Stemflow
The two stemflow systems successfully measured
stemflow on 93% of the days when it was raining.
This high success rate is largely attributed to monthly
servicing. Outside of this comparison period stemflow has
also been successfully measured on a day when rainfall
exceeded 280 mm.
At Mount Lewis, stemflow system 1 included 12 trees
covering the range of diameters found in the plot and
represented a basal area of 1Ð19 m2 (Table III). Stemflow
system 2 included 13 trees, which were on average larger
than those of stemflow system 1. The larger size is
reflected in the higher total basal area of 1Ð73 m2. The
different basal area of the two tree sets provides a means
to test the assumption that stemflow can be scaled using
basal area if sufficient numbers of trees are sampled.
Trees for stemflow systems were selected purely on
the basis of DBH, however the high species diversity
at this site meant that of the 12 trees selected for
stemflow system 1, only two trees were of the same
species (Table III). Similarly, of the 13 trees selected
for stemflow system 2, two species were represented
twice. The species range represented by the two stemflow
systems includes both smooth and rough bark trees
and palms. The palms at this site (Archontophoenix
purpurea) are characterized by tall smooth trunks. Palms
represented only a few stems on the 1600 m2 plot,
therefore no effort was made to separate palms from other
species in the analysis. At sites where palms account for
a large proportion of the total number of stems it may be
advisable to separate palms from other species.
Comparison of the two stemflow systems at Mount
Lewis over 213 rainfall days is shown in Figure 9. At the
end of this period, stemflow system 1 had collected 6 mm
(7Ð5%) more water than stemflow system 2. The high
correlation coefficient (r2 D 0Ð98) shows good agreement
between stemflow measured by the two systems despite
the different species and basal area sampled.