The influence of logging history on second-growth forest structure and ecosystem recovery on Lyell Island, Haida Gwaii

Background/Question/Methods

In forests, disturbances create and maintain structure, the keystone elements for biodiversity.  Second-growth forests have simplified structure compared to old-growth forests.  Logging, however, has varied greatly over the past 70 years, in both techniques and location, and its disturbance legacy is potentially highly variable.  In coastal BC, we do not have a good understanding of the effects of logging in time and space on second-growth forest structure and composition.  Tllga Kun Gwaay.Yaay, (Lyell Island) is located in Gwaii Haanas National Park Reserve and Haida Heritage Site, Haida Gwaii.  Logging varies from A-frame logging along shorelines, to early truck logging in riparian zones and valley bottoms through to modern industrial logging on hillslopes.  Logging ceased when the area was protected in 1987.  Ecosystem recovery on Haida Gwaii is further complicated by black-tail deer introduced a century ago. Their browsing pressure severely impacts the understorey, including regeneration of western redcedar, a culturally important species.  In order to investigate the influence of logging era, I gathered field-based measures of forest structure and composition in three eras of logging; pre-1937 (A-framing); 1937-1966 (truck logging) and 1966-1987 (modern logging).

 Results/Conclusions

There are abundant residual structures in second-growth forests from the truck logging era, which are absent from the modern logging and A-framing eras.  Undesirable trees (culls) were left standing rather than cut and left, so there are large residual trees and snags, especially in second-growth riparian forests, but little large coarse woody debris.  Understorey species persist on stump refugia.  The canopy is not universally closed due to presence of large stumps and residuals.  Despite introduced deer, cedar has been regenerating from the 1880s to 1980.  The spatial and temporal patterns in cedar establishment are more complex than regeneration simply ceased when deer were introduced.   

 The most productive ecologically valuable forests; riparian forests and valley-bottom forests; were logged by the 1960s before biodiversity, including salmon habitat, was even a concern.  However, these are also the most productive forest sites and have the greatest residual structure from past logging practices.  They have a high potential for ecosystem recovery, especially with restoration.  Second-growth forests may also be a potential future source of cedar for cultural use.  In unprotected areas, forests from the truck logging era are close to harvest age.  Because they are second growth, their biodiversity and cultural values are assumed to be negligible, which is not necessarily the case.