|Eitel, Jan -|
|Vierling, Lee -|
Submitted to: Remote Sensing of Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2010
Publication Date: May 1, 2010
Citation: Eitel, J.U., Vierling, L., Long, D.S. 2010. Simultaneous measurements of plant structure and chlorophyll content in broadleaf saplings with a terrestrial laser scanner. Remote Sensing of Environment. 114:2229-2237. Interpretive Summary: Terrestrial laser scanning (TLS) is a relatively new measurement technology in which a laser beam is swept over a scene. Objects are rendered in three-dimensional space. In this study, the intensity of green laser light reflected from leaves of oak and maple were recorded in addition to the 3-D positional information. This information was strongly related to the chlorophyll content of leaves as well as leaf area and leaf angle. These results suggest that TLS is potentially useful for measuring the chlorophyll and nitrogen content of plant canopies. Scanning can be accomplished for objects that are greater than 300-feet away thereby eliminating the need for instruments that require contact with the leaf.
Technical Abstract: Plant structure and chlorophyll content strongly affect rates of photosynthesis. Rapid, objective, and repeatable methods are needed to measure these vegetative parameters to advance our understanding and modeling of plant ecophysiological processes. Terrestrial scanners (TLS) can be used to measure structural and potential chemical properties of objects by quantifying the x,y,z coordinates and intensity of laser light returns from an object's surface. The objective of this study was to determine the potential usefulness of TLS with a green (532 nm) laser to simultaneously measure the spatial distribution of chlorophyll a and b content, leaf area (LA), and leaf angle (LAN). The TLS measurements were obtained from saplings of two tree species (Quercus macrocarpa and Acer saccharum) and from an angle-adjustable cardboard surface. The green laser return intensity value was strongly correlated with wet-chemically determined chlorophyll (r2=0.77). Strong agreement was shown between measured and TLS-derived LA (r2=0.95). The TLS derived LANs of both species followed a plagiophile LAN distribution, and the measured angles of the cardboard surface allowed us to quantify that these LAN values were strongly correlated with TLS derived angles (r2=1.0 and slope = 0.98). Our results show that terrestrial laser scanners are feasible for simultaneous measurement of LA, LAN, and chlorophyll in simple canopies of small broadleaved plants. Further research is needed in more complex and larger canopies.