Agriculture Reference
In-Depth Information
Estimation of Leaf Longevity from Leaf Turnover
at the Stand Level
Litter traps set on the forest understorey of
Alnus japonica
(Hakusan, Ishikawa, Japan)
Leaf longevity is occasionally estimated as the inverse of leaf turnover rates at the
stand level. Leaf biomass, estimated by allometric methods (Clark et al. 2001) and
assumed to be in steady state, is compared to the biomass of falling leaves col-
lected in leaf traps (Tadaki 1965; Edwards and Grubb 1977; Oshima 1977;
Kikuzawa et al. 1984; Takiya et al. 2006). Under the assumption of steady-state
leaf numbers in the canopy, leaf longevity can be estimated as the inverse of the
ratio of leaf biomass (g m
−2
) to annual leaffall adjusted for the length of the
growing season. For example, the standing leaf biomass in an
Alnus inokumae
plantation was 163 g m
−2
, while annual total leaf fall was 315 g m
−2
during a
growing season (Kikuzawa et al. 1984). This finding indicates a leaf turnover rate
of about 2 over the season, and hence an average leaf longevity of the order of 93
days, about one-half the length of the growing season. There are, however, serious
problems with this method. First, from a practical point of view the approach is
too time consuming to acquire species-specific estimates except in monospecific
stands. Second, the assumption of steady-state leaf biomass is commonly unrealistic.
Third, the variance associated with the allometric estimates of canopy biomass
will often be of the order of magnitude as the biomass of fallen leaves. Fourth, the
biomass of individual leaves at abscission is not equal to their biomass in the
canopy. This method of estimating leaf longevity is best avoided in comparisons
at the species level.
