The Hubbard Brook watershed deforestation experiment

Why is the transfer of energy in an ecosystem referred to as energy flow, not energy cycling?

You are studying nitrogen cycling on the Serengeti Plain in Africa. During your experiment, a herd of migrating wildebeests grazes through your study plot. What would you need to know to measure their effect on nitrogen balance in the plot?

Review the discussion of the second law of thermodynamics in Concept 8.1 (p. 144). How does this physical law explain why an ecosystems energy supply must be continually replenished?

Based on the second law of thermodynamics, would you expect the typical biomass of primary producers in an ecosystem to be greater than or less than the biomass of secondary producers in the same ecosystem? Explain your reasoning.

Why is only a small portion of the solar energy that strikes Earths atmosphere stored by primary producers?

How can ecologists experimentally determine the factor that limits primary production in an ecosystem?

Concept 10.3 (pp. 198199) describes the Calvin cycle of photosynthesis. Explain how nitrogen and phosphorus, the nutrients that most often limit primary production, are necessary for the Calvin cycle to function.

What additional variable do you need to know the value of in order to estimate NEP from NPP? Why might measuring this variable be difficult, for instance, in a sample of ocean water?

If an insect that eats plant seeds containing 100 J of energy uses 30 J of that energy for respiration and excretes 50 J in its feces, what is the insects net secondary production? What is its production efficiency?

Tobacco leaves contain nicotine, a poisonous compound that is energetically expensive for the plant to make. What advantage might the plant gain by using some of its resources to produce nicotine?

Figure 40.20 describes relative energy budgets for four animals. What are some ways in which the energy expenditures of the caterpillar described in Figure 55.10 would differ from the woman pictured in Figure 40.20?

Why would a long-distance runner typically have a lower production efficiency than a more sedentary person?

For each of the four biogeochemical cycles detailed in Figure 55.14, draw a simple diagram that shows one possible path for an atom of that chemical from abiotic to biotic reservoirs and back.

Why does deforestation of a watershed increase the concentration of nitrates in streams draining the watershed?

Why is nutrient availability in a tropical rain forest particularly vulnerable to logging?

If decomposers usually grow faster and decompose material more quickly in warmer ecosystems, why is decomposition in hot deserts so slow?

Identify the main goal of restoration ecology

How do bioremediation and biological augmentation differ?

In what way is the Kissimmee River project a more complete ecological restoration than the Maungatautari project (see Figure 55.19)?

In preparing a site for surface mining and later restoration, what would be the advantage of removing the shallow topsoil first and setting it aside separately from the deeper soil, rather than removing all soil at once and mixing it in a single pile?

Which of the following organisms is incorrectly paired with its trophic level? a. cyanobacteriumprimary producer b. grasshopperprimary consumer c. zooplanktonprimary producer d. eagletertiary consumer e. fungusdetritivore

Which of these ecosystems has the lowest net primary production per square meter? a. a salt marsh d. a grassland b. an open ocean e. a tropical rain forest c. a coral reef

The discipline that applies ecological principles to returning degraded ecosystems to a more natural state is known as a. population viability analysis. d. restoration ecology. b. landscape ecology. e. resource conservation. c. conservation ecology

Nitrifying bacteria participate in the nitrogen cycle mainly by a. converting nitrogen gas to ammonia. b. releasing ammonium from organic compounds, thus returning it to the soil. c. converting ammonia to nitrogen gas, which returns to the atmosphere. d. converting ammonium to nitrate, which plants absorb. e. incorporating nitrogen into amino acids and organic compounds

Which of the following has the greatest effect on the rate of chemical cycling in an ecosystem? a. the ecosystems rate of primary production b. the production efficiency of the ecosystems consumers c. the rate of decomposition in the ecosystem d. the trophic efficiency of the ecosystem e. the location of the nutrient reservoirs in the ecosystem

The Hubbard Brook watershed deforestation experiment yielded all of the following results except: a. Most minerals were recycled within a forest ecosystem. b. The flow of minerals out of a natural watershed was offset by minerals flowing in. c. Deforestation increased water runoff. d. The nitrate concentration in waters draining the deforested area became dangerously high. e. Calcium levels remained high in the soil of deforested areas.

Which of the following would be considered an example of bioremediation? a. adding nitrogen-fixing microorganisms to a degraded ecosystem to increase nitrogen availability b. using a bulldozer to regrade a strip mine c. dredging a river bottom to remove contaminated sediments d. reconfiguring the channel of a river e. adding seeds of a chromium-accumulating plant to soil contaminated by chromium

If you applied a fungicide to a cornfield, what would you expect to happen to the rate of decomposition and net ecosystem production (NEP)? a. Both decomposition rate and NEP would decrease. b. Both decomposition rate and NEP would increase. c. Neither would change. d. Decomposition rate would increase and NEP would decrease. e. Decomposition rate would decrease and NEP would increase.

Draw a simplified global water cycle showing ocean, land, atmosphere, and runoff from the land to the ocean. Add these annual water fluxes to the figure: ocean evaporation, 425 km3 ; ocean evaporation that returns to the ocean as precipitation, 385 km3 ; ocean evaporation that falls as precipitation on land, 40 km3 ; evapotranspiration from plants and soil that falls as precipitation on land, 70 km3 ; runoff to the oceans, 40 km3 . Based on these global numbers, how much precipitation falls on land in a typical year?

Some biologists have suggested that ecosystems are emergent, living systems capable of evolving. One manifestation of this idea is environmentalist James Lovelocks Gaia hypothesis, which views Earth itself as a living, homeostatic entitya kind of superorganism. If ecosystems are capable of evolving, would this be a form of Darwinian evolution? Why or why not?

Using two neighboring ponds in a forest as your study site, design a controlled experiment to measure the effect of falling leaves on net primary production in a pond.

As described in Concept 55.4, decomposition typically occurs quickly in moist tropical forests. However, waterlogging in the soil of some moist tropical forests results in a buildup of organic matter (peat; see Figure 29.11) over time. In a short essay (100150 words), discuss the relationship of net primary production, net ecosystem production, and decomposition for such an ecosystem. Are NPP and NEP likely to be positive? What do you think would happen to NEP if a landowner drained the water from a tropical peatland, exposing the organic matter to air?