Reading Questions
Vitousek and Reiners (1975): Ecosystem succession and nutrient retention: a hypothesis.
1. What is the specific hypothesis that the authors are testing?
a. As an ecosystem ages/matures its ability to retain nutrients increases.
2. The authors refer to ecosystems being open systems. In your own words, what does
mean? Give an example (not necessarily from the paper) of an ecosystem input and
of an ecosystem output.
a. Answers will vary slightly. Basically, ecosystems are not closed. Rather
ecosystems receive inputs of energy while also having a systems of outputs by
which energy and nutrients leave the ecosystem. Typically, such a system has a
series of transformation that occur before the energy and nutrients exit through the
output mechanisms.
b. Input: Photosynthesis; Output: Denitrification
3. (A) What is biological succession? (B) According to your definition, how does the
concept of ecosystem succession as used by Vitousek and Reiners compare?
a. The process by which the structure of a biological community changes over time.
b. Answers will vary.
4. What is one of the dangers of clear cutting a forest as mention by Vitousek and
Reiners?
a. Rapid loss of nutrients from the soil since there is no incorporation of nutrients
into biomass of the forest.
5. In your own words summarize Figure 1a with respect to time/forest maturity and
nutrient retention. What would a major disturbance like forest fire do to the
placement of an ecosystem on this figure?
a. Answers will vary but should highlight the initial lag, then rapid increase, and
subsequent decline in nutrient retention.
b. A major disturbance like forest fire “resets the clock.” There will be a major loss
of nutrients initially follow up an increase in nutrient retention as the forest begins
to recover and mature.
6. What does the stream nitrate data suggest about the relationship of forest age and
nutrient retention?
a. As a forest ages its ability to retain nutrients begins to decrease as older forests
slow growth rates and biomass accumulation. Excess nutrients now begin
building up in the soils and are lost to local streams via groundwater and/or
runoff.
7. Using the framework of the Vitousek and Reiners’ paper, offer an ecosystem
management solution to limiting the loss of nutrients from forested ecosystems
which may be contributing to eutrophication of downstream aquatic ecosystems.
a. Answer will vary but likely will touch upon the concept of a managing for a
mosaic of successional time-points across the landscape.