Using small-footprint, discrete return LiDAR to obtain stand level age of loblolly pine in central Virginia, USA

The objective of this study was to evaluate the utility of small-footprint discrete return LiDAR for determining loblolly pine stand age. The study area was in the Appomattox-Buckingham State Forest, Virginia, USA. LiDAR data were acquired in 2008 using an Optech ALTM 3100. A stratified random sampling approach was used to select over 200 circular plots (15 m radius) with ages (the dependent variable) varying from 5 to 71 years old. LiDAR-derived independent variables were obtained using metrics computed from normalized point densities, heights (above ground) and intensities. The three best models have only one to two variables, as follows: 100th percentile of height alone (adjusted R2 = 88.3%, RMSE = 1.2 years), 100th percentile of height along with the variance of intensity (adjusted R2 = 90.8%, RMSE = 1.17 years), and the 99.5th percentile along with the density of points between the 20th and 40th percentiles (adjusted R2 = 90.6%, RMSE = 1.17 years). These results show that small-footprint, discrete return LiDAR can be used to estimate plot level age of loblolly pine stands - and may, by inference, be used to establish indices of site quality if age is known.