Use of understory vegetation in classifying soil moisture and nutrient regimes

Abstract

One-hundred-and-two white spruce [ Picea glauca (Moench) Voss] stands sampled in the sub-boreal spruce biogeoclimatic zone of British Columbia were used to examine the role of understory vegetation in assessing soil moisture and nutrient regimes. Based on the existing knowledge, each species of indicator value was assigned into one of six indicator species groups for soil moisture and/or one of three indicator species groups for soil nitrogen. On each stand, the frequency of each indicator species group was calculated using % covers of all indicator species. Soil moisture and nutrient regimes were then classified based on calculated frequencies following the criteria proposed in the study. As a result, 16 stands were classified as moderately dry, 27 stands slightly dry, 25 stands fresh, 15 stands moist, 12 stands very moist, and 7 stands as wet; 10 stands were classified as very poor, 20 stands poor, 41 stands medium, 24 stands rich, and 7 stands as very rich. These classifications compared favorably with the two soil-based classifications reported earlier for the same data, with 47-59% of stands in agreement and 38-46% of stands in disagreement in only one class. Testing the classification against soil moisture and nutrient measures and white spruce foliage nitrogen and site index further supported the indicator plant approach to soil moisture and nutrient regime classification. It is concluded that the indicator plant approach is a good alternative to the soil-based approaches that have been commonly applied in site classification systems across Canada.