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Selected Papers of the Workshop on Development of Models and Forest Soil Surveys for Monitoring of Soil Carbon.

Countries need to assess changes in the carbon stocks of forest soils as a part of national greenhouse gas (GHG) inventories under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol (KP). Since measuring these changes is expensive, it is likely that many countries will use alternative methods to prepare these estimates. We reviewed seven well-known soil carbon models from the point of view of preparing country-scale soil C change estimates. We first introduced the models and explained how they incorporated the most important input variables. Second, we evaluated their applicability at regional scale considering commonly available data sources. Third, we compiled references to data that exist for evaluation of model performance in forest soils. A range of process-based soil carbon models differing in input data requirements exist, allowing some flexibility to forest soil C accounting. Simple models may be the only reasonable option to estimate soil C changes if available resources are limited. More complex models may be used as integral parts of sophisticated inventories assimilating several data sources. Currently, measurement data for model evaluation are common for agricultural soils, but less data have been collected in forest soils. Definitions of model and measured soil pools often differ, ancillary model inputs require scaling of data, and soil C measurements are uncertain. These issues complicate the preparation of model estimates and their evaluation with empirical data, at large scale. Assessment of uncertainties that accounts for the effect of model choice is important part of inventories estimating large-scale soil C changes. Joint development of models and large-scale soil measurement campaigns could reduce the inconsistencies between models and empirical data, and eventually also the uncertainties of model predictions.

We integrate a carbon net sink and stand-level wood production to analyze their simultaneous optimization as an economic problem. Carbon is included in living trees, wood products, and forest soil. Forestry is specified by a size-structured model for optimizing thinning timing and intensity, rotation period, and the optimal choice of rotation versus continuous cover forestry. The optimal inclusion of a carbon net sink increases the carbon pool mainly in living trees and forest soil, while the effect on the product carbon pool remains minor. With a 3% interest rate, increasing the C[O.sub.2] price to 40 [euro] per tC[O.sub.2] increases the total steady-state carbon pool by 131% and the soil carbon accounts for ca. 60% of the increased carbon storage. Omitting soil carbon, as in previous studies, leads to underestimates of the carbon sink, significantly decreasing the optimal total C[O.sub.2] net sink and achievable economic net gain from joint wood production and carbon management. The inclusion of soil carbon suggests that, in contrast to previous results, a higher C[O.sub.2] price does not necessarily favor continuous cover forestry. Key words: carbon sequestration, economic profitability, soil carbon, continuous cover forestry, rotation forestry, optimal rotation, 1. Introduction Climate change and the aim of limiting global warming have strongly increased the attention given to forests as carbon sinks (Shukla et al. 2019). Compared with the tropics, [...]

Spatial variation in the density of soil organic carbon (kg/m) and the thickness of soil horizons (F/H, E) were investigated in a 6 m x 8 m area in Scots pine ( L.) stand in Southern Finland for designing an effective sampling for the C density and studying the effect of trees on the variation. The horizon thickness of the podzolized soil were measured on a total of 126 soil cores (50 cm deep) and the C density of the organic F/H and 0â10 cm, 10â20 cm and 20â40 cm mineral soil layers was analysed.2Pinus sylvestris

Organic soil amendments are used to improve soil quality and mitigate climate change. However, their effects on soil structure, nutrient and water retention as well as greenhouse gas (GHG) emissions are still poorly understood. The purpose of this study was to determine the residual effects of a single field application of four ligneous soil amendments on soil structure and GHG emissions. We conducted a laboratory incubation experiment using soil samples collected from an ongoing soil-amendment field experiment at Qvidja Farm in south-west Finland, two years after a single application of four ligneous biomasses. Specifically, two biochars (willow and spruce) produced via slow pyrolysis, and two mixed pulp sludges from paper industry side-streams were applied at a rate of 9–22 Mg ha-1 mixed in the top 0.1 m soil layer. An unamended fertilized soil was used as a control. The laboratory incubation lasted for 33 days, during which the samples were kept at room temperature (21°C) and at 20%, 40%, 70% or 100% water holding capacity. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured periodically after 1, 5, 12, 20 and 33 days of incubation. The application of ligneous soil amendments increased the pH of the sampled soils by 0.4–0.8 units, whereas the effects on soil organic carbon content and soil structure varied between treatments. The GHG exchange was dominated by CO2 emissions, which were mainly unaffected by the soil amendment treatments. The contribution of soil CH4 exchange was negligible (nearly no emissions) compared to soil CO2 and N2O emissions. The soil N2O emissions exhibited a positive exponential relationship with soil moisture. Overall, the soil amendments reduced N2O emissions on average by 13%, 64%, 28%, and 37%, at the four soil moisture levels, respectively. Furthermore, the variation in N2O emissions between the amendments correlated positively with their liming effect. More specifically, the potential for the pulp sludge treatments to modulate N2O emissions was evident only in response to high water contents. This tendency to modulate N2O emissions was attributed to their capacity to increase soil pH and influence soil processes by persisting in the soil long after their application. [ABSTRACT FROM AUTHOR]

Soil organic carbon (C), accumulated over millennia, comprise more than half of the C stored in boreal and temperate forest landscapes. We used the Norwegian national forest inventory and soil survey network (n = 719, no deep organic soils) to explore the validity of a deterministic model representation of this pool (Yasso07). We statistically compared simulated and measured soil C stocks and related differences (measured - simulated) to site factors (drainage, topography, climate, vegetation, C-to-N ratio, and soil classification). Median C stocks were 5.0 kg C x [m.sup.-2] (model) and 14.5 kg C x [m.sup.-2] (measurements). Soil C differences related to site factors ([r.sup.2] of 0.16 to 0.37). For Brunisols, Gleysols, and wet Organic soils, differences related primarily to topographic wetness. For Regosols, Podzols, and Dystric Eluviated Brunisols, they related to climate, profile depth, and, in some cases, drainage class and site index. We argue that soil moisture regimes in our study area overrule tree productivity effects in the determination of soil C stocks and present conditions for soil formation that the model cannot (and does not explicitly) account for. These are processes such as humification and podsolization that involve eluviation and illuviation of dissolved organic C (DOC) with sesquioxides to form spodic B horizons and carbon enrichment due to hampered decomposition in frequently anoxic conditions. Key words: drainage, national forest inventory (NFI), SOC simulation, soil classification, soil-forming factors, soil moisture regime, soil survey, podsolization, Yasso07. Le carbone (C) organique du sol accumule au fil des millenaires correspond a plus de la moitie du C stocke dans les paysages forestiers boreaux et temperes. Nous avons utilise l'inventaire forestier national norvegien et le reseau d'inventaire des sols (n = 719, aucun sol organique epais) pour etudier la validite d'une representation de ce reservoir (Yasso07) a l'aide d'un modele deterministe. Nous avons statistiquement compare les stocks de C du sol simules et mesures, et relie leurs differences (mesures - simules) a des caracteristiques de la station (drainage, topographie, climat, vegetation, rapport de C a N et classification du sol). Les stocks medians de C atteignaient 5,0 (simule) et 14,5 (mesure) kg C x [m.sup.-2]. Les differences de C du sol etaient reliees aux caracteristiques des stations ([r.sup.2] de 0,16 a 0,37). Pour les brunisols, les gleysols et les sols organiques humides, les differences etaient surtout reliees a l'humidite topographique. Pour les regosols, les podzols et les brunisols dystriques eluvies, les differences etaient reliees au climat, a la profondeur du profil et, dans certains cas, a la classe de drainage et a l'indice de qualite de station. Nous avancons que le regime d'humidite du sol de notre aire d'etude est un facteur plus important que les effets de la productivite ligneuse pour determiner les stocks de C, et qu'il engendre des conditions de formation des sols dont le modele ne peut tenir compte et ne tient pas compte explicitement. Ces conditions sont des processus comme l'humification et la podzolisation qui impliquent l'eluviation et l'illuviation du carbone organique dissout avec des sesquioxydes pour former des horizons B spodiques et de l'enrichissement en carbone cause par l'absence de decomposition sous des conditions frequentes d'anoxie. [Traduit par la Redaction] Mots-cles : drainage, inventaire forestier national, simulation du carbone organique du sol, classification des sols, facteurs de pedogenese, regime d'humidite des sols, inventaire des sols, podzolisation, Yasso07., Introduction Of the total carbon (C) stock in the world's forests, 32% (272 Pg) is stored in the boreal region and only about 20% of this is stored in the [...]