Fires are major disturbances in boreal forests, and forest fire risk is projected to increase in Finland. Despite this, comprehensive large-scale analyses evaluating multiple potential drivers of fire ignition and size remain scarce. The aim of this study was to assess how selected environmental and human-related factors influence the relative ignition probability and fire size in Finnish boreal forests. We utilized data on forest fire occurrence and size, the Finnish Forest Fire Index (FFI), and ignition cause, compiled by rescue authorities across mainland Finland during 2014–2023. We supplemented it with spatial data describing environmental factors (site trafficability, slope, canopy cover, and dominant tree species) and human-related factors (human population density and distance to nearest road). The dataset contained 10 284 forest fire observations and an equal number of pseudo-absence observations. We fitted one generalized additive model (GAM) each to explain relative ignition probability and fire size. The relative ignition probability model explained 51.6% of the deviance and achieved a classification accuracy of 83.7%, while the fire size model explained 21.5% of the deviance. Human-related variables were among the most influential in both models, with human presence increasing relative ignition probability but reducing fire size. Seasonality and weather were also significant, suggesting a major influence of weather and vegetation dynamics on fuel moisture, whereas dominant tree species affected only fire size and slope only relative ignition probability. The contrasting effects of humans on forest fires suggest potential for reducing future fire risk through targeted fire management strategies.
Some locally rare tree species – like European aspen (Populus tremula L.) – contribute disproportionately to forest biodiversity, making their accurate monitoring important for conservation. However, most remote sensing studies of rare tree species ignore their low prevalence/base rate, necessary for model transferability. We aimed to assess European aspen classification under realistic landscape prevalence and find methods to improve classification performance. Across 253 plots from field data in Våler, Norway we detected and segmented 5455 living trees, including 55 European aspens (ca. 1% prevalence), from high-density airborne laser scanning (ALS) data merged with multispectral aerial imagery. Individual segments were then classified as European aspen or non-aspen using random forest and synthetic minority oversampling (SMOTE). We evaluated classification based on tree counts and summed tree volumes. To underpin the importance of prevalence consideration and compare our results, we also re-analysed published Fennoscandian European aspen classification studies. Contrary to a perfect balance, we found an optimal SMOTE-ratio at ca. 0.07 (European aspen–non-aspen ratio). Our count-based classification achieved 32% (16–52) false discovery rate (FDR) and 73% (60–83) false negative rate (FNR), whereas volume-based classification achieved 31% (11–51) FDR and 54% (38–71) FNR. Re-analysed studies averaged 66% FDR and 33% FNR at a 1% prevalence. Our results demonstrate that rare tree species classification benefits from optimising majority–minority ratios and, given the ecological value of larger trees, volume-based approaches are warranted. Finally, we urge reporting landscape prevalence and adjust classification metrics to reflect these to enable transferability to real-world applications in rare tree species classification.
Logging trails are a critical component of modern forest harvesting operations, particularly in thinning and partial cutting, where trail layout strongly influences harvesting efficiency, soil disturbance, future stand growth, and carbon balance. Despite their importance, existing regulations and commonly used metrics – such as mean trail spacing and trail density – primarily address quantitative properties of logging trail networks and do not capture the qualitative aspects of network design. In this study, we introduce a novel concept for assessing the spatial arrangement performance of logging trail networks based on two complementary spatial configuration metrics: a Coverage Coefficient, describing the proportion of forest area reachable by harvesting machinery, and a Structural Efficiency Coefficient, comparing the actual trail length to an idealized network layout. Together, these metrics provide a geometrically meaningful and operationally relevant evaluation of trail network spatial arrangement beyond conventional density-based measures. We also introduce a method for computing a geometrically meaningful mean spacing between adjacent trails. The methodology is demonstrated using ten thinning sites from Central Finland. The results reveal clear differences in the spatial pattern of trail layouts among sites that are not detectable using traditional metrics alone. The proposed approach offers a practical tool for evaluating spatial arrangement performance of logging trail networks after harvesting, supporting operator feedback, regulatory assessment, and the development of automated trail network design and planning procedures. More broadly, the metrics provide a foundation for improving harvesting efficiency, reducing unnecessary trail density, and supporting environmentally sustainable forest management.
Mechanical site preparation (MSP) is essential for successful forest regeneration. However, excessively exposed soil may harm the environment and increase the total costs of seedling stand management. A drill-based MSP device (drill), designed to reduce soil exposure, was recently tested in Finland. This study investigated the quality of drill-based MSP and the early performance of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) seedlings planted in different seasons on five mineral soil stands. The findings showed that the mean area of the drilling spots (0.18 m2) was about 20% of that reported for mounding. The drill mostly resulted in good (61%) or satisfactory (34%) planting spot quality (e.g., good spots were covered with mineral soil). Ground and soil obstacles, such as roots, stones, stumps, and logging residues, negatively affected planting spot quality. About 13% of the planting spots did not have a pure mineral soil cover, which is required to mitigate pine weevil (Hylobius abietis L.) damage. Most seedlings were still alive one year after planting, but the proportion of healthy seedlings was 71% for Norway spruce and 48% for Scots pine two years after planting. Overall, drill-based MSP may be most feasible for drier sites with less competitive ground vegetation. However, the productivity and costs, the performance of the planted seedlings, and other potential benefits of drill-based MSP should be further tested under varying operating conditions and compared with those of conventional MSP methods.
We assessed long-term outcomes of a regeneration experiment comparing clearcutting and shelterwood treatments, each with and without mechanical site preparation (MSP). The experiment was established in the early 1990s across Sweden and combined natural regeneration of Scots pine (Pinus sylvestris L.) with planting of Norway spruce (Picea abies (L.) H. Karst.; 2500 seedlings ha–1). The first assessment showed Norway spruce dominance on southern sites and potential for mixed stands in central and northern regions. In 2022–2023, sites were re-measured to assess stand structure and productivity at mid-rotation, and the measured data were then used to parameterize Heureka decision support system (DSS) for simulations to final harvest. Southern sites developed into Norway spruce-dominated stands, with higher volume in clearcut than shelterwood treatments. Central and northern sites developed into mixed species stands, with higher volumes in shelterwood treatments in central Sweden. In northern Sweden, retained shelterwood negatively affected understory growth, highlighting the importance of active management while using shelterwood. Despite these regional differences, land expectation value (LEV) was consistently higher for clearcut treatments. Even in central Sweden, higher volumes in shelterwood treatments did not compensate for the additional costs associated with shelterwood cuttings. Our results show that establishing mixed species stands through shelterwood and planting can be viable depending on site conditions, but likely results in lower revenue than clearcutting.
