Fróðskaparrit - 01.01.2006, Side 117

ÚTBREIÐSLAN AV LÍVSHÆTTUM RAUNKIÆRS
NIÐAN EFTIR FJALLASÍÐUM í FØROYUM
115
Introduction
In this paper, we investigate vegetation re-
sponse along altitudinal gradients using
functional types expressed as Raunkiær’s
life-forms.
The advantage of using functional types
!s that the diversity of species is reduced into
a more manageable system, and there is min-
unal loss of relevant information. Such a
system, where plant species are grouped to-
gether on the basis of similar attributes or
functions into well-defíned groups, can re-
yeal similarities in the response of group
niembers to environmental disturbance.
Grouping of individuals according to simi-
larities in attributes also makes it possible
to compare areas with taxonomically dif-
ferent floras (Woodward and Cramer, 1996;
f*>az et al., 1999). A variety of functional
systems have been established (Nobel and
Gitay, 1996). These are commonly based on
autecological characteristics such as mor-
Phology, physiology and phenology, de-
niography, etc., or a combination of several
characteristics (Box, 1981; Grime et al.,
1988; Kelly, 1996; Diaz, etal. 1997;Walker,
1997).
In recent years, plant functional classifi-
cation has received much interest arnong
ecologists studying the effect of global cli-
^ate change on ecosystems (Diaz and
Cabido, 1997; Gitay and Nobel, 1997;
I l°bbs, 1997). These classification systems
have been used on a broad scale to desóribe
global vegetation(Box, 1981; Prenticectu/.,
1992), especially in climate change studies
Ie-g. IPCC, 2001), and, on a local scale, to
^scribc the vegetation in a region (Diaz et
al■» 1997; Grime et al., 1997).
Altitudinal transects with steep climatic
gradients are useful settings for studying the
variation of functional types as a result of
climate change. Various studies show that
Raunkiær’s life-forms vary along altitudi-
nal transects (Gomez et al., 1993; Mark et
al., 2000; 2001; Pavon et al., 2000). This has
also been shown for the Faroe Islands
(Raunkiær, 1934; 1936; Hansen, 1972).
It is generally accepted that the effect of
changing land use on most ecosystems is
greater than the effect of climate change (Vi-
tousek et al., 1997). Therefore, it is impor-
tant that the effect of land use also be taken
into consideration in a discussion of global
climate change (Diaz et al., 1997). A num-
ber of different studies dealing with the ef-
fect of land use show that disturbances often
promote certain life-fonns and impede oth-
ers (Mclntyre et al., 1995; 1999; Hadar et
al, 1999; Lavorel et al., 1999). Studies of
land use change and its effects have used
functional characteristics such as Raun-
kiær’s life-forms (Raunkiær, 1934; Mcln-
tyreetal., 1995; Hadar etal., 1999).
Raunkiær based his functional classifí-
cation on the position of over-wintering tis-
sue, which is an indicator of the ability of a
plant to survive unfavourable seasons
(Raunkiær, 1934). Using this system, he was
able tó find relationships between climate
and life-forms in whole floras in different
parts of the world (Table 1).
In this study, we investigate the abun-
dance variation of Raunkiær’s life-forms
along alfitudinal gradients in the Faroe Is-
larids. ln general, the vegetation in the tem-
peráte zone is dominated by hemicrypto-
phytes, however, the abundance of hemi-