Modelling the diurnal and seasonal dynamics of soil CO<sub>2</sub> exchange in a semiarid ecosystem with high plant–interspace heterogeneity
We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant–interspace heterogeneities in regulating soil CO<sub>2</sub> exchanges (<i>F</i><sub>S</sub>) in a dryland ecosystem with sparse vegetation. To simulate the di...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-01-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/115/2018/bg-15-115-2018.pdf |
| Summary: | We used process-based modelling to investigate the roles of carbon-flux
(C-flux) components and plant–interspace heterogeneities in regulating soil CO<sub>2</sub>
exchanges (<i>F</i><sub>S</sub>) in a dryland ecosystem with sparse vegetation. To
simulate the diurnal and seasonal dynamics of <i>F</i><sub>S</sub>, the modelling
considered simultaneously the CO<sub>2</sub> production, transport and surface
exchanges (e.g. biocrust photosynthesis, respiration and photodegradation).
The model was parameterized and validated with multivariate data measured
during the years 2013–2014 in a semiarid shrubland ecosystem in Yanchi,
northwestern China. The model simulation showed that soil rewetting could
enhance CO<sub>2</sub> dissolution and delay the emission of CO<sub>2</sub> produced
from rooting zone. In addition, an ineligible fraction of respired CO<sub>2</sub>
might be removed from soil volumes under respiration chambers by lateral
water flows and root uptakes. During rewetting, the lichen-crusted soil
could shift temporally from net CO<sub>2</sub> source to sink due to the
activated photosynthesis of biocrust but the restricted CO<sub>2</sub> emissions
from subsoil. The presence of plant cover could decrease the root-zone
CO<sub>2</sub> production and biocrust C sequestration but increase the
temperature sensitivities of these fluxes. On the other hand, the
sensitivities of root-zone emissions to water content were lower under
canopy, which may be due to the advection of water flows from the interspace
to canopy. To conclude, the complexity and plant–interspace heterogeneities
of soil C processes should be carefully considered to extrapolate findings
from chamber to ecosystem scales and to predict the ecosystem responses to
climate change and extreme climatic events. Our model can serve as a useful
tool to simulate the soil CO<sub>2</sub> efflux dynamics in dryland ecosystems. |
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| ISSN: | 1726-4170 1726-4189 |