European Journal of Forest Research最新文献

Stomata play a critical role in surface–atmosphere exchange by controlling the flux of water and CO₂ between the leaf and the atmosphere. However, the driving factors for the vital parameter, the marginal water cost of the carbon gain (λ), are poorly understood in the subalpine regions. Therefore, we studied λ in subalpine plants at all across altitudes. There was a parabolic pattern in λ of trees with increasing elevation, the highest at 2700 m asl and 3500 m asl for the broadleaf trees and the coniferous trees, respectively, while the λ of species of herbs and shrub decreased with elevation. For all species, λ were higher during the mid-growing season than during the early and late growing seasons under the same conditions. Mean λ values were higher in herbs and shrubs than in trees, indicating a more conservative strategy for water use in trees than in herbs and shrubs in forest communities. Furthermore, a higher λ value of the broadleaf tree than of the coniferous tree suggests that angiosperm trees use water more profligately than gymnosperm trees. Environmental factors had opposite effects on λ for herbs, shrubs, and trees. Soil conditions were positively correlated with λ for herbs and shrubs, but negatively for trees. Vegetation factors negatively influenced λ for herbs and shrubs, while no significant relationship was found with trees. From the results of the structural equation model, the improved empirical models for the simulation of stomatal conductance(g_s) simulation based on the optimal stomatal behavior theory can accurately estimate the g_s of the main species in subalpine forest communities.

Determining the structure and fuel load is key to know the flammability of vegetation in the Mediterranean Basin where forest fires are frequent. Determine which plant structural variable is best related to living and dead fuel to develop allometric equations in nine species in the Western Mediterranean Basin. In the east of the Iberian Peninsula (Valencia Province), we measured four structural variables (basal stem diameter, height, maximum diameter and perpendicular diameter) that were related, by means of allometric equations, to the living and dead fuel separated into different size classes. We also analyze fuel changes across developmental states of the studied species, and the vertical distribution of dead fuel. General equations that consider all development states can be used to determine living fuel. However to obtain dead fuel, we recommend using specific equations for each development state and fuel fraction for better accuracy. The basal stem diameter was the best structural variable in almost all cases for estimating fuel in the studied species. Dead fuel load throughout species’ ontological development is a key factor to manage Mediterranean plant communities.

Forest tree leaves play a significant role in air purification, but forest fires could offset the dust sink role. This study aims to assess the functions of the forest in atmospheric dust sink and source and assess the dust capturing capacity of individual leaves of various tree species in the tropical mixed deciduous forest in the dry season (November 21, 2021, to January 23, 2022), along with its influencing factors—climatic variables, environmental variables, and leaf morphology. The result shows that the downward flux or the forest dust sink role was predominant midday when air–mass turbulence played a role. Nonetheless, net mass PM₁ and PM₁₀ concentration trapped by the forest canopy was low, 0.79 and 2.24 µg m⁻³, respectively. For PM_2.5, forest fires could outrun the PM_2.5 sink role for the entire dry season. Considering the individual tree leave, maximum dust capturing capacities for the forest trees ranged from 0.95 to 5.197 g m⁻². Leaf dust capturing capacity was enhanced under cold and dry weather, strong winds, and for trees with defoliated or irregular shape. Leaf/leaflet enhancing the dust capturing capacity exhibited large size; either thick and leathery texture (Coriaceous) or thin, semi-translucent, membrane-like texture (Membranaceous); indumentum top being short, stiff trichomes (Scabrous); or indumentum bottom surface being densely short, soft trichomes (Tomentose). The various dust capturing dynamics among tree species could benefit dust capturing by the forests in the dry season.

To better guide Cedrus libani provenances movement to northerly and higher-altitude sites for afforestation, the limits of hardiness to cold should be better known. In this study, we quantified the cold hardiness of seven C. libani provenances sampled from a provenance trial in Ankara, Türkiye, a site located outside the natural range of distribution of the species. Visual damage observation and chlorophyll fluorometry screening methods were used to assess variation in cold hardiness (LT50, the temperature estimated at which 50% of the needle tissue is damaged) among populations. Overall, C. libani can tolerate winter temperatures down to − 21.5 °C. Even though there were significant differences in cold hardiness among populations, the maximum difference was only 1.9 °C between the most and the least cold-resistant provenances. Cold tolerance was generally greater for provenances that experienced colder temperatures in March and lower levels of total precipitation in their native ranges. We also conclude that the fluorometry method provides a more efficient and stable comparison of cold hardiness than visual observation for C. libani. The results of this study may be useful for assisted migration and breeding programs, as well as for developing guidelines for genetic materials transfer, to increase productivity or adaptability of C. libani.

The available amount of wood supply is essential for national strategic planning and evaluation of forestry in Sweden. Since Sweden holds a large part of the forests in the European Union and plays a significant role in the global trade of wood-based products, a precise estimate of the potential of the Swedish forest resource is also important in regional and global outlook studies. In this study, we analyse factors influencing the availability and mobilization of wood supply. By comparing data from the Swedish National Forest Inventory with the stand registers of the five largest forest owners in Sweden, we estimate the productive forest area not included in the forest owners' stand databases. Our results show that 0.4 million hectares, or 5% of these large-scale forest owners productive forest area, is outside their stand registers and therefore neither included in their long-term harvesting plans nor in their nature conservation plans. For small-scale forest owners, we analyse the final felling rate during 2004–2020 using satellite imagery to estimate the proportion of properties that abstain from final fellings and thereby could affect the potential mobilization of wood supply. During this period, 32% of the forest properties owned by small-scale forest owners have not done any final felling. These forest estates hold in total 1.1 million hectares of productive forest land or 9% of the area owned by small-scale forest owners. This implies a gap between the potential and realistic estimates for Forest Available for Wood Supply.

Quantitative structural models (QSMs) are frequently used to simplify single tree point clouds obtained by terrestrial laser scanning (TLS). QSMs use geometric primitives to derive topological and volumetric information about trees. Previous studies have shown a high agreement between TLS and QSM total volume estimates alongside field measured data for whole trees. Although already broadly applied, the uncertainties of the combination of TLS and QSM modelling are still largely unexplored. In our study, we investigated the effect of scanning distance on length and volume estimates of branches when deriving QSMs from TLS data. We scanned ten European beech (Fagus sylvatica L.) branches with an average length of 2.6 m. The branches were scanned from distances ranging from 5 to 45 m at step intervals of 5 m from three scan positions each. Twelve close-range scans were performed as a benchmark. For each distance and branch, QSMs were derived. We found that with increasing distance, the point cloud density and the cumulative length of the reconstructed branches decreased, whereas individual volumes increased. Dependent on the QSM hyperparameters, at a scanning distance of 45 m, cumulative branch length was on average underestimated by − 75%, while branch volume was overestimated by up to + 539%. We assume that the high deviations are related to point cloud quality. As the scanning distance increases, the size of the individual laser footprints and the distances between them increase, making it more difficult to fully capture small branches and to adjust suitable QSMs.

Abstract

Forest dynamics are undergoing profound alteration due to the fact that climate change is increasing the frequency and severity of abiotic and biotic forest disturbances. Because of the unpredictable nature of the drought periods and the variation in their severity, Mediterranean forests are typically more vulnerable. Mediterranean Pinus pinaster forests are showing decay symptoms linked to climate change. There is clear evidence that promoting mixtures can serve as an effective forest adaptation strategy. In this regard, we sought to better understand the responses of P. pinaster radial growth dynamics to various factors, in both mixed and pure forest stands, and provide valuable insights into P. pinaster dynamics when mixed with P. sylvestris. In this study, we examined the variation of intra-annual cumulative radial increment patterns in response to the climate of P. pinaster between pure and mixed stands with P. sylvestris. Using data from band dendrometers collected over five consecutive climatically distinct years (2016–2020), a nonlinear mixed-effect model approach was used to analyze the differences in intra-annual cumulative radial increment patterns for P. pinaster between years in mixed and pure stands. The intra-annual radial increment pattern of P. pinaster showed significant year-to-year variation and varied with tree size, with greater increment in larger trees. Trees in mixed stands had a higher mean radial increment compared to corresponding ones in pure stands. Increased summer maximum temperatures negatively affected tree cumulative annual increment regardless of composition, but with a lower impact on trees in pure stands. Spring precipitation increased the length of the growing season, while higher spring maximum temperatures triggered an earlier inflection point. Our results highlight the high plasticity of P. pinaster in adapting to varying intra- and inter-annual environmental conditions and competition with other species and suggest that promoting mixtures with P. sylvestris may be an interesting management strategy for adaptation to climate change.

In this study, wildfire susceptibility is mapped using various multi-criteria decision analysis techniques (AHP, SAW and VIKOR) and machine learning algorithms (MaxEnt and logistic regression) to reveal the response of models for wildfires. In this study, it is suggested that using natural weights generated by machine learning algorithms instead of artificial weights in MCDA methods can increase the reliability of susceptibility maps because wildfires have very close relationship with climatic, topographic and environmental variables. The contribution rates (natural weights) were obtained using machine learning algorithms and incorporated into MCDA methods to make the spatial relationships between variables more obvious. As a result, eight susceptibility maps were generated using MCDA methods, MaxEnt and logistic regression algorithms. Correlation analysis showed that using natural weights instead of artificial weights increased the correlation between MCDA methods and machine learning algorithms. Each correlation value increased by 10% on average and the highest increase was determined between VIKOR and logistic regression from 0.6286 to 0.7580 when natural weights were used. In addition, 1035 existing wildfire locations were used to evaluate the reliability of generated maps. The results showed that the average risk values of 1035 wildfire locations increased from 6.04 to 7.23 using AHP, from 0.66 to 0.79 using SAW and from 0.35 to 0.25 using the VIKOR method. This indicates a significant increase in the accuracy and reliability of susceptibility maps produced when natural weights determined by machine learning algorithms are used in MCDA methods.

Abstract

In continuous cover forestry, plenter silviculture is regarded as an elaborated system for optimizing the sustainable production of high-quality timber maintaining a constant but heterogeneous canopy. Its complexity necessitates high silvicultural expertise and a detailed assessment of forest stand structural variables. Terrestrial laser scanning (TLS) can offer reliable techniques for long-term tree mapping, volume calculation, and stand variables assessment in complex forest structures. We conducted surveys using both automated TLS and conventional manual methods (CMM) on two plots with contrasting silvicultural regimes within the Black Forest, Germany. Variations in automated tree detection and stand variables were greater between different TLS surveys than with CMM. TLS detected an average of 523 tree stems per hectare, while CMM counted 516. Approximately 9.6% of trees identified with TLS were commission errors, with 6.5% of CMM trees being omitted using TLS. Basal area per hectare was slightly higher in TLS (38.9 m³) than in CMM (38.2 m³). However, CMM recorded a greater standing volume (492.7 m³) than TLS (440.5 m³). The discrepancy in stand volume between methods was primarily due to TLS underestimating tree height, especially for taller trees. DBH bias was minor at 1 cm between methods. Repeated TLS inventories successfully matched an average of 424 tree positions per hectare. While TLS adequately characterizes complex plenter forest structures, we propose enhancing this methodology with personal laser scanning to optimize crown coverage and efficiency and direct volume measurements for increased accuracy of wood volume estimations. Additionally, utilizing 3D point cloud data-derived metrics, such as structural complexity indices, can further enhance plenter forest management.

Forest health is being challenged worldwide due to changing disturbance regimes. These changes could promote the abundance and diversity of secondary forest pests, like the Agrilinae (Coleoptera: Buprestidae) borers, which are frequently involved in oak decline in Europe. We assessed the contribution of environmental factors to local abundance and temporal dynamics of oak-dwelling borers in France. We set up green multi-funnel traps in oak stands exhibiting a gradient of decline across six forests in 2021 and monitored the traps for six consecutive years in one forest. The community of borers was homogeneous among the forests and included several Mediterranean species. Increasing severity of decline at the plot and stand scales enhanced the abundance and species richness of the borers and influenced the composition of their community. Tree density, longitude and spring temperature also influenced the abundance of several species and of the community. Our multi-year survey indicated that inter-annual fluctuations in decline level weakly correlated with those of borer species. Most of the species experienced a major crash in 2017, suggesting that extreme climate events such as a warm early spring followed by a late frost can decimate borer populations. This may explain why borer damage has recently been relatively limited in France.