Scaling of total leaf area per culm with the product of a representative leaf length and the sum of leaf widths in a few-leaved bamboo: which leaf length metric works best?

Total leaf area per culm (AT) is a key functional trait influencing light interception and carbon gain in graminoid species with few leaves per culm. The Montgomery–Koyama–Smith equation (MKSE) assumes a proportional relationship between AT and the product of maximum leaf length (Lmax) and the sum of leaf widths (ΣWi). However, whether different leaf length (Lx) metrics, together with the sum of leaf widths, can reliably calculate AT using this isometric relationship remains unclear. We measured individual area, length, and width of all laminae from 241 Pleioblastus viridistriatus culms with 4–7 leaves per culm. We tested four leaf length metrics: maximum leaf length (Lmax), minimum leaf length (Lmin), mean leaf length (Lmean), and the length of a randomly selected leaf from the two largest leaves per culm (Lran). We also tested the power‑law form AT ∝ (Lx ΣWi)α for each. To evaluate the robustness of Lran, we performed 2000 simulations; all RMSEs were below 0.05, and most 95% confidence intervals of α included unity, validating isometry. The accuracy ranking (based on RMSE) was Lmean > Lmax > Lran > Lmin. The MKSE is thus validated for calculating AT of P. viridistriatus, and Lmax can be replaced by a more convenient measure without significant loss of accuracy, enabling rapid non‑destructive estimation of total leaf area for population surveys of P. viridistriatus and similar few‑leaved dwarf bamboos.