Agriculture Reference
In-Depth Information
leaves (Coley 1983). These relationships are not considered causal in and of
themselves because tree growth is affected by very many other traits, but it is clear
there is a functional linkage between overall growth and leaf turnover. This linkage
is also apparent in the relationship between wood density and leaf longevity.
Fast-growing, early successional species on Barro Colorado Island such as
Cecropia
insignis
with a wood density of only 0.15 g cm
−3
had shorter leaf longevity than
slower-growing, late successional species with wood densities in the range of 0.34-
0.64 g cm
−3
(King 1994). Ishida et al. (2008) report the same trend for woody species
on the subtropical Bonin Islands. Chave et al. (2009) have characterized a “wood
economic spectrum” that associates increasing wood density with slower growth
rates, which suggests these relationships may prevail generally across species.
Seedling Growth and Leaf Longevity
The relationship between growth rate and leaf longevity also is expressed at the
seedling stage where the initial growth of current-year seedlings depends on seed
size. For example, seed size varies among deciduous broad-leaved trees in northern
Japan from nearly 10 g in
Aesculus turbinata
to less than 1 mg in
Betula platyphylla
(Seiwa and Kikuzawa 1989). A large-seeded species such as
A. turbinata
typically
attains the large part of its annual height growth within a month of germination
(Fig.
7.3
). In contrast, the height growth of a small-seeded species such as
B. platy-
phylla
has a long lag before shoot growth takes off later in the season. The seedling
shoot growth of the large-seeded species is essentially determinate, the small-seeded
is essentially indeterminate, and the leaf longevities are correspondingly long and
short, respectively (Seiwa and Kikuzawa 1991). The leaf longevity of seedlings,
however, is shorter than that of adult trees for both large- and small-seeded species,
perhaps because the costs of transport associated with each leaf are greater in adults
than in seedlings (Kikuzawa and Ackerly 1999). There is, however, no significant
difference in leaf longevity of saplings and adult trees (Reich et al. 2004).
Fig. 7.3
Growth curves of seedlings from germination for
Betula platyphylla
(
Bp
), a small-
seeded species, and for
Aesculus turbinata
(
At
), a large-seeded species at open (
open circles
) and
shaded (
closed circles
) sites. (From Seiwa and Kikuzawa 1989, 1991; redrawn by KK)
