Quantification of Lichen Cover and Biomass Using Field Data, Airborne Laser Scanning and High Spatial Resolution Optical Data—A Case Study from a Canadian Boreal Pine Forest

Ashley C Hillman,Scott E Nielsen

doi:10.3390/f11060682

Abstract

Ground-dwelling macrolichens dominate the forest floor of mature upland pine stands in the boreal forest. Understanding patterns of lichen abundance, as well as environmental characteristics associated with lichen growth, is key to managing lichens as a forage resource for threatened woodland caribou (Rangifer tarandus caribou). The spectral signature of light-coloured lichen distinguishes it from green vegetation, potentially allowing for mapping of lichen abundance using multi-spectral imagery, while canopy structure measured from airborne laser scanning (ALS) of forest openings can indirectly map lichen habitat. Here, we test the use of high-resolution KOMPSAT (Korea Multi-Purpose Satellite-3) imagery (280 cm resolution) and forest structural characteristics derived from ALS to predict lichen biomass in an upland jack pine forest in Northeastern Alberta, Canada. We quantified in the field lichen abundance (cover and biomass) in mature jack pine stands across low, moderate, and high canopy cover. We then used generalized linear models to relate lichen abundance to spectral data from KOMPSAT and structural metrics from ALS. Model selection suggested that lichen abundance was best predicted by canopy cover (ALS points > 1.37 m) and to a lesser extent blue spectral data from KOMPSAT. Lichen biomass was low at plots with high canopy cover (98.96 g/m2), while almost doubling for plots with low canopy cover (186.30 g/m2). Overall the model fit predicting lichen biomass was good (R2 c = 0.35), with maps predicting lichen biomass from spectral and structural data illustrating strong spatial variations. High-resolution mapping of ground lichen can provide information on lichen abundance that can be of value for management of forage resources for woodland caribou. We suggest that this approach could be used to map lichen biomass for other regions.

Highlights

Terricolous macrolichens can form extensive mats on the boreal forest floor, and in some cases become the dominant understory vegetation in mature open pine stands [1]
Lichen abundance was lowest within the high canopy cover strata averaging cover (SE = 5.1) and 98.96 g/m2 of dry biomass
We developed and applied an approach to quantify lichen cover and biomass based on field data, airborne laser scanning, and high spatial resolution optical data, using a pine dominated site in boreal Canada as a case study area

Summary

Introduction

Terricolous macrolichens can form extensive mats on the boreal forest floor, and in some cases become the dominant understory vegetation in mature open pine stands [1]. In the boreal forest of Northern Alberta, Canada, a heterogeneous patchwork of lowlands and upland forests form a mosaic of suitable and unsuitable habitat for ground lichens. Since these terricolous macrolichens have specific growth requirements and are slow growing, these lichens are outcompeted by bryophytes and vascular plants in more mesic upland sites [1]. Terricolous reindeer lichens of the genus Cladonia can form large mats, in open pine stands, where they often dominate the forest floor. Monitoring available lichen abundance (biomass) is important for quantifying the distribution and abundance of Cladonia lichen in Alberta’s boreal forest, including other species that depend on it

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