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Background and aims: Plant‐derived, ester‐bound substituted fatty acids have been used for decades as biomarkers to identify input of plant materials in sediments and soils. However, the long‐term decomposition patterns of these biomarker compounds under natural conditions are not well understood, although this is a basic prerequisite for quantitative biomarker applications. Methods: For this study, we analyzed the decomposition patterns of root‐ and needle‐specific compounds of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) in a litterbag study conducted over 3 years. Samples were analyzed by methanolic KOH extraction with previous removal of free extractable lipids. Results: The concentrations of most detectable compounds had decreased after three years of incubation. The observed changes of concentrations followed a non‐linear path and cannot be explained by microbial uptake and metabolism alone. Other factors controlling the breakdown of ester‐bound lipids, like lipid oxidation must play a role. Between similar plant parts and different plant parts of the same species, the observed degradation patterns were heterogeneous. The estimated ratio of remaining root and needle biomass that may arise with the choice of a particular biomarker varies in this study between 0.6 and 40 times after three years. Conclusion: This range of variation does not allow reliable conclusions about the contribution of roots and needles to decomposed organic matter based on biomarkers ratios. [ABSTRACT FROM AUTHOR]

The article focuses on effect of biochar amendment on the properties of growing media and growth of containerized Norway spruce, Scots pine, and silver birch seedlings. Topics include the common practices and several studies have demonstrated the positive effect of biochar amendment on climate change mitigation, and plant growth, and the greenhouse experiment to assess the potential of wood biochar to improve the properties of the growing media and growth of seedlings in boreal tree species.

Finland has a long tradition of utilizing forest-based biomass for energy and industry purposes and the use has steadily increased in the past decade due to changes in international and regional energy policies. Intensive harvesting practices, in which a larger proportion of the woody biomass is removed from the forest stand, are becoming more common. The objectives of this study were (i) to evaluate the spatial and temporal extent of soil surface disturbance caused by stump-root system harvesting and (ii) to quantify how much biomass and nitrogen is removed from the stand in stump and coarse root harvesting. The extent of surface disturbance was assessed in three clear-cut Norway spruce ( Picea abies , (L . ) Karst.) stands in southern and central Finland, differing in time since harvest. To determine the biomass distribution of the stump-root system, stumps and coarse roots were excavated at one of the experimental stands. Across all age classes (time since harvest) less soil surface had remained undisturbed at the stump harvesting sites (52%) than at the sites where only mechanical site preparation (28%) had been carried out. Thus, the findings of this study indicate that soil disturbance caused by stump harvesting can exist on forest soil surface for more than a decade following harvest. The total biomass of the stump-root system in the stand was estimated to 39.3 Mg ha −1 and 79% of this biomass was removed during stump harvesting and consequently, 8.3 Mg ha −1 of stump-root biomass remained in soil. The stump-root system accounted for 17% of the whole-tree biomass, and coarse roots and fine coarse roots represented a significant portion of it (73%). Thus, the stump-root system represents a large biomass component in boreal forest stands. However, forest management utilizing stumps may result in carbon losses from the stand. [ABSTRACT FROM AUTHOR]

The use of forest-derived biomass has steadily increased in Finland and Sweden during the past decades leading to more intensive forest management practices in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting results in a direct removal of stump and coarse-root carbon (C) from the stand and can cause extensive soil disturbance, which has been suggested to increase C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied in two different clear-felled Norway spruce ( Picea abies ) sites in Central Finland. The treatments were whole-tree harvesting (WTH, removal of stems and logging residues), and WTH and stump harvesting (WTH + S). Both sites, Honkola (2 stands) and Haukilahti (6 stands) were mounded. In both treatments, soil samples were taken from different soil layers down to a total depth of 20 cm in the mineral soil from (i) mounds, (ii) undisturbed soil and (iii) pits. The sampling was performed 11–12 years after treatments. Soil C and N mineralization rates were determined in laboratory incubation experiments. In addition, total C and N pools (g m −2 ) were estimated for each disturbance class and soil layer. Soil C and N pools had a tendency to be lower following stump harvesting, but no statistically significant treatment effect was detected. Stump harvesting increased soil mixing as indicated by a significant decrease in C concentration in the mound disturbance class. There was no significant effect of stump harvesting on soil C mineralization rates. A combination of mineralization rates and soil pool data showed that field C mineralization (g CO 2 -C m −2 yr −1 ) did not significantly differ between stands where stumps were removed or were retained. Further, stump harvesting did not seem to have any stimulating effect on soil CO 2 efflux 11–12 years after treatment. [ABSTRACT FROM AUTHOR]

Effects of stump harvesting on coarse woody debris (CWD), soil and vegetation were investigated 8–13 years after clear-cutting of eight forest stands located at two sites, Honkola and Haukilahti, in Central Finland. Norway spruce ( Picea abies ) was the dominant tree species in the harvested stands. Four of the stands were subjected to mounding and four were stump-harvested. Logging residues were removed at harvest from all eight stands. The amount of CWD remaining after stump harvesting was estimated from basal area of remaining stumps, diameter and length of logs and by weighing smaller pieces of dead wood. Moss and field layer vegetation cover was estimated by a point-intercept method and the diameter of young trees was measured to estimate basal area. Soil carbon and nitrogen stocks and pH were determined in the humus layer and down to 25 cm depth in the mineral soil. The degree of soil disturbance was visually assessed in the field. Basal area measurements on remaining stumps suggested that about 75% of the stumps had been removed from the stump-harvested stands, which is a typical stump harvesting rate in Finland. The amount of remaining stumps and root biomass was significantly lower in stump-harvested stands than in stands where stumps had been retained, whereas differences between mounding and stump harvesting were not significant for the other types of CWD. Stump harvesting had no significant effect on the cover of field layer species, total moss cover or vegetation composition. Total stem density was almost twice as high in stump-harvested stands as in stands where stumps were not harvested, due to significantly higher stem density of Betula pendula Roth., whereas no effect was observed on the basal area of the other tree species. No significant treatment effect on soil carbon and nitrogen stocks or on degree of soil disturbance was detected, but the higher density of Betula indicates higher exposure of mineral soil during the years following stump removal. In conclusion, stump harvesting seems to promote natural establishment of Betula seedlings, but does not change tree productivity. [ABSTRACT FROM AUTHOR]

Abstract: Tree stumps are integral constituents of managed forest ecosystems, but their role in nutrient cycling is poorly understood. We studied phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) dynamics in decomposing Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and silver birch (Betula pendula) stumps in southern Finland in a chronosequence of 0-, 5-, 10-, 20-, 30- and 40-year-old clear-cut areas. Along with the decomposition of pine and spruce stumps, the amount of P in stumps increased, but K and Ca were released, and the amount of Mg initially decreased and then increased. All nutrients, except K, accumulated in birch stumps during the first ten years, but were released thereafter. After 40 years of decomposition, pine and spruce stumps contained 180% and 202% of their initial amounts of P, respectively. In addition, the amounts of Mg were larger than the initial amounts in 40-year decomposed pine (126%) and spruce (202%) stumps. In contrast, birch stumps lost 64% and 75%, respectively, of their initial amounts of P and Mg over a 40-year period. The stumps of all the species were found to release K and Ca. Pine, spruce and birch stumps lost 48%, 64% and 87% of their initial amount of K, and 49%, 35% and 42% of their initial amount of Ca, respectively, during the 40-year period. The results indicate that decomposing stumps of the major tree species in Fennoscandian forests are long-term nutrient pools and they serve as P sinks, thus potentially reducing P leaching after clear-cutting. [ABSTRACT FROM AUTHOR]

Abstract: Stumps are the largest coarse woody debris component in managed forests, but their role in nutrient cycling is poorly understood. We studied carbon (C) and nitrogen (N) dynamics in Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and silver birch (Betula pendula) stumps, which had decomposed for 0, 5, 10, 20, 30 and 40 years after clear-cutting in southern Finland. Carbon and N were released significantly faster from birch stumps than from conifer stumps. In 40 years, conifer stumps lost 78% and birch stumps 90% of their initial C. In contrast, the amount of N in stumps increased, indicating that external N accumulated in the stumps. After 40 years of decomposition, the amount of N was 1.7 and 2.7 times higher than the initial amount in pine and spruce stumps, respectively. Nitrogen was released from birch stumps, but only after they had decomposed for 20 or more years. On average, 59% of N stored in birch stumps was released during 40 years. The results indicate that the stumps of the major tree species in Fennoscandian forests are long-term C and, especially, N pools which serve as N sinks, thus potentially diminishing N leaching into ground water and watercourses after harvesting. This suggests that the removal of stumps for bioenergy production may markedly affect the nutrient status and nutrient cycling of boreal forests. [Copyright &y& Elsevier]

The contents of nitrogen (N) have generally been observed to increase in the early stages of decomposition in coarse woody debris and then to decrease slowly. This is potentially an important mechanism of nutrient retention in ecosystems after disturbances. We studied N dynamics in decomposing Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and silver birch (Betula pendula Roth.) stems in Finland. The oldest stems had decomposed for 34 (spruce and birch) or 45 (pine) years. Concentrations of N in both fallen logs and standing snags increased and C/N ratios decreased with time, and birch had significantly higher N concentrations and lower C/N ratios than pine and spruce. Even though increased N contents were observed in some cases, N was generally already released in the early stages of decomposition and more rapidly from birch than from conifers. Based on model analysis, from 40% (pine and spruce) to 50% (birch) of initial N was released within 30 years. The results suggest that decomposing stems of especially Scots pine and Norway spruce retain N rather effectively in boreal forest ecosystems and form a long-term, small but steady N pool with a slow release rate. [ABSTRACT FROM AUTHOR]

Ground vegetation may act as a sink for nutrients after clear-cutting and thus decrease leaching losses. Biomass and nutrient (N, P, K, Ca) pools of ground vegetation (mosses, roots and above-ground parts of field layer) were determined one year before and five years after clear-cutting of a Norway spruce (Picea abies (L.) H. Karst.) dominated boreal mixed forest stand in eastern Finland (63°51′ N, 28°58′ E). Before clear-cutting the average biomass of ground vegetation was 5307 kg ha−1, with nutrient contents of 46.9 kg N ha−11, 4.1 kg P ha−11, 16.2 kg K ha−11 and 13.9 kg Ca ha−11. The biomass and nutrient pools decreased after clear-cutting being lowest in the second year, the biomass decreasing by 46–65% in the cut plots. The nutrient pools decreased as follows: N 54–72%, P 36–68%, K 51–71% and Ca 57–74%. The decrease in ground vegetation nutrient uptake, and the observed reduced depth of rooting may decrease nutrient retention after clear-cutting and decomposing dead ground vegetation is a potential source of leached nutrients. These negative effects of clear-cutting on the nutrient binding capacity of ground vegetation was short-lived since the total biomass and nutrient pools returned to pre-cutting levels or were even greater by the end of the 5-year study period. [ABSTRACT FROM AUTHOR]

Potassium (K), calcium (Ca), iron (Fe) and aluminium (Al) release from Norway spruce (Picea abies Karsten), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) logging residues (fine roots, foliage and small branches) were studied by means of litterbags over a period of three years in clear-cut area and adjacent uncut Norway spruce dominated mixed boreal forest in eastern Finland (63°51′ N, 28°58′ E, 220 m a.s.l) to determine the amounts and rates of release for these elements and to evaluate whether clear-cutting accelerates mineralization. Almost all K was released from logging residues already during the first year. Calcium was released from foliage and roots but accumulated in branches. Most of the roots Fe and Al content were released during three years while the absolute amounts of Fe and Al in branches and foliage generally increased with decomposition. The results indicate that mineralization is slightly accelerated as a result of clear-cutting since K from foliage and branches of all studied tree species and Ca from pine and spruce roots was released significantly faster at the clear-cut plot than at the forest plot. In three years the initial K pool in the logging residues declined by 90%, Ca by 8%, Fe by 55% and Al by 61% in the clear-cut area. These results indicate that Ca is retained a long time; but Fe, Al and in particular, K are soon released from logging residues. Fine roots of the logged trees release large amounts of Fe and Al and can significantly affect Fe and Al fluxes. [ABSTRACT FROM AUTHOR]

Biochar is formed in a pyrolysis process in which organic material is heated under low oxygen concentration. Biochar has porous structure, large specific surface area and high cation exchange capacity, and it is thus capable of adsorbing nutrients and other dissolved compounds from water. However in forest areas, biochar has so far mainly been used as a soil amendment, but as a good adsorbent, it may provide an innovative, cheap, renewable and 100% recyclable material for active water purification and nutrient recycling in forestry. For a laboratory experiment, we collected runoff water from boreal peatland forest site which has been recently clear-cut. In these kind of fertile spruce fens, the risk of high nutrient export is particularly severe after final cutting. We conducted an adsorption experiment where biochar and runoff water were stirred at constant temperature (20°C) for 10 days. We quantified adsorption rate and adsorption isotherm (maximum adsorption) for total N, NH4-N, NO3-N, total P, H+ and dissolved organic carbon (DOC). We tested two different wood biochars (Picea abies and Betula pendula) and two particle sizes (2-4 mm and > 4 mm). During the experiment, the concentrations of elements and pH were measured from the filtered solution at regular time intervals. Biochar adsorbed effectively H+, N and DOC. Thus, biochar has a good potential for use in the removal of nutrients and DOC, and decreasing the acidity of runoff waters. The study will continue with meso-scale column experiments, where runoff water is directed through biochar-filled columns, and water quality is monitored in inlet and outlet of the columns. Based on these results we will construct a simulation model describing the water purification process, and the model will be applied in the design of a biochar reactor which finally will be tested in field conditions. [ABSTRACT FROM AUTHOR]