Abstract
Abstract. Assessing moisture contents of lichens and mosses using ground-based high spectral resolution spectrometers (400–2500 nm) offers immense opportunities for a comprehensive monitoring of peatland moisture status by satellite/airborne imagery. This information may be valuable for present and future carbon balance modeling. Previous studies are based upon point measurements of vegetation moisture content and water table position, and therefore a detailed moisture status of entire northern peatlands is not available. Consequently, upscaling ground and remotely sensed data to the desired spatial resolutions is inevitable. This study continues our previous investigation of the impact of various moisture conditions of common sub-Arctic lichen and moss species (i.e., Cladina stellaris, Cladina rangiferina, Dicranum elongatum, and Tomenthypnum nitens) upon the spectral signatures obtained in the Hudson Bay Lowlands, Canada. Upscaling reflectance measurements of the above species were conducted in the field, and reflectance analysis using a singularity index was made, since this study serves as a basis for future aircraft/satellite research. An attempt to upscale current and new spectral reflectance indices developed in our previous studies was made as well. Our findings indicate that the spectral index C. rangiferina is to a lesser amount influenced by scale since it has a small R2 values between the log of the index and the log of the resolution, reduced slopes between the log of the index and the log of the resolution, and similar slopes between log reflectance and log resolution (α) of two wavelengths employed by the index. Future study should focus on concurrent monitoring of moisture variations in lichens and mosses both in situ and from satellite and airborne images, as well as analysis of fractal models in relations to the upscaling experiments.
Highlights
Spatial scaling of land surface processes has been acknowledged as one of the most complicated and challenging issues in environmental sciences (Chen, 1999)
The singularity index estimated from Eq 3 has the following properties (Cheng, 2008): densityρ(ε) in the space of α dimension; for example, if Ref stands for spectral reflectance (%) with spatial resolution of size ε, c has the unit (%/cm)α
The higher reflectance observed in the greater scales may be related to the incident irradiance of the area; that is, the larger the area or the spatial resolution, the greater the radiance that is returned into the sensor, and so is the reflectance (Unsworth, 2008)
Summary
Spatial scaling of land surface processes has been acknowledged as one of the most complicated and challenging issues in environmental sciences (Chen, 1999). Scaling refers to the use of information available at one scale to derive processes that occur at a finer (down-scale) or a coarser (up-scale) scale (Ehleringer and Field, 1993; El Maayar and Chen, 2006). Reference spectra from a highly reflective (99%) Lambertian spectralon white reflectance panel (“white reference”) was collected in order to convert spectral measurements to absolute percent reflectance (Eq 1). For this purpose, a measurement of the noise inherent in the instrument (“dark”) was made with no illumination (Eq 1). The thick underlying peat deposits form peat plateau made up of high center ice-wedge polygons which cover approximately 12 000 km within the province of Manitoba (Ricketts et al, 1999)
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