Agriculture Reference
In-Depth Information
m
per tree (LAI,
c
and Palmer and Jackson (
) a leaf area of
.
.
.
)for
trees ha
−
.
Cropping and pruning also influence tree leaf area. Barlow and Smith (
'Golden Delicious'/'M.
' planted at
)
found that consistently deblossomed trees had up to
times the leaf weight
of cropping trees. Trees that had consistently been lightly pruned had up to
twice the leaf weight of heavily pruned trees. Lightly pruned or unpruned
trees also show a much more rapid development of their leaf area early in the
season than heavily pruned trees because a higher proportion of their leaves
are borne on spurs (Lakso,
).
Temperature has major effects that result in differences in tree leaf area at
different latitudes. Annual mean daily air temperature is a linear function of
latitude. Leafing out and blossoming is earlier at low latitudes, leading to an
increase in leaf area duration, i.e. leaf area integrated over the season (Heim
et al.
,
). Apple flower development starts
.
days earlier per degree lower
◦
N and
◦
N and apple trees on 'M.
latitude between
'have
% and
◦
than at
◦
and at
◦
than at
◦
, respectively
% more leaf area at
(Wagenmakers,
a). Areas with a late onset of winter, especially if late-
fruiting cultivars are used, may have an increase in leaf area duration because
of delayed senescence.
Orchard leaf area, or leaf area indexin m
leaf m
−
ground (LAI) depends,
as shown above, on individual tree leaf area and plant population. These
are not independent. Wagenmakers (
) found that leaf area per tree of
'Comice'/'Quince C' pears decreased linearly with planting density over the
range of
trees ha
−
although total orchard LAI still increased with
planting density. Verheij (
-
) showed that with apple the leaf area per tree
declined with increasing planting density even with unpruned trees, and was
accompanied by a relative suppression of lateral growth in the lower parts of
the trees.
It is obvious from the magnitude of the differences in leaf area per tree and
per orchard, and from the trend towards much higher densities of planting but
with lower leaf area indices, that tree and orchard leaf canopy development are
best regarded as variables under management control. The relevant choices of
rootstock, plant population and tree management systems are largely in order
to optimize light interception and distribution.
Although in detailed studies tree leaf area may be assessed by different
sampling and measuring procedures an approximate technique is often used.
In general a given leaf area is associated with a certain cross-sectional area of
subtending stem, both with respect to leaf area per branch and to leaf area
per tree (Holland,
; Barlow,
; Verheij,
; Jackson,
). The basic
linear regression equation is
log
A
=
log
K
+
b
log
G
(
.
)
