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Rabbit Grazing and Species Diversity in a Dune Area
Author(s): H. J. Zeevalking and L. F. M. Fresco
Source: Vegetatio, Vol. 35, No. 3 (Nov. 30, 1977), pp. 193-196
Published by: Springer
Stable URL: http://www.jstor.org/stable/20145524
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vol.
Vegeratio
& L.F.M. FRESCO
of Plant Ecology, University
Department
1977
IN A DUNE AREA*
RABBIT GRAZING AND SPECIES DIVERSITY
H.J. ZEEVALKING
35, 3: 193-196,
of Groningen,
Biological Centre, Haren (Gn), theNetherlands
Keywords:
Diversity, Dune vegetation, Frisian Islands, Rabbits
Introduction
environmental
Small grazing mammals such as rabbits (Orictolagus
cuniculus (L.)) often strongly affect vegetation structure and
species
observations
Superficial
composition.
show
that
variation in rabbit density in space and in time is an impor
tant
environmental
factor
carried
vestigations,
are directed
out
in a dune
to unravel
to vegetational
area.
Most
changes
level of an environmental
stability
diversity (van Leeuwen
a temporary
a disturbance
it is not always
1966). Therefore
or decrease
of
in structural
decrease
rabbit
factor
Another
is an anal
approach
investigated.
of animal
variation
Gilham
(1955)
density.
has been
of
ysis
spatial
concerning
are available.
However,
such
one
as nutrient
hand
a
level,
climate
potential
and predator
for more
basis
com
Some
to
contribution
on
comments
the
the
solution
relation
of
management
between
number
of
plant species and rabbit population density were made by
Gilham (1955). Tansley & Adamson (1925), Farrow (1917)
and van Leeuwen & van der Maarel (1971). However,
more
data
precise
are
required
in order
to
con
draw
clusions. This study tries to investigate the effects of both
rabbit grazing and changes in rabbit grazing on plant spe
cies diversity; both topics being of importance inmanage
ment
of
rabbit
areas.
grazed
of a controlling
clear whether
influence
models
quantitative
ecosystems
prehensive theories, while on the other hand theymay be a
scientific
cause
factor may
and
factors
are on
problems.
the
rabbit density by fencing or after the outbreak of myxo
matosis (van Leeuwen & Westhoff
1960, Ranwell 1960,
Thomas 1960,Watt 1957,Watt 1960,White 1961,Meyers
& Poo le 1963,Thomas 1963, van Leeuwen & van derMaa
rel 1971). A difficulty here is that a sudden change in the
a system's
sity and
density
in
of
in complex
simple field descriptions of relations between species diver
relations,
complex
of
after a reduction
these
Few
factors.
this subject
Investigated
area
and methods
employed countings of pellet density. Little is known about
the
the grazing
between
relation
a rabbit,
of
so
it is more
area
area
and manuring
to use
obvious
of
observations
direct grazing effects (Williams et al. 1974) as has been
done in this project.
An
ural
aim
of modern
biocoenoses
diversity.
Therefore
of natural
management
or
is preservation
the manager
has
increase
to become
or
semi-nat
of
species
acquainted
with the relation between species diversity and the principal
The
-
investigated
Schiermonnikoog.
area was
one
Three
of
dune
the Dutch
Frisian
Islands
can
complexes
be
dis
tinguished here :the old West Dunes (more than 300 years
old), the younger Kooi Dunes (roughly 130 years old) and
the most recently formed Kobbe Dunes (about 80 years).
Relations between the amount of rabbit grazing and species
diversity have been described in terms of the existing
situation
:a mosaic
pattern
of microhabitats
with much
and
with little rabbit grazing. Plots of 1meter square containing
*
a
Nomenclature
follows
Heukels-van
Ooststroom,
Flora
van
18e druk,
1975.
Nederland,
**
The work has been done by Mrs Ada Zeevalking-van
Yperen
and Mr Hein Zeevalking
as part of their study for a doctoral
homogeneous
vegetation
to represent
both
chosen
were
selected.
the observed
The
variation
plots
were
in vege
tation structure and the variation in the amount of rabbit
grazing in the Kooi Dunes and the Kobbe Dunes. Plots
degree.
193
were
south
In the Kobbe
slopes.
were
slopes
on north
in (dry) valleys,
situated
and on
studied
no plots
Dunes,
in rabbit
variation
because
dune
exposed
slopes
on
south
activity
was
low.
very
To
for
rabbit
quantify
each
plant
a measure
grazing,
Gs
estimated
i-1?i?i?i?i
?oJ
012345
S
oJ ,?,?,?,?,?,
012345
and
bryophytes
(phan?rogames,
species
was
oJ i-,-1-,-1?
012345
E Gp Gp Gp
lichens) in a plot:
=
Gs
0, not
or <
grazed
1% of stems
and
leaves
;
grazed
1, 1-10% grazed;
2, 10-50% grazed;
3, ^ 50% grazed.
The total amount of grazing in a plot has been expressed in
:
a grazing index
Gp
= 0, all
Gs equal 0;
l,allGs S 1;
=
2, all Gs ^ 2, N(GS
2) (number
=
<
with
2;
2)
|GS
=
=
= 0 and
3, either N(GS
3)
N(GS
or N(GS = 3) = 1 and N(GS =
=
=
= 1 and
4, either N(GS
3)
N(GS
or 2 ^ (Gs = 3) S 3;
=
3)^4;
5,N(GS
Gp
^
of
the calculation
For
were
1%
taken
was
diversity
Species
species
Gp, only
into consideration.
simply
with
an
Thus,
the reverse
connections
has
been
of
of
in a transect
described
of adjacent 1 sq.m plots through a rabbit field from which
(as seen
it is known
from
air photos)
that
the borders
have
changed in the last 20 years. By comparing the species
diversity of these plots with the mean species diversity of
the same
with
plots
on
some
Gp,
information
has
and
been
this matter.
(which
the
of
the
the
rabbit,
tol
for our
often
purposes.
plants
Woody
for
characteristic
ungrazed
as intolerant to grazing. On the
called
'rabbit avoided'
hand,
(e.g.
species were
or
'rabbit
resistant'
mosses)
(e.g. Trifolium
repens) which
we found were
in grazed
present
plots. Williams
frequently
et al.
found
(1974)
that hairy
as Holcus
such
species
lanatus
were not preferred by rabbits. On Schiermonnikoog
are
frequently
grazed
plots.
the
own
Our
can
versity
be
the areas
from
expected
rabbit
grazing
caged
in species
wild
rabbits
thus
et al.
supports
and richness have been
the above
results,
near
is lowest
is absent
severely
and Williams
richest
of the transect-plots
where
field,
on
of Gillham
they
in
dominant
observations
conclusions
of
even
and
present
or
low
di
species
the border
the
of
{Fig. 2). Yet
spe
cies diversity is not entirely predictable with the results of
Fig. 1.Near the border of the field, the number of species is
clearly
lower
than
the expected
values
on account
of mean
values in other Kobbe Dune valleys (plots 1-6 and 17-22).
curve.
194
of
some
other
As
ing affects
were
found
the view that both composition
determined by rabbit grazing.
conclusions
in species
a study
from
result
might
the preference
is useful
which
we
support
In Figure 1, species diversity is clearly highest in the plots
with moderate rabbit grazing (Gp = 3). Poorest in species
are the plots without rabbit grazing. The relation between
rabbit grazing and species diversity turned out to be paral
lel in all sites investigated ; the graph presents an optimum
From
answer
? The
is : is the variation
erance of the plant species and the presence of the species in
relation to grazing pressure. Gillham (1955) gives some in
Composition
Results
af
the vegetation
on the amount of rabbit grazing,
between
formation
measured
of
composition
question
important
diversity dependant
or
number
species
plots) were mentioned
the vegetation
obtained
and/or
fects the pattern of rabbit grazing.
To get some insight in the effects of changes of rabbit
other
:
B Kooi
Dunes,
north slopes; E: Kobbe Dungs,
Dunes,
valleys; F: Sum of A-E.
over the points give the number of recorded plots.
The numbers
structure
2) > 3
2) ^ 3;
2) > 3
a coverage
as
the amount of rabbit grazing and num
between
south slopes;
in 1 sq. m plots. A: Kooi Dunes,
:
:
Kobbe
north slopes ;C Kooi
;
Dunes,
valleys D
of species
species/plot.
activities,
Fig. 1. Relation
ber of species
this,
it does
the
not
differences
become
clear whether
in the
vegetation,
rabbit
graz
or whether
The
negative
values
the border of plots
correlate
with
the unstable
situation
1-6 is sharp, with dead Hippophae
:
20
Frisian Islands, thismay be effected by promoting a grazing
15
intensity
since
10
U
species
then be
ity must
crease
of average
a
-5J
12
i-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
610
12
3 4 5
8
lower
average
Species
14
16
18 2220
plot nr.
of species in a trasect in a Kobbe Dune
Fig. 2. Number
valley.
The dotted
line gives the mean number of species in the Kobbe
Dune valleys (Fig. IE) with equal grazing pressure. The shadow
ed blocks give the mean deviation
(expected Nr. minus observed
in four parts
Nr.)
the transect.
of
3
in many
turns
out
However,
places.
to be
on
dependant
shrubs
a
indicating
recent
extension
of
of
use'
the outbreak
since
of myxomatosis
and
the
decrease of population density of the rabbit since then
This might mean that both a sudden increase and a sudden
decrease
in rabbit
species
grazing
Once
diversity.
higher
These
between
really
to uwer
and
earlier
studies
The
simple.
(1967)
another
of van Leeuwen
showed
of
results
an
demonstrated
that
van
these
points
out
verifi
relations
&
between
(1971)
the causal
of
such
Leer
grazing
i.e. d?salinisation.
complexity
are
effects.
The
(1969),
Van
(1971) and van Leeuwen & van der Maarel
der Maarel
observed
coarser
vegetaion
after
patterns
a decrease
of rabbit grazing. The species diversity may be kept low
rabbits,
development.
a
longer
generally,
between
and
intensively
or
increase
of
period
community
extensively
de
about
bring
time.
diversity
length of the
areas,
grazed
and b) grazing gradients instead of sharp borders or 'limes
convergens'. To know the rabbit density which is optimal
for plant species diversity, grazing patterns in connection
with
population
density,
structure
vegetation
and
geo
need further investigation.
Summary
The relation between density of rabbit populations and
plant species diversity is discussed. In the dunes of the
Dutch Frisian Island of Schiermonnikoog,
the rabbit
on
has
been
the
of traces
basis
pressure
grazing
quantified
of recent grazing activity. Moderate
bring
about
in grazing
maximal
pressure
species
(either
grazing turned out to
richness.
decrease
or
Current
increase)
changes
can result
in plant species diversity that is lower than in other places
with equal but stabilized grazing pressure.
in very
however,
The
present
young
investigation
stages
of
shows
vegetation
that a cer
tain (intermediate) rabbit density brings about a maximal
Sudden
species diversity.
a decrease
in diversity.
changes
in grazing
References
(1966). A
der Maarel
interaction
process,
controlling
another
same phenomenon has been observed by Westhoff
who
over
An
necessarily
in a
variation
are
in time
and
cation of some postulations
of
and
grazing
and
diversity
in space
factor
number
between
not
again.
relations
controlling
the balance
in plant
has been redressed, diversity might
species composition
become
a decrease
cause
pressure
account.
will
the
field, while the still living shrubs are seriously damaged by
rabbits. The opposite border is vague :as air photographs
show, it shifted in the direction of the centre of the field
in the direction of the centre of the field since 1954. Possibly
this border has been sharper in the past and has become
'out
into
can be increased by promoting :a) a maximal
morphology
rhamnoides
taken
density
diversity
and, more
diversity
borders
by
composition
rabbit density, a far frommaximal plant community divers
"o
c 0
not
=
G
approaching
pressure
cause
One aim of the management may be (and is often) the
obtaining and preservation of maximal plant species di
versity. For Schiermonnikoog, and possibly for the other
of the vegetation
of Breck
E.P.
1917. On the ecology
Farrow,
land. HI. General
effects of rabbits on the vegetation.
J. Ecol.
5:
1-18.
E.M.
1955. Ecology
of the Pembrokeshire
Gillham,
The effect of grazing on the vegetation.
J. Ecol.
van.
Leeuwen
1966. A relation
theoretical
CG.
Islands.
43:
III.
172-207.
to
approach
in vegetation.
Wentia
and process
15: 25-46.
van & E. van der Maarel.
1971. Pattern and pro
Leeuwen, CG.
cess in coastal dune vegetations.
Acta Bot. Neerl. 20:191-198.
pattern
van & V. Westhoff.
en suc
1960. Myxomatose
Leeuwen, CG.
cessie op Schiermonnikoog.
Bilthoven.
RIVON-report,
E. van der. 1971. Plant species diversity
to
in relation
Maarel,
of animal and plant
management
Ed. E. Duffey
& A.S. Watt.
45-63.
Blackwell,
Oxford,
London,
Edinburgh:
E. van der & J. Leertouwer.
1967. Variation
in vegeta
Maarel,
tion and species diversity along a local environmental
gradient.
management.
communities
Acta
Myers,
The
Bot. Neerl.
K. & W.E.
Scientific
for conservation.
16: 211-221.
Poole.
rabbit, Oryctolagus
J. Ecol.
51:435-451.
1963. A study of the biology of the wild
(L.) in confined
populations.
cuniculus
195
D.S.
1960. Newborough
Warren,
Anglesey,
on parts of the dune system after
in vegetation
Changes
J. Ecol. 48: 385-397.
loss of rabbits by mycomatosis.
Ranwell,
A.G. & R.S. Adamson.
Tansley,
of the English
chalk. III. The
border.
shire-Sussex
J. Ecol.
AS.
Thomas,
myxomatosis.
A.S.
Thomas,
1925. Studies
chalk
grasslands
13: 177-223.
in vegetation
287-307.
1960. Changes
J. Ecol. 48:
III.
the
of the vegetation
of the Hamp
since
the advent
of
in vegetation
since the
1963. Further
changes
of myxomatosis.
J. Ecol. 51:151-186.
rabbits from grassland
1957. The effect of excluding
A.S.
in Breckland.
J. Ecol. 45: 861-879.
(mesobometum)
advent
Watt,
B
Watt,
1960. The
A.S.
philous
Westhoff,
effect
of
in Breckland.
grassland
V.
1969. Langj?hrige
s?ssungs-Dauerprobefl?chen
an der ehemaligen
Vegetation
Williams,
ment
cattle
D.B., T.CE.
of Woodwalton
and
rabbits.
rabbits
48:
from
acido
601-604.
Beobachtungen
und
beweideter
der
Aus
unbeweideter
Zuiderzee.
R. T?xen
(ed.) Ber.
1965. pp. 246-253.
Junk, Den Haag.
in the vegetation
observations
of
the disappearance
of the
following
Int. Symposium
Rinteln
D.J.B.
1961. Some
White,
Point, Norfolk,
Blakeney
rabbits
in 1954. J. Ecol.
excluding
J. Ecol.
49:
Wells
Fen
J. Appl.
113-118.
and D.A.
Wells.
: seasonal
Ecol.
Grazing manage
in the diet of
changes
11: 499-516.
Accepted 9 April 1977
196