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).
Dotted gayfeather punctuated an otherwise yellow-dominated plant community last week at our family prairie south of Aurora, Nebraska.
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…
Error bars represent 95% confidence intervals
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!
One of the larger plants in the 2016 burn patch
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.
Here is the 2016 burn patch about a year ago, after a spring burn and season-long intensive grazing. You can see ungrazed dotted gayfeather flowers blooming. but most grass leaves have been grazed short.
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!