Abstract Detail

Recent Topics Posters

Nelson, Peter [1], Wheeler, Tim [2].

Lichen persistence and recovery in response to varied volcanic disturbances.

Volcanic eruptions produce a range of disturbances that play important roles in structuring vegetation. While lichens are sensitive to disturbances, little is known about lichen’s response to volcanic disturbances besides colonization of lava. We examined lichen community responses through time in different disturbances produced by the 2008 eruption of Volcan Chaiten in south-central Chile.   The dominant pre-eruption vegetation was old-growth Valdivian temperate dominated by closed-canopy Nothofagus sp. with dense lichen, bryophyte, fern and lliana epiphytic communities. The understory was dark, interspersed with occasional bamboo thickets and shade tolerant sapling tree species. On May 1, 2008, the eruption began with explosions that shattered and ejected the existing, high-density rock, which fell horizontally, severely abrading forests to the northeast of the crater. Simultaneously, a large tephra plume shot 10-16 km vertically but drifted to the southeast depositing 10-20 cm of material, primarily fine ash with some pumice. During the next week, a large blast existed northwest out of the crater generating a fast-moving wall of volcanic ejecta and uprooted trees that leveled the forest over ca. 8 km². Subsequent heavy rains entrained a large amount of freshly deposited volcanic material that flowed downstream, inundating forests in several meters of material killing all the trees in some riparian areas. We categorized these disturbances zones into light tephra fall, deep tephra fall, blast, scorch (edge of blast), gravel rain, gravel rain with pumice, flooded forest and nearby, unimpacted (reference) forest for sampling of lichen communities.   In 2012, we installed thirteen 34.7 m radius plots across disturbance zones. On each plot, a time-constrained search was done for all macrolichen species, each of which was assigned a categorical abundance rating on an approximately logarithmic scale. We also installed a permanent 0.2 m² quadrat on two representative trees per plot for photographic monitoring. Species composition and abundance data were analyzed through summary statistics and ordination to quantify differences between disturbance zones. Tree quadrats were measured through point-intercept lichen cover estimates.   In 2012, the blast, scorch and deep tephra zones had the lowest lichen species richness (5-13 species), followed by reference and shallow tephra (17-20 species) whereas gravel rain, gravel rain plus pumice and flooded forests were species-rich (25-42 species). In 2014, the blast and deep tephra (scorch was not resampled) had regained 2-3 times the number of lichen species than 2012 while the light tephra and reference were essentially unchanged. Gravel rain, gravel rain plus pumice and flooded forest plots all had about the same number of species in 2014 as 2012. Lichen colonization and growth in tree quadrats varied widely, from very little colonization in the blast to prolific in the gravel rain plus pumice zone.   Lichens responded to different volcanic disturbances in markedly different ways attributable to varying degrees of mortality and subsequent availability of substrate, quantity of light and removal of competitors. Lichens persisted in areas with light tephra, apparently unharmed, whereas 10-20 cm of ash killed most lichens species, possible due to a combination of chemical, desiccation or shading. Lichens apparently colonized the forests killed by flood deposits due to the increased light generated by the reduced forest canopy and some reduction in non-lichen epiphytic competitors. In the blast, lichen species richness greatly increased from 2012 to 2014, in part due to the large amount of bare soil available for terricolous species and abundant downed logs for epiphytes. The gravel rain and gravel rain plus pumice forests lost their dense epiphytic bryophyte and lliana cover as well as experiencing moderate tree mortality that allowed impressive lichen colonization and growth due to large amounts of available substrate and increased light.

1 - University of Maine-Fort Kent, 23 University Dr., Fort Kent, Maine, 04743, United States
2 - 6606 Jocko Canyon Road, Arlee, MT, 59821, USA

Keywords:
lichen
Community ecology
Chile
disturbance
Volcano
Temperate forests
succession.

Presentation Type: Recent Topics Poster
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PRT059
Abstract ID:1846
Candidate for Awards:None