Abstract
Abstract Airborne lidar (light detecting and ranging) is a useful tool for probing the structure of forest canopies. Such information is not readily available from other remote sensing methods and is essential for modern forest inventories. In this study, small-footprint lidar data were used to estimate biophysical properties of young, mature, and old cottonwood trees in the San Pedro River basin near Benson, Arizona. The lidar data were acquired in June 2004, using Optech’s 1233 ALTM during flyovers conducted at an altitude of 600 m. Canopy height, crown diameter, stem dbh, canopy cover, and mean intensity of return laser pulses from the canopy surface were estimated for the cottonwood trees from the data. Linear regression models were used to develop equations relating lidar-derived tree characteristics with corresponding field acquired data for each age class of cottonwoods. The lidar estimates show a good degree of correlation with ground-based measurements. This study also shows that other parameters of young, mature, and old cottonwood trees such as height and canopy cover, when derived from lidar, are significantly different (P < 0.05). Additionally, mean crown diameters of mature and young trees are not statistically different at the study site (P = 0.31). The results illustrate the potential of airborne lidar data to differentiate different age classes of cottonwood trees for riparian areas quickly and quantitatively. West. J. Appl. For. 21(3):149–158.
Highlights
Vegetation patterns and associated canopy structure influence landscape functions such as water use, biomass production, and energy cycles
In previous studies, regression models for developing equations relating lidar-derived variables with corresponding field inventory data were used to differentiate between different forest types; but in this study, these models are used to differentiate between different ages of one forest type
The scatterplots comparing lidar-derived and field-measured crown diameter for each age class of cottonwood trees are presented in Figure 4, d–f
Summary
Vegetation patterns and associated canopy structure influence landscape functions such as water use, biomass production, and energy cycles. Airborne laser scanning is a measurement system in which pulses of light (most commonly produced by a laser) are emitted from an instrument mounted in an aircraft, directed to the ground in a scanning pattern. This method of recording the travel time of the returning pulse is referred to as pulse ranging (Wehr and Lohr 1999). The foundations of lidar forest measurements lie with the photogrammetric techniques developed to assess tree height, canopy density, forest volume, and biomass. Nelson et al (1988b) predicted the volume and biomass of southern pine (Pinus taeda, Pinus elliotti, Pinus echinata, and Pinus palustris) forests using several estimates of canopy height and cover from small-footprint lidar, explaining between 53% and 65% of the variance in field measurements of these variables
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