Seasons: The Global Plant Waves

Personnel

Dave Verbyla, Associate Professor
Department of Forest Sciences
School of Natural Resources and Agricultural Sciences
University of Alaska Fairbanks
Email: dverbyla@lter.uaf.edu

Elena Sparrow, Associate Professor
Department of Plant, Animal, and Soil Sciences
School of Natural Resources and Agricultural Sciences
University of Alaska Fairbanks
Email: ffebs@uaf.edu

Leslie Gordon, Science Education Specialist
Fairbanks North Star School System
Email: lgordon@northstar.k12.ak.us

Heather Goldman, Graduate Research Assistant
School of Natural Resources and Agricultural Sciences
University of Alaska Fairbanks
Email: goldman@salrm.uaf.edu

Teaching:

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Teaching References

WWW Links:

Alberta Plantwatch

Global Phenological Monitoring

Global Phenology Networks

Eastern North America Phenology Network

UK Phenology Network

Photosynthesis Center

Research:

Estimating Growing Season From Satellite Data

Every year a wave can be seen from outer space...the wave of greenup where conditions stimulate new plant growth. In other areas of the globe a simultaneous wave of greendown or senescense occurs as conditions for plant growth decline.

Greenup example from Alaska

With global climate change, the period between greenup and senescence known as the growing season may change. For example, Ranga Myneni and his colleagues published a paper last spring claiming that growing season has increased in northern latitudes by eight days since the early 1980s.

Increased Growing Season From Satellite Estimates

Is the growing season really increasing in length?

What is really needed are on-the-ground observations of plant greenup and senescence.

Another need for on-the-ground observations is to determine the appropriate satellite remote sensing greenness values that really represents greenup and senescense. Satellite remote sensing around the globe records a greenness index called the Normalized Difference Vegetation Index. This greenness index is typically scaled from less than 100 for unvegetated areas, to a maximum of 200 for areas with extremely high leaf areas.

What is the appropriate greenness value representing the growing season?
For example, for the rain forest near Sitka, Alaska, what is the appropriate value representing spring greenup and fall senescence?

From the above figure, a greenness value of 125 would seem to be an appropriate threshold value representing the plant growing season. The problem is each biome will have a different appropriate greenness threshold value. For example, here is the satellite greenness index from the coastal tundra near Barrow, Alaska.

Obviously, the greenness threshold of 125 from the coastal forest would not apply to the arctic coast region...

What is really needed are on-the-ground observations of plant greenup and senescence.

The observations should be:

Taken at least twice a week.

Taken across broad regions of the globe.

Taken using consistent protocols.

We are currently developing protocols for such observations through the GLOBE program. The GLOBE program has already started a spring budburst protocol which is a good start.

See Budburst Protocol

We will build on the spring budburst protocol to include protocols for non-broadleaf biomes and for senescense. We also will be developing learning activities centered on plant phenology. Stay tuned as this page develops.

Last modified 16 March 2004 by Joy Clein

email: dverbyla@merlin.salrm.uaf.edu