title: Improving the statistical preparation for measuring soil N2O flux by closed chamber.
abstract: Nitrous oxide emissions from soil are known to be spatially and temporally volatile. Reliable estimation of emissions over a given time and space depends on measuring with sufficient intensity but deciding on the number of measuring stations and the frequency of observation can be vexing. The question of low frequency manual observations providing comparable results to high frequency automated sampling also arises. Data collected from a replicated field experiment was intensively studied with the intention to give some statistically robust guidance on these issues. The experiment had nitrous oxide soil to air flux monitored within 10 m by 2.5 m plots by automated closed chambers under a 3h average sampling interval and by manual static chambers under a three day average sampling interval over sixty days. Observed trends in flux over time by the static chambers were mostly within the auto chamber bounds of experimental error. Cumulated nitrous oxide emissions as measured by each system were also within error bounds. Under the temporal response pattern in this experiment, no significant loss of information was observed after culling the data to simulate results under various low frequency scenarios. Within the confines of this experiment observations from the manual chambers were not spatially correlated above distances of 1m. Statistical power was therefore found to improve due to increased replicates per treatment or chambers per replicate. Careful after action review of experimental data can deliver savings for future work.
authors.affiliation: New South Wales Department of Primary Industries, Wollongbar, NSW 2477, Australia. Electronic address: stephen.morris@dpi.nsw.gov.au.
authors.forename: S G
authors.initials: SG
authors.lastname: Morris
authors.forename: S W L
authors.initials: SW
authors.lastname: Kimber
authors.forename: P
authors.initials: P
authors.lastname: Grace
authors.forename: L
authors.initials: L
authors.lastname: Van Zwieten
keywords: Closed chamber; Frequency; Replication; Soil nitrous oxide flux; Statistical power