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Ecosystem maps are foundational tools that support multi-disciplinary study design and applications including wildlife habitat assessment, monitoring and Earth-system modeling. Here, we present continuous-field cover maps for tundra plant functional types (PFTs) across ~125,000 km2 of Alaska’s North Slope at 30-m resolution. To develop maps, we collected a field-based training dataset using a point-intercept sampling method at 225 plots spanning bioclimatic and geomorphic gradients. We stratified vegetation by nine PFTs (e.g., low deciduous shrub, dwarf evergreen shrub, sedge, lichen) and summarized measurements of the PFTs, open water, bare ground and litter using the cover metrics total cover (areal cover including the understory) and top cover (uppermost canopy or ground cover). We then developed 73 spectral predictors derived from Landsat satellite observations (surface reflectance composites for ~15-day periods from May–August) and five gridded environmental predictors (e.g., summer temperature, climatological snow-free date) to model cover of PFTs using the random forest data-mining algorithm. Model performance tended to be best for canopy-forming PFTs, particularly deciduous shrubs. Our assessment of predictor importance indicated that models for low-statured PFTs were improved through the use of seasonal composites from early and late in the growing season, particularly when similar PFTs were aggregated together (e.g., total deciduous shrub, herbaceous). Continuous-field maps have many advantages over traditional thematic maps, and the methods described here are well-suited to support periodic map updates in tandem with future field and Landsat observations. [ABSTRACT FROM AUTHOR]

Lichens in the Arctic play important ecological roles. They also face the threats of increasing fire and shrub and tree expansion, exacerbated or caused by climate change. These forces may lead to changes not only in lichen community composition but also in the abundance, diversity and distribution of lichen functional traits. We sought to connect landscape-scale patterns of lichen community composition and traits to environmental gradients to both monitor lichen communities and clarify community-trait-environment relationships. We measured lichens throughout one of the largest and most remote U.S. National Parks within the Arctic. We then analyzed lichen community composition and species richness within ecologically informative lichen trait groups along environmental and vascular vegetation gradients. Macrolichen species richness in 0.4 ha plots averaged 41 species with a total landscape level observed gamma diversity of 262 macrolichen species. Jackknife estimators placed the landscape level macrolichen diversity at 307 to 331 species. A gradient from low-elevation forests to high elevation rocky areas was the dominant ecological gradient as expressed by the lichen community, representing 68% of the variation in species composition. Low-elevation forests hosted more epiphytic lichens characteristic of boreal forests, whereas high-elevation lichen communities were characterized by saxicolous lichens, varying between siliceous, basic or mafic rock types. Along this gradient, species reproducing vegetatively and lichens with filamentous growth form were more frequent in forests while the diversity of traits was highest in alpine habitats. Simple cladoniiform, as opposed to erectly branched fruticose lichens in the genus Cladonia, were the only functional group associated with tussock tundra. Vegetation types differed significantly in lichen species composition and richness and trait richness; characteristic suites of lichen species and traits are associated with the particular vegetation types in the Arctic. We also extended the range of Fuscopannaria abscondita reported new to North America and Zahlbrucknerella calcarea new to Alaska. [ABSTRACT FROM AUTHOR]

Questions Popular methods to analyse community-trait-environment relationships constrain community patterns by trait and environment relationships. What if some traits are strongly associated with community composition but unrelated to environmental variables and vice versa? We take a different approach, unconstrained by this assumption using non-parametric methods. We applied this technique to lichen (fungal/algal and/or cyanobacterial symbioses) communities across environmental and fire age gradients by measuring richness and cover of four important functional traits: energy generation (type of photosynthetic symbiont), water relations (inferred from growth form), dispersal capability (from vegetative propagules) and microsite specificity (measured by substrate affinity). Location Denali National Park and Preserve, Alaska, USA. Methods We ordinated plots in species space and regressed trait and environmental variables against ordination axes, resulting in one- or two-dimensional trait and environment surfaces. We then superimposed these surfaces on the ordination to create a new visual display, the 'hilltop plot', which enabled simultaneous measurement and display of one- and two-dimensional, non-linear community-trait-environment associations. Results Most traits examined show non-linear relationships with community structure. Fire favoured simple cladoniiform lichens, species with higher vegetative dispersal capacity and specificity to grow on wood, but excluded the 'reindeer' lichens, which had lower cover even more than 20 yrs after fire. Forests had more sorediate lichens than non-forested habitats, whereas high elevation, rocky areas had more green algal and fruticose lichens. Cyanobacterial lichen richness was positively related to shrub cover, while tripartite (cyanobacteria and green algae in a single lichen) and foliose lichen richness was highest in areas with higher moss cover. Conclusions Different combinations of lichen functional traits peaked along environmental and disturbance gradients, which we interpreted as balancing energy generation, water relations, vegetative dispersal and habitat specificity. Our method of trait-environment-community analysis revealed numerous one- and two-dimensional, non-linear relationships between community composition and functional traits, environmental variables and fire age gradients, which informed mechanisms behind community assembly. Our results indicate non-parametric and non-linear methods of trait-environment-community analysis have the potential to detect patterns that would have been missed using current popular techniques. [ABSTRACT FROM AUTHOR]