Soil respiration under Miscanthus x giganteus and an adjacent barley crop

Soil respiration (Rs) was measured using automated chambers and infrared gas analysers (IRGA, Licor LI-8100-101A, Lincoln NE, USA) with multiplexers (Electronic workshops, Department of Biology, University of York, York UK) beneath a seven year-old stand of Miscanthus and an April-sown spring barley in adjacent fields on a farm in the east of the United Kingdom, with one IRGA and one multiplexer deployed in each crop. Chambers (n= 6) were placed at random within separate plots at least 1.5 m apart in the two fields and were seated over PVC collars (diameter 20 cm, height 10 cm) which were inserted ca. 2 cm into the soil in order to minimise the effect of cutting fine roots and these remained in situ throughout the study, which was undertaken from May to August 2013. The chambers were programmed to close for two minutes during measurement, with a 30 second 'dead band' to allow for mixing of the headspace, in a continuous cycle between chambers. Collars did not exclude roots and no above-ground vegetation was included. Soil temperature and moisture at 5 cm depth were also measured every 15 minutes adjacent to each chamber collar and averaged over hourly intervals using vertically-installed sensors (Delta-T DL2 and GP1 loggers, SM200 soil moisture probes and ST1 temperature probes; Delta-T, Cambridge UK), and hourly meteorological data (solar radiation, air temperature) were recorded onsite using a weather station (WP1, Delta-T, Cambridge UK). Rs fluxes were calculated as linear regressions of CO2 concentration against time and corrected for volume and temperature using the manufacturer's software (see manufacturer's manual https://www.licor.com/documents/jtpq4vg358reu4c8r4id.pdf).