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- Ortiz, Carina, et al.
(författare)
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Measurements and models –a comparison of quantificationmethods for SOC changes in forestsoils
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish UNFCCC1-reporting of the LULUCF2-sector is based on methods incompliance with the “Good practice” as described by the Intergovernmental Panelon Climate Change (IPCC). Biomass and soil inventory data from the SwedishInventory of Forests is the major source of information used to quantify changes inthe various carbon pools on forest land. Even if the reported uncertainties in soilcarbon changes are small from a statistical perspective, they are large in relation tothe total Swedish emissions of green house gases. This is due to the fact that thesoil carbon pool is so large, that even small and statistically non-significantchanges may have an impact on the Swedish CO2 balance. Sampling based methodsmay also result in considerable inter annual variations that may look conspicuousin the reporting. Because of the uncertainty and inter annual variations therehas been a discussion on the methods used and if there are possibilities to lower theuncertainty and to get more stable estimates of soil carbon changes by combiningmeasurements and models. In this study results from the two soil carbon models,Yasso07 and Q, were compared with repeated measurements of the soil inventoryduring the years 1994 to 2000. Soil carbon fluxes were simulated with the twomodels from 1926 to 2000 with Monte Carlo methodology to estimate uncertaintyranges. The results from the models agreed well with measured data. The simulationsof Yasso07 and Q resulted in a soil organic carbon stock in year 2000 of1600 Mton C and 1580 Mton C, respectively while the measured carbon pool was1670 Mton C. The annual change in soil organic carbon varies substantially betweenthe three methods mainly due to different assumptions regarding annualclimate variation. However, the five year averaged mean of annual soil organiccarbon change for the two periods 1994-1998 and 1996-2000 indicate the size anddirection of the estimated annual changes agree reasonable well. The mean annualchange for the two periods was for the Q-model 5.5 Mton C yr-1 and 5.6 Mton C yr-1with a confidence interval of 2.1-10.7 Mton C yr-1, and for the Yasso07-model 3.7Mton C yr-1 and 0.9 Mton C yr-1 respectively with a confidence interval rangingbetween -5 to 12.6 and -7 to 9.8 Mton C yr-1 respectively. The mean annual changefor the two periods estimated using NFI-data was 1.6 M ton C yr-1 and 2.5 M ton Cyr-1 with a standard error of 2 The general conclusion drawn from this study is thatboth sampling and the models Yasso07 and Q are possible tools to predict the soilorganic carbon accumulation and annual changes for Swedish forest soils. Theestimates based on measurements as well as the modelled results indicate an increasein carbon stocks in Swedish forest soils. This study does not support achange of method from inventory to model predictions. However, the agreementbetween the methods shows that the models are suitable as a complement to othersoil carbon estimation methods. They are particularly useful for projections and werecommend a further development of the modelling tools.
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- Ortiz, Carina, et al.
(författare)
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Modelling soil carbon development in Swedish coniferous forest soils-An uncertainty analysis of parameters and model estimates using the GLUE method
- 2011
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 222, s. 3020-3032
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Tidskriftsartikel (refereegranskat)abstract
- Boreal forest soils such as those in Sweden contain a large active carbon stock. Hence, a relatively small change in this stock can have a major impact on the Swedish national CO(2) balance. Understanding of the uncertainties in the estimations of soil carbon pools is critical for accurately assessing changes in carbon stocks in the national reports to UNFCCC and the Kyoto Protocol. Our objective was to analyse the parameter uncertainties of simulated estimates of the soil organic carbon (SOC) development between 1994 and 2002 in Swedish coniferous forests with the Q model. Both the sensitivity of model parameters and the uncertainties in simulations were assessed. Data of forests with Norway spruce, Scots pine and Lodgepole pine, from the Swedish Forest Soil Inventory (SFSI) were used. Data of 12 Swedish counties were used to calibrate parameter settings: and data from another 11 counties to validate. The "limits of acceptability" within GLUE were set at the 95% confidence interval for the annual, mean measured SOC at county scale. The calibration procedure reduced the parameter uncertainties and reshaped the distributions of the parameters county-specific. The average measured and simulated SOC amounts varied from 60 t C ha(-1) in northern to 140 t C ha(-1) in the southern Sweden. The calibrated model simulated the soil carbon pool within the limits of acceptability for all calibration counties except for one county during one year. The efficiency of the calibrated model varied strongly; for five out of 12 counties the model estimates agreed well with measurements, for two counties agreement was moderate and for five counties the agreement was poor. The lack of agreement can be explained with the high interannual variability of the down-scaled measured SOC estimates and changes in forest areas over time. We conclude that, although we succeed in reducing the uncertainty in the model estimates, calibrating of a regional scale process-oriented model using a national scale dataset is a sensitive balance between introducing and reducing uncertainties. Parameter distributions showed to be scale sensitive and county specific. Further analysis of uncertainties in the methods used for reporting SOC changes to the UNFCCC and Kyoto protocol is recommended. (C) 2011 Elsevier B.V. All rights reserved.
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- Ortiz, Carina, et al.
(författare)
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Soil organic carbon stock changes in Swedish forest soils—A comparison of uncertainties and their sources through a national inventory and two simulation models
- 2013
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 251, s. 221-231
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Tidskriftsartikel (refereegranskat)abstract
- Swedish Forest Soil Inventory (SFSI) estimates of SOC stocks and SOC changes for forest on mineral soils under Scots pine (Pinus sylvestris)/lodgepole pine (Pinus contorta) or Norway spruce (Picea abies) were compared with estimates, including uncertainties due to parameter, input and climate variability, from two process-based models (Yasso07 and Q) for the period 1994-2000. We found that the stocks, changes, inter-annual variations and uncertainties were of the same magnitude among the different methods. The mean Swedish national stocks in 2000 were estimated to be 73 (+/- 10) (95% CL) ton ha(-1) C (SFSI); 69 (+/- 9) (95% CL) ton ha(-1) C (Yasso07); and, 67 (+10; -9) (5th and 95th percentiles) ton ha(-1) C (Q). Between 1994 and 2000, the mean estimated SOC change were 6.6 (+/- 7)Tg Cyr(-1) (SFSI), 1.7 (+/- 8.8)Tg Cyr(-1) (Yasso07), and -3.2 (+10.5; -16.9)Tg Cyr(-1) (Q). Spatial variability was the main source of uncertainty for the SOC stocks and changes estimated with the SFSI. The uncertainties in the stock estimates originated from litter input for Yasso07 and from the model parameters for the Q model. In both models, litter input uncertainty was the major source of uncertainty for the estimated SOC changes, followed by climate variability and parameters. We concluded that the level of uncertainty for both methods was similar but the sources of uncertainties varied between models and measurements. Thus, comparing uncertainty between methods is difficult and further studies on SOC change estimates with related uncertainties are warranted. (C) 2013 Elsevier B.V. All rights reserved.
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