Use of understory vegetation in classifying soil moisture and nutrient regimes

One-hundred-and-two white spruce [Picea glauca (Moench) Voss] stands sample d in the sub-boreal spruce biogeoclimatic zone of British Columbia were use d to examine the role of understory vegetation in assessing soil moisture a nd nutrient regimes. Based on the existing knowledge, each species of indic ator value was assigned into one of six indicator species groups for soil m oisture and/or one of three indicator species groups for soil nitrogen. On each stand, the frequency of each indicator species group was calculated us ing % covers of all indicator species. Soil moisture and nutrient regimes w ere 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 v ery 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. T hese classifications compared favorably with the two soil-based classificat ions 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 classi fication against soil moisture and nutrient measures and white spruce folia ge nitrogen and site index further supported the indicator plant approach t o soil moisture and nutrient regime classification. It is concluded that th e indicator plant approach is a good alternative to the soil-based approach es that have been commonly applied in site classification systems across Ca nada. (C) 2000 Elsevier Science B.V. All rights reserved.