Mixed Stands Research Articles

Wood decay and Norway spruce vulnerability to wind-inflicted mortality in monospecific and mixed stands in hemiboreal forests

Pathogen-caused stem and root decay are becoming increasingly common in Norway spruce (Picea abies (L.) H. Karst) which is believed to contribute to greater stand instability and susceptibility to wind-inflicted damage. Thus, this study aims to assess the effect of root and stem decay on Norway spruce vulnerability to wind-inflicted mortality in monospecific and mixed stands, to widen our base of knowledge on potentially more resilient spruce forest management approaches in hemiboreal forest zone. In this study we used data from: i) the National Forest inventory (NFI), ii) 34 observation plots established in wind-affected stands, iii) two transects (9200 m long, 36.8 ha inspection area combined), iv) and monospecific spruce plantation thinning experiment (five thinning intensities with two repetitions of each) affected by wind. We found that the total mortality of spruce during the NFI four five-year re-measurement cycles (2003–2007, 2008–2012, 2013–2017, 2018–2022) was 2.28 %, during which the main disturbance-causing agents were wind at 0.86 %, pests at 0.41 %, intra/interspecific competition at 0.37 %, and diseases at 0.36 %. NFI data-based multinomial logistic regression model revealed that the probability of wind-inflicted spruce mortality is dictated by soil moisture regime, stand age, stand stocking level, and tree decay presence. Results from the 34 established observation plots show that wood decay is a potential risk factor associated with wind damage occurrence in spruce stands. In a spruce stand, when a group of trees are damaged by wind the proportion of undecayed trees increases. Whereas a single tree is more likely to be attributed to decay caused wind damage.Results point towards deciduous broadleaf admixture having a positive effect on mitigating wind damage among non-decayed spruce trees: however, decayed trees, are more likely to be affected in such stands. The thinning experiment portion of this study suggests that increasingly intensive thinning in monospecific spruce stands will lead to an increasing spread of root and stem decay and thus the risk of wind damage. Therefore, from this perspective, the main goal is to reduce the root and stem decay presence in the stand and thus increase wind stability. We suggest further research to be directed into finding the optimal initial spruce seedlings density with a combination of coniferous and deciduous broadleaf species in order to mitigate root and stem decay presence and wind-inflicted spruce mortality in the forest stands.

Estimation of botanical composition of forage crops using laboratory-based hyperspectral imaging and near-infrared spectrometer measurements

Harvested forage is the main raw feed for ruminant animals in Sweden, and is commonly cultivated in mixed stands of legume and grass species. The fraction of legume on a dry matter basis, known as botanical composition (BC) is a very important indicator of forage quality. In this study, hyperspectral imaging and near-infrared spectrometer (NIRS) based methods were used to estimate BC, to overcome the shortcomings of hand separation, which is time and resource consuming. Timothy and red clover mix samples were collected from different harvests in 2017–2019 from multiple sites in Northern Sweden and hand separated. The samples were synthetically mixed to 11 different BC levels, i.e., 0–100 % clover content. Two different instruments (Specim shortwave infrared (SWIR) hyperspectral imaging system and Foss 6500 spectrometer) were used to collect spectral data of samples milled to two levels of coarseness. Three different regression analyses: partial least squares regression (PLSR), support vector regression (SVR) and random forest regression (RFR), were used to build BC estimation models. The effects of the milling particle sizes and the different instruments on the performances of the models were compared. The data from second harvest in 2019 were used for independent validation as evaluation, and the rest of data were randomly split for model calibration (75 %) and validation (25 %). The models were iteratively run 1000 times with different splits, to check the effect from the splitting of calibration and validation datasets. Among different regression analyses, PLSR performed best, with mean Nash-Sutcliffe efficiency (NSE) for model evaluation from 0.76 to 0.87, varying for different instruments and milling sizes. Finer milling made the model accuracies slightly higher. This study developed quick and robust methods to determine the BC of timothy grass and red clover mixtures, which can provide useful information for farmers or researchers.

Thinning strategies impact the productivity, perpetuity and profitability of mixed stands

ABSTRACT In southern Sweden, there is possibility for growing spruce-birch mixed stands. However, the required knowledge to manage these stands effectively, i.e. optimal thinning strategies, is limited. Thus, we utilized data from young mixed-forest experiments in southern Sweden to simulate different thinning strategies. Moreover, we compared results from the mixed stands to spruce and birch monocultures. The regeneration was characterized by soil scarification, natural regeneration of birch and high-density planting of Norway spruce seedlings. Pre-commercial thinning (PCT) was carried out to create spruce-dominated mixed stands, birch-dominated mixed stands, and spruce and birch monocultures. The first commercial thinning strategy in the mixed stands was to retain the initial mixture proportions until final felling, while the other was thinning from below, which prioritized removal of the smallest trees of either species. At the end of the rotation, similar growth (9.6–10.2 m3 ha−1 yr−1) and better economy (ca. 13–28% more) was observed in spruce-dominated mixed stands compared to spruce monoculture. It was possible with the appropriate thinning strategy to maintain birch proportion in the mixed stand when the initial stand at PCT is birch-dominated. However, tradeoff exists between retaining a high birch basal area, sustaining productivity and obtaining a good economy.

Unraveling the influence of afforestation with Liriodendron tulipifera on soil microbial diversity in Korea

Over the past three decades, yellow poplar (Liriodendron tulipifera) has been widely employed in reforestation efforts across the country. This study delves into the potential influence of yellow poplar afforestation on the indigenous soil microbial demography within the original native stand. By scrutinizing microbial populations, a comprehensive understanding is sought. Utilizing pyrosequencing, a total of 92,300 sequencing reads were acquired from soil samples collected at seven distinct sites, each with two replicates. The comprehensive analysis unveiled the presence of 15 phyla, 158 families, 307 genera, and 439 distinct species. Notably, proteobacteria dominated at the phylum level, constituting 50% of the microbial presence, succeeded by acidobacteria (18%) and verrucomicrobia (10.7%). Remarkably, no significant disparities were observed in the microbial community composition across the yellow poplar, mixed, and pitch pine stands, spanning the phylum, family, and genus levels. Particularly noteworthy was the challenge of distinguishing between the microbial compositions of the mixed tree stand and the yellow poplar stand. Remarkably high-rank correlation coefficients underscored the striking similarity in microbe abundance between these two stands, indicating minimal variation in their microbial composition. The beta diversity index revealed parity between the microbial communities of the yellow poplar and mixed tree stands. However, a discernable contrast emerged in the soil microorganism composition of the pitch pine stand.

Investigating hydrological recovery in regenerating coniferous stands in snow‐dominated watersheds using simultaneous localization and mapping‐enabled mobile terrestrial LiDAR

AbstractThe return of snow accumulation and ablation processes in regenerating forests to pre‐disturbance conditions, collectively referred to as hydrological recovery, has been investigated in past decades through manual snow surveys in adjacent open, juvenile, and mature stands. The outcomes of such studies provide a general understanding of hydrological recovery but lack transferability to areas where stand structure and terrain conditions differ from the reference sites. The application of mobile terrestrial LiDAR to investigate peak snow water equivalent (SWE) and ablation rates beneath regenerating trees in a space‐for‐time substitution study design provides new insights on the process of hydrological recovery in snowmelt forests of British Columbia, Canada. Outcomes of this study better quantify the influence of tree growth on peak SWE and ablation rate at both the tree and stand level for north aspect mixed conifer stands. Recovery of these two processes differ with recovery of Peak SWE beginning when the trees in a stand reach 3 m in height and recovery of ablation rates beginning once trees reach 5 m in height. Additionally, the process of negative ablation recovery in early juvenile stands reported in previous studies is herein clearly observed, providing an improved understanding of forest canopy effects on hydrological recovery in juvenile stands. The methods used in this study, which are internationally applicable, increase transferability of outcomes to stands where canopy characteristics (i.e., height, crown cover, and heterogeneity) are not represented in reference sites.

Assessing the impact of Hurricane Ivan on aboveground forest carbon dynamics in the Florida Panhandle: A case study from Perdido Bay watershed

Hurricanes can physically transform forest ecosystems, leading to immediate and potentially long-lasting impacts on carbon dynamics. Using Forest Inventory Analysis (FIA) data from the United States Forest Service, we compared the average carbon in trees (saplings, bole, stump, tops) and foliage pre- (2001–2003) and post- (2005–2007) Hurricane Ivan for different tree categories in the Perdido Bay Watershed located in the Florida Panhandle. The log-linear regression model indicates that variables stand type (softwood/mixed/hardwood), diameter, height, physiographic class (deep sands/flatwoods/rolling uplands/small drains/swamps/bottomlands), elevation, field age and plot affected status were statistically significant (p ≤ 0.05) determinants of carbon loss from the forest stands. Results showed that plots with medium-diameter stands lost more aboveground carbon than large and small-diameter stands, similarly, softwood-dominated stands lost more aboveground carbon than hardwood and mixed wood stands. Aboveground carbon decreased in stands with large (≥ 0.15 m) and medium (≥ 0.12 m) diameter-at-breast height (DBH) by 22.74 and 30.22 metric tons/ha, respectively. We ascertained a decrease of 74.51 and 17.82 metric tons/ha of aboveground carbon in hardwood and mixed plots after Hurricane Ivan, respectively. Aboveground carbon in young (< 25 y) taller trees (> 15 m) decreased by 121.55 metric tons/ha of carbon immediately after the hurricane. These findings underscore the critical necessity of comprehending the interplay between forest structure and hurricane activity to forecast the repercussions of such disturbances on carbon stocks. Our provided framework serves as a valuable tool for researchers and policymakers to assess the vulnerability of coastal forests and facilitate strategic planning to protect forests as carbon sinks.

Tree species identity drives soil carbon and nitrogen stocks in nutrient-poor sites

The establishment of mixed forest stands is an option to enhance soil organic carbon stocks and to protect forest ecosystems from various impacts of climate change. Increasing temperatures and drought potentially affect the vitality of the native coniferous Norway spruce (Picea abies), often used in mixed forests. We investigated the effects of a replacement of Norway spruce by Douglas fir (Pseudotsuga menziesii) admixed to European beech (Fagus sylvatica) on carbon (C) and nitrogen (N) concentrations and stocks, as well as the vertical distribution and changes in forest floor and mineral soil (down to 30 cm depth). Two regions with different soil conditions (loamy vs sandy soils textures) were selected, considering four sites in each region. Each site included a quintet of neighboring forest stands (>85 yrs) of European beech, Douglas fir, and Norway spruce stands as well as mixtures of beech with either Douglas fir or spruce. Our results showed that the C stocks of the organic layer were significantly influenced by tree species, while the C stock of the mineral soil varied among soil types. Total soil organic C stocks demonstrated notable species-specific characteristics, primarily driven by the elevated C stocks in the organic layer. In sandy soils, conifers and mixed forests store 10 % more C and N in the organic layer compared to loamy soils, whereas the C and N stocks under beech remained unaffected, regardless of the site condition. The interaction between species and sites was significant only for Douglas fir and mixed Douglas fir/beech, indicating that the impact of species on C and N varied across sites and was notably pronounced in sandy soils. The higher potential for carbon and N storage in mixed-species forests compared to pure stands emphasizes the capacity of mixed forests to provide valuable ecosystem services, enhancing C sequestration in sandy soils.

Functional traits in soil-living oribatid mites unveil trophic reorganization in belowground communities by introduced tree species

Biodiversity loss and its potential threat on ecosystem functions call for a critical evaluation of human impacts on forest ecosystems. Management practices based on stand diversification offer a possible solution to biodiversity loss due to monoculture plantations, and these practices often involve planting introduced tree species. Although introduced non-native tree species may provide high economic returns, they may also form novel ecosystems and threaten local biodiversity, but this has been little studied. Here, we combined a taxonomic and trait-based approach and investigated communities of oribatid mites (Oribatida, Acari) across forest types of both native and introduced tree species in Northern Germany. Both trophic and life-history traits of oribatid mites were evaluated using native European beech (Fagus sylvatica) as reference, compared to native Norway spruce (Picea abies), introduced Douglas fir (Pseudotsuga menziesii) and beech-conifer mixtures. The abundance and diversity of oribatid mites were generally similar among monocultures of European beech, Norway spruce and Douglas fir. By contrast, species and trait compositions of oribatid mite communities were shifted to include more primary decomposers and more surface-living oribatid mites in Douglas fir, resulting in a trophic reorganization with less predators than in European beech forests. These results suggest that oribatid mites maintain a similar level of trait diversity regardless of forest type, but the changes in trophic guild composition and vertical distribution indicate greater availability of litter-based resources in Douglas fir than in European beech forests. The similar abundance and diversity of oribatid mite communities in Douglas fir mixed stands as in native European beech forests points to mixed forests as a promising management option for future forestry. Overall, our trait-based analyses provided insights into the changes of soil biota composition, revealing the impact of introduced tree species on the structure and functions of soil animal communities.

Mixed forests provide higher levels of growth and yield than monocultures across a broad range of conditions

Compared with single-species forests, mixed forests tend to provide more forest ecosystem functions and services. However, there is a lack of detailed understanding of the basic mechanisms of the impact of species diversity on tree growth and forest productivity. The main drivers of this relationship are also still under discussion. Here, we synthesized information from 93 studies to quantify the increase in tree size, crown size and stand productivity in mixed stands, and conducted a meta-analysis on the response of tree growth and forest productivity to species mixing. Tree size, crown size and stand productivity increased by 7.4 % (2.4–12.5 %), 12.6 % (5.6–20.1 %), and 33.0 % (18.7–49.0 %), respectively, in mixed stands compared with single-species stands. Our results show that when all observations are included, the mean effect sizes of tree size, crown size, and stand productivity were greater than when only the equal stand density observations were included. Stand age and stand density were the most important moderators affecting tree size in mixed forests. Stand age, shade tolerance and soil acidity were the most important moderators influencing the effect sizes of crown size, and shade tolerance was the most important moderator influencing the effect sizes of stand productivity. We found that these positive mixing effects were also modulated by tree functional traits, stand characteristics, and climatic conditions. For different growth variables, the moderators that affect their growth in the mixed forests were different. Therefore, in the afforestation practices for differing management objectives, foresters should give priority to the factors that have the most important impact on them to achieve their goals. Our results have implications for linking biodiversity-ecosystem functioning relationships and forest management practices and may aid the development of more appropriate afforestation strategies.

High resolution remote sensing for biodiversity assessment and monitoring: A case study of dominant tree species in an old-growth forest

Biodiversity assessment and monitoring in old-growth forests (OGFs) is crucial for their effective management and conservation amongst various natural and human-induced challenges. In the present study, the spatial and temporal species diversity were assessed in the mixed stands of Białowieża Forest (BF), a renowned UNESCO world heritage site recognized as an OGF. The BF has encountered challenges due to pest outbreaks peaking in 2016–2017 with adverse impacts on species composition. Utilizing airborne laser scanning (ALS) and color infrared (CIR) datasets from 2015 and 2019 (prior and following the peak, respectively), 30 variables were extracted and employed as input for the Random Forest algorithm to identify 14 species of broadleaved and coniferous individuals at plot levels (458 plots) within the BF. We calculated biodiversity indices (including α, β, and γ diversity), Importance Value Index (IVI), bivariate scale-dependent density of species, and temporal β diversity indices independently for data acquired from both field observation (FO) and species maps obtained through remote sensing analysis (RSA). The study found no significant differences in α diversity indices between the FO and RSA across the BF, however, notable discrepancies existed in species richness. Limited species detection was attributed to low species frequency and therefore, insufficient reference individuals. Average β and γ diversities from both datasets showed no significant differences. The RSA accurately identified top species and their changes in terms of IVI. Additionally, the RSA explored scale-dependent density changes of broadleaved individuals around conifers. Consistency was observed between FO and RSA in identifying dominance shifts from losses to gains within the BF communities. The comparison of diversity indices obtained from FO and RSA suggests that the RSA provided comparable results to FO in capturing the diversity of dominant tree species within the BF, providing a promising approach for advancing our understanding of forest biodiversity in OGFs.

Age changes of birch stands on the permanent sample plots of the Kologrivsky Forest Nature Reserve

The actual patterns of forest stand dynamics can be revealed only if observational data on permanent sample plots are available. The aim of the study is to identify the characteristics of the age changes of stand indicators in permanent birch sampleplots of the Kologrivsky Forest Nature Reserve (Kostroma Region). The object of the study was forest stands in birch stands located in the core of the Kologrivsky Forest Nature Reserve. At present they are represented by mature and over-mature birch stands with the predominance of spruce undergrowth in narrow clearings of 1928 with a width of 100‑150 m. In the permanent sample plots trees were counted according to individual forest elements with the distribution of 4 cm in thickness steps. For 20‑25 trees, heights were measured in the range of varying diameters with further graphical alignment of the values. The stock was calculated using stem volume tables, and the biomass of the stand fractions was calculated using allometric equations. An analysis of the age changes of stand indicators (average height and diameter, number of trees, basal area, stock, biomass fractions, carbon content in biomass) for the period from 1981‑1983 to 2018‑2022 was carried out. In the sample plots considered, the dominant forest element in each age interval is birch. At present, however, the forest stands are approaching the stage of initial decay. Instead of pure birch stands, mixed spruce-linden stands will develop in the future. Comparing the changes of the stand indicators on the plots with a model of the growth of birch stands in the sorrel spruce forest type, it was found that the changes of the average heights of the actual stands are synchronous with the curve obtained from the model, while for other indicators there are significant discrepancies.

Total Carbon Storage in Uneven-Aged Pure Beech Stands in the Western Part of the Balkans

Forest ecosystems represent one of the largest and most important ecosystems on Earth, containing close to 80% of the biomass of our planet. As such, they play a significant role in the global carbon cycle because through photosynthesis, forests absorb more carbon than they emit and thus accumulate it. The most important species in deciduous forests in Europe, European beech (Fagus sylvatica L.), is of exceptional importance from the aspect of carbon storage. Considering that the state of carbon in pure beech forests is poorly investigated in the western part of the Balkans, the need for total carbon research was imposed to complete the picture of its stocks and factors that impact it. Research on total carbon (TC) storage in uneven-aged pure beech stands in the western part of the Balkans was carried out in three regions located approximately at the same latitude, but different longitude, imposing different macro-habitat characteristics. This research aimed to determine the TC stock and to examine the effects of orographic factors, stand canopy, and macroclimate on its values. TC stock in forest biomass was determined using appropriate regression equations and formulas, while soil organic carbon stock was determined using ICP forests methodology. Effects of different factors on carbon stock were examined using ANOVA (Type II Sums of Squares), General Linear Hypothesis Test (GLHT), and regression analyses. It was found that the largest TC stock is located in the region of Eastern Serbia (SRB) where its macroclimate is classified as suitable for hornbeam and sessile oak or mixed beech-oak stands. It was found that anthropogenic activity plays a significant role in the size of the carbon stock stored in above-ground biomass via alteration of forest canopy. The results also indicate that Aboveground Carbon (AGC) stocks are approximately proportional to Belowground Carbon (BGC; C in belowground biomass + soil C) stocks. What makes the difference is the structure of BGC, as the share of Soil Organic Carbon (SOC) is higher in the regions of Eastern Republic of Srpska (ERS) and Western Republic of Srpska (WRS), which are climatically classified as highly suitable for beech. Further analysis has shown that the amount of SOC decreases with increasing aridity levels. Given the results, management goals should be aimed at increasing the stock of biomass for the sake of carbon sequestration and for reducing the adverse effects of climate change, as a large amount of carbon can be stored in the above-ground and belowground biomass.

Stand diversity increases pine resistance and resilience to compound disturbance

BackgroundDrought, fire, and insects are increasing mortality of pine species throughout the northern temperate zone as climate change progresses. Tree survival may be enhanced by forest diversity, with growth rates often higher in mixed stands, but whether tree defenses are likewise aided remains in question. We tested how forest diversity-productivity patterns relate to growth and defense over three centuries of climate change, competition, wildfire, and bark beetle attack. We used detailed census data from a fully mapped 25.6-ha forest dynamics plot in California, USA to conduct a spatially explicit, dendroecological assessment of large-diameter Pinus lambertiana survival following fire reintroduction. Our structural equation models investigated direct and indirect pathways by which growth, defense, and forest composition together mediated pine resistance and resilience.ResultsIn the historical era of frequent, mixed-severity fire (pre-1900), trees that were ultimately resistant or susceptible to the post-fire bark beetle epidemic all showed similar growth and defenses, as measured by axial resin duct traits. During the era of fire exclusion (1901–2012), however, susceptible trees had slower growth. Following fire re-entry in 2013, both growth and defense declined precipitously for susceptible trees, resulting in fatal bark beetle attack. Spatial analysis showed that monodominant crowding by shade-tolerant competitors contributed to the long-term stress that prevented susceptible trees from recuperating defenses quickly following fire re-entry. For beetle-resistant trees, however, we found positive feedbacks between diversity, growth, and survival: trees in species-rich communities had higher growth rates pre-fire, which promoted a rapid recuperation of defenses following fire that helped trees resist bark beetle attack. Overall, this associational resistance outweighed associational susceptibility (+8.6% vs. −6.4% change in individual tree survival odds), suggesting a relaxation effect that ultimately allowed 58% of large pines to survive.ConclusionsThough climate change threatens forest biodiversity, biodiversity is key to forest climate adaptation in return. Our findings demonstrate centennial-scale feedbacks by which forest diversity increases pine resistance and resilience to climate-amplified disturbances. The spatially explicit, dendroecological framework provides new insights into diversity-productivity theory, while also informing climate-adaptive forest management by identifying thresholds of tree density and richness that maximize large pine survival.

Can mixing Quercus robur and Quercus petraea with Pinus sylvestris compensate for productivity losses due to climate change?

The climate change scenarios RCP 4.5 and RCP 8.5, with a representative concentration pathway for stabilization of radiative forcing of 4.5 W m−2 and 8.5 W m−2 by 2100, respectively, predict an increase in temperature of 1–4.5° Celsius for Europe and a simultaneous shift in precipitation patterns leading to increased drought frequency and severity. The negative consequences of such changes on tree growth on dry sites or at the dry end of a tree species distribution are well-known, but rarely quantified across large gradients. In this study, the growth of Quercus robur and Quercus petraea (Q. spp.) and Pinus sylvestris in pure and mixed stands was predicted for a historical scenario and the two climate change scenarios RCP 4.5 and RCP 8.5 using the individual tree growth model PrognAus. Predictions were made along an ecological gradient ranging from current mean annual temperatures of 5.5–11.4 °C and with mean annual precipitation sums of 586–929 mm. Initial data for the simulation consisted of 23 triplets established in pure and mixed stands of Q. spp. and P. sylvestris. After doing the simulations until 2100, we fitted a linear mixed model using the predicted volume in the year 2100 as response variable to describe the general trends in the simulation results. Productivity decreased for both Q. spp. and P. sylvestris with increasing temperature, and more so, for the warmer sites of the gradient. P. sylvestris is the more productive tree species in the current climate scenario, but the competitive advantage shifts to Q. spp., which is capable to endure very high negative water potentials, for the more severe climate change scenario. The Q. spp.-P. sylvestris mixture presents an intermediate resilience to increased scenario severity. Enrichment of P. sylvestris stands by creating mixtures with Q. spp., but not the opposite, might be a right silvicultural adaptive strategy, especially at lower latitudes. Tree species mixing can only partly compensate productivity losses due to climate change. This may, however, be possible in combination with other silvicultural adaptation strategies, such as thinning and uneven-aged management.

Modelling Diameter at Breast Height Distribution for Eight Commercial Species in Natural-Origin Mixed Forests of Ontario, Canada

Diameter at breast height (DBH) is a unique attribute used to characterize forest growth and development for forest management planning and to understand forest ecology. Forest managers require an array of DBHs of forest stands, which can be reconstructed using selected probability distribution functions (PDFs). However, there is a lack of practices that fit PDFs of sub-dominating species grown in natural mixed forests. This study aimed to fit PDFs and develop predictive models for PDF parameters, so that the predicted distribution would represent dynamic forest structures and compositions in mixed forest stands. We fitted three of the simplest forms of PDFs, log-normal, gamma, and Weibull, for the DBH of eight tree species, namely balsam fir (Abies balsamea [L.] Mill.), eastern white pine (Pinus strobus L.), paper birch (Betula papyrifera Marshall), red maple (Acer rubrum L.), red pine (Pinus resinosa Aiton), trembling aspen (Populus tremuloides Michx), and white spruce (Picea glauca [Moench] Voss), all grown in natural-origin mixed forests in Ontario province, Canada. We estimated the parameters of the PDFs as a function of DBH mean and standard deviation for these species. Our results showed that log-normal fit the best among the three PDFs. We demonstrated that the predictive model could estimate the recovered parameters unbiasedly for all species, which can be used to reconstruct the DBH distributions of these tree species. In addition to prediction, the cross-validated R2 for the DBH mean ranged between 0.76 for red maple and 0.92 for red pine. However, the R2 for the regression of the standard deviation ranged between 0.00 for red pine and 0.69 for sugar maple, although it produced unbiased predictions and a small mean absolute bias. As these mean and standard deviations are regressed with dynamic covariates (such as stem density and stand basal area), in addition to climate and static geographic variables, the predicted DBH distribution can reflect change over time in response to management or any type of disturbance in the regime of the given geography. The predictive model-based DBH distributions can be applied to the design of appropriate silviculture systems for forest management planning.

Sessile oak (Quercus petraea [Matt.] Liebl.) and its adaptation strategies in the context of global climate change: a review

Abstract This paper provides characteristic and a comprehensive overview of the adaptation strategies of sessile oak (Quercus petraea [Matt.] Liebl.) in the context of global climate change (GCC). The GCC is primarily manifested by increasing air temperatures and changing precipitation distribution. It poses a significant challenge to tree species including sessile oak, affecting its capacity for adaptation and survival. Despite the challenge, sessile oak shows significant drought tolerance due to its deep-reaching root system, which allows the tree to use available water more efficiently. Other adaptive strategies include the establishment of mixed stands that increase the resilience and biodiversity of the ecosystem. Adjustments of stand density through tending interventions play a significant role, helping to improve the stress resistance of stands. Additionally, coppice forest cultivation is applied on extremely dry sites. The sessile oak is also significant for its ecological plasticity – its ability to thrive on versatile soil and climatic conditions makes it a promising tree species for future forest management. Mixed stands with sessile oak and other tree species can enhance the ecosystem services of forests and also increase their endurance to GCC events. However, sessile oak faces several challenges, including the increasing risk of damage from pests and pathogens that require targeted measures for its protection and sustainable cultivation. The literature review suggests that a comprehensive understanding of sessile oak’s ecological requirements and interactions with the environment is crucial for its successful adaptation to GCC and the formulation of effective strategies for its protection and use in forest management.

European beech (Fagus sylvatica L.): A promising candidate for future forest ecosystems in Central Europe amid climate change

Abstract On the one hand, the European beech (Fagus sylvatica L.) is the tree of the future due to ongoing climate changes, on the other hand, there are questions about its expansion and economic use as a replacement for the declining Norway spruce (Picea abies [L.] Karst.). This literature review examines 140 studies summarizing basic research on beech in the context of climate change. As a climax tree species, beech is becoming dominant again in parts of its original range at the middle and higher altitudes of Central Europe, following spruce. It is a shade-loving species that can thrive in various types of mixed forest stands. To cultivate beech, close-to-nature methods, shelterwood, or selection management are optimal. The occurrence of the beech seed year is influenced by factors such as precipitation, temperature, drought, and air pollution. Although beech is generally considered resistant to abiotic and biotic factors, it often needs protection against hoofed game browsing in the earliest stages of development. As climate change progresses, it is essential to cultivate beech in areas rich in precipitation and nutrients where it can thrive even under more extreme conditions. In optimal conditions, beech has shown intensive regeneration in recent years, aggressively displacing other tree species. However, with insufficient precipitation and prolonged periods of drought, beech loses its vigor, production, and ability to compete. For adaptation to climate change, it is recommended to select appropriate beech provenance, promote natural regeneration, and cultivate structurally differentiated stands through positive-selection thinning from above.

High nutrient utilization and resorption efficiency promote bamboo expansion and invasion

Bamboos are fast-growing, aggressively-spreading, and invasive woody clonal species that often encroach upon adjacent tree plantations, forming bamboo–tree mixed plantations. However, the effects of bamboo invasion on leaf carbon (C) assimilation, and nitrogen (N) and phosphorus (P) utilization characteristics remains unclear. We selected four different stands of Pleioblastus amarus invading Chinese fir (Cunninghamia lanceolata) plantations to investigate the concentrations, stoichiometry, and allometric growth relationships of mature and withered leaves of young and old bamboos, analyzing N and P utilization and resorption patterns. The stand type, bamboo age, and their interaction affected the concentrations, stoichiometry and allometric growth patterns of leaf C, N, and P in both old and young bamboos, as well as the N and P resorption efficiency. Bamboo invasion into Chinese fir plantations decreased leaf C, N, and P concentrations, C:N and C:P ratios, N and P resorption efficiency, and allometric growth exponents among leaf C, N, and P, while it only slightly altered N:P ratios. PLS-PM analysis revealed that bamboo invasion negatively impacted leaf C, N, and P concentrations, as well as N and P utilization and resorption. The results indicate that high N and P utilization and resorption efficiency, along with the mutual sharing of C, N, and P among bamboos in interface zones, promote continuous bamboo expansion and invasion. Collectively, these findings highlight the significance of N and P utilization and resorption in bamboo expansion and invasion and provide valuable guidance for the establishment of mixed stands and the ecological management of bamboo forests.

Whole-genome screening for near-diagnostic genetic markers for four western European white oak species identification

Key messageMining genome-wide DNA sequences enabled the discovery of near-diagnostic markers for species assignment in four European white oaks (Quercus petraea (Matt.) Liebl., Quercus pubescens Willd., Quercus pyrenaica Willd., and Quercus robur L.) despite their low interspecific differentiation. Near-diagnostic markers are almost fully fixed in one species and absent in the three others. As a result, only a handful of markers are needed for species identification, making this genetic assay a very promising operational taxonomic assignment procedure in research and forestry.ContextIdentifying species in the European white oak complex has been a long-standing concern in taxonomy, evolution, forest research, and management. Quercus petraea (Matt.) Liebl., Q. robur L., Q. pubescens Willd., and Q. pyrenaica Willd. are part of this species complex in western temperate Europe and hybridize in mixed stands, challenging species identification.AimsOur aim was to identify near-diagnostic single-nucleotide polymorphisms (SNPs) for each of the four species that are suitable for routine use and rapid diagnosis in research and applied forestry.MethodsWe first scanned existing whole-genome and target-capture data sets in a reduced number of samples (training set) to identify candidate diagnostic SNPs, i.e., genomic positions being characterized by a reference allele in one species and by the alternative allele in all other species. Allele frequencies of the candidates SNPs were then explored in a larger, range-wide sample of populations in each species (validation step).ResultsWe found a subset of 38 SNPs (10 for Q. petraea, 7 for Q. pubescens, 9 for Q. pyrenaica, and 12 for Q. robur) that showed near-diagnostic features across their species distribution ranges with Q. pyrenaica and Q. pubescens exhibiting the highest (0.876) and lowest (0.747) diagnosticity, respectively.ConclusionsWe provide a new, efficient, and reliable molecular tool for the identification of the species Q. petraea, Q. robur, Q. pubescens, and Q. pyrenaica, which can be used as a routine tool in forest research and management. This study highlights the resolution offered by whole-genome sequencing data to design near-diagnostic marker sets for taxonomic assignment, even for species complexes with relatively low differentiation.

Impact of abandonment on leaf morphology traits and nutrient utilization strategies of dominant tree seedlings in Moso bamboo forests

The restoration of ecological functions in abandoned Moso bamboo forests facilitates positive succession in evergreen vegetation. Nevertheless, there is a limited understanding regarding the leaf functional traits and nutrient utilization strategies of understory vegetation after abandonment. This study investigated the impact of abandonment duration (9 and 21 years) on leaf morphological traits, soluble sugars characteristics, carbon (C), nitrogen (N), phosphorus (P), and their ratios in dominant tree seedlings (Lithocarpus brevicaudatus and Schima superba) within Moso bamboo forests. Leaf sizes increased significantly with prolonged abandonment in both species, accompanied by a consistent decrease in leaf thickness and leaf tissue density. These morphological indices were more pronounced in L. brevicaudatus compared to S. superba (P < 0.05), and they showed a positive correlation with tree sizes. Moreover, leaf soluble sugars, C, and C: N: P ratios of both tree species decreased over duration abandonment, while N and P contents increased. Specifically, L. brevicaudatus exhibited elevated levels of fructose, glucose, N, and P, whereas S. superba displayed higher sucrose, C, and C: N: P ratios. Our findings reveal that both species, with extended abandonment, enlarged their leaf area and improved carbon utilization, facilitating adaptation to competitive resource habitats. Particularly, L. brevicaudatus exhibited a propensity to augment leaf sizes, as well as N, and P contents, suggesting a strategy to enhance carbon assimilation through additional N and P nutrient supplementation. Conversely, S. superba primarily focused on bolstering carbohydrate reserves, indicating that moderate thinning or pruning of bamboo forests could boost sunlight penetration, along with the appropriate nutrient supplementation. These insights significantly contribute to the scientific understanding necessary for the classification and management of mixed stands in abandoned bamboo forests.