Global Water and Nitrogen Cycles
Take home message:
“Element cycles are interrelated – you can’t understand them in isolation.”
Main Terms:
Evaporation, Transpiration, and Evapotranspiration
N-fixation, denitrification, mineralization (= decomposition), nitrification
Base saturation
Buffering capacity
Concepts — Water Cycle:
- Why is the water cycle important?
- Accounting of water on earth — what are the major reservoirs for water?
- If a water reservoir on earth has a small or large amount of water in it, does it mean that it is more or less important to life on earth?
- What are the four major pathways for water cycling between the reservoirs?
- What is the residence time of water in each of the reservoirs? Which reservoir has the longest residence time? (Consult your lab exercise.)
- Be able to calculate residence time given the proper information.
- What are the major controls on the water cycle, and how do each of these controls affect the water cycle?
Concepts — Nitrogen Cycle:
- What are the different forms of nitrogen? Do these forms make the nitrogen cycle more or less complicated than the water cycle?
- Accounting of nitrogen on earth — what are the major reservoirs for nitrogen?
- What are the pathways and reactions that transfer nitrogen (generally)?
- What is the residence time of nitrogen in the atmosphere? Which is more reactive, N2 vs. NOX?
- Understand how element “reactivity” is related to residence time and the size of reservoir.
- What are the controls on nitrogen that are related directly to acid rain?
- How does acid rain affect nutrient cycling and rock weathering?
- What effect does acid rain have on trees and other plants?
- How is buffering capacity of the soils related to the effects of acid rain?