Across North America, forests dominated by Quercus rubra L. (northern red oak), a moderately shade-tolerant tree species, are undergoing successional replace-ment by shade-tolerant competitors. Under closed canopies, Q. rubra seedlings are unable to compete with these shade-tolerant species and do not recruit to upper forest strata. In Europe, natural regeneration of introduced Q. rubra is often successful despite the absence of fire, which promotes regeneration in the native range. Considering that under-storey light availability is a major factor affecting recruit-ment of seedlings, we hypothesized that Q. rubra seedlings are more shade tolerant in the introduced range than in the native range. Morphological traits and biomass allocation patterns of seedlings indicative of shade tolerance were com-pared for Q. rubra and three co-occurring native species in two closed-canopy forests in the native range (Ontario, Canada) and introduced range (Baden-Württemburg, Ger-many). In the native range, Q. rubra allocated a greater pro-portion of biomass to roots, while in the introduced range, growth and allocation patterns favored the development of leaves. Q. rubra seedlings had greater annual increases in height, diameter and biomass in the introduced range. Q. rubra seedlings in the introduced range were also younger; however, they had a mean area per leaf and a total leaf area per seedling that were five times greater than seedlings in the native range. Such differences in morphological traits and allocation patterns support the hypothesis that Q. rubra expresses greater shade tolerance in the introduced range, and that natural regeneration of Q. rubra is not as limited by shade as in the native range. The ability of Q. rubra seed-lings to grow faster under closed canopies in Europe may explain the discrepancy in regeneration success of this spe-cies in native and introduced ranges. Future research should confirm findings of this study over a greater geographical range in native and introduced ecosystems, and examine the genetic and environmental bases of observed differences in plant traits.

Peter Nosko;Kerri Moreau;Christian Kuehne;Kelly C.Major;Jürgen Bauhus

Department of Biology and Chemistry,Nipissing University,North Bay,ON P1B 8L7,Canada;Chair of Silviculture,Freiburg University,79085 Freiburg,Germany;Division of Forestry and Forest Resources,Norwegian Institute of Bioeconomy Research,P.O.Box 115,1431?s,Norway;Tulloch Engineering,1942 Regent St,Unit L,Sudbury,ON P3E 5V5,Canada

林业研究（英文版）

[1]Peter Nosko;Kerri Moreau;Christian Kuehne;Kelly C.Major;Jürgen Bauhus-.Does a shift in shade tolerance as suggested by seedling morphology explain differences in regeneration success of northern red oak in native and introduced ranges?)[J].林业研究（英文版）,2022(03):949-962

Baden,rttemburg,Ger,lings

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