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Seasonal response of California grassland NDVI to global change treatments.
Chiariello, Nona*,1, Field, Christopher2, 1 Stanford University, Stanford, CA2 Carnegie Institution of Washington, Stanford, CA
ABSTRACT- The Jasper Ridge Global Change Experiment studies the response of California grassland to four environmental factors changing globally—warming, nitrogen deposition, elevated carbon dioxide, and added precipitation—applied in a full-factorial design. Here we report the response of a vegetation "greenness" index, the normalized difference vegetation index (NDVI), to these treatments during four growing seasons. Treatments varied in the seasonal timing of their effects on NDVI and in the magnitude of their effects in different years. Warming primarily shifted the timing of NDVI, while nitrogen addition increased the maximum values. Elevated carbon dioxide depressed peak NDVI but sometimes prolonged canopy greenness as the season tapered. Watering effects varied among years. Treatments that increased NDVI early in the season tended to also increase biodiversity, while treatments that increased or decreased NDVI during the peak growing season tended to have corresponding effects on annual aboveground production.
Key words: elevated CO2, annual grassland, global change, NDVI