HELLO!
Welcome back fellow bloggers! This week, we are going to be talking about plant dispersion. In this lab specifically, we looked at Dallisgrass or Paspalum dilatatum. It is also sometimes referred to as Dallis Grass, Dallas Grass, or Sticky Heads. Here’s what they look like! You’ll probably recognize them. They tend to be in a lot of places.
Photo by North Carolina State University
Photo by University of Massachusetts Amherst
Let’s get to know this plant a little more first!
According to peer reviewed journal by Elmore, Matthew T., et al. called Seasonal Application Timings Affect Dallisgrass (Paspalum Dilatatum) Control in Tall Fescue, the authors describe Dallisgrass as being “a problematic warm-season perennial weed in the mid-Atlantic and southeastern regions of the United States”.
Whenever my partners and I were in our lab, I would’ve described the grass as being thick, “sharp”,tough, and yes, itchy. I would’ve described the seeds as fragile and full of texture. They look like regular weeds to the normal eye and personally, I would’ve not known what they were if not for this lab.
They are very resilient plants and I can see why a lot of people would hate them. They don’t necessarily look pretty, they’re very tough, and grow fairly quickly. They are a weed. According to Feedipedia, an animal feed resources information system, they are “very adaptive and can grow where annual rainfall is less than 750 mm, on soils in the 4.5-8 pH range. Dallis grass is remarkably tolerant of drought because of its thick rhizomes. It is mildly frost tolerant and its deep root allows it to regrow after frost”. Sounds pretty perfect for the state of Tennessee if you ask me.
However, it does have a major upside! Since Dallisgrass grows very rapidly and has a deep root system, it excels at erosion control. This comes in handy once in a while. What’s interesting is that they have also adapted very well to areas with high salinity. The most common area being pavement!
Now lets get on to the lab my partners and I did!
Basically, we were given this homemade 1m^2 quadrat. With this quadrat, we were to go outside in the cemetery on campus and take a random number of steps before placing the quadrat down and counting the number of Dallisgrass. Let me simplify it into steps:
- Obtain 1m^2 quadrat
- Go outside to the cemetery on campus
- Start in a random place and randomly pick a number on a randomly generated number sheet
- Walk the number of steps selected (rotate every time)
- Put down the quadrat
- Count the number of live Dallisgrass
- Record
- Repeat 14 more times
The entire goal of this experiment was to calculate the density of Dallisgrass in our 15 quadrats. To do this, we were to measure the total number of individuals in all quadrats and divide it by the number of quadrats we had.
Overall, these were the results collected in the field:
As you can see, we had some zeros in the group which kinda surprised my partners and I. It also surprised us that we did not find more Dallisgrass in general. From what I heard, other groups in our class had managed to find hundreds in one quadrat.
However, it is completely possible that not every group counted the same. My group only counted the live ones but other could have counted dead ones. And what technically counts as one Dallisgrass? Do we count the stems or the root system? These are things to be thought about when looking at the class data in the next blog. Human error is definitely a subject to be discussed.
So to calculate the density, we added all the numbers of Dallisgrass then divided by 15. It came out to be 181 then divided by 15, which is 12.06 repeating. This tells us that on average, we found 12.06 Dallisgrass plants in each quadrat.
Though they seem to be very resilient, I found them to be way more abundant in shady areas. They all seemed to be fried to a crisp in the sunny areas we recorded.
There are three different types of dispersions: clumped, random, or uniform.
Clumped means that a population is distributed in a clustered pattern.
Random means that the population is distributed randomly.
Uniform means that the population is distributed evenly.
Heres a more visual representation:
As for this lab with the Dallisgrass, I personally think it turned out to be a clumped dispersion. Clumped dispersion is the most common form of dispersion in nature. It is usually an indication that there is a limited amount of resources available and that the population spreads out and clumps together due to it being an advantage for them. In this case, the Dallisgrass could be clumped due to a certain pH in the soil, the amount of water available, the nutrients available, or even the temperature of the soil. Like I stated before, I noticed a pattern that showed that the Dallisgrass was not doing well in the sunny areas.
Overall, Dallisgrass is an interesting plant that could possibly take over the world. Just kidding. Or am I?
Though they are very resilient, it looks like high heat with low water could kill them. It’s just a matter of if they could come back or not.
This would be an interesting experiment to do in other locations as well, but many many many recordings would need to be made in order to have a relatively accurate set of data. Maybe it would make for an interesting Masters Thesis? Who knows.
Tune in for next week’s blog to talk about the class data set we collected! Maybe other groups found something really interesting. Maybe they decided it was a different type of dispersion. Maybe they counted the plants differently and we have a possible massive skew or inconsistency in the data. I hope that didn’t happen, but it would be interesting and important to talk about.
Until next time!
-Louanne Maes
Peer Review Citation
Elmore, Matthew T., et al. “Seasonal Application Timings Affect Dallisgrass (Paspalum Dilatatum) Control in Tall Fescue.” Weed Technology, vol. 27, no. 3, 2013, pp. 557-564.
Biology3070 Maes 