A Model for Estimating Total Forest Coverage with Ground-Based Digital Photography

Vegetation fractional coverage （VFC） is one of the key indicators of vegetation distribution. In the work a measurementbased model was developed to derive total forest VFC （TG） as well as the VFC of trees （T） and shrub-grasses （G） separately in a subtropical forest area in Nanjing, China. Both upward and downward photographs were taken with a digital camera in 72 quadrats （10 m × 10 m each）. Fifteen models were established and validated. Models jointly using both T and G performed better than those using the T and G separately. The best model, TG = T ＋ G - 1.134× T × G - 0.025 （R2= 0.9115, P 〈 0.01, root mean squared error = 0.0789）, is recommended for application. This model provides a good way to obtain total forest VFC values through taking tree and shrub-grass photos on ground below tree canopy rather than above tree canopy.