Net Primary Productivity
Plants play an important role in Earth’s carbon dioxide budget. Plants take in carbon dioxide via photosynthesis during the day and give off carbon dioxide via respiration at night. The difference between carbon uptake and release by plants is the net primary production. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite monitors this carbon dioxide use.
Go to http://earthobservatory.nasa.gov ; under “Global Maps,” select the “Net Primary Productivity” map. (Page through the map options.)
- What do negative net primary productivity values mean?
- The map is missing data in northern Africa. Would you expect the net primary productivity to be high or low there? Why?
Use the arrows that accompany the map to play the animation.
- The northern half of South America has high positive net primary productivity year round. Why?
- In the United States, the net primary productivity is lower in the Southwest than in the Northeast year round. Why?
Click on the “Vegetation” link. Play the vegetation animation.
- What is displayed on the vegetation map? What factors control this?
- In which months are vegetation values high but net primary productivity is near or below zero in the United States? What season(s) is this in the Northern Hemisphere?
- What does this indicate about the relationship between net primary productivity and day length? Net primary productivity and temperature?
- Look at the winter months in the Southern Hemisphere. Day length is comparable to those in the Northern Hemisphere winter. What factor helps moderate temperatures in the Southern Hemisphere?
Go to NOAA’s Earth System Research Laboratory at www.esrl.noaa.gov/gmd/ccgg/trends to see Trends in Atmospheric Carbon Dioxide.
- How do monthly mean CO2 concentrations change over the course of one year at Mauna Loa Observatory in Hawai’i? Explain this pattern.