| 1. |
- Gundale, Michael, et al.
(författare)
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The effect of biochar management on soil and plant Community properties in a boreal forest
- 2016
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Ingår i: GCB Bioenergy. - : Wiley. - 1757-1693 .- 1757-1707. ; 8, s. 777-789
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Tidskriftsartikel (refereegranskat)abstract
- Biochar management has been proposed as a possible tool to mitigate anthropogenic CO2 emissions, and thus far its impacts in forested environments remain poorly understood. We conducted a large-scale, replicated field experiment using 0.05-ha plots in the boreal region in northern Sweden to evaluate how soil and vegetation properties and processes responded to biochar application and the disturbance associated with burying biochar in the soil. We employed a randomized block design, where biochar and soil mixing treatments were established in factorial combination (i.e., control, soil mixing only, biochar only, and biochar and soil mixing; n=6 plots of each). After two growing seasons, we found that biochar application enhanced net soil N mineralization rates and soil NH4+ concentrations regardless of the soil mixing treatment, but had no impact on the availability of NO3- , the majority of soil microbial community parameters, or soil resPiration. Meanwhile, soil mixing enhanced soil NO3- concentrations, but had negative impacts on net N mineralization rates and several soil microbial community variables. Many of the effects of soil mixing on soil nutrient and microbial community properties were less extreme when biochar was also added. Biochar addition had almost no effects on vegetation properties (except for a small reduction in species richness of the ground layer vegetation), while soil mixing caused significant reductions in graminoid and total ground layer vegetation cover, and enhanced seedling survival rates of P.sylvestris, and seed germination rates for four tree species. Our results suggest that biochar application can serve as an effective tool to store soil C in boreal forests while enhancing NH4+ availability. They also suggest that biochar may serve as a useful complement to site preparation techniques that are frequently used in the boreal region, by enhancing soil fertility and reducing nutrient losses when soils are scarified during site preparation.
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| 2. |
- Pluchon, Nathalie
(författare)
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Functional role of fire-derived charcoal in boreal forest ecosystem processes
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Charcoal is a natural product of wildfires which operate as a major natural disturbance in boreal forested ecosystems. This carbon (C)-rich material is present in most forest soils but its effects on ecosystem processes remain poorly understood. This thesis explores how charcoal, through its characteristics or traits, affects above- and belowground processes in the Swedish boreal forest by using laboratory mesocosm and glasshouse studies and a large field experiment. The relative importance of charring condition and species identity in determining charcoal traits was also investigated. These experiments covered a wide range of humus types, charcoal types and plant species in order to better understand the factors that determine the functional role of charcoal. With regard to aboveground processes, fire-derived charcoal promoted tree seedling growth but had only a minimal effect on seed germination, and plant community characteristics. Belowground processes such as humus decomposition and N mineralization rate were enhanced by the presence of charcoal, even though charcoal had minimal effect on microbial biomass and composition. Charcoal traits were shown to be affected primarily by species identity and to a lesser extent by charring conditions. The magnitude of charcoal effects was influenced by humus type, charcoal type and plant species identity. The mechanisms by which fire-derived charcoal affect ecosystem processes differed between above- and belowground processes; notably, while the effects of charcoal on aboveground processes were linked mostly to the direct input of phosphorus and especially PO43- from charcoal, its effect on belowground processes were mostly determined indirectly through its impact on microbial specific activity. These findings suggest that charcoal is likely to play a role in boreal forest succession, plant-soil feedbacks and ecosystem C dynamics. Moreover, the impacts of charcoal in boreal ecosystems are relevant to better understanding the ecological consequences of forest management practices such as site preparation, prescribed burning, fire suppression and biochar addition. Overall, the findings described in this thesis show that charcoal is a significant component of the C cycle and one that can have strong impacts on boreal ecosystem processes.
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| 3. |
- Pluchon, Nathalie, et al.
(författare)
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Influence of species identity and charring conditions on fire-derived charcoal traits
- 2015
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Ingår i: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 45, s. 1669-1675
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Tidskriftsartikel (refereegranskat)abstract
- Fire is a major disturbance worldwide, and it produces significant amounts of wood-derived charcoal. There is increasing evidence that the key properties ("traits") of charcoal vary greatly, with consequences for ecosystem processes, but how the key factors drive variability of charcoal traits, i.e., species identity and charring conditions, remain poorly understood. Here, we experimentally produced charcoal from three common boreal tree species under six charring conditions representing those encountered during boreal fires and then analyzed their structural and chemical traits. Overall, we found that species identity affected charcoal traits more than did charring conditions. Among the structural traits, density and microporosity varied among tree species, and density decreased with increasing temperature. Among the chemical traits, electrical conductivity, total nitrogen (N) and phosphorus (P) contents, and phosphate concentration differed among species, whereas pH, total N content, and ammonium concentration responded to charring conditions. No traits except nitrate concentration responded to the interactive effect of species identity and charring condition. Our results reveal that traits of charcoal, and potentially its ecological functions, are driven by a combination of fire behavior and tree species identity; such information is relevant for understanding ecological consequences of altered fire regimes due to the changing climate and to forest management.
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| 4. |
- Pluchon, Nathalie, et al.
(författare)
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Recent paludification rates and effects on total ecosystem carbon storage in two boreal peatlands of Northeast European Russia
- 2014
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:9, s. 1126-1136
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Tidskriftsartikel (refereegranskat)abstract
- Forest and peatland ecosystems constitute the two major carbon pools in the boreal region. We assess the evolution in total storage and partitioning of ecosystem carbon following recent paludification of forest into peatland at two sites in Northeast European Russia. Based on radiocarbon dating of basal peat and quantification of total ecosystem carbon storage, our results show that paludification rates and its consequences for carbon storage vary significantly between sites. A peatland expanding on ground with steeper slopes has experienced a slow lateral advance in recent times, about 2.6 m on average per century, whereas a peatland in flatter terrain has expanded much more rapidly, about 35 m on average per century. The total ecosystem carbon storage (sum of phytomass, top soil organics or peat, and 30 cm of underlying mineral soil) showed a long-term trend toward increased ecosystem C storage following the replacement of forest (mean value = 20.8 kg C/m(2), range = 13.0-43.4 kg C/m(2)) by peatland (>100 kg C/m(2) in the deepest peat deposits). However, the transitional stage in which the forest is replaced by the margin of the peatland results in a short-term decrease of carbon stored in the ecosystem with a mean loss of 7.5 kg C/m(2). After the initiation of a peatland through paludification, a period of decades to centuries of peat accumulation is needed to compensate for the initial loss of carbon. In the short term, an intensification of the paludification process could lead to a loss of carbon stored in the boreal region.
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| 5. |
- Pluchon, Nathalie, et al.
(författare)
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Stimulation of boreal tree seedling growth by wood-derived charcoal: effects of charcoal properties, seedling species and soil fertility
- 2014
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 28, s. 766-775
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Tidskriftsartikel (refereegranskat)abstract
- Fire is a major disturbance in many ecosystems world-wide including the boreal forest, and significant quantities of charcoal can be input to the soil from fire. Some recent studies have provided evidence that wood-derived charcoal produced by fire can significantly stimulate plant growth. However, the mechanisms by which charcoal affects plant growth are poorly understood, and little is known about how charcoal effects on plant growth are influenced by charcoal type, soil type and plant species.Seedlings from four common boreal tree species, two evergreen gymnosperms and two deciduous angiosperms, were grown in each of two soils of contrasting nutrient availability amended with charcoal with each of nine charcoal types (each produced from wood from a different plant species) in a greenhouse experiment. We also measured several functional traits for each of the charcoal types, as well as of the wood used to prepare the charcoal.Charcoal addition had either positive or neutral effects on seedling growth, with great variability among charcoal types. The charcoal types that had the strongest positive effect were those that had the greatest concentrations of phosphate and total phosphorus and, in some cases, were derived from woods that had the highest total phosphorus concentration. Addition of charcoal on average had a stronger positive effect on plant growth on soil with the lowest levels of phosphate and total phosphorus.Generally, charcoal derived from angiosperms stimulated seedling growth more than charcoal from gymnosperms. Further, angiosperm seedlings were on average stimulated more by charcoal addition than were gymnosperm seedlings. These results indicate that charcoal produced by fire could contribute to the initial dominance of angiosperm trees in post-fire succession and suggest a possible feedback whereby charcoal from angiosperm tree species favours growth of angiosperm seedlings.This study highlights a new means by which functional trait variation among tree species could potentially exert 'after-life' effects in forested ecosystems through influencing traits (and notably phosphate concentrations) of the charcoal that they produce following wildfire, with potentially important consequences for plant growth and community and ecosystem properties during post-fire succession.
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| 6. |
- Pluchon, Nathalie, et al.
(författare)
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The impact of charcoal and soil mixtures on decomposition and soil microbial communities in boreal forest
- 2016
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 99, s. 40-50
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Tidskriftsartikel (refereegranskat)abstract
- Fire is a natural disturbance that operates as a major ecological driver in many ecosystems worldwide, and it produces charcoal which is incorporated into soil in significant quantities. Charcoal can serve as a long-term carbon (C) sink, but it is not inert, and could potentially impact native soil organic matter and decomposer micro-organisms. However, studies have shown contrasting results for how charcoal impacts the belowground subsystem, and the mechanisms involved are poorly understood, especially in pyrogenic ecosystems. We performed a laboratory experiment in which six contrasting boreal forest soil types and nine charcoal types (each from different woody plant species) were incubated for 9.5 months, both by themselves and in 50:50 mixtures for all possible soil-charcoal combinations. At harvest we measured mass loss, and for several charcoal-soil combinations, we measured microbial properties, and composition of C compounds using C-13 CP-MAS nuclear magnetic resonance (NMR) spectroscopy. Overall, mixtures of charcoal and soil lost more mass than expected based on when the components were incubated separately. The magnitude of increased soil mass loss in mixtures did not differ among charcoal types, but varied among soil types, because greater mass loss occurred when soil from a site dominated with herbaceous vegetation was used, relative to other soil types. The use of NMR spectroscopy showed that enhanced mass loss in mixtures was due mainly to mass loss of soil organic matter rather than charcoal. However, mixing of charcoal and soil did not influence key decomposer microbial groups compared with expected values derived from when components were incubated alone, irrespective of charcoal and soil type. This study shows that when charcoal is incorporated into boreal forest soil (e.g., after wildfire), there is enhanced loss of total C (arising primarily from mass loss of soil organic matter), with this effect being relatively consistent across contrasting charcoal and soil types. This effect, in combination with recently documented impacts of charcoal on aboveground processes, reveals important but largely overlooked legacy effects of charcoal on forest processes that contribute to ecosystem C balance and ecosystem functioning. (C) 2015 Elsevier B.V. All rights reserved.
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