Fróðskaparrit - 01.01.2006, Síða 122

120
DISTRIBUTION OF RAUNKIÆR’S LIFE-FORMS
ALONG ALTITUDINAL GRADIENTS IN THE FAROE ISLANDS
(U
CD
ro
(U
Q_
Fig. 2. The biological
spectra of Raunkiær ’s life-
forms based on the total
Jlora in the Faroe Islands
compared to results from the
present study. The life-forms
are given as % oftotal
number of vascular species
for each of the four life-
forms.
Hem: Hemicryptophytes;
Ch: Chamaephytes;
G: Geophytes and
Th: Therophytes.
the Pearson correlation test (Table 4) and the
results used to determine which environ-
mental variables should be included in the
analysis by choosing the variables that were
least correlated to one another.
The altitudinal variation was determined
by plotting the weighted abundance of each
life-form against altitude at 50 m intervals
and identifying the best fírst or second order
polynomium to fit the data from an ANOVA
table. If the coefficient of the quadratic term
in the second order regression analysis was
significantly different from zero, the second
order polynomium was selected; otherwise,
the linearregression was selected. Life-form
abundances, expressed as percentages, were
determined by dividing the abundance of
each life-form by the sum of all life-form
abundances in each meso-plot. The correla-
tion of life-form abundances with each en-
vironmental variable was determined using
the same type of analysis.
Results
The occurrence of life-forms as a percent-
age of species number ífom this study and
for the whole flora of the Faroe Islands based
on Ostenfeld (1905-1908) is shown in Fig-
ure 2.
Hemicryptophytes were found to be the
most species-rich life-form with an average
value of 66% in our study in contrast to 56%
in the earlier study (Raunkiær, 1936).
Chamaephytes also had slightly more
species in our study, 18% in contrast to 15%
from previous studies. There were signifi'
cantly fewer geophytes in our study, 6% in
contrast to 23%, while therophytes were
more numerous, 10% in contrast to 6% nl
older study (Fig. 2). Thus, we found the
same trend in total flora as in the older
studiy, with the exception of geophytes,
which were markedly less. The reason why
geophytes are less numerous in our study is
that many are rare species or they grow in
lowland habitats which are less represented
in our study.
The relationship between the life-forins
in 50 m altitudinal intervals are shown in
Figure 3. Here we can see that hemicrypto-