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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 understory broadleaf shrubs. – Try to use the same plants for green-up and greendown. 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 greenupdates 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 greenupdates to start observations.