Ds. Green et al., Light-use efficiency of native and hybrid poplar genotypes at high levels of intracanopy competition, CAN J FORES, 31(6), 2001, pp. 1030-1037
Citations number
59
Categorie Soggetti
Plant Sciences
Journal title
CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE
In southern Wisconsin, U.S.A., tree growth and associated canopy traits wer
e compared among five native and hybrid genotypes of poplar (Populus spp.)
in replicated, monoclonal stands planted at a 1 x 1 m spacing. The overall
objective of this study was to assess clonal suitability to cultural condit
ions entailing high levels of intracanopy competition (such as high-density
plantations or long rotations) and to identify selection criteria suitable
to such conditions. Two of the clones were Populus deltoides Bartr., two w
ere P. deltoides x Populus nigra L. (DN) crosses, and the fifth was a P. ni
gra x Populus maximowiczii A. Henry (NM) cross. In the third year after est
ablishment, variation in aboveground biomass gain (ANBG) was analyzed in re
lation to canopy light interception (IPAR) and canopy light-use efficiency
(LUE) during a 31-day period when growing conditions were most favorable (l
ate June through late July). ANBG in this interval varied by twofold among
genotypes (2.76-5.78 Mg.ha(1)), and it was highest in the two P. deltoides
clones, followed by the NM and DN hybrids, respectively. Across genotypes,
ANBG was unrelated to IPAR, which varied by only 5%. Instead, it was strong
ly and positively related (r(2) = 0.99) to the twofold variation in LUE (1.
06-2.22 g.MJ(1)). Among measured canopy traits, the best predictor of LUE (
r(2) = 0.88) was an additive combination of factors associated to the optim
ization of canopy photosynthesis: LUE was negatively related to both the ca
nopy light-extinction coefficient and compensation irradiance at the canopy
base. We infer from these findings that poplar genotypes can vary consider
ably in LUE and, correspondingly, in the extent to which photosynthesis is
optimized in dense canopies. Furthermore, the low LUE among hybrid genotype
s at this level of intracanopy competition may reflect a bias in "tree impr
ovement" efforts towards maximizing biomass production under conditions of
relatively low competition.