Section 6
Chapter 5,037

Conifer and angiosperm fine root biomass in relation to stand age and site productivity in douglas fir forests

Vogt, K.A.; Vogt, D.J.; Moore, E.E.; Fatuga, B.A.; Redlin, M.R.; Edmonds, R.L.

Journal of Ecology 75(3): 857-870


ISSN/ISBN: 0022-0477
DOI: 10.2307/2260210
Accession: 005036454

(1) Conifer and angiosperm fine-root biomass were determined in an age sequence (range 13-160 years) of eight high-productivity and seven low-productivity Douglas-fir stands in western Washington, U.S.A. (2) No significant changes in total (conifer plus angiosperm) root biomass occurred among the different stand ages within each productivity class. Of the total fine-root biomass, however, the proportion of angiosperm to conifer roots varied significantly when stands were in the 'tree initiation' and 'competitive tree-stem exclusion' stages of stand development. (3) Conifer fine-root biomass reached a peak at canopy closure in both low- and high-productivity stands. After canopy closure, conifer fine-root and foliage biomass levelled off as basal area continued to increase in the low-productivity stands; however, conifer fine-root biomass decreased as basal area increased and foliage biomass levelled off in the high-productivity stands. (4) At all stand ages, the low-productivity stands had significantly more total (conifer plus angiosperm) fine-root biomass than those of high-productivity. At canopy closure and later stages of stand development, a significantly higher conifer fine-root biomass was maintained in low-productivity compared to high-productivity stands. (5) Conifer fine-root biomass was positively related to litterfall lignin content, litterfall lignin:nitrogen ratio and forest-floor nitrogen content in low-, but not in high-productivity stands; these patterns followed an asymptotic exponential curve.

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