Exploring the relationship between reflectance red edge and chlorophyll content in slash pine

Area of Science:

• Forestry
• Remote Sensing
• Plant Physiology

Background:

• Chlorophyll content is a crucial indicator of forest health.
• Estimating canopy chlorophyll non-destructively is challenging due to spatial and temporal variability.
• Vegetation reflectance spectra exhibit a 'red edge' feature related to chlorophyll concentration.

Purpose of the Study:

• To assess the utility of the red edge spectral feature for estimating chlorophyll content in slash pine.
• To compare the accuracy of red edge measurements with traditional destructive sampling methods.
• To investigate the influence of canopy cover and understory on red edge-based chlorophyll estimation.

Main Methods:

• Spectroradiometer measurements of the red edge position on individual pine branches and whole canopies.
• Calibration of red edge measurements against laboratory chlorophyll content analysis.
• Spectral mixture modeling to analyze the influence of understory and forest floor reflectance.

Main Results:

• A strong linear relationship (R² = 0.91) was found between the red edge and chlorophyll content for individual branches.
• Red edge estimation of branch chlorophyll content was more accurate than calorimetric methods.
• No significant relationship was observed between the red edge and chlorophyll content for whole canopies, attributed to understory effects.

Conclusions:

• The red edge is a reliable indicator for estimating chlorophyll content at the branch level in slash pine.
• Estimating canopy-level chlorophyll content using the red edge is problematic unless canopy cover is dense.
• Further research may involve refining spectral mixture models to account for understory influences in canopy-level estimations.