Lichen abundance and biodiversity along a chronosequence from young managed stands to ancient forest, 1993

CREATOR(S): Bruce P. McCune, Peter N. Neitlich
ORIGINATOR(S): Peter N. Neitlich
20 Oct 1995
4 Mar 2013
Populations, populations, Long-Term Ecological Research (LTER), biology, conservation, ecology, trophic structure, forest management, arthropods, lichens
Experimental Design - SA011:

Lichens were studied in forested stands originating after stand-replacing fires 510, 140, 70 years ago (Teensma 1987) or after clearcuts 40 years ago. Howe (1978) found that northern aspects in old growth reference stands at the H.J.Andrews had greater lichen biomass than southern exposures, and that cyanolichen abundance was greatly limited beyond 150 m vertical distance above streams. In this study I sought to observe how the lichens of different forest age classes compared under optimal conditions and, therefore, chose northern aspects within riparian environments. I hypothesized that suboptimal conditions might mask differences in abundance and biomass among the younger age classes. To focus primary attention on differences among age classes, I tried to maintain as many other environmental variables as possible constant.

Three study stands were chosen to represent each age class. Stands were chosen according to the following criteria:

  • Elevations ranged from 610 m to 915 m above sea level (2000 to 3000 ft). Stands were chosen to avoid elevational overlap such that each site covered about one-third of the 305 m.
  • Site aspect ranged from N (0') to NW (315').
  • The highest site in each age class was, because of sharp local topography, higher than 150 m vertical distance above the closest stream. The lower two sites were placed within 150m vertical distance above a stream. (Because of a shortage of 140 year old sites that met these criteria, all three of the sites in this age class fell within 150 vertical m of a stream.)
  • Stands were located in or as close as possible to the H.J.Andrews Experimental Forest (Fig. 1, Table 2).
  • Stands presumably resulted from catastrophic disturbance which left no remnant vegetation from an older period (Teensma 1987). Stands which had sub-catastrophic disturbances after the initial year of establishment were avoided.
  • Chen and Franklin (1992) found that edge influence on such biological variables as canopy cover, tree density and seedling regeneration extended up to 80 m into old growth Douglas-fir forests. Edge effects for most variables extended only 60 m -- approximately one old growth tree length. Using these criteria, I chose stands which had a minimum of two hectares located 120 m (two tree lengths) or more from other age classes or remnant trees. Eleven of the twelve stands had between 15 and several thousand hectares greater than 120 m from other age classes or remnant trees.
Field Methods - SA011:

Biomass. Ten 2 m radius circular plots were chosen at random within each site. All lichen litterfall within each plot was gathered according to the protocol of McCune (1993a): Lichens were cleaned of debris, and sorted into bags according to three functional groups-- "cyanolichens","Alectoriod" lichens, and "other" lichens. "Cyanolichens" were defined as those macrolichens employing cyanobacteria as primary or secondary photobionts (mainly Lobaria, Nephroma, Pseudocyphellaria, Sticta, and Peltigera in the western Cascades.) "Alectoriod" lichens were defined as pendulous or tufted fruticose lichens in the genera Alectoria, Bryoria, and Usnea. "Other" lichens included all remaining lichens.

Lichenologists have been traditionally limited in their ability to undertake large scale ecological studies by the time required to rig and sample individual trees. In attempting to design a method to quantify standing lichen biomass without having to climb (and pillage the epophytes of) hundreds of trees, McCune (1993a) studied the relationship between lichen litterfall and standing crop. His litterfall pickup methodology was designed to capture the steady rain of lichens falling freely from the canopy or attached to small branches. He reports that the correlation between litterfall and standing biomass was highest (r2=0.87) when he discounted decomposing lichens and large, anomalous clusters of lichens attached to large limbs. As the latter occur only rarely in litterfall plots, he reasoned, collecting such clusters would have generated unnecessary statistical noise.

Employing McMune's guidelines, lichens were left uncollected if:

  • they were attached to woody debris with a basal diameter greaterr than 10 cm.
  • they were incorporated into the forest floor by fungal hyphae or were mostly buried in decomposing litter.
  • they were suspended in the understory higher than 2 m
  • they had re-established and taken up new residence
  • they normally grew terrestrially, e.g., Peltigera spp., and Cladonia spp., and represented direct, rather than litterfall, biomass samples.

Species capture . Direct observation of the canopy by climbing suggested that biomass sampling plots detected the lichen species that constituted the vast majority of lichen biomass in the forest, but did not adequately detect rare lichens. In characterizing the species composition of stands for forest health/air quality monitoring, McCune and Dey (1992) found that most lichen species in a stand may be found within a 36.56 m (120 ft) radius sample plot (0.42 ha). Adapting this methodology, lichen species not already encountered in the biomass sample plots were collected from within a circle of 11.56 m radius around plot center. The ten combined species plots were equal in area to one 36.56 m circle.

Species collection were limited to epiphytic macrolichens. Terrestrial lichens, though important in the ecosystem, were avoided for two reasons. First, McCune's litterfall ratio did not adequately quantify their biomass or their biomass importance relative to other lichens; and second, neither litterfall plots nor species capture plots adequately sampled them, as they often grow on patchily distributed mineral soil, rocks, or coarse woody debris. Crustose lichens were avoided for the same reasons. Epiphytic macrolichens were defined as those growing higher than 2 m above the ground in order to exclude species found equally on tree bases and coarse woody debris or soil (e.g., Cladonia spp. and Peltigera spp.)

Lab Analysis. Lichens were oven dried at 60 degrees C for 24 hr according to the methodology of McCune (1993a). Functional group bags from each plot were then weighed to the nearest 0.01 g. Species biomass was assessed visually as a percent of the functional group biomass in each bag. Lichens were identified to the most specific taxonomic level possible using Goward et al. (1992), Brodo and Hawksworth (1977), Hale (1979) and herbarium specimens at Oregon State University (OSC). Nomenclature follows Egan (1987).

Identifications were verified by Dr. Bruce McCune.

A total of 59 epiphytic lichen species were found in the four age classes. The maximum species richness (52 species, 90%) occurred in old-growth (510 year-old age class) while the minimum (34 species, 58%) occurred in the 70 year-old age class. Old growth displayed 60% greater mean species richness per stand than 70 or 40 year-old stands.
Study stands are in and around the H. J. Andrews Experimental Forest and Hagan Block Research Natural Area.
once only
Ground condition
This data is published in: Lichen Abundance and Biodiversity Along a Chronosequence from Young Managed Stands to Ancient Forest by Peter Neitlich Master of Science thesis, Department of Botany, Univ of Vermont, December 3,1993