Walt Klenner. 1998. Changing Landscapes in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

CHANGING LANDSCAPES

Monitoring forested habitats in the Montane Cordillera Ecozone
jpgacross large spatial and temporal scales

Walt Klenner

1. SERAL STAGE DISTRIBUTION OF FORESTS

The amount of late mature and old forest will decline in forests managed for timber production as older forests are harvested and few young and mature forests are maintained beyond rotation age (Van Wagner 1983, Swanson and Franklin 1992). Consequently, species dependent on old forests or the conditions associated with old forests (e.g. an abundance of large diameter snags and down wood, abundant arboreal lichens and epiphytes) are likely to decline (Essen et al. 1992, Angelstam and Mikusinski 1994). Although many species in the Pacific northwest use old forest habitats (see Ruggiero et al. 1991, MacKinnon 1998 for reviews), complex life histories and an uncertain relationship between abundance and habitat quality (Van Horne 1983, Pulliam 1988) make it difficult to define precisely the number of species that are dependent on these habitats. There is considerable range in the return frequency of stand-replacing natural disturbances in different forest types (Agee 1993, Parminter 1998), and evidence to suggest that these differences also affect the vertebrate faunas in these habitats (Bunnell 1995). Hence, managed disturbances that modify the seral stage distribution of forests will have considerable impacts on biological diversity, but these impacts will likely be greater in forests that historically contained a high proportion of old-growth habitat.

A monitoring program to track changes in the seral stage distribution should be conducted at a sufficiently fine scale that distinguishes between forest types. The 13 biogeoclimatic zones occurring in the MCE in British Columbia reflect differences in abiotic factors (e.g. soils, precipitation, etc.) and ecological features such as tree species composition. Tracking average seral stage patterns across the entire MCE would obscure the patterns created by biogeoclimatic zone specific average fire return intervals (Bunnell 1995). For example, the boreal black and white spruce biogeoclimatic zone has an average fire return interval of 125 years, while the average interval for the mountain hemlock zone is 400 years. While the overall seral stage distribution of forests in the MCE is of interest, the unique community structure of plants and other organisms in each biogeoclimatic zone will necessitate monitoring seral stage patterns at a finer scale. A suitable resolution at which to track seral stage changes over an extensive area is likely the biogeoclimatic zone (Meidinger and Pojar 1991). More detailed reports at the biogeoclimatic subzone level should be considered to capture the differences in fire intensities (Arno and Davis 1980), average fire return intervals (Arsenault 1998) and harvesting activities that exist between subzones.