Resilience of bryophyte communities in regenerating matrix forests after logging in temperate rainforests of coastal British Columbia

摘要

The resilience (measured as changes in functional group representation and species composition) of bryophyte communities found in the younger-aged ("matrix'') forests surrounding old-growth remnants was examined in two different forest types, warmer, drier (Nimpkish) versus cooler, wetter (Sayward), on Vancouver Island, British Columbia. Bryophytes were sampled within 10 m x 2 m belt transects (species composition only) and using 10 cm x 30 cm microplots (composition and abundance) in two age classes of matrix forest, clearcuts (age 7-20 years), and second-growth (age 2549 years) as well as in remnant old-growth forest stands (age >300 years). The cover of all bryophytes was diminished and more patchily distributed in younger-aged stands; however, the richness and frequency of bryophyte functional groups showed different responses in the two younger age class forests. Disturbance-associated species exhibited both higher richness and frequency in clearcut plots and higher richness in second-growth plots. In comparison, the richness of species associated with old-growth was largely unchanged in younger-aged forests compared with old-growth forests; however, the frequency of occurrence of species associated with old-growth was significantly reduced in younger-aged forests. The cooler, wetter forests exhibited greater resilience, as the difference in species composition between second-growth and old-growth stands was less than that between second-growth and old-growth stands in the warmer, drier forests. The greater difference in second-growth species composition in the warmer, drier forests was attributed mainly to the persistence of disturbance-associated species.