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?