Quantifying the importance of biotic and abiotic drivers in creating lags in soil CO2 efflux
Résumé
Soil respiration influences regional carbon dynamics, yet our limited
understanding of drivers of soil respiration currently constrains robust
modeling of soil CO2 efflux. There is evidence that soil respiration
does not follow the standard Arrhenius relationship with soil
temperature at the daily scale, as used in many ecosystem models, but
demonstrates a hysteretic response. The understanding of this hysteretic
response is critical to soil carbon and greenhouse gas emission
modeling. Why soil respiration deviates from monotonic temperature
dependence may depend on lag effects and antecedent features of abiotic
and biotic drivers associated with above- and belowground process
linkages. We set up a 6 months long experiment to determine the biotic
and abiotic drivers of the hysteretic relationship between soil
respiration and soil temperature. The experiment took place at Ecotron
IleDeFrance (France) using replicated closed environmental facilities
allowing the simultaneous control of environmental conditions and
on-line measurement of ecosystem processes. We reproduced semi-arid
ecosystems using basalt soil mesocosms planted with two functional
groups of plants (shrubs and grasses) in monocultures and in a mixture.
We independently controlled above- and belowground temperatures and
rainfall intensity. The split-plot, repeated-measures design allowed for
diel aboveground and temperature cycle treatments to mimic natural
conditions or for diel cycle aboveground temperature and constant soil
temperature treatments to constrain vertical soil temperature gradients,
yet mimic natural aboveground conditions. Soil CO2 concentrations were
measured under mild and heavy precipitations conditions that represent
current and project conditions. We calculated the soil respiration every
30 minutes using the gradient method and conducted additional plant
photosynthesis measurements to better target the role of biotic factors.
Our data show that abiotic and biotic treatments affect the total soil
respiration but also diel patterns and the strength of the hysteretic
effect. This demonstrates the power of experimental approaches to
disentangle physical and biological drivers of soil respiration and
better predict future CO2 efflux from soils.
Auteurs, date et publication :
Auteurs Yann Dusza , Sabrina Juarez , Simon Chollet , Régis Ferrière , Amandine Hansart , Florent Massol , Mathieu Llavata , Jean-François Le Galliard , Enrique Pérez Sánchez-Cañete , Greg Barron-Gafford
Date : 2018
Volume : 20
Pages : 8461