Jānis Liepiņš, Ieva Jaunslaviete, Kaspars Liepiņš, Līga Jansone, Roberts Matisons, Andis Lazdiņš, Āris Jansons. (2023). Effect of stem rot on wood basic density, carbon, and nitrogen content of living deciduous trees in hemiboreal forests. Silva Fennica vol. 57 no. 3 article id 23040. https://doi.org/10.14214/sf.23040

Keywords: wood specific gravity; birch; climate change mitigation; biomass estimation; alder; aspen; wood decay

Highlights: Stem rot significantly reduces the basic density of wood and increases its nitrogen content in living deciduous trees, while the carbon content appears irresponsive; The effect of the distance from the pith on the basic density and nitrogen content of wood varies, depending on presence of discoloration or decomposition in the wood.

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While numerous studies have focused on analyzing various aspects of the carbon (C) budget in forests, there appears to be a lack of comprehensive assessments specifically addressing the impact of stem rot on the C budget of broadleaf tree species, especially in old-growth forests where stem rot is prevalent. One of the main challenges in accurately quantifying C losses caused by stem rot is the lack of precise data on the basic density and C content of decayed wood, which are crucial for converting decayed wood volume into biomass and C stocks. Using linear mixed-effects models, we examine the variability of wood basic density, C content, and nitrogen (N) content. Discolored and decomposed wood was collected from the stems of 136 living deciduous trees common in hemiboreal forests in Latvia. Our research indicates a noticeable reduction in the wood basic density, coupled with an increase in the N content within the stem wood throughout the decomposition process in birch (Betula spp.), European aspen (Populus tremula L.), grey alder (Alnus incana (L.) Moench), and common alder (Alnus glutinosa (L.) Gaertn.). While aspen wood showed a decreasing trend in C content as decay progressed, a pairwise comparison test revealed no significant differences in C content between discolored and decomposed wood for the studied species, unlike the findings for basic density and N content. This study emphasizes the need to account for stem rot in old-growth forest carbon budgets, especially in broadleaf species, and calls for more research on stem rot-induced carbon losses.

Liepiņš, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0000-0003-3030-1122 E-mail: janis.liepins@silava.lv
Jaunslaviete, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0009-0000-7322-2729 E-mail: ieva.jaunslaviete@silava.lv
Liepiņš, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0000-0002-1179-8586 E-mail: kaspars.liepins@silava.lv
Jansone, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0000-0003-2748-3797 E-mail: liga.jansone@silava.lv
Matisons, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia E-mail: roberts.matisons@silava.lv
Lazdiņš, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0000-0002-7169-2011 E-mail: andis.lazdins@silava.lv
Jansons, Latvian State Forest Research Institute “Silava,” Rigas Street 111, LV-2169 Salaspils, Latvia https://orcid.org/0000-0001-7981-4346 E-mail: aris.jansons@silava.lv

article id 23019, category Research article

Victor F. Strîmbu, Tron Eid, Terje Gobakken. (2023). A stand level scenario model for the Norwegian forestry – a case study on forest management under climate change. Silva Fennica vol. 57 no. 2 article id 23019. https://doi.org/10.14214/sf.23019

Keywords: forest planning; carbon balance; climate change mitigation; forest stand simulator

Highlights: GAYA 2.0: a new scenario analysis model focusing on forest carbon fluxes; Carbon sequestration potential estimated at regional level; GAYA 2.0 may be used to estimate the costs of obtaining carbon benefits by adapting the forest management.

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Carbon sequestration and income generation are competing objectives in modern forest management. The climate commitments of many countries depend on forests as carbon sinks which must be quantified, monitored, and projected into the future. For projections we need tools to model forest development and perform scenario analyses to assess future carbon sequestration potentials under different management regimes, the expected net present value of such regimes, and possible impacts of climate change. We propose a scenario analysis software tool (GAYA 2.0) that can assist in answering these types of questions using stand level simulations, detailed carbon flow models and an optimizer. This paper has two objectives: (1) to describe GAYA 2.0, and (2) demonstrate its potential in a case study where we analyze the forest carbon balance over a region in Norway based on national forest inventory sample plots. The tool was used to map the optimality front between the carbon benefit and net present value. We observed changes in net present value for different levels of carbon benefit as well as changes in optimal management strategies. We predicted future changes in several forest carbon pools as well as albedo and illustrated the impact of gradual increase in forest productivity (i.e., due to climate warming). Having been updated and modernized from its previous version with increased attention to forest carbon and energy fluxes, GAYA 2.0 is an effective tool that offers multiple opportunities to perform various types of scenario analyses in forest management.

Strîmbu, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, NO-1432 Ås, Norway https://orcid.org/0000-0002-0588-2036 E-mail: victor.strimbu@nmbu.no
Eid, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, NO-1432 Ås, Norway E-mail: tron.eid@nmbu.no
Gobakken, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, NO-1432 Ås, Norway https://orcid.org/0000-0001-5534-049X E-mail: terje.gobakken@nmbu.no

article id 243, category Research article

Rupert Seidl, Werner Rammer, Petra Lasch, Franz-Werner Badeck, Manfred J. Lexer. (2008). Does conversion of even-aged, secondary coniferous forests affect carbon sequestration? A simulation study under changing environmental conditions. Silva Fennica vol. 42 no. 3 article id 243. https://doi.org/10.14214/sf.243

Keywords: forest management; Norway spruce; climate change mitigation; PICUS; 4C; model comparison

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To circumvent problems associated with even-aged, pure coniferous stands propagated outside their natural range alternative management strategies and conversion programs are currently discussed in Central Europe. However, a mainstreaming of such adapted silvicultural systems with climate change mitigation objectives is missing to date. In this study the objective was to assess in situ C storage under conditions of climate change in a secondary Norway spruce (Picea abies (L.) Karst.) forest management unit in Austria. Four management strategies (Norway spruce age class forestry, transition to continuous cover forestry with Norway spruce, conversion to mixed conifer/broadleaved stands, no management) were investigated under current climate and two transient climate change scenarios in a simulation study. By comparing the results of two independent forest ecosystem models (PICUS v1.41, 4C) applied under identical forcings and boundary conditions we aimed at addressing uncertainties in model-based projections. A transition to continuous cover forestry increased C storage in all climate scenarios (+45.4 tC·ha^–1 to +74.0 tC·ha^–1 over the 100 year analysis period) compared to the approximately balanced C budget under the age class system. For the mixed conifer/broadleaved management variant predictions of the two models diverged significantly (+29.4 tC·ha^–1 and –10.6 tC·ha^–1 in PICUS and 4C respectively, current climate). With regard to climate change impacts both models agreed on distinct effects on productivity but lower sensitivity of C stocks due to compensation from respiration and adaptive harvest levels. In conclusion, considering the potential effects of silvicultural decisions on C stocks climate change mitigation should be addressed explicitly in programs advocating targeted change in management paradigms.

Seidl, Institute of Silviculture, BOKU, Vienna, Austria E-mail: rupert.seidl@boku.ac.at
Rammer, Institute of Silviculture, BOKU, Vienna, Austria E-mail: wr@nn.at
Lasch, Potsdam Institute for Climate Impact Research e.V., Potsdam, Germany E-mail: pl@nn.de
Badeck, Potsdam Institute for Climate Impact Research e.V., Potsdam, Germany E-mail: fwb@nn.de
Lexer, Institute of Silviculture, BOKU, Vienna, Austria E-mail: mjl@nn.at

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