Aboveground modular component responses to intraspecific competition within density-stressed black spruce stands

• Published in: Canadian journal of forest research Vol. 28; no. 11; pp. 1587 - 1610
• Main Authors: Newton, P.F, Jolliffe, P.A
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.11.1998; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bark; Biological and medical sciences; Boreal forests; branches; Canada; Competition; conifer needles; Demecology; dry matter partitioning; Ecosystems; Fundamental and applied biological sciences. Psychology; growth; Growth kinetics; Heterogeneity; leaves; Mosses; nutrient availability; photosynthesis; Picea mariana; plant competition; plant morphology; Plant populations; Plants and fungi; R&D; Research & development; Resource depletion; Soil nutrients; Solar radiation; Species composition; Spruce; stand density; stress; tree age; Trees; Vegetation; Wildfires; Canada; Pure forest stand; Stand density; Growth; Dry matter; Modeling; Stress; Modular component; Spatial distribution; Morphology; Softwood forest tree; Gymnospermae; Intraspecific competition; Above ground plant part; Coniferales; Spermatophyta; Picea mariana; Adaptation
• ISSN: 0045-5067; 1208-6037
• DOI: 10.1139/x98-134

A broad range of measures of aboveground growth were used to assess whether competition occurs by processes of resource depletion or resource preemption within monospecific, even-aged, density-stressed, and spatially heterogeneous black spruce (Picea mariana (Mill.) BSP) stands. The assessments proceeded by evaluating the relationships between relative growth and partitioning indices of individual subject trees and directional-specific indices of cumulative competition. Significant directional-specific asymmetrical relationships between subject trees and their local competitors were found, indicating the occurrence of competition by resource preemption. All measures of growth, however, did not respond to directional-specific competition to the same degree. Larger responses, characterizing the response of black spruce trees to increasing competition from their larger neighbours, involved decreased branch production and changes in foliar morphology. Such adaptive, plastic responses in phenotype, combined with lesser responses of foliage production and nutrient concentrations, suggest a strategy used by black spruce to compete within density-stressed populations situated on nutrient-limiting sites: decreased allocation of resources to nonphotosynthetic components, maintenance of the photosynthetic apparatus through adjustments in foliage morphology, and nutrient conservation through foliage retention.