Sources of errors and uncertainties in the assessment of forest soil carbon stocks at different scales—review and recommendations
Vanguelova, E.I. ; Bonifacio, E. ; Vos, B. De; Hoosbeek, M.R. ; Berger, T.W. ; Vesterdal, L. ; Armolaitis, K. ; Celi, L. ; Dinca, L. ; Kjønaas, O.J. ; Pavlenda, P. ; Pumpanen, J. ; Püttsepp, ; Reidy, B. ; Simončič, P. ; Tobin, B. ; Zhiyanski, M. - \ 2016
Environmental Monitoring and Assessment 188 (2016)11. - ISSN 0167-6369 - 24 p.
Carbon stocks - European - Forest soils - Landscape - National - Plot - Sampling - Soil profile
Spatially explicit knowledge of recent and past soil organic carbon (SOC) stocks in forests will improve our understanding of the effect of human- and non-human-induced changes on forest C fluxes. For SOC accounting, a minimum detectable difference must be defined in order to adequately determine temporal changes and spatial differences in SOC. This requires sufficiently detailed data to predict SOC stocks at appropriate scales within the required accuracy so that only significant changes are accounted for. When designing sampling campaigns, taking into account factors influencing SOC spatial and temporal distribution (such as soil type, topography, climate and vegetation) are needed to optimise sampling depths and numbers of samples, thereby ensuring that samples accurately reflect the distribution of SOC at a site. Furthermore, the appropriate scales related to the research question need to be defined: profile, plot, forests, catchment, national or wider. Scaling up SOC stocks from point sample to landscape unit is challenging, and thus requires reliable baseline data. Knowledge of the associated uncertainties related to SOC measures at each particular scale and how to reduce them is crucial for assessing SOC stocks with the highest possible accuracy at each scale. This review identifies where potential sources of errors and uncertainties related to forest SOC stock estimation occur at five different scales—sample, profile, plot, landscape/regional and European. Recommendations are also provided on how to reduce forest SOC uncertainties and increase efficiency of SOC assessment at each scale.
Comparison of static chambers to measure CH4 emissions from soils
Pihlatie, M.K. ; Christiansen, J.R. ; Aaltonen, H. ; Korhonen, J.F.J. ; Nordbo, A. ; Rasilo, T. ; Benanti, G. ; Giebels, M. ; Helmy, M. ; Sheehy, J. ; Jones, S. ; Juszczak, R. ; Klefoth, R.R. ; Lobo-do-Vale, R. ; Rosa, A.P. ; Schreiber, P. ; Serca, D. ; Vicca, S. ; Wolf, B. ; Pumpanen, J. - \ 2013
Agricultural and Forest Meteorology 171-172 (2013). - ISSN 0168-1923 - p. 124 - 136.
gas-exchange - flux measurements - co2 efflux - atmosphere - respiration - apparatus - biases
The static chamber method (non-flow-through-non-steady-state chambers) is the most common method to measure fluxes of methane (CH4) from soils. Laboratory comparisons to quantify errors resulting from chamber design, operation and flux calculation methods are rare. We tested fifteen chambers against four flux levels (FL) ranging from 200 to 2300 mu g CH4 M-2 II-1. The measurements were conducted on a calibration tank using three quartz sand types with soil porosities of 53% (dry fine sand, S1), 47% (dry coarse sand, S2), and 33% (wetted fine sand, S3). The chambers tested ranged from 0.06 to 1.8 m in height, and 0.02 to 0.195 m(3) in volume, 7 of them were equipped with a fan, and 1 with a vent-tube. We applied linear and exponential flux calculation methods to the chamber data and compared these chamber fluxes to the reference fluxes from the calibration tank. The chambers underestimated the reference fluxes by on average 33% by the linear flux calculation method (R-Iin), whereas the chamber fluxes calculated by the exponential flux calculation method (R-exp) did not significantly differ from the reference fluxes (p
Evidence for soil water control on carbon and water dynamics in European forests during the extremely dry year: 2003
Granier, A. ; Reichstein, M. ; Bréda, N. ; Janssens, I.A. ; Falge, E. ; Ciais, P. ; Grünwald, T. ; Aubinet, M. ; Berbigier, P. ; Bernhofer, C. ; Buchmann, N. ; Facini, O. ; Grassi, G. ; Heinesch, B. ; Ilvesniemi, H. ; Keronen, P. ; Knohl, A. ; Köstner, B. ; Lagergren, F. ; Lindroth, A. ; Longdoz, B. ; Loustau, D. ; Mateus, J. ; Montagnani, L. ; Nys, C. ; Moors, E.J. ; Papale, D. ; Peiffer, M. ; Pilegaard, K. ; Pita, G. ; Pumpanen, J. ; Rambal, S. ; Rebmann, C. ; Rodrigues, A. ; Seufert, G. ; Tenhunen, J. ; Vesala, T. ; Wang, Q. - \ 2007
Agricultural and Forest Meteorology 143 (2007)1-2. - ISSN 0168-1923 - p. 123 - 145.
droogte - waterbalans - bodemwater - bossen - netto ecosysteem koolstofbalans - west-europa - drought - water balance - soil water - forests - net ecosystem carbon balance - western europe - leaf-area index - fagus-sylvatica l. - ecosystem co2 exchange - sap flow measurements - boreal aspen forest - canopy conductance - deciduous forest - severe drought - beech forest - scots pine
The drought of 2003 was exceptionally severe in many regions of Europe, both in duration and in intensity. In some areas, especially in Germany and France, it was the strongest drought for the last 50 years, lasting for more than 6 months. We used continuous carbon and water flux measurements at 12 European monitoring sites covering various forest ecosystem types and a large climatic range in order to characterise the consequences of this drought on ecosystems functioning. As soil water content in the root zone was only monitored in a few sites, a daily water balance model was implemented at each stand to estimate the water balance terms: trees and understorey transpiration, rainfall interception, throughfall, drainage in the different soil layers and soil water content. This model calculated the onset date, duration and intensity of the soil water shortage (called water stress) using measured climate and site properties: leaf area index and phenology that both determine tree transpiration and rainfall interception, soil characteristics and root distribution, both influencing water absorption and drainage. At sites where soil water content was measured, we observed a good agreement between measured and modelled soil water content. Our analysis showed a wide spatial distribution of drought stress over Europe, with a maximum intensity within a large band extending from Portugal to NE Germany. Vapour fluxes in all the investigated sites were reduced by drought, due to stomatal closure, when the relative extractable water in soil (REW) dropped below ca. 0.4. Rainfall events during the drought, however, typically induced rapid restoration of vapour fluxes. Similar to the water vapour fluxes, the net ecosystem production decreased with increasing water stress at all the sites. Both gross primary production (GPP) and total ecosystem respiration (TER) also decreased when REW dropped below 0.4 and 0.2, for GPP and TER, respectively. A higher sensitivity to drought was found in the beech, and surprisingly, in the broadleaved Mediterranean forests; the coniferous stands (spruce and pine) appeared to be less drought-sensitive. The effect of drought on tree growth was also large at the three sites where the annual tree growth was measured. Especially in beech, this growth reduction was more pronounced in the year following the drought (2004). Such lag effects on tree growth should be considered an important feature in forest ecosystems, which may enhance vulnerability to more frequent climate extremes.