| Passive optical and radar remote sensing have consistently failed to provide reliable estimates of biophysical properties describing canopy and stand structure, and consequently, have not met the data and information needs of forest, landscape, and global ecologists. Lidar remote sensing differs from all other remote sensing technologies in that it samples on a point-wise basis three-dimensional measurements of the surface of the earth and its features. As a result, lidar is capable of providing spatially explicit measurements of canopy height. The research presented in this thesis seeks to enhance our understanding of the application of airborne discrete return lidar for the estimation of canopy and stand structure.; Here, the capability of lidar to measure tree height and estimate various biophysical properties describing canopy and stand structure in deciduous forests is investigated. The biophysical properties considered included maximum tree height, Lorey's mean tree height, mean diameter at breast height, total basal area, canopy openness, effective plant area index, crown closure, aboveground biomass and volume, and stem density. Three lidar metrics were considered for model development and applied successfully for estimating canopy and stand structure.; Based on theories of plant allometry, a conceptual model is proposed that: (i) describes how vertical distributions of leaf area and lidar canopy height are related; and (ii) explains how certain lidar-based metrics are capable of estimating aboveground biomass. This model suggests that quantiles of lidar canopy height are equivalent with respect to predictive power, and that high sampling point densities are not required for estimating forest biophysical properties at the plot and stand level. To test this conceptual model, the following research issues are addressed in this thesis: (1) The equivalency of quantiles of lidar canopy height for estimation of aboveground biomass was examined for deciduous and coniferous forests. (2) Lidar canopy height and density metrics derived from two lidar surveys characterized by different sampling point densities for the same study site were compared.; Results from this research provide support for the conceptual model proposed and in turn, raise several questions for future research. |
