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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #175022


item Goodrich, David - Dave

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2006
Publication Date: 7/15/2006
Citation: Farid, A., Goodrich, D.C., Sorooshian, S. 2006. Using airborne lidar to discern age classes of cottonwood trees. Western J. of Applied Forestry. 21(3):149-158.

Interpretive Summary: Arid and semi-arid regions account for approximately one-third of the land mass of earth. These regions are experiencing continued pressure from population growth in many parts of the world. Water is a critical resource in these regions and is often in short supply. To maintain the economic, social, and ecological viability of these areas it is essential that decision makers and resource managers have a solid scientific basis on which to make watershed based decisions including management of riparian vegetation. Riparian trees use water in proportion to their size, and are especially large users of water in flood plains along rivers in semi-arid environments. It's difficult to measure tree size using traditional ground-based techniques to determine their water use. For this reason new techniques that are more accurate and efficient need to be developed. This study demonstrated that a lidar (light detecting and ranging) system mounted in an airplane can accurately measure features of forest canopies that are related to water use. Such information is not readily available from other remote sensing methods. The results illustrate the potential of airborne lidar data to differentiate different age classes of cottonwood trees for riparian areas quickly and quantitatively. This information can be used in many forestry, ecological and hydrologic applications that will improve management of hydrologic resources and ecological models. This paper describes the challenges of truly collaborative, scientifically-based, watershed management. These challenges are compounded in the bi-national San Pedro River Basin. Based on our experiences in working with policy and decision-makers in the San Pedro we propose a process for fostering collaboration in binational basin. A key aspect of this process is the successful engagement of scientists with community decision-makers and land managers. This requires a long-term commitment by both parties to build trust and establish effective communication to approach problem solving and resource management.

Technical 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 which growth models and ecological assessments are becoming increasingly important. In this study, discrete-return 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 was acquired in June 2003, using Optech's 1233 ALTM (Optech Incorporated, Toronto, Ont.), during flyovers conducted at an altitude of 750 m. The lidar system produced an average footprint of 0.15 m and an average distance between laser shots of 0.9 m. Canopy height, crown diameter, stem diameter at breast height (dbh), canopy cover, and mean intensity of return laser pulses from the canopy surface are estimated for young, mature, and old cottonwood trees from lidar data. Linear regression models were used to develop equations relating lidar-derived tree characteristics with corresponding field inventory.