Mueller, K.E., LeCain, D.R.,
McCormack, M.L., Pendall, E.,
Carlson, M. and Blumenthal, D.M.
2018
"Root responses to elevated CO2,
warming and irrigation in a semi-arid
grassland: Integrating biomass,
length and life span in a 5-year
field experiment."
Journal of Ecology 106:
2176-2189.
Lots of research has covered
the impact of elevated CO2
on the aboveground growth
and biomass of plants.
Far less is known about
such impacts underground.
Mueller et al. (2018) assessed
root biomass and length dynamics
in a mixed-grass prairie ecosystem
over a five-year period.
SUMMARY:
The future looks good
for this mixed-grass
prairie ecosystem
under elevated CO2,
elevated temperature,
or elevated CO2 and
elevated temperature.
Mueller et al. say
stimulation of
total root length
and root life span
under elevated CO2
alone and in combination
with warming likely
enhanced plant access
to needed resources,
such as water and
phosphorus.
Such root responses
"help explain previous
observations of higher,
and more stable,
above-ground
productivity
in these projected
climate conditions."
DETAILS:
Elevated CO2 had a positive impact
on both root biomass and root length
in the upper soil profile (0-15 cm),
though the effect was much stronger
for root length.
Root survivorship (assessed over
the full soil layer, 0-35 cm)
was also enhanced by elevated CO2.
Warming had less of an influence
on root biomass and survivorship,
but positively influenced root length.
And in the combined
elevated CO2 and elevated
temperature treatment,
root biomass and root length
were both enhanced, but root
survivorship remained mostly
unchanged from the
control treatment.
The location was west of
Cheyenne, Wyoming,
in a plant community
dominated by several
C3 graminoid species (>45%)
and a perennial C4 grass (15-40%),
with smaller percentages
of diverse forbs and
subshrubs (5-35%).
Treatments included:
(a)
ambient CO2
(~400 ppm) and
ambient temperature,
(b)
elevated CO2
(600 ppm during
daylight hours
only of the
growing season) and
ambient temperature,
(c)
ambient CO2
and elevated
temperature
(+1.5°C during the day and
+3.0°C during the night)
(d)
elevated CO2 and
elevated temperature.
Elevated CO2 was from
a Free-air CO2 Enrichment
(FACE) system and
elevated temperatures
were achieved using
infrared heaters.
