The vertical distribution of fine-root biomass, its chemical content, and the vertical distribution of overstory root tips were measured in a mature white spruce – subalpine fir stand (Piceaglauca (Moench) Voss – Abieslasiocarpa (Hook.) Nutt.) growing on an infertile sandy soil near Prince George, British Columbia, during July and August, 1975. The study was part of a larger project which described the biomass and chemical content of the tree and minor vegetation. The objective of the project was to provide information on nutrient losses accompanying whole-tree logging and to estimate the possible consequences of such losses for future tree production. Questions concerning the magnitude of the soil nutrient capital available to the vegetation indicated the need for information on the exploitation of the soil by the roots. This paper reports the results of an investigation of the fine roots. Living fine roots (<6.4 mm) of overstory trees and understory plants were sampled separately from 11 soil pits to an average depth of 94 cm. Overstory fine-root biomass was estimated to be about 1870 kg/ha of which 67% was in the forest floor (LFH horizon) and the Ae horizon. The average combined depth of these two horizons was only 8.3 cm, but they contained 88% of the overstory root tips sampled. The 3.3-cm-thick forest floor alone contained half of the fine-root biomass and approximately 70% of the overstory root tips. Understory fine-root biomass was estimated to be about 7880 kg/ha of which 69% was in the forest floor and the Ae horizon. The concentrations of N, P, K, Ca, and Mg generally decreased with increasing depth, while Fe and Al exhibited the opposite pattern.The marked concentration of fine-root biomass and root tips in the forest floor is interpreted as reflecting the very low nutrient status of the mineral soil on the study site. The high value of fine-root biomass for understory vegetation results from the open structure of the stand and is thought to reflect the great importance of this vegetation in nutrient cycling on the study site. The biomass data, together with root chemical concentration data, are consistent with the hypothesis that the forest floor is the major source of several of the macronutrients for the vegetation on the site.
Examination of Vertical Distribution of Fine Root Biomass in a Tropical Moist Forest of the Central Amazon, Brazil
