ACCLIMATE Normalized Difference Vegetation Index

Graphs

Red dots indicate 2025 data while the boxes indicate previous years data.

Points indicate monthly mean Normalized Difference Vegetation Index (NDVI) for each year. Lines indicate the long term linear trend.

Summary Points

• What is it: NDVI (Normalized Difference Vegetation Index) is a measurement taken from different bands of light to capture green wavelengths that are only observed in life. NDVI values fall -1 and +1. $$\text{NDVI} = \frac{\text{(Near-Infrared Light - Red Light Reflectance)}}{\text{(Near-Infrared Light + Red Light Reflectance)}}$$
• Non-Scientific name: Plant Greenness
• Why do we measure it:By measuring plant greenness, we can evaluate plant growth and health.
• How was it measured: NDVI is measured through capturing photos with a specialized camera, which is useful for small-scale NDVI measurements captured between plots at our sites. These photos are then processed through measurement of the light bands within the photo. In the field, NDVI can only be captured during peak hours between 11am and 3pm when the sun is at its highest. A photo captured from an NDVI camera is presented below.
• Long term trends:
• High and low trends: Low trends observed in control plots and in earlier years of the experiment. High trends were observed in warmed plots and in later years of the experiment. This indicates that plants are greening up.
• What happened in 2025: 2025 had higher NDVI values in June, July, and August than previous years. However, peak NDVI values were similar to previous years with high NDVI values. There were also more NDVI values taken to catalog plant greenness across the growing season.
• Where is this science going?:As shown in the figures, plant greenness will likely increase with warming temperatures allowing for more plant growth in the future. Capturing peak NDVI values and dates may also help with cataloging any growing season changes within the environment. Overall, plant greenness influences the ecosystem’s functionality.

Images

This is an NDVI photo taken at the Warming experiment site. The camera only captures the bands of light needed to calculate greenness, which is why the image is overall red. The gray box in the middle is the representative part taken, which has to be perfectly square, for processing.

Ariella Thompson takes NDVI photos with the specialized camera during the field season of 2024 at the Warming experiment site.