Estimating biophysical parameters of Persian oak coppice trees using UltraCam-D airborne imagery in Zagros semi-arid woodlands

• We measured biophysical parameters of Persian oaks on UltraCam-D imagery.
• UltraCam-D is a reliable data for vegetation assessment due to its high resolution.
• The stem per hectare of Persian oaks was estimated by Line Intercept Sampling.
• Crown diameter and area were efficiently estimated on the imagery.
• Stem attributes obtained from regression analysis were similar to the true values.

This study provides insight into the quantitative assessment of biophysical parameters of Persian oak coppice trees using UltraCam-D (UC-D) very high spatial resolution airborne orthoimagery in Zagros semi-arid woodlands, West Iran. We estimated the parameters across two methods: 1) direct quantification of tree density using line intercept sampling (LIS) method, tree height (TH) by shadow length, crown diameter (CD) by manual measurement, and crown area (CA) using support vector machine classifier, and 2) indirect quantification of diameter at root collar (DRC) and basal area (BA) by the allometric equations employing CD. The validation method consisted of taking field measurements of the parameters of a total of 162 coppice trees in a 30 ha study plot. The results of the validation assessment revealed the effective estimation of TH (R2 = 0.85 and RMSE of 1.00 m), CD (R2 = 0.92 and RMSE of 1.19 m), CA (R2 = 0.85 and RMSE of 16.39 m2), DRC (R2 = 0.87 and RMSE of 0.05 m), and BA (R2 = 0.82 and RMSE of 0.04 m2), when compared against the validation data. Hence, we show that UC-D data are a practical alternative to filed measurements for characterization of coppice tree biophysical parameters in semi-arid woodlands which can be applied for woodland planning and management.