Variation of leaf shape with tree size: a case study using Camptotheca acuminata Decne.

Area of Science:

• Botany
• Forestry
• Ecology

Background:

• The Montgomery equation (ME) models leaf area (A) as proportional to leaf length (L) and width (W), with the proportionality constant being the Montgomery parameter (MP).
• The influence of tree size, indicated by diameter at breast height (DBH), on leaf shape and the ME's MP remains under-explored.
• Understanding these relationships is crucial for accurate plant area estimations in ecological and forestry studies.

Purpose of the Study:

• To investigate the influence of tree size (DBH) on leaf shape indices and the Montgomery parameter (MP) in *Camptotheca acuminata*.
• To compare the accuracy of the standard Montgomery equation with a power-law allometric equation for estimating leaf area (A).
• To determine the validity of the ME for calculating leaf area at both individual tree and pooled data levels.

Main Methods:

• Collected 840 leaves from six *Camptotheca acuminata* trees of varying DBH.
• Measured leaf dimensions (L, W) and calculated three shape indices: W/L ratio, roundness index, and centroid ratio.
• Applied the standard Montgomery equation and a power-law equation (A ∝ (LW)α) to estimate leaf area (A) and analyzed the impact of DBH on the MP.

Main Results:

• Leaf shape, specifically the centroid ratio, showed a slight decrease with increasing DBH, suggesting more ovate leaves in larger trees.
• DBH did not significantly affect the W/L ratio or leaf roundness index.
• The estimated MP for pooled data was 0.6466 and was not significantly influenced by DBH. The power-law equation showed minimal improvement over the ME (percent error < 5%).

Conclusions:

• The Montgomery equation is a valid and reliable method for calculating leaf area (A) in *Camptotheca acuminata*, irrespective of tree size (DBH).
• The influence of DBH on the Montgomery parameter (MP) can be disregarded, simplifying leaf area estimation.
• The standard ME is sufficient, negating the need for more complex allometric models for leaf area calculations in this species.