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Competitive relations between Douglas-fir and Pacific madrone on shallow soils in a Mediterranean climate

Forest Science
By: , and 

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Abstract

A large area of Pacific Coast forests is characterized by shallow soil, with negligible rainfall in the growing season. This study explores water-seeking strategy on such a site. We studied availability of bedrock water and its effects on growth and ecophysiology of 11-yr-old planted Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and sprouting Pacific madrone (Arbutus menziesii Pursh). The study was carried out at three regulated densities of madrone sprouts on shallow (<50 cm) residual soils in southwest Oregon. Total bedrock water depleted from March to September, as observed in drill holes by neutron probe, did not differ significantly (P > 0.05) among three densities of madrone. However, cover in plots with the highest density of madrone (1322 sprout clumps/ha) depleted 50 mm of water from the 1.5 m layer by June, whereas vegetation on lower density treatments withdrew 15-28 mm by June, with later withdrawal distributed more uniformly through the growing season. Madrone density significantly affected basal diameter (P a?? 0.0001) and height growth (P a?? 0.002) of Douglas-fir. Madrone was consistently taller than Douglas-fir in all plots. The height of 11-yr-old madrone sprout clumps (424-465 cm) did not differ significantly among densities. Madrone leaf area index and biomass were higher at the high density of madrone than at medium density (P a?? 0.045, LAI; P a?? 0.001, biomass). Physiological advantages and rooting habits of madrone give it a competitive advantage over Douglas-fir in this area that it might not have if bedrock did not provide the principal water reservoir for summer growth.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Competitive relations between Douglas-fir and Pacific madrone on shallow soils in a Mediterranean climate
Series title Forest Science
Volume 41
Issue 4
Year Published 1995
Language English
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description p. 744-757
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Forest Science
First page 744
Last page 757