Temporal Stability of Soil Water Storage, Carbon Dioxide, and Nitrous Oxide Flux.

Field measurements of CO₂and N₂O fluxes are time consuming. Numerous measurements are required to quantify either the mean and variance or the spatial patterns of CO₂ or N₂O fluxes at the field scale.  The objective of this work is to characterize the temporal stability of spatially measured water storage, CO₂, and N₂O fluxes.  A research site (4125 m²) was selected with two established land use types, pasture and cropland. A total of 60 collars were inserted into the soil along four transects. In situ CO₂ and N₂O fluxes were measured at each location 25 times (June 2010 until June 2011) in two-week intervals by a photo acoustic environmental gas monitor (INNOVA Model 1412).   Soil moisture content was measured using a capacitance probe in 0.1-m depth increments down to 1 m depth each time gas fluxes were measured.  Two statistical approaches, i.e., temporal analysis of the differences between individual and spatial average values and Spearman’s rank correlation, were used to evaluate the temporal stability of soil water storage and CO₂ and N₂O fluxes. The temporal analysis of the differences between individual and spatial average values can be used to identify a few locations representing the mean and variance of CO₂ and N₂O fluxes in the field. Data analysis showed that there is an obvious time stability of spatial patterns of water storage and CO₂ and N₂O fluxes. Some locations represent mean and extremes of field water storage and CO₂ and N₂O fluxes at any time.