Disentangling root responses to climate change in a semiarid grassland.
Carrillo, Y., F.A. Dijkstra, D. LeCain, J.A. Morgan, D. Blumenthal, S. Waldron and E. Pendall. 2014. Oecologia
Abstract
Future ecosystem properties of grasslands
will be driven largely by belowground biomass responses
to climate change, which are challenging to understand
due to experimental and technical constraints. We used a
multi-faceted approach to explore single and combined
impacts of elevated CO2 and warming on root carbon
(C) and nitrogen (N) dynamics in a temperate, semiarid,
native grassland at the Prairie heating and CO2 enrichment experiment. To investigate the indirect, moisture mediated effects of elevated CO2, we included an irrigation treatment. We assessed root standing mass, morphology, residence time and seasonal appearance/disappearance
of community-aggregated roots, as well as mass and n
losses during decomposition of two dominant grass species
(a C3 and a C4). In contrast to what is common in mesic
grasslands, greater root standing mass under elevated CO2
resulted from increased production, unmatched by disappearance. elevated CO2 plus warming produced roots that
were longer, thinner and had greater surface area, which,
together with greater standing biomass, could potentially
alter root function and dynamics. Decomposition increased
under environmental conditions generated by elevated CO2,
but not those generated by warming, likely due to soil desiccation with warming. elevated CO2, particularly under
warming, slowed n release from C4- but not C3-roots,
and consequently could indirectly affect n availability
through treatment effects on species composition. elevated
CO2 and warming effects on root morphology and decom-
position could offset increased c inputs from greater root
biomass, thereby limiting future net c accrual in this semi-
arid grassland.
Key Words
Elevated CO2 · Warming · roots · Decomposition · Production · Death · Turnover · Morphology
