Abstract Detail

Bryological and Lichenological Section/ABLS

Nelson, Peter [1], McCune, Bruce [1], Roland, Carl [2].

Nonlinear lichen community functional trait variation along environmental and fire age gradients revealed by nonparametric methods.

Popular methods to analyze 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 nonparametric 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, nonlinear community-trait-environment associations. 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 (determined by the photosynthetic symbiont), water regulation (inferred from growth-form), dispersal capability (from vegetative propagules) and microsite specificity (measured by substrate affinity). Lichens with erect, branched, three-dimensional growth form (mostly “reindeer lichen”) had lower cover after fires, even more than 20 years afterward. In comparison to unburned forests nearby, recently burned areas had higher richness of simple, three-dimensional, wood-dwelling and cyanobacterial lichens. Lichens with the smallest vegetative propagules (soredia) peaked in richness in recent fires. Green algal lichen species richness peaked in rocky, high elevation areas. Conversely, cyanobacterial lichen richness was positively related to shrub cover and tripartite lichens (cyanobacteria and green algae in a single lichen) richness was highest in areas with higher moss cover and lower pH. Fruticose lichens of most types also peaked in richness in high elevation, rocky habitats. Different combinations of lichen functional traits peaked along environmental and disturbance gradients which we interpreted as balancing energy generation, water regulation, vegetative dispersal and habitat specificity. Our method of trait-environment-community analysis revealed numerous one and two-dimensional, nonlinear relationships between community composition and functional traits, environmental variables and fire age gradients, which informed mechanisms behind community assembly. Our results indicate nonparametric and nonlinear methods of trait-environment-community analysis have the potential to detect patterns that would have been missed using currently popular techniques.

1 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, United States
2 - National Park Service, 4175 Geist Road, Fairbanks, AK, 99709, USA

Keywords:
Alaska
Denali National Park and Preserve
vegetative dispersal
disturbance
functional traits
lichen
growth-form
photobiont.

Presentation Type: Oral Paper:Papers for Sections
Session: 2
Location: Firs North/Boise Centre
Date: Monday, July 28th, 2014
Time: 10:30 AM
Number: 2010
Abstract ID:384
Candidate for Awards:None