From the Arctic to the tropics: multibiome prediction of leaf mass per area using leaf reflectance

Authors: Shawn P. Serbin(1), Jin Wu(1,2), Kim S. Ely(1), Eric L. Kruger(3), Philip A. Townsend(3), Ran Meng(1,4), Brett T. Wolfe(5,6), Adam Chlus(3), Zhihui Wang(3) and Alistair Rogers(1)
(1-Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA; 2-School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong; 3-Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA; 4-College of Natural Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, China; 5-Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama; 6-School of Renewable Natural Resources, Louisiana State University, Baton Rouge, LA, US)

Summary: Aeolian sedimentary processes and corresponding facies shape the Earth’s surface and control the evolution of dune fields. The Namib Sand Sea with its Sossusvlei playa-lake is a perfect example to investigate the spatial distribution of fluvially influenced aeolian deposits. Remote sensing in combination with ground observations allowed for mapping of the facies distribution pattern of associated fluvial and aeolian sediments. Laboratory spectral signature measurements were used to further improve the separation between six groups of facies: modern aeolian sand, deflation surface, mud pool/mud drapes, heavy mineral lag, reworked fluvial–aeolian sediments, and fossil dune remnant. The best results were achieved through a supervised classification algorithm trained by field observations, a combination of Principal Component Analysis, band ratios, texture and geomorphologic indices. Consequently, a map outlining the facies distribution pattern of the Sossusvlei area at a scale of 1:10,000 was created. We propose this as a possible workflow to efficiently map and monitor desert environments and to investigate the interplay of aeolian and fluvial sediments.

The PSR+ Spectroradiometer was one of the instruments used during this study:

• Fast, full-spectrum UV-VIS-NIR measurements (350 – 2,500 nm)
• High Resolution Field Portable Spectroradiometer with 512 element Si array and two 256 element extended InGaAs arrays
• Various optics ranging from 1° to 25° for reflectance, radiance and irradiance measurements

Field-based operation:
• The PSR+ spectroradiometer is powered by batteries and connected to a rugged tablet which provides GPS, photo tagging, and voice notes
• Our self-developed software allows in-field mineral identification and classification
• Usage of handheld contact probe allows field measurements on outcrops or mapping open pits even at cloudy conditions

Laboratory operation:
• Best signal-to-noise ratio for improved reflectance values by using full range tungsten lamps
• Detailed analysis of field samples in order to build Arctic spectral libraries from natural covers

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