Systematic drainage of farmed organic soils is responsible for the occurrence of land subsidence, caused by loss of organic mass in form of CO2 efflux to the atmosphere. This results in an increased risk of surface flooding, accompanied by higher drainage and pumping costs. 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, and the settlement rate. The latter, of the order of 1 – 2 cm/year, has been proved to be related to soil CO2 efflux due to organic matter oxidation. Quantifying this process is thus extremely important for the management and protection of these areas. A series of CO2 emission surveys has been performed between the years 2003 and 2005 by means of the non- steady-state chamber method, to measure 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, highlight a significant spatial and temporal variability of the CO2 emissions. While the time-dependent behavior can be explained by the seasonal fluctuations 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 log- normally 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. Finally, the collected data show that invasive agricultural practices such as deep plowing, tilling, and harrowing, largely used in the Zennare Basin, induce significant disturbances that are not easily recognizable during the flux surveys and that casually affect the temporal and spatial variability of the oxidation process.

Spatial variability of CO2 emissions in a drained farmed peatland of the Venice watershed, Italy

CAMPORESE, MATTEO;PUTTI, MARIO;SALANDIN, PAOLO;TEATINI, PIETRO
2011

Abstract

Systematic drainage of farmed organic soils is responsible for the occurrence of land subsidence, caused by loss of organic mass in form of CO2 efflux to the atmosphere. This results in an increased risk of surface flooding, accompanied by higher drainage and pumping costs. 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, and the settlement rate. The latter, of the order of 1 – 2 cm/year, has been proved to be related to soil CO2 efflux due to organic matter oxidation. Quantifying this process is thus extremely important for the management and protection of these areas. A series of CO2 emission surveys has been performed between the years 2003 and 2005 by means of the non- steady-state chamber method, to measure 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, highlight a significant spatial and temporal variability of the CO2 emissions. While the time-dependent behavior can be explained by the seasonal fluctuations 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 log- normally 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. Finally, the collected data show that invasive agricultural practices such as deep plowing, tilling, and harrowing, largely used in the Zennare Basin, induce significant disturbances that are not easily recognizable during the flux surveys and that casually affect the temporal and spatial variability of the oxidation process.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2482295
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