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  • Tropic Topic: What Is Known About the Limestone Zone?
The cover for the 'Tropic Topic' article. The main image is a photo of exposed limestone karst pavement.
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Tropic Topic: What Is Known About the Limestone Zone?

  • Article
  • Middle School
  • 1 Classroom Period
  • Active Forest Management
  • Water
  • Calcium
  • Climate
  • Karst
  • Phosphorus
  • Soil
  • Water Usage
The cover for the 'Tropic Topic' article. The main image is a photo of exposed limestone karst pavement.
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The scientists in this study wanted to compare the chemistry of soils and leaves in Puerto Rico’s northern wet and southern dry karst forests. The scientists wondered whether southern dry karst forests, since they grow in a semi-arid region, use water more efficiently than northern wet karst forests.

Tropic Topic: What Is Known About the Limestone Zone?

Jump To

  • Meet the Scientists
  • Thinking About Science
  • Thinking About the Environment
  • Introduction
  • Methods
  • Findings
  • Discussion

Meet the Scientists

Ernesto Medina

Ernesto Medina

Plant Ecophysiologist

My favorite science experience is being outside in the field, observing how plants respond physiologically to their environment. I like designing experiments to answer the questions that arise from observations,... Read Full Bio
Elvira Cuevas

Elvira Cuevas

Ecologist

I like being a scientist because I get to discover new things about the natural environment. My favorite science experience is working in the field. I can see how the... Read Full Bio
Ariel Lugo

Ariel Lugo

Ecologist | Tropical Ecologist

“My favorite science experience is trying to understand the functioning of natural ecosystems in collaboration with bright people, including high school students.” “[Another] favorite science experience is interacting with other... Read Full Bio

What Kinds of Scientists Did This Research?

  • Ecologist: This scientist studies the relationship of living things with their living
    and nonliving environment.
  • Tropical ecologist: A tropical ecologist studies the relationship of living things with their environment in the tropics. The tropics make up the region between the Tropic of Cancer and the Tropic of Capricorn (see Figure 5).
  • Plant ecophysiologist (ē kō fi zē ä lǝ jist): A plant ecophysiologist studies how the environment, both physical and biological, interacts with the physiology of an organism. It includes the effects of climate and nutrients on physiological processes, or normal functioning, in plants.

Thinking About Science

Plants receive nutrients from air, water, and soil. Chemicals move throughout the air, water, and soil, and then into plants. Plants absorb 14 nutrients from the soil. Plants have a disadvantage when faced with unfavorable conditions, such as poor soil conditions. They cannot move quickly to a new environment when conditions are unfavorable. When soil or rainfall conditions are not optimum for plant growth, plants must adapt to thrive. When conditions are not favorable for plants, one way they may adapt is to increase the percentage of their root structure compared with the rest of the plant’s aboveground structure. They may grow their roots deeper and spread them out farther away from the main root stem.

 

The scientists in this study were interested in how trees growing in similar soil types, but living in different rainfall conditions, adapt so they can thrive. To understand such tree adaptation, the scientists compared the soil’s chemical content with the tree leaves’ chemical content. Studying the chemical content of soil and leaves helps scientists understand how plants adapt to their environment.


Thinking About the Environment

Karst is a geochemical landform from which caves and sinkholes are formed (figures 1 and 2). Karst is made up of limestone and other soluble rocks. Limestone erodes easily, especially when groundwater or rainfall is slightly acidic. As limestone erodes, water seeps into the ground and further erodes the limestone underneath. This erosion forms sinkholes, caves, and underground streams and lakes.

 

A figure showing different parts of a karst landscape

Figure 1. Karst is mainly a carbonate landform from which caves and underground waterways are formed. FIND Outdoors illustration by Stephanie Pfeiffer.

A mogote karst landform

Figure 2. Mogotes are an unusual karst landform. Mogotes are found in tropical and subtropical regions, including Puerto Rico, Cuba, and parts of China. The sides of some mogotes are almost vertical. University of Puerto Rico photo by Ernesto Medina.

Karst landscapes are found worldwide, covering about 20 percent of Earth’s land surface. All of Florida, for example, is karst (figure 3).

 

A map of the United States highlighting all the areas where Karst are located.
Figure 3. Karst landscapes are found across the United States. FIND Outdoors map by Carey Burda and Stephanie Pfeiffer

 

Karst landscapes are an important source of drinking water, provide wildlife habitat, and provide outdoor recreation opportunities such as caving. In this study, the scientists were interested in learning about forests growing on karst in Puerto Rico.


Introduction

Puerto Rico is an island in the Caribbean and is located in Earth’s tropical region (figures 4 and 5).

 

An illustration of Puerto Rico highlighted on a map

Figure 4. Puerto Rico is a United States territory.
FIND Outdoors map by Carey Burda and Stephanie Pfeiffer.

AN illustration of the globe with the tropical zone highlighted

Figure 5. Puerto Rico is located in Earth’s warm tropical region. FIND Outdoors illustration by Stephanie Pfeiffer.

The northern region of Puerto Rico experiences a lot of rainfall. The southern region of Puerto Rico, in contrast, is semi-arid, an area with light rainfall (figure 6).

 

An illustration showing the rain shadow effect on a mountain
Figure 6. Puerto Rico is wet in the north and dry in the south due to the rain shadow effect. The rain shadow effect is the result of a large barrier, like a mountain range, that causes rain to fall on one side of the mountain range while the other side of the mountain remains dry. FIND Outdoors illustration by Stephanie Pfeiffer.

 

About 27 percent of Puerto Rico contains karst landscapes (see “Thinking About the Environment”). Karst is found in both Puerto Rico’s northern wet region and its southern dry region. Karst soils are shallow, and most karst soil is built from the leaves that fall from forest trees (figure 7). Soils in Puerto Rico’s southern dry karst forests build slowly in the crevices between the pavement sections (figures 8 and 9).

A karst with several mogotes hills.

Figure 7. In some karst areas with mogotes, most of the soil is found in the valleys between the steep mogote hills.

University of Puerto Rico photo by Ernesto Medina.

A body of water with rock formations growing into it, soil on the rock is thin.

Figure 8. Soil is thin in the southern dry karst forests of Puerto Rico.

Photo courtesy of Clare McFadden.

Limestone karst pavement seen between plants
Figure 9. Exposed limestone karst pavement is flat and looks similar to concrete pavement. In karst pavement areas, soil is built in the crevices between the pavement blocks. Photo courtesy of Ernesto Medina.

 

The scientists in this study wanted to compare the chemistry of soils and leaves in Puerto Rico’s northern wet and southern dry karst forests. The northern wet karst forests receive an average of between 1,000 and 1,500 mm of rainfall every year. The southern dry karst forests receive an average of less than 1,000 mm of rainfall every year. The scientists wondered whether southern dry karst forests, since they grow in a semi-arid region, use water more efficiently than northern wet karst forests.

 

 

Number Crunch

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Reflection Section

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Methods

The scientists collected leaves from trees growing in both the northern wet and southern dry karst forests. Leaves from the northern wet karst forest were collected from trees on the mogote tops. Leaves from the southern dry karst forest were collected from trees growing on the ridges and pavement. All leaves were collected from tree canopies.

 

Recall that the scientists were also interested in the differences in how trees use water in northern wet and southern dry karst forests. After the scientists collected the leaves, they dried the leaves in an oven for 3 to 7 days and then finely ground the leaves. The scientists used specialized equipment to determine which chemicals were found in the leaves collected from the two karst regions. Measuring the chemical content of leaves enabled the scientists to compare leaf chemistry with the chemical content of the soil. This comparison helped the scientists to determine how trees growing in similar soils, but different environmental conditions, adapted to those conditions. The scientists tested leaves for the presence of:

  • Carbon
  • Nitrogen
  • Phosphorus
  • Sulfur
  • Potassium
  • Calcium
  • Magnesium
  • Aluminum
  • Manganese
  • Iron

The scientists were also interested in stomatal conductance. The word stomatal comes from the fact that leaves have small openings, called stomata, through which gases enter and exit the leaf (figure 10). You can see in Figure 10 that carbon enters the leaf as carbon dioxide gas.

 

An illustration showing the small openings on a leaf that allow gas to enter and exit.
Figure 10. Small openings that open and close, called stomata, allow gases to enter and exit leaves. FIND Outdoors illustration by Stephanie Pfeiffer.

Carbon atoms have different atomic masses. Carbon atoms are either Carbon 12, a lighter atom, or Carbon 13, a heavier atom. Carbon 12 atoms are the most plentiful on Earth, making up 98.93 percent of all carbon atoms. When plants have plenty of water, they open their stomata completely. The plant enzyme responsible for the uptake of CO2 in most plants readily takes up the more plentiful Carbon 12 atoms entering the leaf, preferring Carbon 12 atoms to the heavier Carbon 13 atoms.

When plants have a limited supply of water, the stomata do not open completely. In this case, the plant enzyme responsible for the uptake of CO2 will take up all available carbon atoms. Plants in water-restricted environments, therefore, may be more likely to have a greater amount of Carbon 13. The scientists measured the proportion of Carbon 13 to that of Carbon 12 in the leaf tissues. The ratio of Carbon 13 to Carbon 12 (Carbon 13/Carbon 12), therefore, is related to how well a plant efficiently uses water.

 

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Findings

For the most part, leaves were similar in Puerto Rico’s two karst regions. Leaves from the northern wet and southern dry karst forests contained similar amounts of magnesium, phosphorus, and nitrogen. Leaves in both the northern wet and southern dry karst forests contained large amounts of calcium. The scientists also found that leaves in both Puerto Rico’s northern wet and southern dry karst forests are limited in phosphorus. Leaves in the southern dry karst forests, however, contain more potassium than leaves in the northern wet karst forests. The scientists believe this difference is because higher rainfall in the northern wet karst region leaches potassium from the soil.

 

The scientists found that leaves in the southern dry karst forests contained more carbon-13 than leaves in the northern wet karst forests. Leaves that use water more efficiently contain higher levels of carbon-13. Therefore, the leaves from the southern dry karst forests use water more efficiently, meaning that leaf stomata do not completely open, and less water vapor exits the leaves.

 

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The potassium element as it appears on the periodic table

Why Do Plants Need Potassium?

Potassium is one of 17 essential plant nutrients. Plants absorb potassium from the soil through their root hairs and root tips. Among other uses, plants use potassium in photosynthesis. During photosynthesis, potassium regulates the opening and closing of stomata, and therefore regulates carbon dioxide uptake and water vapor loss.


Discussion

The soils in northern wet and southern dry karst forests were similar. Soils from both regions contained limited phosphorus. Low phosphorus levels limit the growth of karst forests in Puerto Rico. The soil in both regions contained high amounts of calcium. Calcium aids plants by holding cell walls together. The southern dry karst forest soils contained more potassium than northern wet karst forest soils. Northern wet and southern dry karst forests can primarily be distinguished by the amount of rainfall they receive.

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Adapted from Medina, E., Cuevas, E., and Lugo, A. E. Substrate chemistry and rainfall regime regulate elemental composition of tree leaves in karst forests. Forests, 8, 182, https://www.fs.usda.gov/treesearch/54455.

The cover for the Natural Inquirer Caves and Karst journal. The main image is a photo of a cave with an opening high above the land below with a view of a green valley.

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Caves and Karst Natural Inquirer - Vol. 20 No. 1

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  • PDF preview for the 'Tropic Topic' FACTivity.
    In this FACTivity, you will answer the question: What is the difference between how much water is transpired by different types of plant leaves during the day? Materials (for each...

    FACTivity – Tropic Topic

    • Activity
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    • Water
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    • Observation
    • Plants
    • Transpiration
    • Water
    In this FACTivity, you will answer the question: What is the difference between how much water is transpired by different types of plant leaves during the day? Materials (for each...
    • Explore Activity
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    Tropic Topic: What Is Known About the Limestone Zone?

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  • Education Standards
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Standards addressed in this Article:

The Next Generation Science Standards (NGSS) are a set of K-12 science education standards emphasizing inquiry-based learning, real-world applications, and integrating engineering practices, aiming to deepen understanding of science while promoting critical thinking and problem-solving skills.
  • ESS2.C-M1
    Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land.
  • ESS2.D-M1
    Weather and climate are influenced by interactions involving Sunlight, the ocean, the atmosphere, ice, landforms, and living things. These interactions vary with latitude, altitude, and local and regional geography, all of which can affect oceanic and atmospheric flow patterns.
  • LS1.A-M2
    Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.
  • LS1.A-M3
    In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions.
  • LS1.B-M4
    Genetic factors as well as local conditions affect the growth of the adult plant.
  • LS1.C-M1
    Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use.
  • LS1.C-M2
    Within individual organisms, food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules, to support growth, or to release energy.
  • LS2.A-M1
    Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors.
  • LS2.A-M3
    Growth of organisms and population increases are limited by access to resources.
  • LS4.C-M1
    Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes.
  • PS3.D-M1
    The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen.
  • PS3.D-M2
    Cellular respiration in plants and animals involve chemical reactions with oxygen that release stored energy. In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials.
The Common Core Standards are educational benchmarks in the United States that outline clear expectations for what students should know and be able to do in English language arts and mathematics from kindergarten through 12th grade, aiming to ensure consistency and coherence in education nationwide.
  • Cite specific textual evidence to support analysis of science and technical texts.
  • By the end of grade 8, read and comprehend science/technical texts in the grades 6-8 text complexity band independently and proficiently.
  • Determine the central ideas or conclusions of a text; provide an accurate summary of the text distinct from prior knowledge or opinions.
  • Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
  • Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 6-8 texts and topics.
  • Analyze the structure an author uses to organize a text, including how the major sections contribute to the whole and to an understanding of the topic.
  • Analyze the author's purpose in providing an explanation, describing a procedure, or discussing an experiment in a text.
  • Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).
  • Distinguish among facts, reasoned judgment based on research findings, and speculation in a text.
  • Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.
Social Studies Standards are educational guidelines outlining the essential knowledge, skills, and concepts students should learn in subjects such as history, geography, civics, and economics, aiming to provide a comprehensive understanding of societal structures, historical events, and global perspectives.
  • People, Places, and Environments
  • Science, Technology, and Society
  • Time, Continuity, and Change

What Is a Natural Inquirer Journal?

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A Natural Inquirer journal is a collection of 4-8 articles on a related science topic. Journals are written for a middle school audience, but they can also be adapted for both high school students and advanced upper elementary students. Some journals are particularly suited to high school students; you can find our grade level recommendations in the tags on the product page or by filtering journals by grade level.

Journals include:

  • Four to eight articles based on published, peer-reviewed research papers; the articles keep the research paper format (see more below) but are written in language students can understand.
  • A FACTivity for each article, which is an activity to complete after reading the article. The FACTivity helps reinforce major science concepts from the article. These activities are designed to be easy to implement, with few material requirements and options for adapting them for your audience or available resources. Some articles in a journal may have two FACTivities.
  • A short “Welcome to the journal” article about key background information and science concepts that unify the articles included in the journal
  • A glossary of new terms for each article and the introductory materials.
  • A list of related Natural Inquirer publications for each article as well as outside references.
  • Standards correlations, including Next Generation Science Standards, addressed in the articles and the FACTivities.

Journals may also include additional essays (called spotlights), other activities (like crossword puzzles or vocabulary challenges), and more.

 

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Reading Modes

Journals are available in three different formats:

  • Hard copies can be ordered from the website and shipped, all free of charge.
  • PDF versions of the printed journal can be downloaded free on the website. The PDF version directly replicates the content and layout of the printed version. You can also download individual articles as pdfs.
  • The “Read Distraction Free” option allows the individual articles to open in their own window, without the rest of the website being visible. These articles can be found under the “Articles” tab. This version allows readers to scroll to particular sections of the article using the sidebar menu on the left side of the screen. This version also has interactive Reflection Sections and Number Crunches. Students can enter their answers, submit them, and then receive the correct answers to double-check their work. Submitted answers are not saved on the website and will disappear once the window is closed.

What's in a Natural Inquirer Article?

Here, we'll go into more detail about the parts of a Natural Inquirer article and give you some ideas about how they can be used.
  1. Meet the Scientists

    This section introduces the scientists (and others) who worked on the study. In their own words, they each share a memorable science experience, a favorite research project, or something they learned during the course of their education or research.

    Use this section to:

    • Introduce kids to the variety of people who work in science
    • Introduce kids to the variety of scientific fields and give brief descriptions of science-related jobs
    • Explore ways that people interact with science every day

    Next Generation Science Standards (NGSS) applications:

    • Science and Engineering Practices
    • Crosscutting Concepts: Influence of Science, Engineering, and Technology on Society and the Natural World

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    Many of the scientists and engineers featured in this section are also featured on our collector cards. Learn more about their work, how they got interested in their fields, and interesting projects they worked on. Cards can be printed as posters, too.

    A sample Meet the Scientists page, showing four different scientists
  2. Thinking About Science

    This section briefly describes a concept about science or scientific research. This overview can touch on topics like

    • study type (longitudinal study, quantitative vs. qualitative data),
    • behaviors of scientists (conducting literature reviews, collaborating with other specialists, replicating earlier studies),
    • the practice of science (the scientific method, engineering design, data collection, randomization, controls and variables),
    • or other aspects of science (bias, correlation vs. causation).

    Use this section to:

    • Reinforce steps in the scientific method and the process of science
    • Encourage students to think about the practice of science and what it can and cannot tell us
    • Consider the many types of scientific study and what information each type can provide

    Next Generation Science Standards applications:

    • Science and Engineering Practices
    • Life Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    You can use key words to search for other or related scientific topics on our website (e.g. “longitudinal study,” “bias,” or “sampling”).

    A sample Thinking About Science page from a recent monograph
  3. Thinking About the Environment

    This section provides a brief overview of a topic or concept in environmental/life science. The topic or concept is directly related to the research study that follows. Examples of topics include the carbon cycle, the water cycle, habitat fragmentation, phenology, biodiversity, and ecosystem services.

    Use this section to:

    • Provide important background information to help students understand the research study
    • Serve as a quick reference during reading or class instruction
    • Connect the research article with other activities or media on the same topic

    Next Generation Science Standards applications:

    • Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    You can use key words to search for more resources on life or earth science topics on our website (e.g. “habitat,” “carbon,” or “genetics”).

    A sample "Thinking About the Environment" section from a recent monograph
  4. Introduction

    This section begins the scientific article format. Much like the published, peer-reviewed study this article is based on, the introduction provides background information for the study – what is currently known and what remains unknown. The introduction culminates in the question(s) the study hopes to answer.

    The introduction is also the first section with a Reflection Section. This section includes two or three questions to help kids reflect on what they’ve just learned in the Introduction. If they are using the online distraction-free reading mode, they can answer these questions directly on the website.

    Use this section to:

    • Review important background information that kids need to understand the study
    • Connect the study to the concepts addressed in the Thinking About Science and Thinking About the Environment sections
    • Understand research questions and hypotheses, including generating their own hypotheses given what they already know

    Next Generation Science Standards applications:

    • Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    Use one of the guided reading lesson plans to help kids follow the format of a scientific paper.

    A sample introduction page from "Hidden in Plain Sight"
  5. Methods

    This section is the nuts and bolts of the study design – the who, what, when, where, why, and how of the research. Contained within the Methods section are usually maps of the study location or the set-up of study plots, as well as details about what data was collected and how.

    The Methods section also ends with a Reflection Section – two or three questions to help students think through what they just read. These questions are interactive on the distraction-free reading mode.

    Use this section to:

    • Show students how experiments and studies are designed and carried out
    • Explore sampling methods and randomization
    • Introduce various data collection tools (e.g. camera traps, surveys, insect collection tools, weather stations, etc.)
    • Explain bias and how studies are designed to remove bias
    • Help students gain experience with map reading

    Next Generation Science Standards applications:

    • Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    Many Methods and Findings sections contain Number Crunches, which are simple math exercises designed to help students interact with the data from the study.

    A sample methods section of a monograph article showing a map
  6. Findings

    This section summarizes the data collected during the study. The Findings section usually includes data tables or graphs and highlights the significant data points from the study. This section often mentions statistical analysis or the use of computer programs to model or analyze the data, though these methods are only discussed generally.

    The Findings section also ends with a Reflection Section – two or three questions to help students think through what they just read. These questions are interactive on the distraction-free reading mode.

    Use this section to:

    • Have students practice reading and interpreting graphs and tables
    • Compare results between variables and controls
    • Explain the concept of statistical significance
    • Discuss how no data or negative results still provide valuable information

    Next Generation Science Standards applications:

    • Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    Search the website for “map” or “graph” to find activities where students can practice making and reading maps and graphs.

    The beginning of a Findings section featuring a large data table
  7. Discussion

    This section concludes each article. In it, we summarize the main findings of the scientists’ study. Additionally, we present the scientists’ ideas about the limitations of their study, the big-picture impacts of their research, and the scientists’ plans for future study or action.

    The Discussion section ends with a Reflection Section – two or three questions to help students think through what they just read, especially general take-aways from the study. These questions are interactive on the distraction-free reading mode.

    Use this section to:

    • Discuss what conclusions can and cannot be drawn from the available data
    • Explain the difference between correlation and causation
    • Explore study limitations and opportunities for further study
    • Brainstorm ways the study findings could be applied to real-world situations

    Next Generation Science Standards applications:

    • Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
    • Most Crosscutting Concepts (depending on topic)

    Note that specific standards for this particular journal are linked on this educator guide tab.

    Other resources:

    Use the “Designing Your Own Study” resource page for videos of scientists discussing their own research studies. The page also includes educator resources to help students plan their own scientific studies.

    The beginning of the conclusion of "Hidden in Plain Sight"

Additional Resources on the Website

A screenshot of the product tabs for an NI monographOn the website, we pair each journal with a variety of other resources, as well. Use the tabs on the product page to browse through the following:

  • Related activities, including the FACTivity for each article
  • An “About” essay that gives some larger context for the research the scientists conducted or more information about the science topic from the journal
  • A glossary of all boldfaced terms from the journal
  • A “Scientists and Collaborators” page that lists the people involved in the studies in the journal; click on a researcher to reach their bio page and see what other articles they might be featured in
  • A “Related Content” page that lists both Natural Inquirer resources about similar topics and also outside reference materials

Article Selection and Review

Natural Inquirer partners with the USDA Forest Service, so we source research studies by Forest Service scientists that have been peer-reviewed and published in reputable journals. Some of our articles have also been created in collaboration with scientists from other Federal agencies, such as U.S. Geological Survey and the United Nations Food and Agriculture Organization, universities, and other non-profits.

All journal articles are reviewed by scientists who conducted the original research study to verify scientific accuracy. Journals are also reviewed by student editorial review boards of middle or high school students before publication. Additionally, all journals are reviewed by the Forest Service and the U.S. Department of Agriculture before publication.

A screenshot of the citation for "Lights, Camera, Tracks"Every journal article includes a citation of its source study. Many educators pair the original research paper with our article to help more advanced students learn how to read formal research papers. The journal article then serves as adapted primary literature, bridging the two articles.

Lessons

  • PDF preview of Haikus Lesson Plan.
    In this lesson plan, students will complete a guided reading activity while reading their chosen article. As they read, they will complete a double-entry graphic organizer where they will note...

    Lesson Plan – Haikus

    • Lesson Plan
    • Middle School
    • 2-3 Classroom Periods
    • Active Forest Management
    • Agriculture
    • Carbon
    • Citizen Science
    • Engineering and Forest Products
    • Fire
    • Insects
    • Pollinators
    • Pollution
    • Recreation
    • Social Science
    • Water
    • Wilderness
    • Wildlife
    • Creative Writing
    • Graphic Organizer
    • Guided reading
    • Reflection
    In this lesson plan, students will complete a guided reading activity while reading their chosen article. As they read, they will complete a double-entry graphic organizer where they will note...
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)

    Part Of

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  • PDF Preview of Lesson Plan for Flower Power
    Identify and write the main idea of the section using one sentence. Fill out the provided graphic organizer. This lesson plan can be used with any Natural Inquirer article.

    Lesson Plan – Block Graphic Organizer

    • Lesson Plan
    • High School
    • Middle School
    • 1 Classroom Period
    • Active Forest Management
    • Agriculture
    • Carbon
    • Citizen Science
    • Engineering and Forest Products
    • Fire
    • Insects
    • Pollinators
    • Pollution
    • Recreation
    • Social Science
    • Water
    • Wilderness
    • Wildlife
    • Graphic Organizer
    Identify and write the main idea of the section using one sentence. Fill out the provided graphic organizer. This lesson plan can be used with any Natural Inquirer article.
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)

    Part Of

    Flower Power: Planting for the Past and the Future

  • PDF Preview of the ^-W Questions Lesson Plan
    In this lesson plan, students will read a Natural Inquirer article and write short summary notes from each section. Students will then create “6-W Poems” that reflect their understanding of...

    Lesson Plan – The 6-W Questions

    • Lesson Plan
    • High School
    • Middle School
    • 2-3 Classroom Periods
    • Active Forest Management
    • Agriculture
    • Carbon
    • Citizen Science
    • Engineering and Forest Products
    • Fire
    • Insects
    • Pollinators
    • Pollution
    • Recreation
    • Social Science
    • Water
    • Wilderness
    • Wildlife
    • Graphic Organizer
    • Guided reading
    • Poem
    • Reading Comprehension
    • Writing
    In this lesson plan, students will read a Natural Inquirer article and write short summary notes from each section. Students will then create “6-W Poems” that reflect their understanding of...
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)
    • Explore Lesson Plan
    • Download Lesson Plan (PDF)

    Part Of

    Show Me the Money: Promoting Sustainable Forests in the South

Education Files

Project Learning Tree

If you are a trained Project Learning Tree educator, you may use “Every Tree For Itself,” “Rain Reasons,” “How Plants Grow,” “Field, Forest and Stream,” and “Soil Stories” as additional resources.

Glossary

View All Glossary
  • acidic

    (ə si dik): Acid-forming or like an acid (an acid is a substance with a pH less than 7).

  • advantageous

    (ad van tā jǝs): Giving an advantage.

  • canopy

    (ka nə pē): A protective covering, such as the uppermost spreading branchy layer of a forest.

  • conductance

    (kən dək tən(t)s): The readiness with which gases pass into and out of a leaf’s surface.

  • crevice

    (kre vəs): A narrow opening caused by a crack or a split.

  • erode

    (i rōd): To wear away by the action of water, wind, or glacial ice.

  • geochemical

    (jē ō ke mi kəl): Having to do with the chemical composition of and chemical changes in the solid matter of the Earth or a celestial body (such as the Moon).

  • leach

    (lēch): To dissolve out a substance by the action of a percolating liquid.

  • nutrient

    (nü trē ǝnt): A substance or ingredient that promotes growth, provides energy, and maintains life.

  • optimum

    (äp tǝ mǝm): The amount or degree of something that is most favorable to some end.

  • physiologically

    (fi zē ə lä ji k(-ə)lē): Related to an organism’s healthy or normal functioning.

  • semi-arid

    (se mē er əd): Characterized by light rainfall, especially having from about 10 to 20 inches (25 to 51 centimeters) of annual precipitation.

  • sinkhole

    (siŋk hōl): A hollow in a limestone region that is related to a cave or underground passage.

  • soluble

    (säl yə bəl): Capable of being dissolved in or as if in a liquid, especially water.

  • Ernesto Medina standing with colleagues in a forest

    Ernesto Medina

    Plant Ecophysiologist

    My favorite science experience is being outside in the field, observing how plants respond physiologically to their environment. I like designing experiments to answer the questions that arise from observations,...
    View Profile
  • Elvira Cuevas sits on a kayak and lets her legs dangle over the sides.

    Elvira Cuevas

    Ecologist

    I like being a scientist because I get to discover new things about the natural environment. My favorite science experience is working in the field. I can see how the...
    View Profile
  • A photo of Dr. Ariel Lugo and a group of people hiking along a river.

    Ariel Lugo

    Ecologist | Tropical Ecologist

    “My favorite science experience is trying to understand the functioning of natural ecosystems in collaboration with bright people, including high school students.” “[Another] favorite science experience is interacting with other...
    View Profile

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    Leaf Me Alone! The Movement of Nutrients Between Trees and the Soil

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Additional Resources

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The Natural Inquirer program produces a variety of science education materials for PreK through grade 12. Natural Inquirer products are produced by the USDA Forest Service, FIND Outdoors, and other cooperators and partners.

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