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Vertical distribution and biomass of fine roots in three subalpine forest plant associations in southwestern British Columbia Nuszdorfer, Friedrich Carl


Roots smaller than 5 mm in diameter were studied in three typical high elevation forested plant associations of coastal Southwestern British Columbia. The objectives were to quantify their distribution with depth, examining changes with plant association and time; to examine their relationships with foliage; and to seek correlations with soil properties. Coring randomly in three replicates of each plant association was followed by washing of soil and organic matter from roots with water in combination with manual sorting. Length and surface area were estimated for all samples. Standard analytical methods were used for determining soil physical and chemical properties. Soil temperature and moisture were measured during the growing season. The peak in mass of both overstory and understory < 2 mm roots was within the upper 10 cm of the soil. Overstory 2-5 mm roots peaked between 5 and 30 cm. Understory 2-5 mm roots peaked within 10 cm of the surface of the forest floor. The large variation between replicates of the plant associations made it impossible to determine if changes in root mass with time of sampling were real or due to random variation. Unsuberized roots of the overstory vegetation contributed very little to biomass of ≤ 5 mm roots. Biomass of ≤ 5 mm roots of the overstory vegetation varied from 740 to 1320 g m⁻², length from 3.8 to 6.5 km m⁻², and surface area from 7.3 to 11.9 m² m⁻². The ridgetop association had the most overstory and understory roots and its soil (including organic horizons) was lowest in total nitrogen concentration and CEC. The midslope association had intermediate amounts of overstory roots, the lowest amount of understory roots, and its soil was intermediate in nitrogen concentration and CEC. The receiving association had the lowest amounts of overstory roots, intermediate amounts of understory roots, and its soil had the highest nitrogen concentration and CEC. The ridgetop ecosystems had the highest ratio of root-to-shoot and ratio of root-to-foliage plus twig, being approximately double the ratio for the receiving association. The midslope association was intermediate. Correlations of root mass with soil properties were generally poor.

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