Digital cover photography for estimating leaf area index (LAI) in apple trees using a variable light extinction...

Area of Science:

• Agricultural Science
• Forestry
• Remote Sensing

Background:

• Leaf Area Index (LAI) is crucial for crop modeling and understanding plant physiology.
• Traditional LAI measurement methods for orchards are labor-intensive and prone to errors.
• Existing devices for LAI estimation often require difficult site-specific calibrations.

Purpose of the Study:

• To evaluate a modified digital cover photography technique for estimating apple tree LAI.
• To compare the accuracy of this method with destructive LAI measurements.
• To optimize the method by investigating different approaches for the light extinction coefficient (k).

Main Methods:

• Utilized conventional digital photography to capture canopy images.
• Measured incident (Io) and transmitted (I) radiation through the apple tree canopies.
• Destructively measured leaf area for 40 apple trees to obtain ground-truth LAI (LAI(D)).
• Compared destructive LAI with estimates from the modified digital photography method (LAI(M)).

Main Results:

• The digital photography method estimated LAI(D) with a 25% error using a constant k (0.68).
• Estimating k using foliage cover fraction (f(f)) reduced the error to 18%.
• Using light intercepted by the canopy (Ic) as a proxy for k achieved the lowest error of 9%.

Conclusions:

• The modified digital photography method offers a viable alternative for estimating apple tree LAI.
• Incorporating canopy light interception measurements significantly enhances the accuracy of LAI estimation.
• This approach provides a more precise and efficient tool for orchard management and research.