Spatial variability of CO2 efflux in a drained cropped peatland
south of Venice, Italy
M. Camporese, P. Salandin
Department of Hydraulic, Maritime, Environmental and Geotechnical
Engineering, University of Padova, Padova, Italy
M. Putti, P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
A field experimental study has been performed in a drained cropped peatland
located in the Zennare Basin (south of the Venice Lagoon, Italy), to measure
land subsidence due to peat oxidation and to address the primary relationships
between the hydrological regime, the soil mass loss (in form of
CO2 efflux to the atmosphere), and the settlement rate. The latter,
of the order of 0.01-0.02 m/a, has been proved to be related to soil
CO2 efflux due to organic matter oxidation. A series of
CO2 emission measurement campaigns has been performed between
the years 2003 and 2005. The non-steady-state chamber method was employed
to assess the efflux spatial variability and detect its relationship with
the main hydrological parameters controlling the oxidation reaction, i.e.,
soil temperature, soil moisture, and organic matter content. The measurements,
carried out in two sites located 1.5 km apart, point out a great variability
of the CO2 emissions both in space and time. While the
time-dependent behavior can be explained by the seasonal fluctuation of soil
temperature, spatial variability shows a weak correlation with the variation
of environmental variables. Statistical data analyses show that
CO2 efflux can be considered lognormally distributed and that the
process is stationary within each site but not in the whole basin, though the
properties of the outcropping peat layer and the soil surface seem apparently
uniform. A geostatistical analysis reveals two different spatial correlation
structures, with scales of spatial dependence
of »30 m and »180 m.
