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Ch. 53 - Ecosystems and Global Ecology
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
Chapter 53, Problem 13

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth.
Researchers have measured the effects of periodic forest fires on primary productivity in Amazon rain forest plots, comparing years with average precipitation and years with severe drought. Propose which controls would be necessary for such studies.

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1
Identify the variables: Determine the independent variable (e.g., presence or absence of forest fires) and the dependent variable (e.g., primary productivity of the forest).
Establish control plots: Set up control plots in the Amazon rainforest that are not affected by forest fires to serve as a baseline for comparison.
Ensure consistent conditions: Make sure that the control plots and experimental plots have similar conditions such as soil type, elevation, and species composition to isolate the effect of forest fires.
Monitor environmental factors: Record other environmental factors such as temperature, humidity, and precipitation in both control and experimental plots to account for their influence on primary productivity.
Use temporal controls: Compare data from years with average precipitation to years with severe drought to understand the interaction between forest fires and climate conditions on primary productivity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Primary Productivity

Primary productivity refers to the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances. In ecosystems like the Amazon rainforest, it is crucial for understanding how energy flows and supports biodiversity. Measuring changes in primary productivity can reveal impacts of environmental stressors like drought and forest fires.
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Deforestation

Deforestation involves the large-scale removal of trees, which can drastically alter ecosystems by reducing biodiversity, disrupting water cycles, and increasing carbon emissions. In the context of the Amazon rainforest, deforestation can exacerbate the effects of climate change and natural disturbances, making it a critical factor to control in studies assessing ecosystem productivity.
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Experimental Controls

Experimental controls are essential for isolating the effects of specific variables in scientific studies. In the context of studying the Amazon rainforest, controls might include plots with no fire exposure, consistent precipitation levels, and undisturbed areas to compare against affected plots. These controls help ensure that observed changes in productivity are due to the variables being tested, such as drought or fire.
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Related Practice
Textbook Question

During the Carboniferous period, plant growth was extensive but rates of decomposition slowed (probably due to the formation of vast, oxygen-poor swamp habitats). As a result, large amounts of biomass accumulated in terrestrial environments (much of this biomass is now coal). The fossil record indicates that atmospheric oxygen increased, atmospheric carbon dioxide decreased, and global temperatures dropped. Explain why.

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Textbook Question

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth.

Which of the following biomes typically has the highest net primary productivity?

a. Temperate forest

b. Tropical dry forest

c. Tropical grassland

d. Tropical wet forest

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Textbook Question

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth.

Select True or False for each statement about the effects of clear-cutting on the Amazon rain forest, then explain your reasoning.

T/F Nutrient export is likely to decline.

T/F Atmospheric CO2 is likely to decline.

T/F Soil moisture is likely to decline.

T/F Species diversity is likely to decline.

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Textbook Question

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth.

This box-and-arrow model summarizes some of the feedback links observed in the Amazon rain forest. Select True or False for the statements that follow, based on whether they are represented by the model. (Note that the boxes and arrows in this model are used differently than those in the nutrient cycle models).

T/F The burning of fossil fuels increases atmospheric CO2.

T/F Tree growth reduces atmospheric CO2.

T/F The death of trees promotes the invasion of grasses.

T/F An increase in CO2 increases the frequency of droughts.

T/F Drought increases the frequency of forest fires.

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Textbook Question

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth.

Many studies have raised the concern that positive feedback loops among numerous variables in the Amazon will cause an ecosystem tipping point—a rapid and irreversible transition from forest to grassland. Use the model in Question 14 as a tool to summarize a possible sequence of effects that could cause a transition from forest to grassland.

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Textbook Question

Scientists around the world are collaborating to understand how deforestation, climate change, and natural processes will interact to affect one of the most productive and biodiverse ecosystems on Earth. Journalists must be concise when reporting science news. Why might journalists and the public struggle to understand and discuss ecosystems ecology and global warming?

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