The influence of plant functional groups on ecosystem function in a grassland in northern Canada
McLaren, J. R.. 2010. PhD Dissertation, University of British Columbia, Vancouver, BC
Abstract
Human development,
climate
change,
diseases
and
habitat
degradation
and
loss
are
resulting
in
species
extinction
rates
up
to
a
thousand
times
faster
than
pre-human
levels.
Biodiversity-ecosystem
functioning
research
examines
how
this
loss
of
species
and
changes
in
the
composition
of
plant
communities
are
likely
to
influence
numerous
ecosystem
functions.
The
effects
of
biodiversity
loss
on
ecosystem
properties
may
also
be
highly
dependent
on
the
identity
of
the
organisms
lost.
I
investigated
the
influence
of
plant
functional
group
identity
in
determining
ecosystem
properties.
I
established
a
removal
experiment
in
a
grassland
in
northern
Canada
in
2003
with
four
treatments:
a
no removal
control
and
independent
removal
of
forbs, graminoids
and
legumes.
As
biodiversity
loss
is
occurring
in
concert
with
environmental
change,
I
crossed
removals
with
a
fertilizer
and
a
mycorrhizal
reduction
(fungicide)
treatment
to
determine
the
context
dependency
of
effects.
I
showed
that
graminoids
have
the
largest
influence
on
ecosystem
properties
in
this
community,
despite
not
being
the
most
abundant
group.
Short-term
(4 years)
biomass
compensation
for
the
removals
showed
no
compensation
for
graminoid
removal,
but
after
7
years
there
was
full
biomass
compensation
for
this
treatment.
Light
interception,
soil
moisture,
and
soil
nutrients
were
all
largely
determined
by
the
presence
of
graminoids
in
the
plant
community,
and
surprisingly
legumes
had
very
few
effects
on
any
ecosystem
property.
Graminoids
also
showed
plant-driven
environmental
effects
on
leaf
decomposition,
although
no
removal
treatment
resulted
in
changes
in
the
decomposition
of
roots.
Graminoids
promoted
decomposition
of
leaf
litter
through
2
mechanisms:
influence
on
the
decomposition
microenvironment
and
changes
in
the
litter
composition.
Finally,
I
have
demonstrated
that
very
few
of
the
effects
of
functional
group
identity
were
context
dependent
on
either
fertilization
or
fungicide
treatments.
These
results
highlight
the
importance
of
considering
plant
functional
group
identity
when
predicting
the
effects
of
species
loss,
and
indicate
that
plant
identity,
more
so
than
dominance,
determines
effects
on
ecosystem
properties.
