| Data Set Citation |
Rowlings D of Institute for Sustainable Resources, Queensland University of Technology.Mooloolah_Pasture_2007-09.
Rowlings.21.1
(http://www.n2o.net.au/knb/metacat/Rowlings.21.1/default).
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| Data Set Owner(s): |
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Individual: | Dr David Rowlings |
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Organization: | Institute for Sustainable Resources, Queensland University of Technology |
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Position: | principle investigator |
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Address: |
| Gardens Point campus, 2 George St, |
| Brisbane, Queensland 4001 Australia |
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Email Address:
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| Abstract: |
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| Greenhouse gas emissions from a well established, unfertilized tropical grass-legume pasture were monitored over two consecutive years using high resolution automatic sampling. Nitrous oxide emissions were highest during the summer months and were highly episodic, related more to the size and distribution of rain events than WFPS alone. Mean annual emissions were significantly higher during 2008 (5.7 ± 1.0 g N2O-N ha day) than 2007 (3.9 ± 0.4 and g N2O-N ha day) despite receiving nearly 500 mm less rain. Mean CO2 (28.2 ± 1.5 kg CO2 C ha day) was not significantly different (P < 0.01) between measurement years, emissions being highly dependent on temperature. A negative correlation between CO2 and WFPS at >70% indicated threshold for soil conditions favouring denitrification. The use automatic chambers for high resolution greenhouse gas sampling can greatly reduce emission estimation errors associated with temperature and WFPS changes. |
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| Keywords: |
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- N2O
- CH4
- CO2
- Subtropical
- Humid
- improved pasture
- interannual variation
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| License and Usage Rights: |
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| permission required from data owner |
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| Geographic Coverage: |
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Geographic Description: | Humid subtropical Australia, Mooloolah, Queensland |
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Bounding Coordinates:
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| West: | 152.375 degrees
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| East: | 153.5 degrees
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| North: | -26.5 degrees
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| South: | -28.625 degrees
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| Temporal Coverage: |
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Begin:
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End:
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| Taxonomic Coverage: |
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| Rank Name | Rank Value | Common Names |
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| Taxon: |
| Species | Desmodium uncinatum | |
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| Taxon: |
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| Contact: |
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Individual: | Professor Peter Grace |
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Organization: | Institute for Sustainable Resources, Queensland University of Technology |
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Position: | Director ISR |
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Address: |
| Gardens Point campus, 2 George St, |
| Brisbane, Queensland 4001 Australia |
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Email Address:
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| Methods Info: |
| Step 1: |
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Description:
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| Automated GHG fluxes |
Two continuous years of high temporal resolution soil and environmental data was collected from Site 1 between 01 March 2007 and 28th February 2009. For determination of soil borne CH4, N2O and CO2 fluxes an automated gas sampling system was utilized, similar to the one described in detail by Breuer et al. (2000) and Kiese et al. (2003). Despite short-term breakdowns due to the hot and humid conditions, flooding and the destruction of sampling lines by native rodents, over 11,000 emission rates from each of the 3 greenhouse gases were obtained.
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Instrument(s):
| This system consisted of pneumatically operated static chambers (non-steady-state, non-through-flow), linked to an automated sampling system and a gas chromatograph. The clear acrylic glass chambers covered a surface area of 0.25 m2 (500 mm x 500 mm) with a height of 150 mm and were secured to stainless steel bases inserted permanently into the soil to a depth of 100 mm. Three replicate sampling chambers were randomly placed within an area roughly 5 x 4 metres within a larger 20 m x 30 m experimental plot. A transparent tinted plastic coating was placed on the lids to reduce heat build-up within the chambers when closed. A tipping bucket rain gauge (Davis Instruments Corp. CA, USA) connected to the system allowed for automated opening of the lids during rainfall events. |
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Instrument(s):
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Instrument(s):
| Nitrous oxide and CH4 concentrations were determined using a gas chromatograph (SRI GC8610, Torrance, CA, USA) equipped with 63N Electron Capture Detector for N2O and a Flame Ionisation Detector for CH4. Carbon dioxide was measured continuously with a non dispersive infrared CO2 analyser (LI-820; LI-COR, Lincoln Nebraska, USA). To minimize interference from moisture vapour and CO2 on N2O measurement, a precolumn filled with sodium hydroxide coated silica was installed ahead of the analytical column and changed regularly. |
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Instrument(s):
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Instrument(s):
| A full measurement cycle for flux determination commenced with lid closure and finished when the lids opened 48 minutes later. The lids remained open for a further 96 minutes before the commencement of the next cycle. Fluxes of N2O, CH4 and CO2 were calculated from the slope of the linear increase or decrease in concentrations within the chambers over the closure time. An optimization function was used that selected the best regression coefficient (r2) from either 3 or 4 of the measured gas concentrations. Flux rates were discarded if the r2 was <0.81 for N2O and CH4 and <0.90 for CO2. The flux rate was then calculated and corrected for air temperature during measurement and site pressure using the procedure outline by Barton et. al. (2008). |
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Instrument(s):
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Instrument(s):
| A FDR (EnviroSCAN Sentek, Stepney, South Australia) moisture probe located centrally to the chambers recorded half-hourly readings of volumetric water content (5-10 cm) while soil temperature (10 cm) was measured at 5 minute intervals (Hobo Pendant temperature/light data logger, Onset Computer Corporation). For climate data an automatic weather station (Davis Instruments Corp. CA, USA) installed nearby recorded half-hourly rainfall, temperature, relative humidity and wind speed and direction values |
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Sampling Area And Frequency:
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| Sampling Area And Frequency:
01 March 2007 - 28 February 2009
Mooloolah, Queensland |
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Sampling Description:
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| 3 replicate chambers.
Chambers were moved between 2 sets of bases every month to avoid plant growth limitations |
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| Access Control: |
| Auth System: | knb |
| Order: | allowFirst |
| Access Rules: |
ALLOW:
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