Late summer is definitely a season of yellow flowers in prairies, with goldenrods and sunflowers in the vanguard. However, there are exceptions to the yellow rule, and one of the most prominent of those in our prairies right now is dotted gayfeather (Liatris punctata).
Last week, I was collecting data on the number of flowering stems within various management treatments at our Platte River Prairies, and noticed an apparent pattern with dotted gayfeather. In particular, I thought I was seeing more flowering stems on gayfeather plants in one treatment than another right next to it. I had a little extra time, so I tested the observation by counting the stems on a bunch of plants in each treatment, and sure enough – I was right. Where we had burned and intensively grazed the prairie last year, there were more than twice as many flowering stems per plant (on average) as there were in the unburned, lightly grazed patch right next to it. Both areas were in the same restored prairie (planted in 2000). You might recall a post I wrote back in mid-August about this same site, which included photos of both the 2016 burn and unburned areas…
I collected my dotted gayfeather data pretty simply – I just walked through each part of the prairie and counted the ramets (stems) of every plant I encountered. In total, I counted stems on 58 plants in the unburned patch and 53 plants in the 2016 burn. The average number of stems per plant in the unburned/lightly grazed patch was 6.12, compared to 12.5 in the burned/grazed patch. A big majority (76%) of the plants in the unburned area had 10 or fewer stems per plant, and the highest number of stems on any plant was 17. By comparison, only 56% of the plants in the 2016 burn patch had 10 or fewer stems and eleven plants (21%) had more than 17 stems. There were some extraordinarily large plants in the 2016 burn patch, including plants with 39, 40, 42, and even 51 stems!
Now, this is a single site and it’s really important not to draw too many conclusions from a one year sample. I’ll be looking at the same site again over the next couple years to see how things change as future management is applied differently to each patch. The unburned area is slated to be burned and grazed in 2018, for example, so it will be really interesting to see how dotted gayfeather plants look in both 2018 and 2019. I’m not sharing my data from this year because I think there are conclusions to be drawn from it, but rather because it’s fun to speculate about what might have caused the apparent pattern. I’m hoping some of you will enjoy speculating with me, and maybe even look around in prairies near you for similar patterns.
In that spirit, here are a few thoughts running through my head. First of all, the 2016 burn patch in this restored prairie was grazed really intensively all of last season, which severely weakened the vigor of dominant grasses. Coming into this season, most of those grasses were very short in stature, allowing a lot of light to hit the ground, and their root systems were greatly reduced, allowing space for a flush of opportunistic plants to flourish – including dandelions (Taraxacum officinale), yarrow (Achillea millefolium), hoary vervain (Verbena stricta), stiff goldenrod (Solidago rigida) and many others. However, we also saw abundant seedlings of long-lived, more conservative plants as well, especially white and purple prairie clover (Dalea sp).
Many of the opportunistic plants that flourish in times of abundant light and root space do so through establishment of new plants from seeds waiting in the soil. However, that’s not the only way plants can respond. Most perennial plants, including dotted gayfeather, grow new stems each year from buds that are produced at the base of the plant or on rhizomes (underground stems). Each bud represents a potential future flowering stem, and healthy plants can have quite a few of those buds and deploy them as needed.
It makes sense to me that dotted gayfeather plants in our 2016 burn patch deployed more buds this spring than plants in the nearby unburned patch where surrounding vegetation is more dense. Long-lived plants like dotted gayfeather should benefit from producing extra flowers/seeds in years when their competition is weakened. Maybe abundant bud deployment happened because gayfeather plants were able to expand their root systems last year and reach new resources, or maybe the short stature of surrounding vegetation allowed more light to hit the base of the plant this spring, triggering buds to open.
Of course it’s also possible that all my speculation is complete bunk. Maybe the plants in the 2016 burn patch are always bigger than those to the east, regardless of management, and I just hadn’t noticed before. If so, I’ll know that after a couple more years of sampling. Either way, it’s sure fun to wonder what might be happening and then collect data to test whether or not I’m right. Opportunities like that are exactly why I love being a scientist.
Please share your thoughts and experiences related to this topic, and if you get a chance to go look at dotted gayfeather plants in patch-burned grazed prairie or other similar situations, let me know what you see!
Today I learned a new plant name. I always zeroed in on these for butterfly photography. Your posts are always good for filling in a patch of ignorance, and encouraging future questions. Thanks!
I’m wondering if you can expand and/or quantify the statement “grazed really intensively all of last season”? What does all of last season mean? And what does grazed really intensively mean? I have struggled with quantifying the timing of burning (i.e., people seem to have different timing in mind when they say ‘late season burn’), and now I’m struggling with differences in what people are determining intensive grazing to mean in terms of AUM’s.
Hi Jessica, using AUMs can be helpful, but can also be misleading when comparing across different geographies, since a specific stocking rate that is high at our site might be low at a site with higher soil moisture and high where there is lower soil moisture. My definition of season-long intensive grazing in this case is that cattle were in the pasture from mid-April through September and kept the grasses cropped low to the ground the entire time. With patch-burn grazing, of course, the burned patch is grazed intensively all season while other areas were lightly to moderately grazed. Figuring stocking rates for the entire pasture doesn’t say much because the effective stocking rate in the burned patch is much higher than in unburned areas.
Liatris punctata is a gayfeather with deep roots. Some of the genus have tuberous roots (corms according to wikipeadia) near the surface,
Chris, I manage woody fruit shrubs in a research orchard in ND. If I want the plants to really branch out instead of growing spindly or doing their own thing, I will prune them down to 2-4 inches tall in their 1st or 2nd spring to force more buds to be activated, gaining a nice, thicker shrub with more fruiting potential in following years. It sets fruiting back 1 year, but it’s more important to grow roots early. This works the same way at any time in the life of a shrub. Perhaps it’s the grazing that really helped the plants set more buds.
Kathy, that’s a great hypothesis as well.
It sounds brilliant until the germination of invasive species is unleashed and you must subsequently spend all your time controlling them. In the eastern tallgrass prairie I would only graze an area in this manner if I had the additional resources to control the invasive species that would take advantage of the reduced competition.
I have a prairie garden in my yard and the liatris that receive more sunlight get larger and have more stems and flowers. Some of my plant are 3 years old and some 4 years old though so it could be a maturation issue.
Very interesting, Karen. I was thinking it’d be fun to shade one side of a plant and not the other and see if it would respond with more flowering stems on the sunny side than the shady side…
I had some in my prairie garden too, but the voles ate them. So that makes me wonder whether the short grass could also reduce the abundance of voles in the area, and therefore limit underground herbivory on the corms.
Although I think sunlight/competition is likely to have a larger role than herbivory in this case…
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