School of Forestry

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Forestry
Research
Carbon Flux
Measurements and Results

Carbon Flux Measurements and Results

Measurements

MEASUREMENTS		SPATIAL SCALE	TEMPORAL SCALE
Eddy covariance	Following Ameriflux standard	Few km2, 1 replicate per site	Continuous (20 hz), 30 min averages
Soil CO₂ flux	It is measured in two ways: 1) by monitoring surface CO₂ fluxes regularly with a static chamber and Li-Cor 6400-09 gas exchange system and 2) by using buried CO₂ sensors (model GT222, Vaisala, Helsinki, Finland) to monitor continuously the soil depth concentration gradient of CO₂ (Tang et al. 2003).	30 cm diameter, 9 replicates per site 10 cm diameter, 3 depth (2, 10, 20 cm), x 3 plots, 27 sensor per site.	1 month interval, more frequent during growing season Continuous (1 s), 30 min averages
Soil CH₄ flux	We use the static chamber approach for measuring rates of CH₄ consumption by soils in the three treated sites (Holland et al. 1999).	30 cm diameter, 20 chamber bases located systematically per site	1 month interval, more frequent during growing season
Productivity	NPP is estimated by summing annual estimates of litterfall, aboveground tree production, fine root production, and coarse root production.	3 plots 25 m diameter per site

Eddy covariance

The eddy covariance system uses two, fiber composite, light weight, 28 m towers in the forests sites, and a 4 m pole in the fire site. The equipment used (see Table below) is the same for the 3 sites. We use a closed path analyzer, a 4 mm 4 m long tubing (9 in the fire site) and a flow rate of 10 l min-1.

The software (Giovanni Manca, CEALP, Italy), apply linear detrending, coordinates rotation and corrections for flux losses. we flag carbon flux, H and LE for quality, considering: rain, variances of CO₂, H2O, spikes and follows the proposed Ameriflux and already implemented CarboEurope criteria of Foken (Steady state test and Integral turbulence characteristic test, http://www.bitoek.uni-bayreuth.de/qaqc/en/forschung/21826/QC_Spoleto.php).

Equipment

	INSTRUMENTS
AIR
Wind	CSAT3 Campbell
CO₂ and H₂O	li-7000 licor
PAR - total - diffuse - sunshine	BF3 deltaT
Par reflected	Li190 Licor
Fine wire thermocouple	FW05 Campbell
Precipitation	5.4103.20.041 Thies clima
- Precipitation - Air temperature Air humidity - Wind speed & directions - Hail and rain intensity and duration.	WXT510 Vaisala
Short/long-wave incoming/ outgoing and Net Radiation	CNR1 Kipp & Zonen
Precipitation	TR525 USW Texas inst.

SOIL
Soil temp profile (2, 10, 20, 45 cm)	107 Campbell
Soil water content profile (2, 10, 20, 45 cm)	ECH2O-EC20 Decagon
Soil water content profile (2, 10, 20, 30, 70-100 cm) second profile since March 2006	CS616 Campbell
Soil heat flux	HFP01SC Hukseflux, Rebs

EDDY SYSTEM
Tubing diameter and length	4 mm 9 m (F) 4 mm 4 m (C and R)
Air flow	9.5 l min-1
Canopy and instrument height	<0.5m 4 m until Feb 2007, then 2.5 m (F) 18 m, 23 m (C and R)
Profile system	CO₂, H2O (LI-840, Licor) and temperature sampled at 1, 8, and 16 m (C and R only)

NPP

Litterfall is been collected quarterly from 15 circular litterfall traps (60 cm in diameter) per subplot. Prior to the first NEE measurement year, we tagged and measured the DBH of all trees within the subplots. At the end of second growing season of NEE measurements (late fall), we will measure the DBH of all trees again, and will extract two short increment cores. Annual radial growth increments will be averaged per tree, doubled, and added to the measured initial (year 0) DBH to calculate DBH values for subsequent years. Annual changes in DBH will be combined with local allometric equations to estimate annual growth in stem wood and bark, branch wood and bark, and foliage.

Soil CO₂ and CH₄

CO₂ diffusion probe technique:

Small solid-state infra-red gas analyzers (GMM 220, Vaisala Inc., Finland) were buried at three depths in the soil profile and measured CO₂ concentration at Â½ hour intervals every day

Soil volumetric water content and temperature were measured with Decagon ECH2O probes and thermocouples, respectively

Using a model of soil diffusivity including soil water content and temperature (Moldrup et al.,1999) the rate of CO₂ diffusion between the different depths was used to calculate CO₂ flux at the soil surface

CO₂ and CH₄ Static-chamber technique:

30-cm diameter PVC rings were permanently placed in the soil, distributed at 15 locations around each study site
Samples of gas headspace were taken at regular intervals
Gas samples were analyzed for CO₂ and CH₄ using gas chromatography. Changes in concentration over time were used to calculate fluxes

Results

Papers

Kolb, T., S. Dore, M. Montes-Helu. 2013. Extreme late-summer drought causes neutral annual carbon balance in southwestern ponderosa pine forests and grasslands. Environmental Research Letters 8:015015. http://stacks.iop.org/1748-9326/8/015015

Dore, S., M. Montes-Helu, S. Hart, B. Hungate, G. Koch, J. Moon, A. Finkral, T.E. Kolb. 2012. Recovery of southwestern ponderosa pine ecosystem carbon and water fluxes from thinning and stand replacing fire. Global Change Biology. DOI: 10.1111/j.1365-2486.2012.02775.x

Niu, S., Y. Luo, S. Fei, W. Yuan, D. Schimel, C. Ammann, M. Altaf Arain, A. Arneth, M Aubinet, A. Barr, J. Beringer, C. Bernhofer, A.T. Black, N. Buchmann, A. Cescatti, J. Chen, K.J. Davis, E. Dellwik, A.R. Desai, H. Dolman, S. Etzold, L. Francois, D. Gianelle, B. Gielen, A. Goldstein, M. Groenendijk, L. Gu, N. Hanan, C. Helfter, T. Hirano, D.Y. Hollinger, M.B. Jones, G. Kiely, T.E. Kolb, W.L. Kutsch, P. Lafleur, B.E. Law, D.M. Lawrence, L. Li, A. Lindroth, M. Litvak, D. Loustau, M. Lund, S. Ma, M. Marek, T.A. Martin, G. Matteucci, M. Migliavacca, L. Montagnani, E. Moors, J.W. Munger, A. Noormets, W. Oechel, J. Olejnik, K. Tha Paw U, K. Pilegaard, S. Rambal, A. Raschi, R.L. Scott, G. Seufert, D. Spano, P. Stoy, M.A. Sutton, A. Varlagin, E. Weng, G. Wohlfahrt, B. Yang, Z. Zhang, X. Zhou. 2012. Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms. New Phytologist. DOI: 10.1111/j.1469-8137.2012.04095.x.

Sullivan, B.W., S. Dore, M.C. Montes-Helu, T.E. Kolb, S.C. Hart. 2012. Pulse emissions of carbon dioxide during snowmelt at a high-elevation site in northern Arizona, USA. Arctic, Antarctic, and Alpine Research 44:247-254. DOI: http://dx.doi.org/10.1657/1938-4246-44.2.247

Lee, X., et al. 2011. Observed increase in local cooling effect of deforestation at higher latitudes. Nature 479:384-387. DOI:10.1038/nature10588.

Sorensen, C.D, A.J. Finkral, T.E. Kolb, C.H. Huang. 2011. Short- and long-term effects of thinning and fire on carbon stocks in ponderosa pine stands in northern Arizona. Forest Ecology and Management 261:460-472. DOI 10.1016/j.foreco.2010.10.031.

Sullivan, B.W., T.E. Kolb, S.C. Hart, J.P. Kaye, B.A. Hungate, S. Dore, M. Montes-Helu. 2010. Wildfire reduces carbon dioxide efflux and increases methane uptake in ponderosa pine forest soils of the southwestern USA. Biogeochemistry: DOI 10.1007/s10533-010-9499-1.

Yi, C., et al. 2010. Climate control of terrestrial carbon exchange across biomes and continents. Environmental Research Letters 5: 03400. DOI 10.1088/1748-9326/5/3/034007.

Sullivan B. W., S. Dore, T. E. Kolb, S. C. Hart, and M. C. Montes-Helu. 2010. Evaluation of methods for estimating soil carbon dioxide efflux across a gradient of forest disturbance. Global Change Biology doi: 10.1111/j.1365-2486.2009.02139.x

Dore S., T. E. Kolb, M. Montes-Helu, S. E. Eckert, B. W. Sullivan, B. A. Hungate, J. P. Kaye, S. C. Hart, G. W. Koch, and A. Finkral. 2010. Carbon and water fluxes from ponderosa pine forests disturbed by wildfire and thinning. Ecological Applications 20(3):663-683.

Roman, M.O., C.B. Schaaf, C.E. Woodcock, A.H. Strahler, X. Yang, R.H. Braswell, P. Curtis, K.J. Davis, D. Dragoni, M.L. Goulden, L. Gu, D. Hollinger, T.E. Kolb, T.P. Meyers, J.W. Munger, J. Privette, A. Richardson, T.B. Wilson, S.C. Wofsy. 2009. The MODIS (Collection V005) BRDF/albedo product: Assessment of spatial representativeness over forested landscapes. Remote Sensing of Environment 113:2476-2498.

Montes-Helu, M., T.E. Kolb, S. Dore, B. Sullivan, S. Hart, G. Koch, B. Hungate. 2009. Persistent effects of fire-induced vegetation change on energy partitioning and evapotranspiration in ponderosa pine forests. Agricultural and Forest Meteorology 149:491-500. doi:10.1016/j.agrformet.2008.09.011.

Sullivan et al. 2008. Thinning reduces soil carbon dioxide but not methane flux from southwestern USA ponderosa pine forests. Forest Ecology and Management 255:4047-4055.