11.17.23

The prairie burns with desire

Stuart showing an Echinacea flower setting seed.

The activities are as follows:

Fire plays a crucial role for prairie habitats across North America. Native Americans have long observed that lush and green pastures grow after a wildfire. In many areas, it is part of current and historical native culture to imitate this natural process by deliberately burning the prairie in a controlled way. This land management practice has many benefits, such as helping native grasses form seeds, thinning out plants, and enhancing habitat for prairie animals. By using controlled fires to cultivate these areas, Native Americans increase the availability of food and connect to the environment and their cultural traditions.

Some land management agencies plan prescribed burns to increase the health of prairie ecosystems. However, fire is still suppressed in many North American prairies due to the possible damage to human development. In these areas, scientists have observed that fire suppression contributes to local plant species extinctions, but we do not know why.

Stuart is a scientist interested in how fire can help prairie plants. In the late 1990s, Stuart was in central Minnesota searching for prairie plants in the Echinacea genus. The prairie was ablaze with flowers, so he had no difficulty finding plenty of plants. He tagged each plant so that he could study them again in the future. However, when he returned the following year, the field had almost no flowers! He kept returning to this same field. A few years later he found the site was again filled with flowers. That year there had been a prairie fire. Visually seeing the impacts of fire on the landscape is a memory he will not forget.

Stuart became interested in learning more about how fire affects the reproduction of native prairie plants. He knew that Echinacea plants grow in many places, but they have a hard time making seeds. This genus cannot self-pollinate, meaning they must be fertilized with pollen from a genetically different plant. Echinacea plants are also dependent on insects, such as bees, to pollinate them.

Echinacea flower

In 1996, a research team started collecting data on Echinacea plants in a large research site in Minnesota. This prairie site had a schedule for prescribed burns, or controlled fires that are started by experts to manage the land. These burns would happen every 4-6 years during the spring.

The team established a set of plot locations that they visited each summer. They searched for and mapped the location of all flowering Echinacea plants within these plots. They took measurements on each Echinacea plant – whether it was flowering, and the distance to its second closest Echinacea neighbor.

Stuart decided to take a new look at this long-term dataset. He had two ideas for how fire might be helping Echinacea plants. First, fire might help all the plants get on the same schedule and make flowers at the same time. This synchrony, or flowering at the same time, could help pollen get from one flower to another. Second, fire might remove competing plants from the area, opening up bare ground for new seeds to establish. This would allow Echinacea plants to be closer to one another, again making it easier for pollen to move between flowers.

With these data, Stuart could compare years with and without prescribed burns to see whether fire helped Echinacea flowering. To look at whether fire decreased the space between blooming Echinacea plants, he looked at the distance between a focal plant and its second-closest neighbor. To see whether fire increased the synchrony of flowering, Stuart used the data to calculate the proportion of Echinacea plants that were in bloom during the summer sampling period.

Featured scientist: Stuart Wagenius from the Chicago Botanic Gardens Written by: Harrison Aakre

Flesch–Kincaid Reading Grade Level = 8.6

Additional teacher resources related to this Data Nugget:

More information about the Echinacea project, based in Minnesota. There are additional datasets to explore, blog posts from the field, identification guides, and pictures of the experiments.

Article to learn about cultural perspectives that are traditionally not represented in textbooks. Native Americans have, and continue to incorporate ecology, observations, and making sense of patterns for millennia.

For more information about indigenous knowledges, or traditional ecological knowledge, check out the following websites:

Published journal article about this research. Wagenius, S. et al. 2020. Fire synchronizes flowering and boosts reproduction in a widespread but declining prairie species. Proceedings of the National Academy of Sciences.

11.14.22

Does more rain make healthy bison babies?

A bison mom and her calf.
A bison mom and her calf.

The activities are as follows:

The North American Bison is an important species for the prairie ecosystem. They are a keystone species, which means their presence in the ecosystem affects many other species around them. For example, they roll on the ground, creating wallows. Those wallows can fill up with water and create a mini marsh ecosystem, complete with aquatic plants and animals. They also eat certain kinds of food – especially prairie grasses. What bison don’t eat are wildflowers, so where bison graze there will be more flowers present than in the areas avoided by bison. This affects many insects, especially the pollinators that are attracted to the prairie wildflowers that are abundant in in the bison area. 

Not only do bison affect their environment, but they are also affected by it. Because bison eat grass, they often move around because the tastiest meals might be scattered in different areas of the prairie. Also, as bison graze down the grass in one area they will leave it in search of a new place to find food. The amount of food available is largely dependent upon the amount of rain the area has received. The prairie ecosystem is a large complex puzzle with rain and bison being the main factors affecting life there. 

The Konza Prairie Biological Station in central Kansas has a herd of 300 bison. Scientists study how the bison affect the prairie, and how the prairie affects the bison. Jeff started at Konza as a student, and today he is the bison herd manager. As herd manager, if is Jeff’s duty to track the health of the herd, as well as the prairie. 

One of the main environmental factors that affect the prairie’s health is rainfall. The more rain that falls, the more plants that grow on the prairie. This also means that in wetter years there is more food for bison to eat. Heavier bison survive winters better, and then may have more energy saved up to have babies in the following spring. Jeff wanted to know if a wet summer would actually lead to healthier bison babies, called calves, the following year.

Jeff and other scientists collect data on the bison herd every year, including the bison calves. Every October, all the bison in the Konza Prairie herd are rounded up and weighed. Since most of the bison calves are born in April or May, they are about 6 months old by the time are weighed. The older and the healthier the calf is, the more it weighs. Very young calves, including those born late in the year, may be small and light, and because of this they may have a difficult time surviving the winter. 

Jeff also collects data on how much rain and snow, called precipitation, the prairie receives every year. Precipitation is measured daily at the biological station and then averaged for each year. Precipitation is important because it plays a direct role in how well the plants grow. 

Jeff and a herd of bison on the Konza prairie.
Jeff and a herd of bison on the Konza prairie.
Konza LTER logo

Featured scientist: Jeff Taylor from the Konza Prairie Biological Station

Written by: Jill Haukos, Seton Bachle, and Jen Spearie

Flesch–Kincaid Reading Grade Level = 8.7

Additional teacher resources related to this Data Nugget include:

  • The full dataset for bison herd data is available online! The purpose of this study is to monitor long-term changes in individual animal weight. The datasets include an annual summary of the bison herd structure, end-of-season weights of individual animals, and maternal parentage of individual bison. The data in this activity came from the bison weight dataset (CBH012).
  • For more information on calf weight, check out the LTER Book Series book, The Autumn Calf, by Jill Haukos.
1.8.21

Fertilizer and fire change microbes in prairie soil

Christine collecting samples from the experimental plots to measure root growth.
Christine collecting samples from the experimental plots to measure root growth.

The activities are as follows:

Stepping out into a prairie feels like looking at a sea of grass, with the horizon evoking a sense of eternity. Grasses and other prairie plants provide important benefits, such as creating habitat for many unique plants, mammals, insects, and microbes. They also help keep our water clean by using nutrients from the soil to grow. When plants take up these nutrients, they prevent them from going into streams. High levels of plant growth also keeps carbon bound up in the bodies of plants instead of in the atmosphere.  

Prairies grow where three environmental conditions come together – a variable climate, frequent fires, and large herbivores roaming the landscape. However, prairies are experiencing many changes. For example, people now work to prevent fires, which allows forest species to establish and eventually take over the prairie. In addition, a lot of land previously covered in prairie is now being used for agriculture. When land is used for agriculture, farmers add nutrients through fertilizer. With all these changes, prairie ecosystems have been declining globally. Scientists are concerned that as they disappear so will the benefits they provide. 

Lydia and Christine are two scientists contributing to the effort to learn more about how to preserve prairies. They both became interested in studying soil because of their appreciation for prairies at a young age. For Lydia, she lived in an area that was covered by trees and farmland, but knew at one time it used to be prairie. This made her want to learn more about prairie environments and how places like where she grew up have changed through history. For Christine, she grew up surrounded by prairies where she developed a passion and curiosity for the natural world. Especially for the organisms living in the soil that you cannot see, called microbes. 

These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.
These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.

Lydia and Christine read about how grassland scientists have been doing research to learn more about what happens when fire is stopped and excess nutrients are added. These changes reduce biodiversity and affect which species of plants can grow in the prairie. However, Lydia and Christine noticed that the research had been mostly focused on what happens aboveground.  Lydia and Christine had a hunch that the aboveground communities were not the only things changing. They thought that belowground components would be changed by fire and fertilizer too. They turned their focus to microbes in the soil, because they also use nutrients. In addition, they thought these microorganism would be affected by the changes in aboveground plant biodiversity. 

To see if this was true, they used data that they and other scientists collected at Konza Prairie Biological Station from a large field experiment. The experiment was set up in 1986 and the treatments were applied at the field site every year until 2017! Lydia and Christine focused on the fertilizer (nitrogen) addition and prescribed burning treatments to answer their questions. The nitrogen treatment had eight plots where nitrogen had been added and eight with no nitrogen as a control. Similarly, the prescribed burn treatment was applied to eight plots, while eight plots had no burning as a control. These two treatments were also crossed with each other, meaning that some plots were burned and nitrogen was added.

Lydia and Christine expected the types of microbes in the soil to change in response to the nitrogen and burning treatments because of the different aboveground plant communities and difference in soil nutrients. Soil microbial communities can change in multiple ways. First, the number of unique species can increase or decrease, measured as richness. The other way is how many individuals of each species there are in the community, measured as evenness. Taken together, richness and evenness give a measure of diversity, which can be summarized using the Shannon-Wiener index. The value will get bigger if either richness or evenness increases because it incorporates both. For example, a community with five species that has equal abundance of each will have a larger Shannon-Wiener index than a community with five species where one species has a lot more individuals than the other four.  

Featured Scientists: Lydia Zeglin and Christine Carson from the Konza Prairie Biological Station. Written By: Jaide Allenbrand

Flesch–Kincaid Reading Grade Level = 10.4