Scots pine (Pinus sylvestris) and silver birch (Betula pendula) mixed-species growth dynamics in the North York moors

Only less than one percent of the territory of Latvia is occupied by broadleaved (trees having relatively wide flat leaves) forests. The aim of the research is to assess forest vegetation in the island of Upursala of Cirišs lake. The data is collected in four forest areas of the island. Totally 12 plots, each with an area of 200 m2 (20 x 20 m) have been created. In each plot, the accounting of growing trees and deadwood is carried out. The vegetation is measured in each forest area - the projective vegetation cover and cover of each plant species by tree, shrub, herb and moss layer are determined. The research founds that the average stock of growing trees on the island of Upursala is 565.8 m3 ha-1. The average amount of dead wood is 108 m3 ha-1, it consists mainly of fallen deadwood. Totally 45 species are listed in the vegetation plots, of which seven are determinants of European broadleaved forests. The largest number of determinant species of European broadleaved forests have been observed in stands with mixed forests (aspen - small-leaved lime – pedunculate oak, aspen – Scots pine - pedunculate oak and Scots pine – Silver birch – aspen). It can be argued that these stands will become the European broadleaved forests in the future.

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing.

Variability in short root morphology of the three main tree species of Europe's boreal forest (Norway spruce (Picea abies L. Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth)) was investigated in four stands along a latitudinal gradient from northern Finland to southern Estonia. Silver birch and Scots pine were present in three stands and Norway spruce was present in all stands. For three fertile Norway spruce stands, fine root biomass and number of root tips per stand area or unit basal area were assessed from north to south. Principal component analysis indicated that short root morphology was significantly affected by tree species and site, which together explained 34.7% of the total variability. The range of variation in mean specific root area (SRA) was 51-74, 60-70 and 84-124 m(2) kg(-1) for Norway spruce, Scots pine and silver birch, respectively, and the corresponding ranges for specific root length were 37-47, 40-48 and 87-97 m g(-1). The range of variation in root tissue density of Norway spruce, Scots pine and silver birch was 113-182, 127-158 and 81-156 kg m(-3), respectively. Sensitivity of short root morphology to site conditions decreased in the order: Norway spruce > silver birch > Scots pine. Short root SRA increased with site fertility in all species. In Norway spruce, fine root biomass and number of root tips per m(2) decreased from north to south. The differences in morphological parameters among sites were significant but smaller than the site differences in fine root biomass and number of root tips.

Functional diversity of soil microbial communities under Scots pine, Norway spruce, silver birch and mixed boreal forests

• Previous studies on competitive interactions among silver birch, Scots pine, and Siberian larch have not addressed the direct importance of the species identity of nearby competitors.• We examined the joint importance of competition and species identity, using subject trees with a high local abundance of a single dominant neighboring species. Interspecific neighbors influenced annual height increment, shoot length, and branch number per unit crown length, especially in Scots pine. Silver birch and Siberian larch were predominantly affected by the level of competition alone, as estimated with competition indices.• In Scots pine, the effects may have been a direct consequence of the species identity of neighbors or they may have acted as a substitute for the effect of some non-measured variable associated with species-specific characteristics. These functionally equivalent alternatives suggest that simple indices are not adequate measures of the neighbor effect for Scots pine.• A simple extrapolation of individual tree growth to the stand level suggested that Scots pine and silver birch may grow faster in mixed than in pure stands. Siberian larch showed negative growth responses to interspecific neighbors, but the effects may be counterbalanced at the stand level by a corresponding increase in pine or birch growth.

Six experiments were established between 1955 and 1962 in different parts of northern and western Britain which used replicated randomized block designs to compare the performance of two species 50:50 mixtures with pure stands of the component species. The species involved were variously lodgepole pine (Pinus contorta Dougl.), Japanese larch (Larix kaempferi Lamb. Carr.), Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth.), Sitka spruce (Picea sitchensis Bong. Carr.) and western hemlock (Tsuga heterophylla Raf. Sarg.). The first four species are light demanding, while Sitka spruce is of intermediate shade tolerance and western hemlock is very shade tolerant: only Scots pine and silver birch are native to Great Britain. In three experiments (Bickley, Ceannacroc, Hambleton), the mixtures were of two light-demanding species, while at the other three sites, the mixture tested contained species of different shade tolerance. The experiments were followed for around 50 years, similar to a full rotation of even-aged conifer stands in Britain. Five experiments showed a tendency for one species to dominate in mixture, possibly reflecting differences in the shade tolerance or other functional traits of the component species. In the three experiments, the basal area of the mixtures at the last assessment was significantly higher than predicted based on the performance of the pure stands (i.e. the mixture ‘overyielded’). In two of these cases, the mixture had had a higher basal area than found in the more productive pure stand indicating ‘transgressive overyielding’. Significant basal area differences were generally more evident at the later assessment date. The exception was in a Scots pine: western hemlock mixture where greater overyielding at the earlier date indicated a nursing (‘facilitation’) effect. In the remaining experiments, the performance of the mixture conformed to predictions from the growth of the component species in pure stands. Taken overall, the results suggest that functional traits can be used to interpret the performance of mixtures but prediction of the outcome will require better understanding of the interplay between species and site characteristics plus the influence of silvicultural interventions.

SummaryThe aim of this study was to investigate the differences in infections caused by Agrobacterium tumefaciens in a conifer, Scots pine (Pinus sylvestris), and in a non‐host deciduous species, silver birch (Betula pendula). All the Agrobacterium tumefaciens strains tested caused crown‐gall formation in both tree species, but the infection rates varied remarkably. In Scots pine, the development of galls was rare, and slower than in silver birch. Inoculation into the base of the stem were the most successful in gall induction. Silver‐birch galls were large, often surrounding the whole stem, in contrast to Scots pine galls, which were characterized by their small size and neck‐like connection with the host plant. In silver birch, no other morphological changes could be seen. In Scots pine, abnormal phenotypes with proliferating short shoots above the galls were observed during the second and third growing season. The results indicate that, of the two non‐host tree species, the deciduous one, silver birch, is more susceptible to an A. tumefaciens infection than the conifer, Scots pine. The matrix for A. tumefaciens infection in silver birch differs from that in Scots pine, since the terpene compounds of Scots pine seem either to kill the agrobacteria or to suppress their growth. The differences between the species could be partly caused by their difference in sensitivity to phytohormones. These features reflect evolutionary incompatibility between A. tumefaciens and a gymnosperm.

Aim of the study: We analysed the effects of thinning intensity and canopy type on Scots pine growth and stand dynamics in a mixed Scots pine-beech forest. Area of the study: Western Pyrenees. Material and methods: Three thinning intensities were applied in 1999 (0, 20 and 30% basal area removed) and 2009 (0, 20 and 40%) on 9 plots. Within each plot, pure pine and mixed pine-beech patches are distinguished. All pine trees were inventoried in 1999, 2009 and 2014. The effects of treatments on the tree and stand structure variables (density, basal area, stand and tree volume), on the periodic annual increment in basal area and stand and tree volume, and on mortality rates, were analysed using linear mixed effects models. Main Results: The enhancement of tree growth was mainly noticeable after the second thinning. Growth rates following thinning were similar or higher in the moderate than in the severe thinning. Periodic stand volume annual increments were higher in the thinned than in the unthinned plots, but no differences were observed between the thinned treatments. We observed an increase in the differences of the Tree volume annual increment between canopy types (mixed < pure) over time in the unthinned plots, as beech crowns developed. Research highlights: Moderate thinning is suggested as an appropriate forest practice at early pine age in these mixed forests, since it produced higher tree growth rates than the severe thinning and it counteracted the negative effect of beech on pine growth observed in the unthinned plots.Keywords: competition; Fagus sylvatica L.; Pinus sylvestris L.; forest management; mortality; Mediterranean forest.

Boreal forests hold about 32% of the global forest carbon (C) stock and the majority of this C is stored in the soil. Forest management affects species composition, microclimate, plant growth, and litter production, and thus affects the soil organic carbon (SOC) storage. Hence, it is important to understand the effects of forest management practices on SOC storage and to adopt management strategies that protect SOC storage.We aimed to assess how two major forest management approaches differ in their impact on SOC quality and degradability to evaluate their effects on long-term SOC storage. Rotation forest management (RFM) based on clear-cut harvesting is the most common forest management practice worldwide. Continuous-cover forestry (CCF) as an integrated forest management approach has been suggested to enhance SOC storage. It uses repeated partial harvesting and retains a continuous tree cover.We present our recently published results from a field study in Ruunaa, Lieksa, eastern Finland. We compared the effects of logging methods applied in CCF and RFM on SOC storage and quality in boreal Scots pine (Pinus sylvestris) dominated forests ten years after the logging operations. We sampled gap-cuts as logging method applied in CCF, retention-cuts (20% of tree volume retained), and uncut mature forests and clear-cuts as two opposing stages of RFM. We tested the hypotheses: (1) colder microclimate and continuous litter input lead to higher SOC stocks in CCF plots than in clear-cuts and (2) more labile litter of grass- and herb-rich vegetation typical for clear-cut sites enhances SOC decomposition rates. We analyzed the SOC concentration and stock and modelled annual above- and belowground litter inputs based on stand characteristics (diameter at breast height, basal area, dominant tree height, understory species coverage). We used sequential chemical fractionation of organic layer samples and laboratory incubation to analyze the quality of SOC and its degradability under standardized conditions. To estimate the decomposition rate as impacted by the environment we incubated cellulose bags in situ. We assessed the impact of varying microclimate with field measurements of soil temperature and soil moisture. We analyzed the microbial biomass C pool with chloroform fumigation extraction.The SOC content and stock did not differ significantly between the treatments, despite the warmer microclimate and lower litter input recorded in clear-cut plots than in CCF plots. However, we detected differences in quality and degradability of SOC. Soils in clear-cut sites held lower proportions of labile SOC compounds than the other treatments. As hypothesized, decomposition rate was elevated in clear-cuts, but was equally high within the canopy gaps of gap-cuts. Accumulation of labile SOC due to cooler microclimate, combined with decreased decomposition rate – both found in uncut forests and retention-cuts – indicate a higher potential for future SOC accumulation in these treatments than in clear-cuts. Our study highlights that forest management affects the quality, degradability, long-term accumulation and storage of SOC. Thus, the chosen logging method can be an important tool in climate change mitigation and the forest management regime needs to be adapted accordingly. Publication in Forest Ecology and Management [2023]: https://doi.org/10.1016/j.foreco.2023.121144

Reduction of stand density increases drought resistance in xeric Scots pine forests

Investing in planting genetically improved silver birch ( Roth) in Swedish plantations requires understanding how birch stands will develop over their entire rotation. Previous studies have indicated relatively low production of birch compared to Norway spruce ( (L.) Karst.) and Scots pine ( L.). This could result from using unrepresentative basic data, collected from unimproved, naturally-regenerated birch ( spp.) growing on inventory plots often located in coniferous stands. The objective of this study was to develop a basal area development function of improved silver birch and evaluate production over a full rotation period. We used data from 52 experiments including planted silver birch of different genetic breeding levels in southern and central Sweden. The experimental plots were established on fertile forest sites and on former agricultural lands, and were managed with different numbers of thinnings and basal area removal regimes. The model best describing total stand basal area development was a dynamic equation derived from the Korf base model. The analysis of the realized gain trial for birch showed a good stability of the early calculated relative differences in basal area between tested genotypes over time. Thus, the relative difference in basal area might be with cautious used as representation of the realized genetic gain. On average forest sites in southern Sweden, improved and planted silver birch could produce between 6–10.5 m ha year, while on fertile agriculture land the average productivity might be higher, especially with material coming from the improvement program. The performed analysis provided a first step toward predicting the effects of genetic improvement on total volume production and profitability of silver birch. However, more experiments are needed to set up the relative differences between different improved material.Betula pendulaPicea abiesPinus sylvestrisBetula3–1–1

Key messageWe have applied various silvicultural treatments to enhance the adaptation of Scots pine (Pinus sylvestris L.) mixed forests to climate change in Montesquiu Castle Park (Catalonia, NE Spain). Some treatments have shown positive effects, such as increased growth, reduced defoliation, and greater resistance of Scots pine to drought. However, other treatments may lead to a shift in vegetation from pine-dominated to oak-dominated forests. Future extreme droughts could increase pine mortality, potentially accelerating this shift. These findings are significant for forest management aimed at adapting these species to climate change in their southern distribution range: forest thinning could improve Scots pine’s ability to cope with stress, while pine removal may promote the growth of pubescent oak.ContextForested systems around the globe are being modified and climate change is one of the main drivers. Many regions of Spain, especially in the south and the east, where aridity is predicted to increase, could be some of the most vulnerable places for Scots pine (Pinus sylvestris L.) in Western Europe. In some cases, defoliation, mortality, and lack of regeneration of this species have induced a vegetation shift, as has been seen with Quercus spp. Adaptive forest management might help adjust the vulnerable forest systems to new climatic conditions.AimsThis study, carried out in north-eastern Spain, applies silvicultural treatments to promote changes in species composition for improving the adaptation to climate change of a Scots pine mixed forest. The main objective is to evaluate how different silvicultural treatments give rise to more adapted stands in terms of survival, growth, and regeneration.MethodsThree experimental treatments (and one control) were applied, two of them to reduce competition for Scots pine and a third pursuing the acceleration of replacement of Scots pine by pubescent oak (Quercus pubescens Willd.). The response of the stands to the treatments was monitored during 6 years.ResultsMortality of Scots pine was nil or very low in the different treatments, but defoliation showed significant differences among treatments at the end of the study: 42% in the control treatment (CO), 25% in the understory clearing treatment (C), and 18% in the understory clearing and pine thinning treatment. The increment in the basal area of Scots pine between 2015 and 2021 did not show significant differences among silvicultural treatments (F = 3.9, p > 0.05), but that of pubescent oak was higher in the pine logging than in the other treatments. Regeneration of Scots pine and pubescent oak did not differ among silvicultural treatments.ConclusionsThese findings have relevant implications for the use of management to adapt forests to climate change: in its southern distribution range, forest thinning could improve the capacity of Scots pine to cope with stress conditions, whereas pine removal may promote pubescent oak.

The effects of species mixture on the growth and yield of mid-rotation mixed stands of Scots pine and silver birch

The breeding of forest tree species in the Baltic region has notably contributed to wood production for the bioeconomy. Growth modelling is used for long-term estimates of forest development. However, usually based on data from unimproved stands, they may underestimate the growth of improved trees. Accordingly, it is important to identify and integrate the altered stand dynamics associated with improved planting stock into existing growth models to accurately capture the resulting gains or, alternatively, develop new functions specifically designed for improved trees. We used the generalized algebraic difference approach to model and analyze height growth patterns of Scots pine and silver birch with different genetic improvement levels (improved forest reproductive material categories ‘qualified’ and ‘tested’). Modelling was based on 14 260 and 55 926 height–age series from open-pollinated progeny trials in Latvia and Lithuania with an age range of 3–46 and 5–22 years for pine and birch, respectively. Dynamic generalized algebraic difference approach forms of commonly applied height growth functions with forest reproductive material-category-specific sets of coefficients were tested. The dynamic form of the Chapman–Richards and King–Prodan equations had the best fit for Scots pine and silver birch, respectively. The expected height growth of the category ‘tested’ was slightly better than the one for ‘qualified’, with more distinct differences in silver birch. The model with forest reproductive material-category-specific coefficients reflected the actual growth of improved trees; however, such application is limited to sites with medium and high site indices, where improved planting stock is typically used. We recommend the model for young stands up to the age of 20 and 40 years for pine and birch, respectively, considering the empirical data cover on which the functions are based. A unified dynamic height model with the same functional form but category-specific parameterization for different improvement levels allows a practical applicability and effective communication amongst diverse users, thereby promoting the utilization of the model amongst forest owners and managers who possess information regarding the origin of planting stock.

The removal of the most prevalent heavy metal ions [cadmium(II), lead(II), copper(II), and zinc(II)] by adsorption on Scots pine (Pinus sylvestris L.) biochar and Silver birch (Betula pendula) biochar has been investigated, following the determination of physical and chemical adsorption properties of biochar. The efficiency of adsorption of heavy metal ions [cadmium(II), lead(II), copper(II), and zinc(II)] on biochar was studied at different concentrations of heavy metals [onefold maximum contaminant level, twofold maximum contaminant level, fivefold maximum contaminant level (in accordance with the requirements set out in the Water Framework Directive 2000/60/EC), dosages of biochar (1.6–140 g), and biochar types (Scots pine (P. sylvestris L.) biochar and Silver birch (B. pendula) biochar produced at slow and fast pyrolysis) at constant pH of leaching solution, temperature, and contact time. Adsorption capacity of Scots pine (P. sylvestris L.) biochar and Silver birch (B. pendula) biochar was assessed by the application of extended Freundlich isotherm. In this study, biochar was evaluated as a potential adsorbent to efficiently reduce concentration of heavy metal ions in metal-contaminated water. The maximum adsorption capacity were reached of copper(II) on Silver birch (B. pendula) biochar (128.7 µg g−1) and of zinc(II) on Scots pine (P. sylvestris L.) biochar (107.0 µg g−1). Adsorption capacity of lead(II) on Silver birch (B. pendula) and Scots pine (P. sylvestris L.) biochar varied from 1.29 to 3.77 and from 2.37 to 4.49 µg g−1, respectively.