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An ecological investigation of western redcedar sites on western Vancouver Island

University of British Columbia

A pilot study was conducted in which a wide range of sites, dominated by western redcedar, were sampled and described to provide background information on western redcedar sites on western Vancouver Island. A total of 40 sample plots, representing a wide range of environmental conditions, were sampled from 14 study sites in the Bamfield, Ucluelet, and Kennedy Lake areas. Descriptive vegetation data were supplemented with additional environmental information and utilized for classification, interpretation and comparison of the study sites. The classical tabular method of comparing vegetation data was used to classify the sample plots into six associations. An ordination of the sample plots, by species composition, confirmed the classification scheme. The associations have been described and discussed, but must be considered tentative due to the small sample size. The productivity of the study sites, as expressed by site index of western redcedar at age 100, was evaluated against a variety of soil parameters. No significant correlations were found between site index and the concentration of soil nutrients, which included total N (%), available P (ppm), organic C (%), and exchangeable Ca, Mg, Na, and K (meq/100g), in the effective and total rooting zones. A significant correlation was found between site index and soil depth, especially the depth to a restrictive layer. This relationship is not surprising since the volume of soil available for rooting integrates many soil factors important to tree growth. The observations and findings based on the sites sampled for this study indicated that productivity of western redcedar is strongly related to edaphic conditions. The most productive of the 14 study sites was characterized by deep, well-drained soils, with a rich nutrient regime as reflected by indicator plant species. Other productive sites were situated either on seepage slopes, where they presumedly received inputs of nutrients through seepage water; or on fertile floodplains with rich nutrient regimes as reflected by indicator plant species. The poorest sites had very shallow soils with a restrictive layer, and poor nutrient conditions (as reflected by indicator plant species), and were situated on either flat depressional areas or rock outcroppings. A new species of earthworm was observed in 11 of the 14 study sites. Results from a preliminary study (Spiers et al. 1983) indicated that these worms break down organic material and improve nutrient availability in west coast ecosystems. This may have important implications for management practices in this region.

Text

2010-05-08

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http://hdl.handle.net/2429/24515

Forestry

University of British Columbia

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