midwest? I visited a few remnant tallgrass prairies in the Kansas City area this summer and the dominant grass species was Andropogon gerardii. I didn't get a chance to inventory plants in those natural areas so I'm sure other shorter stature grasses existed in lesser quantities.
ReplyDeleteJoni, there are at least two answers to your good question.
DeleteFirst, yes, of course, there are many differences between Kansas prairies and those of northern Illinois and southern Wisconsin.
But second, and more important perhaps, is that Dan and others were writing about the very highest-quality remnants. Most remnants have been somewhat degraded, most often by at least mild over-grazing and lack of frequent fire. The species that are lost first are the high conservatives including white prairie clover, prairie lily, prairie gentian, and such grasses as prairie dropseed and Leiberg's panic grass. Even when a remnant once was mostly dropseed, today it might be mostly big bluestem. One indication of whether degradation caused a lost of the dropseed is whether or not the other high conservatives are missing.
One reason these distinctions are important is that many high-quality prairies continue to degrade. They need to be monitored at a level that shows whether the high conservatives are being lost, and if so the management needs to be changed. If the high conservatives are being lost, many other plants, animals, and other biota are likely being lost too. High-quality remnants are so rare and precious.
The Konza Prairie Biological Station [in eastern Kansas] website (https://kpbs.konza.k-state.edu) has images of vast tracts of dense tall grass; with a site plant list containing 721 taxa of forbs and grasses, the presence of dense tall grass does not appear to adversely affect diversity.
DeleteThe real estate industry’s refrain “It’s location, location, location” seems to be a useful consideration in determining if there are restoration sites with soil in Chicagoland where “too much tall grass” would, in fact, be appropriate. To borrow from the real estate industry, “It’s season, season, season (late summer)” that brings to the forefront the visual effect of too much tall grass in a prairie restoration.
Joni, I'm really writing about the entire "tallgrass" from E. NE to S. WI and Illinois. High quality mesic remnants in particular that were not long overgrazed and which have seen fire are actually stunningly similar between E. NE and W. IA and SE WI / NE IL. A huge reason prairies in E. NE, KS, OK are so different is because of their very long grazing history and very long history of mid/late spring burning to maximize big bluestem forage production. But, for instance, a railroad remnant where the cattle were fenced off but there at least was some fire is very similar. I did some of my graduate work on prairies in western Iowa, and the main difference between there and sites I know in SE WI is the absence of nodding oniony.
Delete@Kirk. That's where I did my graduate work, and believe me it does. There is more than 5000 acres there across a lot of ecological gradients, with vastly different management regimes. Richness at scale scale does not imply ecological integrity. Vast areas, like the area shown in the picture of the burn above are extremely over-dominated by big bluestem and Indiangrass due to land use history and very frequent late spring burning. Many species are present in small refuges that fall outside the experimental treatments, or, for example, on steep rocky slopes or rocky breaks that receive lower fire intensity or minimize the impact of fenced grazing treatments. The most diverse part of Konza when I was there was an area called White Pasture, which was not a part of any treatment and was burned not enough (treatments get the priority), but also not often enough in late spring to push it to such extreme tall grass dominance. It also was only sparingly grazed. That watershed has since been put into a patch-burn-graze study. Areas with high small-scale richness are generally in the grazed watershed, but the forbs that contribute most to that are things like plains ragweed, Canada or tall goldenrod, Baldwin's ironweed, stiff goldenrod, and hoary vervain (see one of my actual quadrats:https://bastardtoadflax.files.wordpress.com/2022/06/full_dcarter_1645107082_1-1.jpeg). The record quarter meter square richness is from a W. Missouri remnant with over 45 species, and in many high quality remnants that number is above 25. Even the richest parts of Konza don't compare to that. But I should say richness is a poor measure too, because it increases as sites degrade, because opportunistic species colonize and it takes a while to extirpate the conservative species (especially as scale increases), so floristic metrics that incorporate conservatism are vital.
DeleteI just noticed this. Thank you! I was was continually perplexed during my time at Kansas State with the constant use of big bluestem as a proxy for prairie and richness (suppressed big bluestem releasing opportunistic and not conservative species) as a proxy for ecosystem integrity.
ReplyDeleteI will also say that a lot of the most important writing is in Journals, but a lot of the most relevant work for understanding old growth is in old articles--especially pattern, even where authors didn't fully grasp process. A lot of newer stuff is really studying dynamics in grassland systems that have undergone a state change--not herbaceous to woody, but a very functionally significant shift within the herbaceous elements. But that altered grassland is what many understand to be true tallgrass prairie, except those that are always seeking out old growth remnants and asking why. It is important to readers of more recent work to make the effort to understand what the authors are truly studying and not take characterizations made by authors at face value. Sometimes even April/early May burning in E. Kansas gets characterized as "dormant season."
ReplyDelete