European Journal of Forest Research最新文献

Taxus baccata L. is a highly valuable species with wide distribution but scattered and locally rare occurrence. Human intervention, including forest management practices and fragmentation, can significantly impact the species’ genetic diversity, structure, and dynamics. In this study, we investigated these factors within T. baccata populations in the Bavarian Forest National Park (NP) in Germany and their implications for conservation. We used 13 EST-SSRs to assess the genetic diversity and structure of the population. Our analysis revealed a scarcity of small-diameter trees, indicating limited natural regeneration over time. However, conservation efforts, like selectively removing competitor species and using protective fencing, have improved growth conditions and promoted seedling emergence. The NP’s natural zone has no active management, which is confined to the development and management zones. Genetic diversity assessments revealed high genetic diversity (H_e: 0.612 and 0.614 for seedlings and adults, respectively) compared to other studies in Taxus baccata, dispelling concerns of significant inbreeding and showcasing a stable genetic structure. However, significant spatial clustering of related individuals (family structures) in both cohorts and low effective population size in the progeny hints at restricted gene flow, necessitating conservation efforts prioritizing safeguarding and promoting natural regeneration in development and management zones. Limited natural regeneration and the recent decrease in effective population size in the NP populations indicate habitat fragmentation and human interventions. Effective population size estimates emphasize the need for diverse conservation strategies. Conservation efforts should prioritize protecting natural regeneration and enhancing gene flow by actively promoting European yew, e.g., by shelterwood cutting, to ensure the long-term viability of T. baccata in the region outside the NP.

Pine resin is a valuable non-wood forest product with an increasing interest in multiple industrial sectors. Resin-tapping activities also provide valuable ecosystem services in timber-oriented and highly productive pine forest of Atlantic regions, where little previous experience in resin-tapping is available. The objectives of this study were to determine the efficiency of different stimulant pastes and its variation with pine species, site conditions, seasonality and frequency of tapping interventions. We conducted parallel experiments using both conventional and micro-tapping techniques in mature pine stands in NW Spain. We tested four stimulants (control and Zeta, Cunningham and Salicylic pastes) and two groove frequencies (every 2 or 3 weeks). All stimulant pastes significantly increased resin yield compared to the control, being resin stimulation highly consistent across years, sites and species. In conventional resin tapping, resin yield was maximized with the Cunningham and Salicylic pastes while in micro-tapping Salicylic was the most outstanding stimulant treatment. According to the rapid decay of resin flow after wounding, total resin yield decreased with more spaced grooves. However, the reduction was low, and the global efficiency of the tapping operations are likely maximized with grooves applied every three weeks, which would allow increasing the number of tapped trees. Micro-tapping techniques were valuable for screening stimulant pastes and anticipating variation among sites in resin production. Altogether, the Salicylic paste is recommended, especially at the beginning of the resin campaign, when the effect of the pastes was maximized, and if tapping is conducted using closed atmospheres and containers.

In forest ecosystems, interception of rainwater on foliar and woody surfaces and the subsequent partitioning into stemflow is largely controlled by physical and hydrological properties of bark. Few forest ecohydrology studies have explored the role of bark properties (e.g., thickness, density) on bark water storage capacity and stemflow production. Even fewer have explored how different phases of water (e.g., liquid, vapor) may affect bark through bark swelling properties across the stem and how the degree of swelling affects tradeoffs between bark water storage and stemflow generation. Thus, the objective of this study was to analyze changes in a bark swelling index (BSI) vertically along stems of Picea abies (Norway spruce) after exposure to both water vapor and liquid water, as a function of tree age and bark moisture content. We found that tree age influenced BSI and bark moisture content, wherein BSI was ∼ 6.5% lower in older trees (70 years) compared to younger trees (35 and 50 years), and average moisture content was 10.4–13.2% lower. BSI increased when bark was exposed to hygroscopic water vapor and reached maximum swelling after 1 day of water saturation. BSI also increased from the base of the tree to 20–30% of total tree height, beyond which BSI remained relatively stable across all age classes. Enhanced understanding of bark swelling mechanisms as a result of stem position, age, and moisture content and exposure provide stronger foundations for understanding canopy hydrologic partitioning and the fate of rainwater moving through forest canopies.

Tree size is one of the major factors that determines harvester productivity and is heavily influenced by forest managerial activities. Stand silvicultural management can lead to managing tree size, the distribution of tree size, and tree height amongst others. Understanding the effect of tree size distribution on harvesting productivity is central for optimizing management of operations. To investigate the effects of tree size distribution on harvester productivity, productivity functions for a medium and larger-sized harvester were applied to harvester derived tree size distributions from 35 clearfelled pine stands. These functions were applied to a normal distribution of trees covering the same tree size ranges. Productivity differences were analysed on a stand-by-stand basis. Results showed that for the larger harvester, productivity rates remained constant (67.1 vs. 67.6 m³·PMH^− 1) indicating relatively little sensitivity to variations in tree size distributions. Although the standard deviation (SD) halved from 11.6 to 5.6 in the case of the uniform tree distribution. The smaller harvester productivity decreased by 15% from 47.3 to 40.1 m³·PMH^− 1 and the coefficient of variation (CV) by 6% in the same transition to a uniform distribution. Further investigation was done on more skewed tree size distributions, a family of nine Weibull distributions was generated, representing combinations of three mean DBH classes (25 cm, 30 cm, and 35 cm) and three levels of CV (15%, 20%, 25%), for each DBH class. Results clearly indicate that different distribution shapes have different effects on different machine sizes, and that a low CV correlates to a higher productivity in larger tree sizes. A more uniform tree size distribution also provides more predictable results (lower CV), which would promote machine scheduling and result in fewer discrepancies on production rates.

Understanding the genetic diversity and origin of plantations will support the genetic monitoring and provenance selection in restoration projects and help to enhance the adaptation and resilience of plantation forests under climate change. However, information on the origin and genetic variation for plantations with native tree species is inadequate. Taiwania cryptomerioides Hayata is a threatened tree species and has been used as an important tree species for plantation in montane areas of South China. Information on the genetic diversity and origin of the existing Taiwania plantations is needed to facilitate their further development. In this study, using 12 nuclear microsatellite markers, the genetic diversity and structure were investigated in seven previously assumed natural populations and 19 plantation populations of T. cryptomerioides in South China. The Taiwania plantations showed lower genetic diversity and closer genetic distance than natural populations, indicating that most plantations were established with a narrow genetic basis. The results revealed that the majority of Taiwania plantations originated from two areas of the species’ natural distribution: northwestern Yunnan and southeastern Guizhou. Interestingly, we found that part of plantations in western Yunnan might represent unique genetic resources. Finally, conservation strategies of germplasm resources and genetic guidelines for seed sourcing of T. cryptomerioides are recommended. This study could facilitate the sustainable development of Taiwania plantations and also serve as a valuable reference for plantation management in China and elsewhere. We suggest that genetic monitoring of plantation forests should be considered in future restoration programs.

Abstract

Herbivorous insect assemblages are functionally diverse, with each species exploiting plant tissues in different ways. Availability and palatability of plant tissues influence the diversity and composition of herbivorous insect assemblages. However, few studies have compared herbivorous insect assemblages and their ecological correlates across multiple plant species within the same plant community. Here, we sampled insect assemblages from the canopies of 1060 plants belonging to 36 woody species in two mixed Mediterranean forest stands. 401 insect species were classified as herbivores and grouped into sucker or chewer guilds. We explored differences in the diversity and composition of each insect guild across plant species, and tested their relationships with plant leaf traits, abundance or phylogeny, and explored whether the structures of plant-herbivorous insect networks depended on any of the studied plant traits. Plant identity accounted for the highest proportion of variation in the composition of each insect guild. Plant species abundance showed a positive effect on both insect guilds’ diversity. Suckers’ diversity was higher in plant species with deciduous leaves and low SLA, while the composition was more similar between phylogenetically closer plant species. Chewers diversity increased with the leaf area, while plants with similar LA, leaf nitrogen, SLA and distinct leaf habit showed more similar assemblages. Similarly, closely related angiosperms showed similar chewer assemblages. Plant–insect interaction networks present a modular structure, in which plants belonging to the same module tend to be related and share more sucker species. We add to the evidence supporting the role of plant species features as filters for structuring their associated herbivore insect assemblages.

Recently, the connection between multispecies tree planting and the production of high-quality wood has received much attention. The branch diameter ((BOD)) is a crucial factor that influences tree growth and wood quality. Research on (BOD) in mixed plantations has lagged behind that on monocultures, where the effects of trees, stands, and competitive forces on the (BOD) have been extensively studied. In this paper, 105 Manshurian ash (Fraxinus mandshurica Rupr.) and 105 Changbai larch (Larix olgensis Henry) trees from different row-wise mingling patterns on plantations in northeastern China were destructively sampled to construct two-level mixed-effects (BOD) models. We examined how tree vigor and species mixture affect (BOD) at various positions within the crown. The results showed that in addition to tree vigor, competition and stand structure had impacts on mixed plantation (BOD). Furthermore, in mixed plantations, the (BOD) of Changbai larch was affected by intraspecific and interspecific competition, while that of Manshurian ash was affected only by intraspecific competition. The (BOD) in the upper crown was strongly influenced by the position of the branches, while the (BOD) in the lower crown was strongly influenced by tree vigor, competition, and stand structure. The introduction of a two-level mixed-effects model significantly improved the prediction accuracy of (BOD), for which the ({R}^{2}) values were 0.85 and 0.88 for Manshurian ash and Changbai larch, respectively. The size of branches is an important factor affecting wood properties and prices, and it is a variable that is important to control. The quantitative simulation of (BOD) provides a theoretical basis that can inform silvicultural and management plans and that can determine the appropriate proportion of species based on actual timber quality requirements and stand development needs.

Social relationships influence physical health, yet questions remain regarding the nature of this association. For instance, when it comes to predicting health-relevant processes in daily life, few studies have examined (a) the relative importance of both positive and negative relational experiences, and (b) variability in relational experiences (in addition to mean levels). To address these gaps, we conducted a daily study (N = 4,005; ~ 30,000 observations) examining relationships, stress, and physiology in daily life. Heart rate and blood pressure were assessed using an optic sensor and integrated with an app-based study. Results demonstrated that higher mean levels of positive and lower mean levels of negative relational experiences predicted lower stress, better coping, and better physiological functioning in daily life, such as lower systolic blood pressure reactivity. Greater variability in negative (but not positive) relational experiences predicted lower stress, better coping, and lower systolic blood pressure reactivity.

This article introduces a new basis for optimising cable corridor layouts in timber extraction on steep terrain by using a digital twin of a forest. Traditional approaches for generating cable corridor layouts rely on less accurate contour maps, which can lead to layouts which rely on infeasible supports, undermining confidence in the generated layouts. We present a detailed simulational approach which uses high-resolution tree maps and digital terrain models to compute realistic representations of all possible cable corridors in a given terrain. We applied established methods in forestry to compute feasible cable corridors in a designated area, including rope deflection, determining sufficient tree anchors and placing intermediate supports where necessary. The proposed individual cable corridor trajectories form the foundation for an optimised overall layout that enables a reduction of installation and operation costs and promotes sustainable timber extraction practices on steep terrain. As a next step we aim to mathematically optimise the layout of feasible cable corridors based on multiple criteria (cost, ergonomic aspects, ecological aspects), and integrate the results into an user-friendly workflow.

Precise assessment of bark stripping damage is of high economic importance, since bark stripping makes wood unusable for saw timber and it is important for compensation payments for game damage. Bark stripping is clustered and decreases with increasing tree diameter, so that common forest inventories, optimized for assessing timber production variables such as standing timber volume, do not provide adequately precise estimates of bark stripping damage. In this study we analysed different sampling designs (random sampling, systematic sampling), tree selection methods (fixed radius plot, angle count sampling) and number of plots and plot sizes (plot radius: 2–20 m; basal area factor: 1–6m²/ha) for bark stripping assessment. The analysis is based on simulation studies in 9 fully censused stands (9026 trees). Simulations were done for actually assessed damage and randomly distributed damage and each scenario was repeated 100 times with different random points or different random grid locations. Systematic sampling was considerably more precise than random sampling in both scenarios. Sampling intensities to attain a standard error of 10% ranged between 12 and 18% dependent on the plot size. For a given sampling intensity, precision increased with decreasing plot size or increasing basal area factor. This implies, however, a large number of plots to be measured, which is expensive, when travel costs are high. Differences between tree selection by fixed radius plots or angle count sampling were minor. For bark stripping damage, we recommend sampling with fixed radius plots with a radius of 4–6 m and the measurement of approximately 230 or 150 plots, respectively.