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Date Creek Lichen colonization data

Citation

Lilles, Erica; Bartemucci, Paula; Gauslaa, Yngvar (2021), Date Creek Lichen colonization data, Dryad, Dataset, https://doi.org/10.5061/dryad.k0p2ngf7f

Abstract

Conservation of epiphytic lichens in managed forest landscapes relies on understanding limitations to their dispersal and establishment after harvesting. A hot-spot for cephalo- and cyanolichens, the Kispiox inland temperate rainforest of British Columbia, Canada, is an example of where forest managers seek silviculture options that allow for forest harvesting to continue, while also conserving threatened species. To characterize colonization of these lichens (including the nationally-threatened Nephroma occultum and Lobaria retigera), we quantified thalli on 25-year-old regenerating spruce trees at varying distances from forest edges in logged openings of different sizes surrounded by mature (160 years) or old-growth (≥350 years) forest. This dataset records colonies observed along with the tree they were observed on and their size. The second dataset has information about each opening that was sampled.

Methods

We sampled 213 trees at varying distances from the forest canopy edges. For clearcuts and large gaps with a transect length ≥ 100m, we sampled one tree every 10 m until 50 m, then every 25 m afterwards. For gaps with transects 50 - 70 m we sampled a tree every 10 m. For smaller gaps, we sampled five equally-distributed trees along the transect. For the smallest gaps (transect < 15 m) we sampled the best-colonized trees along the transect (up to 5 trees per opening). In general, we used a 20 m2 search zone for large openings (5 m × 2 m on either side of transect) at each transect distance to select the tree with the best cephalo- and cyanolichen colonization, though for small openings, this search zone was smaller.

At each tree, all cephalo- and cyanolichens > 0.1 cm2 were counted and measured on branches below 1.5 m. To allow for efficiencies in data collection, the common species were only recorded on the three branches with the best lichen colonization. We used a 1 cm × 1 cm wire grid to estimate the surface area of each lichen thallus. The grid was placed on top of each lichen and the grid cells or fractions of grid cells occupied by the lichen were estimated. This approach gave a repeatable method of measuring thallus area compared to more subjective visual estimates of lichen loading. The same person measured all lichens to decrease measurement error. Taxonomically difficult specimens, as well as voucher specimens from each site, were examined in the lab. Nomenclature follows Esslinger (2019).   

Using likelihood methods and Akaike’s Information Criterion (AIC) in a multiple alternate hypothesis framework (Burnham and Anderson 2002, Canham and Uriarte 2006), we examined the relationship between various measures of abundance per sample tree (total number of thalli, number of species (richness), number of thalli of each taxon) and distance from the closest forest edge along a north-south bearing (model 1). We also examined three additional effects on lichen colonization: age of the surrounding forest (model 2), size of the logged opening (model 3), and position within the opening (distance from north vs. south edge) (model 4). We also compared the models to a null model, which estimated lichen abundance as a simple mean multiplied by the tree size effect.

The model with the lowest AIC value was considered to have the most support from the data. When models differed by AIC values (ΔAIC) less than 2, the more parsimonious (fewer parameters) model was considered superior. A simulated annealing algorithm (likelihood package; Murphy 2015) in the statistical software R v. 3.5.1 calculated maximum-likelihood estimates and approximate 95% support intervals for the parameters in each model after 40,000–100,000 iterations (Goffe et al. 1994; R Development Core Team 2018).

Usage Notes

Column header descriptions:

TU - The treatment unit from the Date Creek Research Forest where the data were collected, with the additional clear-cuts given the codes B6 and C4

Gap and NewGap - The gap numbers from the Date Creek Research Forest where the data were collected

Tree.distance_m - The distance in meters from North to South along the transect through each gap

DBH_cm - The diameter of the tree at 1.3 m high where the lichens were observed on in cm

Branch_vs_Tree - Branch means the species was searched for on the three best branches of a tree, Tree means the species was searched for on the whole tree everywhere lower than 1.5 m high

Species - 7 digit code for species name

Area_cm - estimated surface area in cm2 of each lichen thallus

CC_YN - Y for opening is the size of a clear-cut (>1 ha) and N for smaller openings

Size - estimated size of opening in m2

NS line - distance from north to south edge of opening in m

EW line - distance from east to west edge of opening in m

Paula NS length - distance from north to south edge of opening in m remeasured by Paula during lichen study

SurroundingStandAge - whether surrounding unharvested forest for each opening is better described as mature (~165 years) or old growth (350+ years) at the beginning of the experiment in 1992

Notes - comments on area and how calculated for different openings

Funding

BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development

BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development