Phenology

• Phenology is the study of living organisms’ response to seasonal and climatic changes in their environment.

• Seasonal changes include variations in day length or duration of sunlight, precipitation, and temperature.

Phenology

• Plant growing season generally corresponds to the period between green-up and green-down.

• Growing season directly related to global carbon fixation and the amount of CO2 in the atmosphere.

• Timing of green-up and green-down is important for understanding the global water cycle.– As plants photosynthesize, they also transpire water

from the soil into the atmosphere

Phenology

• Green-up and green-down data are used to examine:– regional and global vegetation patterns– year-to-year trends– vegetation responses to climate change– wild fire danger– animal migrations

Phenology

• Why Take Phenology Measurements– Estimates of greenness values from remote

sensing data vary because of problems from atmospheric properties, sun angle, aging of satellite detectors.

– GLOBE ground-based observations will help scientists validate estimates of growing seasons.

Phenology

• Green-Up and Green-Down Site Selection– Select native trees, shrubs or grasses.– Avoid sites near buildings or where watering or

fertilization is done.– Select accessible sites.

Phenology

• Green-Up and Green-Down Site Selection– Select deciduous trees, shrubs or grasses.

– Choose dominant over-story species. Green-up and green-down data from satellites affected mostly by these dominant species.

– If over-story plants are evergreen conifers, use under-story broadleaf shrubs.

– Try to use the same plants for green-up and green-down.

Phenology

• Green-Up and Green-Down Site Selection– If possible, choose a location close to the Atmosphere

and Soil Moisture Study Sites.

– Local topography can cause weather to vary even within short distances.

– Keep the horizontal distance between Phenology and Atmosphere and Soil Moisture Study Sites less than 2 kilometers.

– Keep the elevation difference less than 100 meters.

Phenology

• When are green-up observations made?– Twice weekly, starting at least two weeks

before initial budburst until leaf length stops increasing.

– Check with local sources for average green-updates to start observations.

Phenology

• When are green-down observations made?– Twice weekly, starting two weeks before initial

green-down until leaf color change is complete or leaves fall off.

– Check with local sources for average green-updates to start observations.