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Relationships between site index, and soil moisture and nutrient regimes for western hemlock and sitka spruce

Author(s) or contact(s): G.J. Kayahara and A.F. Pearson
Source: Research Branch
Subject: Conifers
Series: Working Paper
Other details:  Published 1996. Hardcopy is available.


Knowledge of the ecological characteristics of forest sites and the growth of forest trees on different sites is essential for making silvicultural decisions. In British Columbia, the biogeoclimatic ecosystem classification (BEC) is widely used to recognize forest ecosystems according to the ecological quality (climate, moisture, nutrients) of their sites (Pojar et al. 1987; MacKinnon et al. 1992). Recent research has focused on determining the potential produc tivity of various tree species on different sites defined by the BEC system. These efforts should assist forest managers to select the most suitable crop species and silvicultural regimes.

Forest productivity is one focus of forest management, and traditionally, site index (height at a reference age) has been the most widely accepted estimate of forest productivity (Mader 1963; Tesch 1981). However, in cases where the site index for a certain species cannot be determined directly, alternative methods of estimating site index are required to estimate forest productivity. For example, alternative methods are required in situations where the species of interest is absent, is too young or too old for site index calculations, or has suffered mechanical or pathogenic damage.

Various combinations of individual environmental measures have been used to estimate site index indirectly (see Jones 1969; Carmean 1975; Spurr and Barnes 1980, Hagglund 1981). In British Columbia, the relationship between the site index of the province's major tree species and site units of the BEC system has been the focus of recent research (Kabzems and Klinka 1987; Green et al. 1989; Carter and Klinka 1990, 1991; Klinka and Carter 1990; Wang 1992; McLennan 1993; Wang 1993; Wang et al. 1994a, b).

This working paper summarizes two studies that were conducted to determine the relationship between site index and soil moisture and nutrient regimes. Samples were from 102 immature western hemlock (Tsuga hetero- phylla (Raf.) Sarg.) stands in southwestern coastal British Columbia (Kayahara 1992) and 55 immature Sitka spruce (Picea sitchensis (Bong.) Carr.) stands in the eastern Queen Charlotte Islands (Pearson 1992).

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Updated November 04, 2009