Quantifying the effects of moisture change on the spectral signatures (350-2500 nm) of Arctic mosses, liverworts, and lichens

Abstract:

Increasing temperatures in the Arctic are causing a series of environmental shifts, including the alteration of hydrological and ecological regimes, with effects on carbon (C) cycling across the landscape. Peat-accumulating wetlands are particularly important to the Arctic’s C budget because they act as natural CO₂ sinks and significant CH₄ sources. Peatland vegetation (e.g., mosses, lichens, liverworts) has been found to offer information on the ecosystem structure and function, as each plant functional type exerts a fundamental control on ecosystem C exchange based on biomass productivity and decay rate. Bryophytes (e.g., mosses, liverworts), which are sensitive to moisture shifts, can also be used as proxies for soil moisture conditions and thus, C sequestration/emission and drought level. Yet, despite the dominance of mosses, liverworts, and lichens in Arctic ecosystems and their aforementioned biogeochemical roles, they are often not considered and/or are inadequately represented in earth system models due to the lack of ability to identify these plants and represent/scale-up their unique biophysical traits using remote sensing data. Here we present a new spectral library of over 20 species of Arctic mosses, lichens, and liverworts from Victoria Island, Nunavut, Canada. Preliminary results indicate diagnostic spectral differences across those plant types, and in some cases at the species level, that can be used to identify those types or species. In addition, using water table depth manipulations in the lab, we simulated moisture shifts from saturation (100% moisture content) to desiccation (0% moisture content), with daily hyperspectral measurements using a ASD FieldSpec 4 Hi-Res spectroradiometer (350-2500nm). These results are being analyzed and suggest that significant changes occur within each plant’s spectral response as moisture is lost. Furthermore, cross-species analyses show promise in identifying moisture thresholds beyond which distinct plant species are no longer spectrally discriminable. Overall, this spectral library uniquely offers information on an array of Arctic non-vascular vegetation species’ biophysical changes under a range of hydrological conditions, and is particularly novel for Arctic liverworts, as to our knowledge, their spectra have never been collected.