Testing the tolerance of invasive plants

Casey out in the field.

The activities are as follows:

Casey is a biologist who grew up with dogs as pets. His dogs were all the same species and had some things in common – they all had a tail, ears, and fur. But, each dog also had its own unique appearance – tail length, ear shape, and fur color. These things are called traits. Casey became interested in how slight differences in traits make individuals unique. 

As Casey observed in dogs, not all individuals in the same species are exactly alike. This is also true in plants. When we look closely at individual plants of the same species, we often see that each is slightly different from the next. Some grow faster. Some have more leaves than others. Some are better at defending themselves against herbivoresthat might eat them. 

People move species around the globe, and some of these species cause problems where they are introduced. These trouble-making species are called invasive species. Casey wanted to apply what he knew about trait differences to the environment around him, so he chose to study invasive plants and their traits. He wants to know what it is about invasive species that make them able to invade. Casey thought that maybe certain traits cause invasive species to be more troublesome than others. The individual plants that have invaded other parts of the world might have different traits that made them successful in that environment. Plants in their new invasive range might be slightly different than plants in the native range where they came from.  

Along with other members of his lab, Casey is studying an invasive plant species called burr clover. The lab collected seeds of burr clover from all different parts of the world. Some of the seeds came from the native range around the Mediterranean Sea (e.g. Italy, France, and Morocco) and some came from areas where they are invasive (e.g. Japan, Brazil, and the United States). The plants from the invasive range have already proven that they can invade new areas. Studying traits in native and invasive ranges would allow Casey to learn more about how those individuals invaded in the first place. Because Casey thought trait differences might have caused certain individuals of burr clover to become invasive, he predicted that individuals from the invasive range would have different traits than those from the native range. 

Casey’s field site where he studies Burr Clover

The lab decided to look at one trait in particular – how much an individual plant was affected by herbivores, which is called tolerance. The most tolerant individuals can still grow and produce fruits, even when herbivores eat a lot of their tissue. Casey thought that individuals from the invasive range would be more tolerant than individuals from the native range. One reason the invading individuals may have been successful is that they were more tolerant of herbivores in their new environment.The fruits contain seeds that make new plants, so plants that make more fruits can invade more easily. If individuals from the invasive range can make more fruits, even when herbivores are around, then they may reproduce and spread more quickly. 

So, Casey and his lab collected seeds from 22 individual plants from the native range and 22 individual plants from the invasive range. Each plant produces many seeds, so they collected several seeds from each individual. They created 24 2×2-meter plots in a field in California. Into each plot they planted 2-4 seeds from each individual plant and the seeds were planted in a random order in each plot. In all, there were 3,349 plants! In half of the plots, they removed any insects that might eat the plants. To do this they randomly chose half of the plots and sprayed them with insecticide, which kills insects. They sprayed the other half of the plots with water as a control. They wanted to know how many fruits were made by plants under good conditions so they could compare to plants that are being eaten by herbivores. After the plants grew all spring, they measured how many small, spiky fruits each plant produced. They compared how many fruits each plant produced in the plots with insects and the plots without insects. 

Featured scientist: Casey terHorst from California State University, Northridge

Flesch–Kincaid Reading Grade Level = 8.3

Fast weeds in farmer’s fields

Native and weedy radish plants.

The activities are as follows:

Weeds in agricultural fields cost farmers $28 billion per year in just the United States alone. When fields are full of weeds the crops do not grow as well. Sometimes weeds even grow better than the crops in the same field. This may make you wonder, how do weeds grow so well compared to other types of plants? Scientists think that weeds may have evolved certain traits that allow them do well in agricultural fields. These adaptationscould allow them to grow better and pass on more of their genes to the next generation.

Weedy radishis considered one of the world’s worst agricultural weeds. This plant has spread around the world and can now be found on every continent except Antarctica. Weedy radish commonly invades wheat and oat fields. It grows better than crops and lowers the amount of food produced in these fields. Weedy radish evolved from native radish only after humans started growing crops. Native radish only grows in natural habitats in the Mediterranean region. 

Because weedy radish evolved from native radish recently, they are still very closely related. They are so closely related they are actually listed as the same species. However, some traits have evolved rapidly in weedy radish. For example, native radish grow much slower and take a few months to make flowers. However, weedy radish can make flowers only three weeks after sprouting! In a farmer’s field, the crop might be harvested before a native radish would be able to make any seeds, while weedy radish had plenty of time to make seeds.

Ashley collecting data on the traits of weedy and native radish. 

The differences between native versus weedy radish interested Ashley, a teacher in Michigan. To learn more she sought out a scientist studying this species. She found Jeff, a plant biologist at the Kellogg Biological Station and she joined his lab for a summer to work with him. That summer, Ashley ran an experiment where she tested whether the rapid flowering and seed production of weedy radish was an adaptation to life in agricultural fields.

Ashley planted four populations of native radish and three populations of weedy radish into fields growing oat crops. Ashley made sure to plant multiple populations of radish to add replication to her experiment. Multiple populations allowed her to see if patterns were the same across populations or if each population grew differently. For each of these populations she measured flowering frequency. This trait is the total number of plants that produced flowers within the limited time between tilling and harvesting. Ashley also measured fitness, by counting the total number of seeds each plant produced over its lifetime. Whichever plant type produced a greater number of seeds had higher fitness. Oats only grow for 12 weeks so if radish plants were going to flower and make seeds they would have to do it fast. Ashley predicted the weedy radish population would produce more flowers and seeds than native radish during the study. Ashley expected few native radish plants would flower before harvest.

Featured scientists: Ashley Carroll from Gull Lake Middle School and Jeff Conner from the Kellogg Biological Station at Michigan State University

Flesch–Kincaid Reading Grade Level = 9.1

Hold on for your life! Part II

In Part I the data showed that, after the hurricanes, anole lizards had on average larger bodies, shorter legs, and larger toe pads. The patterns were clear and consistent across the two islands, indicating that these traits are adaptations shaped by natural selection from hurricanes. At this point, however, Colin was still not convinced because he was unable to directly observe the lizards during the hurricane.

Still shot of lizard clinging to an experimental perch in hurricane-force winds. Wind speed meter is displaying in miles per hour

The activities are as follows:

Colin was unable to stay on Pine Cay and Water Cay during the hurricanes and directly observe the lizards. To be more confident in his explanation, Colin needed to find out how lizards behave in hurricane-force winds. He thought there were two options for what they might do. First, he thought they might get down from the branch and hide in tree roots and cracks. Alternatively, they might hold onto branches and ride out the storm. If they tried to hold on in high winds, it would make sense that traits like the length of their limbs or the size of their toepads would be important for their survival. However, if they hid in roots or cracks, these traits might not be adaptations after all.

To see how the lizards behaved, Colin needed to design a safe experiment that would simulate hurricane-force winds. He bought the strongest leaf blower he could find, set it up in his hotel room on Pine Cay, and videotaped 40 lizards as they were hit with high winds. Colin first set up this experiment to observe behavior, but he ended up learning not only that, but a lot about how the traits of the lizards interacted with high winds.

To begin the experiment, Colin placed the anoles on a perch. He slowly ramped up the wind speed on the leaf blower until the lizards climbed down or they were blown, unharmed, into a safety net. He recorded videos of each trial and took pictures. 

Featured scientist: Colin Donihue from Harvard University

Written with: Bob Kuhn and Elizabeth Schultheis

Flesch–Kincaid Reading Grade Level = 8.4

Additional teacher resources related to this Data Nugget:

To engage students in this activity, show the following video in class. This video gives some information on the experiment and Colin’s research.

Hold on for your life! Part I

Anolis scriptus, the Turks and Caicos anole, on Pine Cay.

The activities are as follows:

On the Caribbean islands of Turks and Caicos, there lives a small brown anole lizard named Anolis scriptus. The populations on two small islands, called Pine Cay and Water Cay, have been studied by researchers from Harvard University and the Paris Natural History Museum for many years. In 2017, Colin, one of the scientists, went to these islands to set up a long-term study on the effect of rats on anoles and other lizards on the islands. Unbeknownst to him, though, a storm was brewing to the south of the islands, and it was about to change the entire trajectory of his research.

While he was collecting data, Hurricane Irma was developing into a massive category 5 hurricane. Eventually it became clear that it would travel straight over these small islands. Colin knew that this might be the last time he would see the two small populations of lizards ever again because they could get wiped out in the storm. It dawned on him that this might be a serendipitous moment. After the storm, he could evaluate whether lizards could possibly survive a severe hurricane. He was also interested in whether certain traits could increase survival. Colin and his colleagues measured the lizards and vowed to come back after the hurricane to see if they were still there. They measured both male and female lizards and recorded trait values including their body size, femur length, and the toepad area on their forelimbs and hindlimbs.

Colin was not sure whether the lizards would survive. If they did, Colin formed two alternative hypotheses about what he might see. First, he thought lizards that survived would just be a random subset of the population and simply those that got lucky and survived by chance. Alternatively, he thought that survival might not be random, and some lizards might be better suited to hanging on for their lives in high winds. There might be traits that help lizards survive hurricanes, called adaptations. He made predictions off this second hypothesis and expected that survivors would be those individuals with large adhesive pads on their fingers and toes and extra-long legs – both traits that would help them grab tight to a branch and make it through the storm. This would mean the hurricanes could be agents of natural selection.

Not only did Hurricane Irma ravage the islands that year, but weeks later Hurricane Maria also paid a visit. Upon his return to Pine Cay and Water Cay after the hurricanes, Colin was shocked to see there were still anoles on the islands! He took the measurements a second time. He then compared his two datasets from before and after the hurricanes to see if the average trait values changed.

Featured scientist: Colin Donihue from Harvard University

Written with: Bob Kuhn and Elizabeth Schultheis

Flesch–Kincaid Reading Grade Level = 9.9

Additional teacher resources related to this Data Nugget:

To engage students in this activity, show the following video in class. This video gives some information on the experiment and Colin’s research. For Part I stop the video at minute 1:30.

All washed up? The effect of floods on cutthroat trout

The activities are as follows:

Mack Creek, a healthy stream located within the old growth forests in Oregon. It has a diversity of habitats because of various rocks and logs. This creates diverse habitats for juvenile and adult trout.

Streams are tough places to live. Fish living in streams have to survive droughts, floods, debris flows, falling trees, and cold and warm temperatures. In Oregon, cutthroat trout make streams their home. Cutthroat trout are sensitive to disturbances in the stream, such as pollution and sediment. This means that when trout are present it is a good sign that the stream is healthy.

Floods are very common disturbances in streams. During floods, water in the stream flows very fast. This extra movement picks up sediment from the bottom of the stream and suspends it in the water. When sediment is floating in the water it makes it harder for fish to see and breathe, limiting how much food they can find. Floods may also affect fish reproduction. If floods happen right after fish breed and eggs hatch, young fish that cannot swim strongly may not survive. Although floods can be dangerous for fish, they are also very important for creating new habitat. Floods expand the stream, making it wider and adding more space. Moving water also adds large boulders, small rocks, and logs into the stream. These items add to the different types of habitat available. 

A cutthroat trout. It is momentarily unhappy, because it is not in its natural, cold Pacific Northwest stream habitat.

Ivan and Stan are two scientists who are interested in whether floods have a large impact on the survival of young cutthroat trout. They were worried because cutthroat trout reproduce during the spring, towards the end of the winter flood season. During this time juvenile trout,less than one year old, are not good swimmers. The fast water from floods makes it harder for them to survive. After a year, juvenile trout become mature adults.These two age groups live in different habitats. Adult trout live in pools near the center of streams. Juvenile trout prefer habitats at the edges of streams that have things like rocks and logs where they can hide from predators. Also, water at the edges moves more slowly, making it easier to swim. In addition, by staying near the stream edge they can avoid getting eaten by the adults in stream pools.

Ivan and Stan work at the H.J. Andrews Long Term Ecological Research site. They wanted to know what happens to cutthroat trout after winter floods. Major floods occur every 35-50 years, meaning that Ivan and Stan would need a lot of data. Fortunately for their research they were able to find what they needed since scientists have been collecting data at the site since 1987!

To study how floods affect trout populations, Ivan and Stan used data from Mack Creek, one of the streams within their site. They decided to look at the population size of both juvenile and adult trout since they occupy such different parts of the stream. For each year of data they had, Ivan and Stan compared the juvenile and adult trout population data, measured as the number of trout, with stream discharge, or a measure of how fast water is flowing in the stream. Stream discharge is higher after flooding events. Stream discharge data for Mack Creek is collected during the winter when floods are most likely to occur. Fish population size is measured during the following summer each year. Since flooding can make life difficult for trout, they expected trout populations to decrease after major flooding events.

Featured scientists: Ivan Arismendi and Stan Gregory from Oregon State University

Written by: Leilagh Boyle

Flesch–Kincaid Reading Grade Level = 7.5

Additional teacher resource related to this Data Nugget:

Can biochar improve crop yields?

Buckets of pine wood biochar.

The activities are as follows:

If you walk through the lush Amazon rainforest, the huge trees may be the first thing you see. But, did you know there are wonderful things to explore on the forest floor? In special places of the Amazon, there exist incredible dark soils called “Terra Preta”. These soils are rich in nutrients that help plants grow. The main source of nutrients and dark color is from charcoal added by humans. Hundreds of years ago the indigenous people added their cooking waste, including ash from fire pits, into the ground to help their food crops grow. Today, scientists and farmers are trying out this same ancient method. When this charcoal is added to soil to help plants grow, we call it biochar.

Biochar is a pretty unique material. It is created by a special process that is similar to burning materials in a fire place, but without oxygen. Biochar can be made from many different materials. Most biochar has lots of tiny spaces, or pores, that cause it to act like a hard sponge when it is in the soil. Due to these pores, the biochar can hold more water than the soil can by itself. Along with that extra water, it also can hold nutrients. Biochar has been shown to increase crop yield in tropical places like the Amazon.

Farmers in western Colorado wanted to know what would happen if they added biochar to fields near them. Their farms experience a very different climate that is cooler and drier than the Amazon. In these drier environments, farmers are concerned about the amount of water in the soil, especially during droughts. Farmers had so many questions about how biochar works in soils that scientists at Colorado State University decided to help. One scientist, Erika, was curious if biochar could really help farms in dry Colorado. Erika thought that biochar could increase crop yield by providing pores that would hold more water in the soil that crop plants can use to grow.

Matt, a soil scientist, applying biochar to the field in a treatment plot.

To test the effects of biochar in dry agricultural environments, Erika set up an experiment at the Colorado State University Agricultural Research and Development Center. She set up plots with three different soil conditions: biochar added, manure added, and a control. She chose to include a manure treatment because it is what farmers in Colorado were currently adding to their soil when they farmed. For each treatment she had 4 replicate plots, for a total of 12 plots. She added biochar or manure to a field at the same rate (30 Megagrams/ ha or 13 tons/acre). She didn’t add anything to control plots. Erika then planted corn seeds into all 12 plots.

Erika also wanted to know if the effects of biochar would be different when water was limited compared to when it was plentiful. She set up another experimental treatment with two different irrigation levels: fullirrigationandlimitedirrigation. The full irrigation plots were watered whenever the plants needed it. The limited irrigation plots were not watered for the whole month of July, giving crops a drought period during the growing season. Erika predicted that the plots with biochar would have more water in the soil. She also thought that corn yields would be higher with biochar than in the manure and control plots. She predicted these patterns would be true under both the full and limited irrigation treatments. However, she thought that the biochar would be most beneficial when crops were given less water in the limited irrigation treatments.

To measure the water in the soil, Erika took soil samples three times: a few weeks after planting (June), the middle of the growing season (July), and just before corn harvest (September). She weighedout 10 gofmoistsoil, thendried the samples for24 hoursin an oven and weighed them again. By putting the soil in the oven, the water evaporates out and leaves just the dry soil. Sarah divided the weight of the water lost by the weight of the dry soil to calculate the percent soil moisture. At the end of the season she measured crop yield as the dry weight of the corn cobs in bushes per acre (bu/acre).

Featured scientist: Erika Foster from Colorado State University

Flesch–Kincaid Reading Grade Level = 8.9

Resources to pair with this Data Nugget:

Beetle, it’s cold outside!

Frozen lady beetles.

The activities are as follows:

Walking across a snowy field or mountain, you might not notice many living things. But if you dig into the snow, you’ll find a lot of life!

Until recently, climate change scientists thought warming in winter would be good for most species. Warmer winters would mean that species could avoid the cold and would not need to deal with freezing temperatures as often or for as long. Caroline is a scientist who is thinking about winter climate change in a whole new way. Snow covers the soil, acting like an insulating blanket. Many species rely on the snow for protection from the winter’s cold. When temperatures climb in the winter, snow melts and leaves the soil uncovered for longer periods of time. This leads to the shocking pattern that warmer temperatures actually means the soil gets colder!

Caroline is interested in how species that rely on the snow will respond to climate change. She studies a species of insect called lady beetles. Lady beetles are ectotherms, meaning their body temperature matches that of their environment. Because climate change is reducing the amount of snow in the lady beetle habitat, Caroline wanted to know how they would respond to these changes.

Caroline and her team, Andre and Nikki, decided to investigate what happens to lady beetles when they are exposed to longer periods of time in cold temperatures. When soil temperatures drop below freezing (0℃), lady beetles go into a chill coma, or a temporary, reversible paralysis. When temperatures are below freezing, it is so cold that they are unable to move. When temperatures rise back above freezing, they wake from their chill comas. When lady beetles are in chill comas, they are easier for predators to catch because they can’t escape. They are also unable to find food or mates. Scientists can measure how fast it takes lady beetles to recover from chill coma, called chill coma recovery time, and use this as a measure of their performance.

Beetles in their pre-testing habitat are on the right; tubes with beetles about to be immersed in a cooler filled with crushed ice are on the left.

They designed an experiment to test whether the amount of time lady beetles spend in freezing temperatures affects how long it takes them to wake up from a chill coma. Caroline thought that lady beetles exposed to lengthy freezing temperatures would be harmed because freezing causes tissue damage and the insect must use more energy to survive. She predicted that the longer the lady beetles had been exposed to the cold, the longer it would take them to wake up from their chill comas.

To begin the experiment, Andre and Nikki placed groups of lady beetles in tubes. They then placed the tubes in an ice bath, bringing the temperature down to 0℃, the point when lady beetles enter chill coma. They varied the amount of time each tube was in the ice baths and tested chill coma recovery times after 3, 24, 48, 72, or 96 hours. After removing the tubes from the ice baths, they put the lady beetles on their backs with their legs in the air and left them at room temperature, 20℃. Andre and Nikki timed how long it took each beetle to wake up and turn itself over.

In the experiment, they used two different populations of lady beetles. Population 1 had been living in the lab for several weeks before the experiment began. They were not in great health and some had started to die. In order to make sure they had enough beetles for the experiment, Caroline purchased more lady beetles, which she called Population 2. Population 2 only spent a few days living in the lab before testing and were in much better health. Caroline noted the differences in these populations and thought their age, health, and background might affect how they respond to the experiment. She decided to track which population the lady beetles were from so she could analyze the data separately and see if the health differences between Population 1 and 2 changed the results.

Featured scientists: Caroline Williams & Andre Szejner Sigal, University of California, Berkeley, & Nikki Chambers, Biology Teacher, West High School, Torrance, CA

Flesch–Kincaid Reading Grade Level = 9.8

Alien life on Mars – caught in crystals?

Magnesium sulfate crystals trapping liquid water.

The activities are as follows:

Is there life on other planets besides Earth? This question is not just for science fiction. Scientists are actively exploring the possibility of life beyond Earth. The field of astrobiology seeks to understand how life in the universe began and evolved, and whether life exists elsewhere. Our own solar system contains a variety of planets and moons. In recent years scientists have also discovered thousands of planets around stars other than our Sun. So far, none of these places are exactly like Earth. Many planets have environments that would be very difficult for life as we know it to survive. However, there are life forms that exist in extreme environments that we can learn from. On Earth there are extremely hot or acidic environments like volcanic hot springs. Organisms also live in extremely cold places like Antarctic glacier ice. Environments with extremely high pressure, like hydrothermal vents on the ocean floor, also support life. If life can inhabit these extreme environments here on Earth, might extreme life forms exist elsewhere in the universe as well?

A view of the astrobiology lab.

Charles is an astrobiologist from Great Britain who is interested in finding life on other planets. The list of places that we might look for life grows longer every day. Charles thinks that a good place to start is right next door, on our neighboring planet, Mars. We know that Mars currently is cold, dry, and has a very thin atmosphere. Charles is curious to know whether there might still be places on Mars where life could exist, despite its extreme conditions.While there is no liquid water on the surface of Mars anymore, Mars once had a saltwater ocean covering much of its surface. The conditions on Mars used to be much more like Earth. Liquid water is essential for life as we know it. If there are places on Mars that still hold water, these could be great places to look for evidence of life. Charles thought that perhaps salt crystals, formed when these Martian oceans were evaporating, could trap pockets of liquid water.

Charles and his fellow researcher Nikki knew that there are a number of kinds of salts found in Martian soils, including chlorides, sulfates, perchlorates and others. They wanted to test their idea that water could get trapped when saltwater with these salts evaporate. They decided to compare the rate of evaporation for solutions with magnesium sulfate (MgSO4) with another commonsalt solution: sodium chloride, or table salt (NaCl). They chose to investigate these two salts because they are less toxic to life as we know it than many of the other chloride, perchlorate, or sulfate salts. Also, from reading the work of other scientists, Charles knows the Martian surface is particularly rich in magnesium sulfate.

Charles and Nikki measured precise quantities of saturated solutions of magnesium sulfate and sodium chloride and placed them into small containers. Plain water was used as a control. There were three replicate containers for each treatment – nine containers in total. They left the containers open to evaporate and recorded their mass daily. They kept collecting data until the mass stopped changing. At this point all of the liquid had evaporated or a salt crust had formed that was impermeable to evaporation. They then compared the final mass of the control containers to the other solutions. They also checked the resulting crusts for the presence or absence of permanent water-containing pockets. Charles and Nikki used these data to determine if either saltmakes crystals that can trap water in pockets when it evaporates.

Featured scientists: Charles Cockell, UK Centre for Astrobiology, University of Edinburgh, & Nikki Chambers, Astrobiology Teacher, West High School, Torrance, CA

Flesch–Kincaid Reading Grade Level = 8.7

Additional teacher resource related to this Data Nugget:

Clique wars: social conflict in daffodil cichlids

A male and female daffodil cichlid

The activities are as follows:

Have you ever thought about what it would be like to live completely alone, without contact with other people? Nowadays, humans are constantly connected by phones, texting, and social media. Our social interactions affect us in many unexpected ways. Strong social relationships can increase human lifespan, and lower the risk of cancer, cardiovascular disease, and depression. Social relationships are so important that they are actually a stronger predictor of premature death than smoking, obesity, or physical inactivity! Like humans, social interactions are important for other animals as well.

Jennifer is a behavioral ecologist who is interested in daffodil cichlids, a social species of fish from Lake Tanganyika, a Great Lake in Africa. Daffodil cichlids live in social groups of several small fish and one breeding pair. Each group defends its own rock cluster in the lake. The breeding male and female are the largest fist in the group, and the smaller fish help defend territory against predators and help care for newly hatched baby fish. About 200 social groups together make up a colony.

Social groups of daffodil cichlids in Lake Tanganyika

Behavior within a social group may be influenced by the presence of other groups in the colony. For example, neighboring groups can be a threat because they may try to take away territory or resources. After reading about previous research on social interactions in species that live in groups, Jennifer noticed there were very few studies that looked at how neighboring groups affected behavior within the group. Jennifer thought that the presence of neighboring groups may force the breeding pair to be less aggressive towards each other and work together to protect their group’s resources against the outside threat.

To test her idea, Jennifer formed breeding pairs of daffodil cichlids in an aquarium laboratory. She first observed the breeding pairs for any aggressive behaviors when they were isolated and could not see other groups. She observed each group for 30 minutes a day for 10 days. Next, Jennifer set up a clear barrier between the breeding pair and a neighboring group. The fish could see each other but not physically interact. Jennifer again watched the breeding pair and documented any aggressive behaviors to see how the presence of a neighboring group affected conflict within the pair. She again observed each group with neighbors for 30 minutes a day for 10 days.

During these behavioral tests, Jennifer counted the total number of behaviors done by the breeding pair. She measured several behaviors. Physical attacks were counted every time contact between the fish was made (biting or ramming each other). Aggressive displays were counted when fish give signals of aggression without making physical contact (raising their fins or swimming rapidly at another fish). Submissive behaviors, or actions used to prevent aggression between the breeding pair, were also counted. Finally, behaviors used to encourage social bonding were counted and are called affiliative behaviors. Jennifer predicted that the breeding pair would perform fewer physical attacks and aggressive displays when a neighboring group was present compared to when the breeding pair was alone. She also thought the breeding pair would perform more submissive and affiliative behaviors when the neighboring group was present. In this way, the presence of an outside group would impact the behaviors within a group.

Featured scientist: Jennifer Hellmann from The Ohio State University

Flesch–Kincaid Reading Grade Level = 11.3

Tree-killing beetles

A Colorado forest impacted by a mountain pine beetle outbreak. Notice the dead trees mixed with live trees. Forests like this with dead trees from mountain pine beetle outbreaks cover millions of acres across western North America.

The activities are as follows:

A beetle the size of a grain of rice seems insignificant compared to a vast forest. However, during outbreaks the number of mountain pine beetles can skyrocket, leading to the death of many trees. The beetles bore their way through tree bark and introduce blue stain fungi. The blue stain fungi kills the tree by blocking water movement. Recent outbreaks of mountain pine beetles killed millions of acres of lodgepole pine trees across western North America. Widespread tree death caused by mountain pine beetles can impact human safety, wildfires, nearby streamflow, and habitat for wildlife.

Mountain pine beetles are native to western North America and outbreak cycles are a natural process in these forests. However, the climate and forest conditions have been more favorable for mountain pine beetles during recent outbreaks than in the past. These conditions caused more severe outbreaks than those seen before.

Logs from mountain pine beetle killed lodgepole pine trees. The blue stain fungi is visible around the edge of each log. Mountain pine beetles introduce this fungus to the tree.

When Tony moved to Colorado, he drove through the mountains eager to see beautiful forests. The forest he saw was not the green forest he expected. Many of the trees were dead! Upon closer examination he realized that some forests had fewer dead trees than others. This caused him to wonder why certain areas were greatly impacted by the mountain pine beetles while others had fewer dead trees. Tony later got a job as a field technician for Colorado State University. During this job he measured trees in mountain forests. He carefully observed the forest and looked for patterns of where trees seemed to be dead and where they were alive.

Tony thought that the size of the trees in the forest might be related to whether they were attacked and killed by beetles. A larger tree might be easier for a beetle to find and might be a better source of food.To test this idea, Tony and a team of scientists visited many forests in northern Colorado. At each site they recorded the diameter of each tree’s trunk, which is a measure of the size of the tree. They also recorded the tree species and whether it was alive or dead. They then used these values to calculate the average tree size and the percent of trees killed for each site.

Featured scientist: Tony Vorster from Colorado State University

Flesch–Kincaid Reading Grade Level = 8.3

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below: