Short-term impacts of partial cutting on lichen retention and canopy microclimate in an Engelmann spruce – subalpine fir forest in north-central British Columbia

Abstract

The retention of canopy lichens (Alectoria, Bryoria, and foliose) in group selection (GS) and single-tree selection (STS) partial cuts (30% removal) was studied within a subalpine spruce–fir forest (Picea englemannii Parry ex Engelm. – Abies lasiocarpa (Hook.) Nutt.) in north-central British Columbia. Baseline canopy lichen loading (preharvest and immediate postharvest) was compared with lichen loading 2 years after harvesting, using both ground- and canopy-based sampling techniques. Additionally, canopy microclimate was compared between GS and adjacent stand areas with no harvest treatment (NT). Partial cutting did not have a significant effect on lichen loading in residual trees, although a trend of declining lichen abundance was observed in each of the GS, STS, and NT areas. Partitioning of lichen abundance data showed significant postharvest declines for upper canopy STS Bryoria and smaller, but significant, changes in foliose lichen abundance in the NT and STS areas. No significant changes in canopy microclimate were observed between treatments, with the exception of south-facing aspects in GS trees, which showed reduced duration of lichen hydration. Taken together, these factors suggest that although the placement of Bryoria in residual trees may shift towards lower canopy exposures, partial-cut harvest treatments can maintain short-term lichen loading and associated ecosystem values (e.g., caribou forage) in subalpine spruce–fir stands.

Influence of high-contrast and low-contrast forest edges on growth rates of Lobaria pulmonaria in the inland rainforest, British Columbia

“…A second response pattern that might be anticipated in lichens growing at the forest edge is that of reduced net annual growth due to reduction in the amount of time that thalli are hydrated. The increased insolation exposure and greater convection near stand edges should each contribute to the more rapid drying of lichen thalli after precipitation events as has been reported for alectorioid lichens exposed to edges of small forest openings (Coxson et al, 2003). Although this phenomenon undoubtedly occurred in both large and small thalli of L. pulmonaria placed at forest edges in the current study, increased exposure to light likely compensated for any reduction in the amount of time thalli were hydrated, at least for large thalli.…”

Impacts of silvicultural treatments on arboreal lichen biomass in balsam fir stands on Québec's Gaspé Peninsula: Implications for a relict caribou herd

“…In addition, the close alternation of lichen propagule sources with regularly recruited host trees in the regeneration strata is likely to maintain high and regular lichen productivity in uneven-aged, managed forests. Such results support Dettki and Esseen (1998) and Coxson et al (2003) conclusions that, although negative impacts are sometimes observed, partial cutting should be preferentially chosen over clearcutting in order to maintain macrolichen communities most similar to natural forests.…”

“…They were unable, however, to attribute this loss to the treatment since the control exhibited the same pattern. A trend consistent with that of Coxson et al (2003) suggested a greater decline in standing crop of canopy lichens in the single-tree selection area. Our results suggest that the uneven-aged group-selection cut maintained more favourable environmental conditions for lichen retention than the partial cut.…”

Variation in microclimate associated with dispersed-retention harvests in coniferous forests of western Washington

“…On the other hand, changes in light availability at lower levels of retention indicate that small increases in canopy cover can yield large reductions in light. If sensitivity to excess solar radiation dictates biological responses (Svenning, 2000;Coxson et al, 2003;Fenton and Frego, 2005), small changes in canopy retention could yield large effects.…”