Soil carbon and nitrogen contents in forest soils are related to soil texture in interaction with pH and metal cations

The aim of this study was to better understand how soil carbon (C) and nitrogen (N) contents and the C:N ratio are related to soil texture, pH, and exchangeable aluminum and calcium in forest soils.For this purpose, we studied 1992 temperate and boreal forest soils located all over Sweden. We measured organic C and N as well exchangeable aluminum, calcium, and pH in the organic layer and three depth increments in the mineral soil (down to 65 cm), and analyzed the relationship between element contents, soil texture, and soil pH as well as their interactions.Soil C concentration and the C:N ratio were negatively related to soil pH. The C concentration was on average 2.6 times higher in very acidic soils (pH 5.0, in the uppermost 10 cm of the mineral soil. In contrast, N varied much less with pH, particularly in the organic layer, but was related to soil texture. The N concentration was 2.3 times higher in clayey and fine silty soils than in sandy soils, while the C concentration was only 1.85 times higher in clayey and fine silty soils than in sandy soils (in the uppermost 10 cm). Differences in C and N concentrations between clayey and fine silty soils compared to sandy soils were largest in the class of soils with pH > 5.0 and smallest in the class of soils with pH <= 4.0. Furthermore, C and N concentrations were both positively correlated with the concentration of exchangeable aluminum in the mineral soil, and these correlations were stronger in coarse-textured than in fine-textured soils. In addition, the C concentration was positively correlated with the concentration of exchangeable calcium in the organic layer.In conclusion, our results show that C concentration varied much more strongly with pH than N concentration, likely due to effects of pH on microbial respiration. The N concentration was more strongly related to soil texture than the C concentration, which is very likely due to the high charge density of organic N, which gives organic N a high affinity to adsorb to mineral surfaces. Furthermore, exchangeable aluminum seems to play an important role in the sorptive stabilization of organic matter in the mineral soil

Carbon, nitrogen, and phosphorus stoichiometry of organic matter in Swedish forest soils and its relationship with climate, tree species, and soil texture

While the carbon (C) content of temperate and boreal forest soils is relatively well studied, much less is known about the ratios of C, nitrogen (N), and phosphorus (P) of the soil organic matter, as well as the abiotic and biotic factors that shape them. Therefore, the aim of this study was to explore carbon, nitrogen, and organic phosphorus (OP) contents and element ratios in temperate and boreal forest soils and their relationships with climate, dominant tree species, and soil texture. For this purpose, we studied 309 forest soils located all over Sweden between 56 and 68 degrees N. The soils are a representative subsample of Swedish forest soils with a stand age > 60 years that were sampled for the Swedish Forest Soil Inventory. We found that the N stock of the organic layer increased by a factor of 7.5 from -2.0 to 7.5 degrees C mean annual temperature (MAT), which is almost twice as much as the increase in the organic layer stock along the MAT gradient. The increase in the N stock went along with an increase in the N : P ratio of the organic layer by a factor of 2.1 from -2.0 to 7.5 degrees C MAT (R-2 = 0.36, p < 0.001). Forests dominated by pine had higher C : N ratios in the organic layer and mineral soil down to a depth of 65 cm than forests dominated by spruce. Further, also the C : P ratio was increased in the pine-dominated forests compared to forests dominated by other tree species in the organic layer, while the C : OP ratio in the mineral soil was not elevated in pine forests. C, N, and OP contents in the mineral soil were higher in fine-textured soils than in coarse-textured soils by a factor of 2.3, 3.5, and 4.6, respectively. Thus, the effect of texture was stronger on OP than on N and C likely because OP adsorbs very rigidly to mineral surfaces. Further, we found that the P and K concentrations of the organic layer were inversely related to the organic layer stock, while the N : P ratio was positively related to the organic layer stock. Taken together, the results show that the N : P ratio of the organic layer was most strongly related to MAT. Further, the C : N ratio was most strongly related to dominant tree species even in the mineral subsoil. In contrast, the C : P ratio was only affected by dominant tree species in the organic layer, but the C : OP ratio in the mineral soil was hardly affected by tree species due to the strong effect of soil texture on the OP concentration

Spatial patterns of nitrogen isotope ratios in forest soils are related to latitude and soil phosphorus concentration

The aim of this study was to identify the parameters that affect the nitrogen (N) isotope ratio (& delta;N-15) in soils of temperate and boreal forests. We measured the & delta;N-15 in 30 soil profiles of temperate and boreal forests in Sweden and analyzed the relationships between & delta;N-15 in the soils and soil chemical properties as well as site characteristics. In addition, we conducted a meta-analyses of & delta;N-15 in the organic layer of European forests. We identified two types of & delta;N-15 patterns; in type D soils, the & delta;N-15 in the mineral soil decreases with depth, whereas in type C soil, the & delta;N-15 in the soil profile is almost constant. Type D soils had a significantly higher & delta;N-15 in the organic layer and upper mineral soil than type C soils, which is likely due to N isotope fractionation by ectomycorrhizal fungi in the topsoil. Type D soils were found in boreal forests, but not in temperate forests. They had a significantly lower atmospheric N deposition rate than type C soils, by a factor of 2.3, and a significantly higher phosphorus (P) concentration of the organic layer than type C soils, by a factor of 1.5. We also found that the & delta;N-15 was negatively correlated with the N:P ratio of the organic layer (R-2 = 0.21, p < 0.001). Across Europe, the & delta;N-15 of the organic layer was positively correlated with latitude (R-2 = 0.58, p < 0.001), and negatively with mean annual temperature (R-2 = 0.52, p < 0.001) and atmospheric N deposition (R-2 = 0.42, p < 0.001). In conclusion, our results show that the & delta;N-15 of the organic layer and microbial N (re-)cycling in forest soils is positively related with latitude and the P concentration of the organic layer

Efecte de la topografia en la variabilitat espacial del contingut de carboni total i d?òxids solubles de ferro i alumini a l?horitzó B del sòl a una catena forestal a Suècia

L'objecte d'aquest estudi és la variabilitat espacial i l'efecte de la topografia en un procés com és l'acumulació de sesquiòxids solubles de ferro i alumini juntament amb la matèria orgànica il·luviada a l'horitzó Bhs. La metodologia aplicada en l'estudi de la variabilitat espacial ha estat l'anàlisi geoestadística. Aquesta es va dur a terme a 96 mostres on es va valorar el carboni total, per l'analitzador elemental LECO, i els òxids solubles de ferro i alumini complexats a la matèria orgànica, extractats en pirofosfat sòdic 0,1N i valorats per ICP. L'anàlisi de la variància entre totes les variables analitzades ens mostra que hi ha diferències significatives (P-value: 0,0000), però si comparem els òxids solubles llavors les sèries són significativament semblants (P-value: 0,1839). La influència de l'hidromorfisme es va estudiar mitjançant ANOVA comparant els continguts analitzats tenint en compte l'estat de saturació d'aigua. Els resultats ens mostren que totes tres variables es troben afectades per l'hidromorfisme, però en especial els òxids solubles de ferro (P-value: 0,0000). Respecte a les relacions entre les variables, el carboni total i els òxids solubles d'alumini es troben amb una bona correlació (R2 = 0,74, P0 = 0,001). Segons l'ajust del semivariograma el paràmetre que té una variabilitat espacial més elevada són els òxids solubles de ferro, que tenen una correlació espacial amb un abast de 20 m. La raó d'aquesta variabilitat ve donada per l'efecte en el ferro de l'hidromorfisme que va ser localitzat a 26 dels 96 punts mostrejats, i a causa de a les característiques d'aquest element ha estat reduït i rentat de forma més fàcil que els sesquiòxids d'alumini o el carboni.El objeto de este estudio es la variabilidad espacial y el efecto de la topografía en un proceso como es la acumulación de sesquióxidos solubles de hierro y aluminio complejados a la materia orgánica iluviada en el horizonte Bhs en los suelos de una catena sueca. La metodología aplicada en el estudio de la variabilidad espacial ha sido el análisis geoestadístico. Éste se aplicó a 96 muestras en las que se valoró el carbono total, por el analizador elemental LECO, y los óxidos solubles de hierro y aluminio complejados a la materia orgánica, extractados en pirofosfato sódico 0,1N y valorados por ICP. El análisis de la varianza ANOVA entre las variables analizadas nos muestra que hay diferencias significativas (P-value: 0,0000), pero si comparamos los óxidos solubles entonces las series son significativamente similares (P-value: 0,1839). La influencia del hidromorfismo se estudió mediante la varianza ANOVA, comparando los contenidos analizados teniendo en cuenta el estado de saturación de agua. Los resultados nos indican que las tres variables están afectadas por el hidromorfismo pero en especial los óxidos solubles de hierro (P-value: 0,0000). El carbono total y los óxidos solubles de aluminio están bien correlacionados (R2 = 0,74, P0 = 0,001) y ambas series tienen semejanzas significativas y representativas. Según el ajuste del semivariograma teórico, el parámetro que tiene una variabilidad espacial más elevada son los óxidos solubles de hierro, que tienen una correlación espacial con un alcance de 20 m. La razón de esta variabilidad viene dada por el efecto en el hierro del hidromorfismo que fue localizado en 26 de los 96 puntos muestreados, y debido a las características de este elemento ha sido reducido y lavado de forma más fácil que los sesquióxidos de aluminio o el carbono.The object of this study is the spatial variability of and the effect of the topography on the accumulation of soluble iron and aluminium oxides togethen with the illuviated the organic matter in the Bhs horizon of the soil. The spatial variability has been analysed geostatistically. This has been done with 96 samples where total carbon has been measured using the elemental analysator LECO. The soluble oxides of iron and aluminium complexed to the organic matter were extracted in 0.1N Na-pyrophosphate and determined by ICP. A one-way ANOVA analisys of variance between the three series showed that there are significant differences (P-value: 0,0000), but if we compare the soluble oxides there are significant similarities (P-value: 0,1839). The influence of waterlogging was studied by ANOVA; the results are that all three variables are affected, but especially the soluble iron oxides (P-value: 0,0000). The relationship between the variables are well correlated as the total carbon and the the soluble oxides of aluminium (R2 = 0.74, P0 = 0.001). When the theoretical semivariogram is fitted, the parameter with the highest spatial variability is the soluble iron oxides content. This has a good spatial correlation in a range of 20 meters. The high spatial variability is due to the effect of the waterlogging on the iron, 26 of the 96 soil samples being waterlogged. Iron is more easily reduced and leached than the carbon or the aluminium sesquioxides

Manganese availability is negatively associated with carbon storage in northern coniferous forest humus layers

Carbon sequestration below ground depends on organic matter input and decomposition, but regulatory bottlenecks remain unclear. The relative importance of plant production, climate and edaphic factors has to be elucidated to better predict carbon storage in forests. In Swedish forest soil inventory data from across the entire boreal latitudinal range (n = 2378), the concentration of exchangeable manganese was singled out as the strongest predictor (R-2 = 0.26) of carbon storage in the extensive organic horizon (mor layer), which accounts for one third of the total below ground carbon. In comparison, established ecosystem models applied on the same data have failed to predict carbon stocks (R-2 <0.05), and in our study manganese availability overshadowed both litter production and climatic factors. We also identified exchangeable potassium as an additional strong predictor, however strongly correlated with manganese. The negative correlation between manganese and carbon highlights the importance of Mn-peroxidases in oxidative decomposition of recalcitrant organic matter. The results support the idea that the fungus-driven decomposition could be a critical factor regulating humus carbon accumulation in boreal forests, as Mn-peroxidases are specifically produced by basidiomycetes.Peer reviewe

Pedon-scale silicate weathering : comparison of the PROFILE model and the depletion method at 16 forest sites in Sweden

Weathering of soil minerals is important for the recovery from acidification and for the sustainability of forestry. However, there is still substantial uncertainty about its absolute rate. This study presents a harmonized comparison of field weathering rates estimated with the mechanistic model PROFILE and the depletion method for 16 intensively sampled soil profiles across Sweden representing different site conditions. In general, a correspondence in total weathering rates was found between the two methods except in rare cases where either method yielded deviating results. The weathering rate was higher according to the depletion method than according to PROFILE for Mg, while PROFILE produced higher weathering rates for the other base cations. The Spearman rank correlation (rho) between the two methods indicated significant correlation for Ca (rho = 0.44, p = 0.04) and non-significant correlation for Mg (rho = 0.51, p = 0.09), Na (rho = 0.25, p = 0.34), K (rho = 0.07, p = 0.80), and the sum of the base cations (rho = 0.11, p = 0.67). The variation in weathering rates with depth showed opposite gradients in the upper 50 cm, which reflects the conceptual differences between the methods. This study shows the potential of using multiple methods to identify a probable weathering rate, if harmonized input data are used. Furthermore, it highlights the importance of making comparisons for individual elements in order to interpret differences between methods. Regardless of the method used, weathering rates were below or at the same level as the losses caused by whole-tree harvesting, particularly in southern Sweden, indicating a risk of negative effects on soils and waters. (C) 2013 Elsevier B.V. All rights reserved

Växttillgängligt bor i svensk skogsmark

Syftet med projektet ”Växttillgängligt bor i svensk skogsmark” är att öka kännedomen om halten vattenlösligt bor i vår skogsmark, samt redogöra för sambanden mellan denna halt och ståndortsfaktorer, samt andra markkemiska variabler. Utifrån de ca 4000 permanenta provytor inom Riksskogstaxeringen som inventerades av Markinventeringen åren 2000-2002 valdes 210 provytor ut, vilka var fördelade över större delen av Sverige med varierande egenskaper med avseende på ståndort och markkemi. Från Markinventeringens jordprovsarkiv togs delprover ut från lagrade prov från humuslager och B-horisont från de utvalda 210 provytorna. De totalt 420 proven skickades till Eurofins Food & Agro i Lidköping, där de analyserades på växttillgängligt bor med varmvattenextraktion (BHWE). BHWE-halterna i proven från humuslager låg klart över detektionsgränsen (0,10 mg per kg torrsubstans) och medelvärdet (1,39 mg kg-1 ts) låg något över vad som tidigare rapporterats från ett fåtal humusprov i svensk skogsmark, samt klart över genomsnittet för BHWE-halten i matjord från svensk åkermark (0,41 mg kg-1 ts). BHWE-halten i humuslagret var i genomsnitt nästan en tiopotens högre än motsvarande halt i B-horisonten. I proven från B-horisonten låg 30 % av proven under detektionsgränsen. Vid beräkningarna erhöll dessa prov värdet 0,05 mg kg-1 ts för BHWE-halten. Medelvärdet (0,17 mg kg-1 ts) låg i nivå med eller något under vad som tidigare rapporterats för ett fåtal prov från B-horisonter i svensk skogsmark. För hela datamaterialet fanns inget samband mellan BHWE-halten i humuslagret och underliggande B-horisont. Av de många ståndortsvariabler som BHWE-halterna jämfördes med kunde vi för humuslagret bara se signifikanta positiva samband med beståndets ålder och medelhöjd, samt med ökad markfuktighet. För BHWE-halten i B-horisonten noterades däremot flera signifikanta samband med klimat- och ståndortsvariabler, bl.a. minskade halter med främst ökad longitud, men även för ökad latitud och markfuktighet. Signifikant positiva samband fanns mellan BHWE-halten och bl.a. humiditet, ökad deposition, samt marklutning. När det gäller de markkemiska variablerna så fanns det för BHWE-halten i humuslagret signifikanta positiva samband med kol- och kvävehalt, de utbytbara baskatjonerna, titrerbar aciditet, samt katjonbyteskapaciteten. För BHWE-halten i B-horisonten konstaterades signifikanta positiva samband för i stort sett samma markvariabler, men också signifikant negativt samband med pH. De höga halterna av BHWE i humuslagret, samt sambanden mellan BHWE och främst kolhalt och katjonbyteskapacitet och för humuslagret även beståndsålder samt medelhöjd tyder på att tillgången på växttillgängligt bor i marken till stor del styrs av interncirkulation mellan beståndet, förnan och humuslagret. Detta bör man ta hänsyn till vid skogsskötselåtgärder, speciellt vid helträdsavverkning då en stor del av det växttillgängliga borförrådet i ekosystemet kan exporteras från systemet i samband med uttaget av grenar och toppar från det helträdsavverkade området

Climate effects of a forestry company : including biogenic carbon fluxes and substitution effects

Forestry will play an important role in a future bioeconomy, by providing wood fibres for biomaterial and bioenergy. However, there are contradictory opinions on the climate change mitigation potential of forestry. Stora Enso, an international forestry company, has the ambition to improve its climate impact assessment at corporate level. In this work, a system perspective was applied, where greenhouse gas emissions from value chains, biogenic carbon fluxes from forest land owned or leased by Stora Enso and temporarily stored in harvested wood products, and the substitution effect, i.e. avoided emissions from substituted products and energy were considered. Furthermore, new substitution factors for pulp and paper products were developed. The estimated climate effect at corporate level was a net removal of -11.5 million Mg CO2-eq yr-1 (i.e. a climate benefit) when considering value chain emissions, biogenic carbon fluxes from forest land and harvested wood products, and avoided emissions from substitution. Uptake of biogenic carbon counteracted around 40% of the value chain emissions, while the largest climate benefit (removal of 17.9 million Mg CO2-eq) was due to substitution of more greenhouse gas-intensive products. The new substitution factors developed for pulp and paper products were applied in the climate impact calculation at company level. Important assumptions and possible improvements for future studies were identified, e.g. how to assess the impact of cascading wood use in substitution calculations

Demand-driven climate change mitigation and trade-offs from wood product substitution: The case of Swedish multi-family housing construction

Multi-family housing construction (MFHC) with wood instead of concrete as frame material results in lower greenhouse gas emissions. Hence, substituting wood for concrete in MFHC in Sweden until 2030, and onwards to 2070, could be a promising climate change mitigation option. But to what extent, and how would it impact Sweden's forests? Here we assess climate and biodiversity implications - in terms of the area of old forest - of a completely wood-based future MFHC in Sweden. The wood required is assumed to be exclusively sourced as additional fellings in Swedish forests, thus carbon leakage from wood imports as well as displacement of other wood uses can be disregarded. Different types of timber frame systems and the role of varying future dwelling sizes are considered. We find that the wood needed for a complete substitution of concrete would result in very minor increases in harvests. We further register slight net additional climate change mitigation, irrespective of the wood construction system. There is a small tradeoff between climate change mitigation and biodiversity, as the area of old forest reduces slightly. The largest climate benefit, and lowest impact on Swedish forests, is provided when using timber-light frame combined with reduced dwelling size

Nordic forest management towards climate change mitigation: time dynamic temperature change impacts of wood product systems including substitution effects

Climate change mitigation trade-offs between increasing harvests to exploit substitution effects versus accumulating forest carbon sequestration complicate recommendations for climate beneficial forest management. Here, a time dynamic assessment ascertains climate change mitigation potential from different rotation forest management alternatives across three Swedish regions integrating the forest decision support system Heureka RegWise with a wood product model using life cycle assessment data. The objective is to increase understanding on the climate effects of varying the forest management. Across all regions, prolonging rotations by 20% leads on average to the largest additional net climate benefit until 2050 in both, saved emissions and temperature cooling, while decreasing harvests by 20% leads to the cumulatively largest net climate benefits past 2050. In contrast, increasing harvests or decreasing the rotation period accordingly provokes temporally alternating net emissions, or slight net emission, respectively, regardless of a changing market displacement factor. However, future forest calamities might compromise potential additional temperature cooling from forests, while substitution effects, despite probable prospective decreases, require additional thorough and time explicit assessments, to provide more robust policy consultation