Question 1

Refer to the figure.
 
-Which statement best explains the downward trend that follows the peak of each curve?

Accepted Answer

The downward trend after the peak suggests that too much water reduces oxygen availability, which is necessary for optimal decomposition rates.

Question 2

Refer to the figure.

- Which statement is supported by the figure?

Accepted Answer

The answer of Refer to the figure.

- Which statement is...

Question 3

Decomposition of organic matter with a C:N ratio _______ than 25:1 (the optimal ratio for microbial growth) would result in a net release of nutrients into the soil. The reason is that microbial growth in this situation would be more limited by the _______ supply than by the _______ supply.

Accepted Answer

Microbial growth would be more limited by the nitrogen supply than by the carbon dioxide supply.

Question 4

Some slow-growing trees have leaves that are high in lignin. The most likely advantage of lignin to such trees is that lignin

Accepted Answer

Lignin slows the rate of decomposition, which reduces soil fertility. This can be advantageous for slow-growing trees as it reduces competition from fast-growing plants that require more nutrients.

Question 5

Nitrification by certain chemoautotrophic bacteria occurs in _______ conditions; this process, therefore, occurs primarily in _______ environments.

Accepted Answer

Nitrification is an aerobic process carried out by chemoautotrophic bacteria, and it primarily occurs in terrestrial environments where oxygen is available.

Question 6

Suppose two agents are introduced into soil: one that results in an increase in nitrification and another that results in an equal addition of denitrification. Compared to the soil before, the combination of equal amounts of nitrification and denitrification in the soil would result in a net increase in

Accepted Answer

Nitrification converts ammonium to nitrate, while denitrification converts nitrate to nitrogen gases, including nitrous oxide. The net effect of equal nitrification and denitrification would be the production of nitrous oxide as a byproduct of denitrification.

Question 7

By a process known as _______, certain chemoautotrophic bacteria transform ammonia and ammonium into _______, which tends to be more available to plants than other forms of nitrogen.

Accepted Answer

Nitrification is the process by which chemoautotrophic bacteria convert ammonia and ammonium into nitrate, which is more readily absorbed by plants.

Question 8

According to measurements taken in the 1990s, the levels of inorganic nitrogen in Arctic ecosystems were substantially lower than the amount of nitrogen actually taken up by plants. Which of the following is a possible explanation for this pattern?

Accepted Answer

Microbes in the Arctic soil transform inorganic nitrogen into organic forms, which can then be taken up by plants.

Question 9

Which of the following is one example of the ways in which Arctic plant communities have avoided competition through resource partitioning?

Accepted Answer

Different Arctic plant species take up nitrogen at different depths of the soil, which allows them to avoid direct competition for the same resources by utilizing different parts of the soil profile.

Question 10

Which statement about color change during leaf senescence is false?

Accepted Answer

The plant reabsorbs a much higher percentage of nitrogen (60-70%) from the leaves, not just 5-10%.

Question 11

Which statement best describes the order of the nitrogen cycle?

Accepted Answer

The answer of Which statement best describes the order of...

Question 12

Refer to the table.
 In a series of experiments, a researcher repeatedly measures the mean resident time for phosphate to be approximately 6 years. What ecosystem type is the researcher studying?

Accepted Answer

The answer of Refer to the table.
 In a series...

Question 13

Suppose that the mean residence time of nitrogen in a section of soil is 3.5 years, and the mean rate of input is 150 kilograms per year. If rates of input and output as well as the total pool size have remained roughly constant, what is the expected size of the total pool of nitrogen in that soil?

Accepted Answer

The total pool size can be calculated by multiplying the mean residence time by the mean rate of input: 3.5 years * 150 kg/year = 525 kg.

Question 14

What would be the mean residence time of phosphorus in a pond if the total pool is 1,250 grams and the mean rate of input is 2,500 grams? (Assume that rates of input, output, and the total pool size have remained constant.)

Accepted Answer

Mean residence time = Total pool size / Mean rate of input= 1,250 grams / 2,500 grams per year= 0.5 years= 6 months

Question 15

Which ecosystems have the slowest turnover rates of elements (the greatest mean residence times)?

Accepted Answer

Boreal forests have large nutrient pools and low rates of litter input, leading to slow turnover rates and long mean residence times for elements.

Question 16

The residence times of nutrients in the soils of boreal forests are influenced the most by the

Accepted Answer

In boreal forests, the cold temperatures and presence of secondary compounds slow down decomposition rates, affecting nutrient residence times in the soil.

Question 17

Refer to the figure.
 Which figure best illustrates the relationship between temperature and primary productivity and temperature and rates of decomposition?

Accepted Answer

The answer of Refer to the figure.
 Which figure best...

Question 18

When studying terrestrial ecosystems, ecologists commonly focus on an area that is drained by a single stream, which is called a(n)

Accepted Answer

A catchment is an area of land where all precipitation collects and drains off into a common outlet, such as a single stream.

Question 19

Of nitrogen and phosphorus, which is the most limiting nutrient to primary production early in primary succession, and why?

Accepted Answer

Nitrogen is often the most limiting nutrient early in primary succession because it takes a long time to accumulate in the soil through processes like nitrogen fixation and decomposition of organic matter.

Question 20

What is the input of calcium into a catchment if the flow of water into the catchment is 150 liters per day and the concentration of calcium is 0.04 mg/liter?

Accepted Answer

The answer of What is the input of calcium into...

Quiz 22: Nutrient Supply and Cycling

Refer to the figure. -Which statement best explains the downward trend that follows the peak of each curve?

Refer to the figure. - Which statement is supported by the figure?

Decomposition of organic matter with a C:N ratio ___ than 25:1 (the optimal ratio for microbial growth) would result in a net release of nutrients into the soil. The reason is that microbial growth in this situation would be more limited by the _ supply than by the _____ supply.

Some slow-growing trees have leaves that are high in lignin. The most likely advantage of lignin to such trees is that lignin

Nitrification by certain chemoautotrophic bacteria occurs in _ conditions; this process, therefore, occurs primarily in _ environments.

By a process known as _, certain chemoautotrophic bacteria transform ammonia and ammonium into _, which tends to be more available to plants than other forms of nitrogen.