Silva Fennica vol. 57 no. 3 | 2023

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

In forest inventories, field data are needed for the prediction of tree volumes. However, gathering field data requires resources, such as labour, equipment, and data management operations. This means that time and budget, as well as quality, must be carefully considered when National Forest Inventory (NFI) field measurement activities are planned. Therefore, the development of cost efficient, simple, safe and reliable measurement methods and tools are of great interest. To date, upper stem diameter (d6), which provides a more reliable estimation of tree stem volume, has typically been measured with a parabolic calliper. In this study, the performance of the Criterion laser-based dendrometer was examined for d6 measurements. A total of 326 sample trees were measured multiple times with three different measurement instruments. These instruments were used to measure diameter at breast height (dbh) as well as d6 measurements. Bland-Altman plots and measurement error variances were used to determine measurement instrument reliability. For all trees, the standard deviation for the laser based dendrometer was 18.73 mm at dbh and 15.36 mm for the d6 measurements. When the performance of Criterion was analysed with reference to the mean value of repeated measurements, the standard deviation in the dbh measurements was 12.21 mm, and 8.88 mm in the d6 measurements.

• Stenman, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland https://orcid.org/0000-0003-1176-7840 E-mail: virpi.stenman@helsinki.fi
• Kangas, Natural Resources Institute Finland (Luke), Bio­economy and Environment, P.O. Box 68, FI-80101 Joensuu, Finland https://orcid.org/0000-0002-8637-5668 E-mail: annika.kangas@luke.fi
• Holopainen, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: markus.holopainen@helsinki.fi

Adapting to site conditions is a central part of forest regeneration and can be done through selection of different planting positions. Requirements are tree species specific, and the use of soil moisture maps could be a way to support decision making in forest regeneration planning. At two experimental sites with varying soil moisture conditions in southern Sweden Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and silver birch (Betula pendula Roth) seedlings were planted in four different planting positions following mounding site preparation; Depression, Hinge, Mound and Unscarified. Soil moisture estimates were obtained from a high-resolution depth-to-water raster for each planting spot. The effect of soil moisture, planting position and their interactions on mortality, height and diameter was evaluated for each tree species. In wet conditions mounds proved to be the best option to minimize seedling mortality for conifers, but with decreasing soil moisture, differences between the planting positions decreased. Birch on the other hand had the greatest survival in the hinge. The coniferous species displayed increased height and diameter when planted in mounds independent of the soil moisture conditions, whereas silver birch was less dependent on a specific planting position. Results from this study shows that a soil moisture map can explain mortality, height and diameter and thus can be a useful tool when choosing planting position in different soil moisture conditions.

• Nordin, pcSKOG, Grisslevägen 15, 227 32 Lund, Sweden https://orcid.org/0000-0002-2156-6615 E-mail: per.nordin@skogforsk.se
• Olofsson, Linnaeus University, Department of Forestry and Wood Technology, 351 95 Växjö, Sweden https://orcid.org/0000-0001-5844-6775 E-mail: erika.olofsson@lnu.se
• Hjelm, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Box 190, 234 22 Lomma, Sweden https://orcid.org/0000-0002-6144-8250 E-mail: karin.hjelm@slu.se