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Standing On the Shoulders of Giants: How Well Do Big-Leaf Mahogany Trees Grow in Different Conditions?
To ensure that big-leaf mahogany harvesting is sustainable, scientists and land managers must know the conditions in which mahogany grows. Therefore, the scientists in this study wanted to examine how big-leaf mahogany responds to different amounts of rainfall and availability of nutrients in the soil.
Standing On the Shoulders of Giants: How Well Do Big-Leaf Mahogany Trees Grow in Different Conditions?
Meet the Scientists
Elvira Cuevas
Ecologist
Ariel Lugo
Tropical Ecologist
Ernesto Medina
Plant Ecophysiologist
What Kind 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 (figure 1).
- Plant ecophysiologist: 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 in plants.
Thinking About Science
Scientists from different organizations and in different parts of the world often work together to analyze, study, and understand a problem. Organizations working together to understand common problems may include government agencies, nonprofit organizations, and universities. In this research, the organizations that worked together were the USDA Forest Service’s International Institute of Tropical Forestry (figure 2), the University of Puerto Rico’s Biology Department, Mexico’s Department of Natural Resource Management (Yucatan), and the Center for Investigations in Quintana Roo, Mexico. Scientists from all of these different organizations worked together, or collaborated (kə la bə rā təd).
Collaboration is an important part of the scientific process. Collaboration involves at least two people with different backgrounds or viewpoints discussing a problem and working toward a solution. The process of discussing ideas and debating points may bring clarity to a problem and may provide meaningful solutions. Collaboration can occur during face-to-face meetings, by phone, through email, through virtual meetings, and through other online collaboration methods. In this research, scientists collaborated on research involving a specific tree called big-leaf mahogany. You will learn more about this collaboration and big-leaf mahogany as you read the article. Think of a time you collaborated with someone at school or at home. Why was the collaboration useful to you?
Thinking About the Environment
Balancing the needs and wants of humans with the health of the environment can be a tricky balancing act. As humans move into new areas and build new things, certain resources are used more. Animal and plant habitat is changed, and it is often no longer suitable for the animal or plant to live there.
Humans create changes in the environment that may influence the well-being of plants and animals in the surrounding areas. For example, a new house or building may be built on an area that used to be an animal’s habitat. Once a house or building has been built, the area is no longer suitable for the animal’s habitat (figure 3). Therefore, some animals, plants, and resources may become stressed due to the habitat changes.
The Endangered Species Act (ESA) was passed in 1973 to help protect animals and plants from extinction. The ESA provides for the conservation of species that are endangered or threatened throughout their habitat range.
International organizations and programs like CITES also help animals and plants. CITES stands for the Convention on International Trade in Endangered Species of Wild Fauna and Flora. CITES is an agreement among 181 countries. The agreement’s goal is to ensure that the trade of wild animals and plants does not endanger the survival of these animals and plants. Trade in wild animals and plants involves trading any animal or plant part for money or other items. Examples of illegal trade of wild animals and plants are harvesting, or cutting down, of endangered tree species and trading or selling ivory from elephants.
Introduction
Big-leaf mahogany is a tree species known for its beautiful wood (figure 4a and 4b).
Over time, humans have cut down many big-leaf mahogany trees for use in furniture and other products (figure 5). Because of this regular human use, big-leaf mahogany is considered vulnerable. It has been listed in the appendixes to CITES.
Species are listed in one of three appendixes depending on the level of protection they need. Big-leaf mahogany is listed in Appendix II of the CITES agreement. This listing means that the species is not yet in danger of becoming extinct. However, this listing means the species is at the point where certain precautions need to be taken to ensure its survival.
The listing in CITES is intended to make sure that trade involving big-leaf mahogany is sustainable. Sustainable trade means that big-leaf mahogany could be used and traded without endangering its survival. This listing also helps to address illegal harvesting of big-leaf mahogany and unregulated trade of big-leaf mahogany.
To ensure that big-leaf mahogany harvesting is sustainable, scientists and land managers must know the conditions in which mahogany grows. The scientists in this study knew that the amount of sunlight big-leaf mahogany received was important for its growth. The scientists did not know, however, how the availability of nutrients in the soil and the amount of water received through rainfall affected big-leaf mahogany growth. Therefore, the scientists in this study wanted to examine how big-leaf mahogany responds to different amounts of rainfall and availability of nutrients in the soil.
Reflection Section
Methods
The scientists studied big-leaf mahogany in Central and South America. Specifically, scientists studied trees in the State of Quintana Roo, Yucatan, Mexico; and in the State of Para, Brazil (figure 6). Within each country’s site, leaf samples were taken from several areas.
At each of the sites and areas within the sites, the scientists collected mature, healthy big-leaf mahogany leaves (figure 7). These leaves were selected randomly from three to five trees at each area. When the leaves were taken off the tree, the scientists traced the leaf on paper to measure the area of the leaf.
The scientists then dried the leaves in an oven (figure 8). The scientists dried the leaves to remove water so that they could grind up the leaf samples and analyze them for different nutrients such as nitrogen, potassium, and calcium. The scientists also measured the weight of the leaves and gathered information about the amount of rainfall in each area.
At each of the sites and areas within the sites, the scientists collected three samples of the upper soil layer. The upper soil layer is 0 to 20 centimeters (cm) deep. The scientists used a soil corer to collect each soil sample (figure 9). The scientists collected these soil samples 50 cm away from the trunk of each tree.
Number Crunch
The soil samples were air dried, ground up, and passed through a 2 millimeter (mm) mesh sleeve (figure 10).
The scientists need particles to be 2 mm or smaller to be tested for nutrients. To do this nutrient testing, the scientists used a LECO® elemental analyzer and a spectrometer (figure 11).
The scientists measured the amount of nitrogen, potassium, and calcium in the leaves. The scientists then used computers to help them compare the amount of nutrients in the leaves with the amount of nutrients in the soil at the different sites and areas within the sites.
Reflection Section
Findings
The scientists found an average rainfall of 2,301 mm a year and an average temperature of 26 degrees Celsius in the Para, Brazil, location. In Quintana Roo, Mexico, the average rainfall was 1,290 mm a year and the average temperature was 26 degrees Celsius.
The scientists found that the leaves from the two sites were similar. However, Quintana Roo had one area with smaller leaf sizes. Additionally, the amount of organic matter in the Quintana Roo, Mexico, soils was 12 times higher than the amount of organic material in Para, Brazil’s soils.
The Quintana Roo soils had a higher average concentration of nitrogen, potassium, and calcium than Brazil soils. From previous scientific studies, the scientists knew that calcium played an important role in seedling growth and survival. Overall, the leaves ended up being very similar between the two areas.
Number Crunches
Reflection Section
Discussion
The scientists found that despite differences in the nutrients available in the soil and a differing amount of rainfall, the big-leaf mahogany leaves were similar regardless of location. This finding tells scientists that big-leaf mahogany may possibly be grown in a variety of locations with success. The scientists also noted the importance of calcium to seedling growth and survival. Therefore, soils with higher amounts of calcium would be beneficial to growing big-leaf mahogany. If big-leaf mahogany can be grown successfully in many locations, managers can feel more confident that the tree species can be sustainably harvested.
Reflection Section
This article is a part of our “Time Warp” series. Every article in this series explores a research topic that has been under scientific investigation for a long time. Read more about mahogany tree research completed in 1960 in the spotlight for this article.
Adapted from Medina, E.; Cuevas, E.; Lugo, A.E.; Terezo, E.; Jiménez Osornio, J.; Macario-Mendoza, P. A.; Montañez, Patricia. 2014. Conservative nutrient use by big-leaf mahogany (Swietenia macrophylla King) planted under contrasting environmental conditions. Revista Árvore. 38(3): 479-488.
Part Of
Standing On the Shoulders of Giants (Time Warp Monograph Series) Vol. 1 No. 13
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Glossary
View All Glossaryaccumulate
(ə kyü m(y)e lāt): To gather or pile up little by little; to increase in quantity, number, or amount.
analysis
(ǝ na lǝ sǝs): An examination of a whole to discover its elements and their relations.
appendix
(ə pen diks): (plural: appendixes or appendices) Additional material attached at the end of a piece of writing.
clarity
(kler ət ē): The quality or state of being clear or easily understood.
endangered
(in dān jǝrd): Threatened with extinction.
extinction
(ik stiŋk shən): The state of no longer existing.
fauna
(fȯ nə): Animal life, especially the animals characteristic of a region, period, or special environment.
flora
(flȯr ə): Plant, bacterial, or fungal life, especially such life characteristic of a region, period, or special environment.
hypothetical
(hī pə the ti kəl): (1) Imagined as an example for further thought; (2) assumed.
integral
(in ti grəl or in te grəl): (1) Needed for completeness; (2) lacking nothing essential.
karst
(kärst): An irregular limestone region with sinkholes, underground streams, and caverns.
longitudinal
(län jə tüd nəl): Involving the repeated observation of a set of subjects over time with respect to one or more study variables.
nutrient
(nü trē ǝnt): A substance or ingredient that promotes growth, provides energy, and maintains life.
organic
(ȯr ga nik): Of, relating to, or obtained from living things.
physiology
(fiz ē äl ə jē): A branch of biology dealing with the processes and activities by which life is carried on and which are special features of the functioning of living things, tissues, and cells.
prescribed fire
(pri skrībd fī ǝr): The controlled use of fire under specific weather conditions to restore health to an ecosystem that depends on fire; also known as a prescribed burn or controlled burn.
randomly
(ran dǝm lē): So that each possibility has a definite and especially an equal probability of occurring.
sample
(sam pəl): A small subset group, representative of the entire group.
spectrometer
(spek trä mə tər): An instrument that spreads particles or radiation into an ordered sequence (such as by mass or energy).
stable isotope
(stā bəl ī sə tōp): An isotope that shows no tendency to undergo radioactive decomposition.
sustainable
(sǝ stā nǝ bǝl): Of, relating to, or being a method of harvesting or using a resource so that the resource is not used up or permanently damaged.
unregulated
(ən re gyə lā təd): Not controlled.
vulnerable
(vəl n(ə-)rə bəl): Open to attack or damage.
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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 -
Ariel Lugo
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 -
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
Standards addressed in this Article:
Social Studies Standards
- Culture
- Global Connections
- Individuals, Groups, and Institutions
- People, Places, and Environments
- Science, Technology, and Society
- Time, Continuity, and Change
Note To Educators
The Forest Service's Mission
The Forest Service’s mission is to sustain the health, diversity, and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations. For more than 100 years, our motto has been “caring for the land and serving people.” The Forest Service, an agency of the U.S. Department of Agriculture (USDA), recognizes its responsibility to be engaged in efforts to connect youth to nature and to promote the development of science-based conservation education programs and materials nationwide.
What Is the Natural Inquirer?
Natural Inquirer is a science education resource journal to be used by students in grade 6 and up. Natural Inquirer contains articles describing environmental and natural resource research conducted by Forest Service scientists and their cooperators. These scientific journal articles have been reformatted to meet the needs of middle school students. The articles are easy to understand, are aesthetically pleasing to the eye, contain glossaries, and include hands-on activities. The goal of Natural Inquirer is to stimulate critical reading and thinking about scientific inquiry and investigation while teaching about ecology, the natural environment, and natural resources.
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Meet the Scientists
Introduces students to the scientists who did the research. This section may be used in a discussion about careers in science.
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What Kinds of Scientist Did This Research?
Introduces students to the scientific disciplines of the scientists who conducted the research.
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Thinking About Science
Introduces something new about the scientific process, such as a scientific habit of mind or procedures used in scientific studies.
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Thinking About the Environment
Introduces the environmental topic being addressed in the research.
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Introduction
Introduces the problem or question that the research addresses.
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Method
Describes the method the scientists used to collect and analyze their data.
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Findings & Discussion
Describes the results of the analysis. Addresses the findings and places them into the context of the original problem or question.
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Reflection Section
Presents questions aimed at stimulating critical thinking about what has been read or predicting what might be presented in the next section. These questions are placed at the end of each of the main article sections.
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Number Crunches
Presents an easy math problem related to the research.
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Glossary
Defines potentially new scientific or other terms to students. The first occurrence of a glossary word is bold in the text.
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Citation
Gives the original article citation with an internet link to the original article.
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FACTivity
Presents a hands-on activity that emphasizes something presented in the article.
Science Education Standards
You will find a listing of education standards which are addressed by each article at the back of each publication and on our website.
We Welcome Feedback
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Contact
Jessica Nickelsen
Director, Natural Inquirer program -
Email
Lessons
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This lesson plan provides students a structured way to compare, contrast, and combine information from two texts. It features a graphic organizer to assist students. This can be used with...Lesson Plan – Text to Text
This lesson plan provides students a structured way to compare, contrast, and combine information from two texts. It features a graphic organizer to assist students. This can be used with... -
This lesson plan encourages students to think about a particular research topic across time, including past, present, and future. Students will compare and contrast the historical research with a more...Lesson Plan – Time Warp Monograph Series
This lesson plan encourages students to think about a particular research topic across time, including past, present, and future. Students will compare and contrast the historical research with a more...
Education Files
Project Learning Tree
If you are a trained Project Learning Tree educator, you may use “Forest for the Trees” and “Soil Stories” as additional resources.
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Additional Resources
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USDA Forest Service: International Institute of Tropical Forestry
Visit WebsiteLearn more about the research taking place at IITF.
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USDA: "The Future of Mahogany"
Visit WebsiteRead a blog post on the future of the Mahogany Trees
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Convention on International Trade in Endangered Species of Wild Fauna and Flora: Bigleaf Mahogany
Visit WebsiteLearn more about the Bigleaf mahogany tree and what CITES has done to protect the tree.