Spruce Stands Research Articles

Tree size drives growth interactions in mixed mature stands of black spruce (Picea mariana) and tamarack (Larix laricina)

Little is known about the growth interactions of black spruce (Picea mariana) and tamarack (Larix laricina), two important commercial tree species of the Canadian boreal forest. We investigated growth relations between black spruce and tamarack in mature mixed stands. We sampled tree-rings of 223 black spruce and 103 tamaracks to analyze their basal area increment over 10 years. We mapped, identified the species, and measured the diameter at breast height of each neighbouring tree in 112 circular plots of 400 m2 to analyze basal area increments through spatially explicit models. The model estimating crowding effect of neighbouring tree was adjusted with 4 parameters expressing the effect of distance, size of neighbours, size of target tree and species. Our models suggested that the size of neighbouring trees was the main parameter influencing competition between the studied species. Black spruce basal area increments over 10 years declined up to 22 cm2 when surrounded by large neighbours. Tamarack basal area increments declined by 48 cm2 due to competition by large neighbours. However, the overall crowding effect showed that tamarack was more sensitive to competition than black spruce and the intraspecific and interspecific competition had similar effect. Our research provides insight on growth relations between two important commercial species of the Canadian boreal forest.

Detection of susceptible Norway spruce to bark beetle attack using PlanetScope multispectral imagery

Climate change-related acute or long-term drought stress can weaken forest ecosystems and result in widespread bark beetle infestations. Eurasian spruce bark beetle (Ips typographus L.) infestations have been occurring in Norway spruce [Picea abies (L.) Karst.]-dominated forests in central Europe including the Czechia. These infestations appear regularly, especially in homogeneous spruce stands, and the impact varies with the climate-induced water stress conditions. The removal of infected trees before the beetles leave the bark is an important step in forest pest management. Early identification of susceptible trees to infestations is also very important but quite challenging since stressed tree-tops show no sign of discolouration in the visible spectrum. We investigated if individual spectral bandwidths or developed spectral vegetation indices (SVIs), can be used to differentiate non-attacked trees, assumed to be healthy, from trees susceptible to attacks in the later stages of a growing season. And, how the temporal-scale patterns of individual bands and developed SVIs of susceptible trees to attacks, driven by changes in spectral characteristics of trees, behave differently than those patterns observed for healthy trees. The multispectral imagery from the PlanetScope satellite coupled with field data were used to statistically test the competency of the individual band and/or developed SVIs to differentiate two designated classes of healthy and susceptible trees. We found significant differences between SVIs of the susceptible and healthy spruce forests using the Enhanced Vegetation Index (EVI) and Visible Atmospherically Resistant Index (VARI). The accuracy for both indices ranged from 0.7 to 0.78; the highest among all examined indices. The results indicated that the spectral differences between the healthy and susceptible trees were present at the beginning of the growing season before the attacks. The existing spectral differences, likely caused by water-stress stimuli such as droughts, may be a key to detecting forests susceptible to early infestations. Our introduced methodology can also be applied in future research, using new generations of the PlanetScope imagery, to assess forests susceptibility to bark beetle infestations early in the growing season.

MODERN RECORDS OF THE EUROPEAN HEDGEHOG (<i>ERINACEUS EUROPAEUS</i>, ERINACEIDAE, EULIPOTYPHLA) IN SOUTHEASTERN FENNOSCANDIA

Southeastern Fennoscandia, which encompasses the Republic of Karelia and the adjacent districts of the Leningrad and Arkhangelsk regions, until lately remained an area of Russia’s European North especially poorly prospected as regards the status of the European hedgehog (Erinaceus europaeus). Modern (2001–2022) records of this species obtained through the authors’ original observations and based on reports received from respondents, altogether covering 212 hedgehogs and 182 encounters, are analyzed. Spatio-temporal patterns in the species’ records in the region are demonstrated, viz. an expanding distribution area and a growing frequency of encounters from northwest to southeast. The northernmost records are shown (64.368° N, 30.383° E), including yearlings (63.624°–63.924° N, 30.466°–30.901° E, northern taiga subzone), as well as the first reports of the species east of Lake Onego both in Karelia and the Arkhangelsk Region. The studies have revealed habitat preferences and the rate of use of urban territories in the north of the distribution range: high shares of records come from deciduous (34.0% of the total number of animals reported) and mixed (19.3%) forest sites, as well as farmland (10.8%), second-home communities (16.5%), and rural settlements (9.0%). Hedgehog encounters in cut-over places, pine and spruce stands, wetlands, abandoned hamlets, and solitary buildings in the woods were few (0.5–6.1%). Most of the records were a result of accidental sightings by humans (80.8%), while domestic dogs spotted 19.2% of the hedgehogs. The earliest encounters in spring were recorded on 25.04–11.05, the latest in autumn on 2–17.09. The number of hedgehog encounters during their active life period was the lowest in April (1.1%), growing sharply in May and June (16.7 and 17.8%, respectively), peaking in July and August (30.0 and 24.4%), and falling sharply in September (10.0%). Some of the population parameters were determined: an average brood was 2.8 young of the year, whose share amounted to 24.5% of the total number of records; active single animals prevailed among adults (86.3%), and much smaller shares belonged to active pairs (7.6%) and females with litter (6.1%). The main cause of the deaths was road killing by vehicles (77.4%). Climate warming and forest structure alterations may be reasons to expect further expansions of the area of hedgehog encounters, e.g., to transformed and urbanized boreal areas.

The cumulative impacts of droughts and N deposition on Norway spruce (Picea abies) in Switzerland based on 37 years of forest monitoring

Norway spruce is one of the most important tree species in Central Europe, however, it is facing major problems with recent droughts. In this study we present 37 years (1985–2022) of long-term forest observation data on 82 different forest sites across Switzerland including 134′348 tree observations. The sites consists of managed spruce or mixed forest stands with beech (Fagus sylvatica) and comprise large gradients in altitude (290–1870 m), precipitation (570–2448 mm a−1), temperature (3.6–10.9 °C) or total nitrogen deposition (8.5–81.2 kg N ha−1 a−1).Long-term tree mortality has increased more than fivefold due to the multiple drought years 2019, 2020 and 2022, which is more than double the increase following the 2003 drought. We used a Bayesian multilevel model including three years of lagged drought indicator to predict spruce mortality. Besides stand age, the most important factors were drought and N deposition. Especially under drought conditions spruce mortality was increased on sites with high N deposition. Moreover, N deposition increased the imbalance of foliar phosphorus concentrations, with negative impacts on tree mortality. Mortality was increased by a factor of 1.8 in spruce compared to mixed beech and spruce stands. Stands with high mortality rates showed previously an increased proportion of trees with damaged crowns, especially after the droughts of 2003 and 2018.Taken together, we found evidences of an increase in spruce mortality droughts amplified under high N depositions. The perennial drought of 2018–2020 resulted in a cumulative spruce mortality of 12.1 % (564 dead trees in 82 sites) in only three years. With a Bayesian change-point regression framework we estimated a critical empirical load for nitrogen of 10.9 ± 4.2 kg N ha−1 a−1, which is in line with current thresholds, above which future plantings of spruce in Switzerland may not be a sustainable option due to the observed interaction between drought and nitrogen deposition.

Stand Structure Beats Age for Ground Cover Vegetation in Ageing Hemiboreal Scots Pine and Norway Spruce Stands

Intensifying forest management and a reduction in the rotation period necessitates the development of intensive biodiversity conservation strategies, such as the triad concept, which aims at ensuring habitat connectivity. Such an approach depends on the relationships between biodiversity components and manageable stand characteristics. Mostly, the biological value of stands has been associated with age, although stand structures, which are often intercorrelated with age, might be of primary importance. The relationships between ground cover vegetation, which is a principal component and indicator of the biological value of temperate conifer forests, and stand characteristics were assessed in pre-harvesting/harvesting age and old-growth coniferous stands in the eastern Baltic region (Latvia). The old-growth stands were nearly two times older than the pre-harvesting/harvesting age stands. Both stand groups showed generally similar ground cover flora, though ground cover vegetation showed higher variability in the old-growth stands. The principal gradients of ground cover vegetation were related to light, site fertility, and structural diversity, as well as the degree of deciduous (particularly Betula spp.) admixture in a tree stand. Considering the explicit contrasts, stand age did not affect ground cover vegetation, implying the principal effects of stand structure, which are manageable characteristics. This implies the potential for specific management to aid the ecological connectivity of stands in commercial forest landscapes.

Effects of Norway spruce shelter density and soil scarification method on mortality and height growth of underplanted European beech, European silver fir and Douglas fir

AbstractIn Europe, 6–7 million ha even-aged, pure stands of Norway spruce grown outside its natural range are prone to butt rot, windthrow, and bark beetle infestation. Climate change may well accelerate these problems and there is an urgent need to develop methods for converting Norway spruce plantations into more heterogeneous forest with larger resistance and resilience towards natural disturbances. Based on a field experiment located on former heathland on an outwash plain in western Denmark, we examined the mortality and height growth of European beech (Fagus sylvatica L.), European silver fir (Abies alba Mill.), and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) planted under a shelterwood of 17–19 m tall Norway spruce (Picea abies (L.) Karst.) at shelter densities initially ranging by basal area from 10 to 36 m2 ha−1 (271–1099 stems ha−1). Underplanting included plots of beech (100 per cent) and silver fir (100 per cent) as well as plots with two-species mixtures of silver fir/beech (66 per cent/33 per cent and 33 per cent/66 per cent) and Douglas fir/beech (66 per cent/33 per cent). The experiment also included two soil scarification methods (patch and strip scarification). The experiment was laid out in an unbalanced factorial split-plot design, replicated in time and space, and totaling 144 plots in four blocks. The experiment was followed for 19 years during which a gradual reduction in shelter density took place although in some plots the shelterwood was removed abruptly by windthrow and bark beetle infestation. Shelter densities larger than 10 m2 ha−1 had only a minor effect on the mortality of beech and silver fir, while shelter densities larger than 20 m2 ha−1 resulted in increased mortality of Douglas fir. Subsequent abrupt reduction in shelter density resulted in increased mortality, especially of silver fir. Height growth decreased with increasing shelter density, more for Douglas fir than for beech, and marginally more for beech than for silver fir. For shelter densities <15 m2 ha−1, height growth of silver fir was unaffected. Beech grew faster when mixed with Douglas fir. The soil scarification method did not influence mortality, but strip scarification resulted in marginally larger height growth than patch scarification. We hypothesize that the shelter effect was related mainly to competition for light, while late frost and browsing were important factors in open shelters (<10 m2 ha−1). Based on these results, recommended initial shelter densities are at or <10 m2 ha−1 for the establishment of Douglas fir, at ~15–20 m2 ha−1 for silver fir, and around 15 m2 ha−1 for beech.

Initial responses of soil chemical properties to simulated warming in Norway spruce (Picea abies (L.) H.Karst.) stands in the Western Carpathians

The present-day decline observed in Norway spruce stands in the Western Carpathians is particularly worrying given the large forest area of this species. Relatively little attention has been paid to the contribution of soil chemistry to the Norway spruce decline in the context of global warming. We conducted a field experiment to simulate warming for almost 500 days in the Western Carpathians, in a mature Norway spruce stand. Soil samples were collected approximately every 3 months from the organic and mineral topsoil horizons. Total carbon, total nitrogen, pH, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N), and ammonium (NH4-N) nitrogen concentrations were estimated. Warming caused increase in DOC, TDN, NH4-N, and pH in organic horizon, as well as increased pH in mineral topsoil. A trend for increasing total carbon and total nitrogen concentrations in the warmed organic horizon was observed. Increased concentrations of DOC and TDN may be associated with decrease in SOM stability or increase in production of biomass of the understory vegetation or soil microbial activity. Increased pH in warmed soil may be associated with the increased NH4-N and may contribute to the decrease in soil ability to adsorb DOC. We conclude that soil warming negatively stimulates soil organic matter stability, resulting in higher concentrations of easy migrating labile forms, mostly organic acid anions. Observed changes may contribute to the deterioration of Norway spruce stands.

A comparison of artificial neural networks and regression modeling techniques for predicting dominant heights of Oriental spruce in a mixed stand

Aim of study: This paper introduces comparative evaluations of artificial neural network models and regression modeling techniques based on some fitting statistics and desirable characteristics for predicting dominant height.
 Area of study: The data of this study were obtained from Oriental spruce (Picea orientalis L.) felled trees in even-aged and mixed Oriental spruce and Scotch pine (Pinus sylvestris L.) stands in the northeast of Türkiye.
 Material and methods: A total of 873 height-age pairs were obtained from Oriental spruce trees in a mixed forest stand. Nonlinear mixed-effects models (NLMEs), autoregressive models (ARM), dummy variable method (DVM), and artificial neural networks (ANNs) were compared to predict dominant height growth.
 Main results: The best predictive model was NLME with a single random parameter (root mean square error, RMSE: 0.68 m). The results showed that NLMEs outperformed ARM (RMSE: 1.09 m), DVM in conjunction with ARM (RMSE: 1.09 m), and ANNs (RMSE: from 1.11 to 2.40 m) in the majority of the cases. Whereas considering variations among observations by random parameter(s) significantly improved predictions of dominant height, considering correlated error terms by autoregressive correlation parameter(s) enhanced slightly the predictions. ANNs generally underperformed compared to NLMEs, ARM, and DVM with ARM.
 Research highlights: All regression techniques fulfilled the desirable characteristics such as sigmoidal pattern, polymorphism, multiple asymptotes, base-age invariance, and inflection point. However, ANNs could not replicate most of these features, excluding the sigmoidal pattern. Accordingly, ANNs seem insufficient to assure biological growth assumptions regarding dominant height growth.

Mountain recreation impact on changes in soil penetration resistance of spruce forests

The uniqueness of the Carpathian Mountain Forest ecosystems, a large part of which belongs to nature conservation areas, attracts a significant number of visitors annually. Intensive tourist flow on popular hiking trails leads to recreational digression, topsoil compaction, development of erosion processes and deterioration of forests. The research aims to determine the impact of recreation as an external mechanical impact on soil compaction by determining the soil penetration resistance under the canopy of predominant spruce stands. For this purpose, soil penetration resistance was measured with a penetrometer along two hiking trails within the root layer of the soil at four measuring sites at different distances from the hiking trail. In general, under the canopy of a forest stand, the soil cover is not homogeneous and the obtained penetration resistance values are characterised by considerable variability. It was revealed that for the “Zelene village – Uhorski skeli rocks” hiking trail in the areas close to the path (up to 20 m) there is a significant increase in soil penetration resistance compared to remote areas: at a depth of 10 cm it doubles, at a depth of 20 cm – by 20-40%, but with further deepening, the penetration resistance level off. At the same time, for the more popular “To Mount Pip Ivan Chornohirskyi” hiking trail, in the area adjacent to the trailbed, the penetration resistance reaches 19.6 kg·cm-2 in the upper 10 cm layer, and at a depth of 30 cm, it peaks at 37.8 kg·cm-2 (over 3 MPa), which affects the root spatial distribution of spruce forests. Intensive erosion processes due to soil compaction with an increase in soil penetration resistance above 60 kg·cm-2 (~6 MPa) are observed on the trailbed. The practical significance of the results obtained, and the established patterns is to complement existing methods for assessing the degree of recreational digression in mountainous conditions and can be the basis for designing measures to regulate tourist flows and restore affected areas

Site properties, species identity, and species mixture affect fine root production, mortality, and turnover rate in pure and mixed forests of European Beech, Norway spruce, and Douglas-fir

It is already well known that the effects of tree diversity on aboveground wood productivity depend on tree species identity and site conditions and thus can vary among different tree mixtures and forest sites. The effects of species diversity, specifically on belowground productivity and dynamics, have rarely been studied, so potential interactions with species identity and/or site conditions are largely unknown.Sequential soil coring was applied in mature pure and mixed stands of European beech, Norway spruce, and Douglas-fir in two regions of northern Germany to investigate the potential site, species, and mixing effects on fine root productivity, mortality, and turnover rates. In these ecologically and economically important species mixtures, a strong effect of site conditions on all fine root variables was found. In particular, more fine root growth was observed at the less favorable site conditions than at the more favorable ones. Species identity and interaction between site conditions and species identity were additional explanatory factors, whereat beech showed the strongest effect by site conditions. No overyielding was observed when fine root productivity was plotted against area potentially available (APA), nor were mortality or turnover. However, at specific soil depths, a mixing effect, caused mainly by beech, was observed for all variables and for both species mixtures.This study suggests that site conditions and species identity rather than species mixture are essential in explaining fine root dynamics and that increasing tree species diversity may not guarantee higher belowground productivity. However, in the face of climate change and the demand for wood as a natural and renewable resource, an admixture of Douglas-fir to pure European beech stands seems to be a reasonable alternative to an admixture of spruce, a species that is already seriously suffering by drought and bark beetle attacks.

Conifers and non-native tree species shift trophic niches of generalist arthropod predators in Central European beech forests

BackgroundFunctional diversity is vital for forest ecosystem resilience in times of climate-induced forest diebacks. Admixing drought resistant non-native Douglas fir, as a partial replacement of climate-sensitive Norway spruce, to native beech forests in Europe appears promising for forest management, but possible consequences for associated biota and ecosystem functioning are poorly understood. To better link forest management and functional diversity of associated biota, we investigated the trophic niches (∆13C, ∆15N) of epigeic generalist predators (spiders and ground beetles) in mixed and pure stands of European beech, Norway spruce and non-native Douglas fir in north-west Germany. We assessed the multidimensional niche structure of arthropod predator communities using community-based isotopic metrics.ResultsWhilst arthropod ∆13C differed most between beech (high ∆13C) and coniferous stands (low ∆13C), ∆15N was lowest in non-native Douglas fir. Tree mixtures mitigated these effects. Further, conifers increased isotopic ranges and isotopic richness, which is linked to higher canopy openness and herb complexity. Isotopic divergence of ground beetles decreased with Douglas fir presence, and isotopic evenness of spiders in Douglas fir stands was lower in loamy sites with higher precipitation than in sandy, drier sites.ConclusionsWe conclude that tree species and particularly non-native trees alter the trophic niche structure of generalist arthropod predators. Resource use and feeding niche breadth in non-native Douglas fir and native spruce differed significantly from native beech, with more decomposer-fueled and narrower feeding niches in beech stands (∆13C, isotopic ranges and richness). Arthropod predators in non-native Douglas fir, however, had shorter (∆15N) and simplified (isotopic divergence) food chains compared to native forest stands; especially under beneficial abiotic conditions (isotopic evenness). These findings indicate potential adverse effects of Douglas fir on functional diversity of generalist arthropod predators. As tree mixtures mitigated differences between beech and conifers, mixed stands including (non-native) conifers constitute a promising compromise between economic and conservational interests.

Санитарное состояние коренных ельников тайги Европейской России

The materials of studies carried out in the primary uneven-aged spruce forests of the taiga within European Russia are presented, in the northern taiga spruce forests are studied in the territories of the Arkhangelsk region and the Paanajarvi National Park in the Karelia Republic; in the middle taiga spruce forests are studied in the reserve «Vepssky forest» in the Leningrad region and Andomsky forestry of the Vologda region; in the southern taiga spruce forests of the Central Forest State Biosphere Reserve in the Tver Region are studied. The age and volume of trees growing on permanent test plots were determined, age series of forest stands were modelled, dynamic characteristics were established, estimates of the sanitary condition of trees and stands were made, the infestation of the biotrophic complex with wood-destroying fungi and calculations of the tree waste volume by stages of decomposition were made. A close relationship between the increase in tree damage values and the increase in the age of generations in the age series was revealed, which is interpreted as a pattern: r = 0,98 with mr = 0,05 and t = 140. The dynamics of the formation of age generations in spruce forest stands proceeds much more slowly from 4 to 6 times than the dynamics of wood debris decomposition. The characteristics of the sanitary state of native spruce stands are in the range between weakened and severely weakened communities, with high rates of rotten faults of trees in age generations and stands and significant amounts of tree waste. High rates of rot damage to trees ensure the balance of reproducible and degradable biomass in the dynamics of spruce forests. This balance is formed by differences in the time periods of biomass accumulation and the rate of decomposition of wood waste.

Effects of thinning intensity and rotation length on albedo- and carbon stock-based radiative forcing in boreal Norway spruce stands

Abstract We investigated how thinning intensity and rotation length affect radiative forcing, and thus climate warming or cooling, through changes in albedo and carbon stocks in Norway spruce (Picea abies Kart. (L.)) stands. Forest ecosystem model simulations were conducted under the current climate on sub-mesic sites in central Finland (62oN). Even-aged management regime with a business-as-usual (baseline) thinning from below over an 80-year rotation length was used as the reference management regime with which others were compared. Other even-aged management regimes included baseline thinning with ±20 per cent changes in basal area thinning thresholds over rotation lengths of 80, 100 and 120 years. Additionally, we used as a comparison an uneven-aged management regime, with selective cuttings (from above) at ca. 15-year intervals, and no management regime, over the simulation periods of 80–120 years. Under even-aged management, a simultaneous decrease in thinning intensity and extension of rotation length from 80 to 120 years reduced total radiative forcing compared to the reference management regime. Thus, it had an overall net cooling effect. Under even-aged management with baseline thinning and/or higher thinning intensity with rotation lengths of 80–100 years, and under uneven-aged management, there was little net climatic effect. This was because the opposing effects of changes in albedo and ecosystem carbon stocks largely cancelled each other out. No management regime resulted in the highest net cooling effect but provided no harvest income for timber. Thus, proper incentives for forest owners would likely be required to promote such potential cooling effects in forest management.

Uprooting as a pre-commercial thinning operation in young Norway spruce stands

Uprooting, as a mechanical pre-commercial thinning operation (PCT), removes competitive, undesired trees with roots to prevent or reduce the need for a second PCT. The state of 66 young Norway spruce (Picea abies (L.) H. Karst.) stands was explored 3–5 years after uprooting to assess the quality of uprooting in terms of the number of competing birches (Betula spp.) and the probability of freely growing crop tree spruce (no competing trees taller than 2/3 of the crop tree’s height). In the uprooted spruce stands, the number of birches was, on average, about 3800 stems ha−1, and in every fifth stand, it was less than 2000 stems ha−1. The number of birches increased with increasing site wetness (TWI), site fertility and thickness of the humus layer. In 80% of the stands, there were at least 1000 freely growing spruces ha−1, which is approximately the stem number to be left growing after first thinning in a spruce stand. If the height of crop tree spruces was 125 cm at uprooting, the probability of freely growing stems varied from 0.6 to 0.8 in typical cases. According to simulations at the first thinning stage, in most stands, birch was less than 10% taller than spruce, and the volume of birches was low enough that, in the future, spruce and birch would grow in the same crown layer as a mixed spruce–birch stand. The results showed that uprooting can serve as the only PCT operation in a planted spruce stand. The quality obtained by uprooting can be improved with careful selection of timing and conditions for uprooting; the optimal uprooting time is when crop tree spruces have reached about breast height.

Do admixed conifers change soil nutrient conditions of European beech stands?

Context Establishing mixed forest stands is an option for improving soil nutrient conditions and for increasing the resilience of forest ecosystems. Aims Identify the effects on soil chemistry of spruce and Douglas fir admixed in European beech forest. Methods We analysed pure and mixed species stands in Germany. The pure stands were mature European beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), and Norway spruce (Picea abies). The mixtures were composed of beech with either Douglas fir or spruce. The stands were located in two regions with different soil conditions. Results Our results indicated that pure spruce stands, independent of site condition, had the lowest base saturation while beech showed the highest values. The impact of Douglas fir differed between site conditions. On sandy soils, there was higher pH and base saturation under Douglas fir than under spruce. On loamy soils, however, the pH under Douglas fir and beech was lower than under spruce. The cation stocks (Ca and Mg) on sandy soils were lower under spruce and spruce/beech stands than under Douglas fir and beech. In contrast, under loamy soil, exchangeable Ca and Mg stocks were less under beech than under spruce stands. Soil exchangeable K under mixed stands was among the highest compared to pure stands, independent of site condition. Conclusions Mixed species stands reduce soil base cation depletion compared to conifer stands. Implications Admixture of Douglas fir to European beech seems to be a more reasonable option for forest management than an admixture of spruce, since it does not negatively affect soil chemistry.

Xylotrophs in spruce stands of the Kologrivsky Forest Nature Reserve, Russia

The purpose of the study is to study the species composition of xylotrophic fungi in spruce stands of the Kologrivsky Forest Nature Reserve (Kostroma region, Russia). On the territory of the nature reserve, 20 species of pathogenic fungi were found parasitizing on the trunks of living and dead trees. Dead wood (57%) is the main substrate for fungal fruiting bodies. Producing tree trunks use about 28% of xylophytes as a substrate, dry-standing – 15%.

Growth Dynamics of Young Mixed Norway Spruce and Birch Stands in Finland

Mixed-species forests in Fennoscandia are of increasing interest because they may improve resilience, biodiversity, and productivity. Currently there is scarce knowledge available of the early growth dynamics of mixed spruce–birch stands in even-aged managed production forests with artificial regeneration of spruce. The main objective of our study was to examine the present state and the past growth dynamics of current single-storied, young spruce–birch (Picea abies (L.) Karst., Betula pendula Roth, Betula pubescens Ehrh.) stands (age 17–29 years), where spruce was planted and birch naturally regenerated, and juvenile management practices (early cleaning and precommercial thinning) were carried out. We inventoried ten such stands in Southern Finland, for a total of twenty plots. For 160 spruces and 160 birch trees, we reconstructed the past diameter and height growth through stem analysis. We analyzed mean stand characteristics by tree species, and we modelled the individual tree height and diameter growth using the mixed effects Chapman–Richards model. Spruces had slower initial height growth, but by the age of about 20 years their height growth rate eventually approached and exceeded that of birches regenerated naturally at the time of spruce planting. The diameter growth of planted spruce exceeded that of birches even sooner (at the age of about 10 years). Thus, spruces are not suppressed by birches, and they may coexist in the same canopy layer in managed stands. Contrary to earlier guidelines, due to the fast growth of planted spruces, birch mixture needs to be maintained already in the first juvenile stand management (i.e., early cleaning). The growth dynamics of young, planted spruce, and naturally regenerated birch allow the establishment and management of such mixtures and also maintenance of the mixture in the future until the end of the rotation, thus improving biodiversity in boreal, planted spruce forests.

Early detection of Ips typographus infestations by using Sentinel-2 satellite images in windthrow affected Norway spruce forests in Smolyan region, Bulgaria

Strong winds uprooted more than 100 thousand m3 of coniferous trees in natural forest stands nearby the town of Smolyan (the Western Rhodopes) in January 2018. Although damaged trees were quickly removed from the stands, the European spruce bark beetle (Ips typographus) attacked the healthy Norway spruce trees near the windthrow areas in August 2020. Our hypothesis was that the trees were infested by the pest in previous years when no symptoms of attacks were observed. This study was conducted in three spruce stands, located near the windthrow areas and attacked by I. typographus, and in three control (healthy) stands located 5-10 km from the affected areas. We used satellite images captured by Sentinel-2 in September 2017-2020. It was established that in September 2017 (a year before the windthrow), the mean values of the Normalized difference vegetation index (NDVI) in the attacked stands were concentrated between 0.60 and 0.75 (with a maximum at 0.70), indicating that the trees were in good health. During the period 2018-2020 the distribution of mean values of NDVI was stretched between 0.35 and 0.75, which is an indication of evidence of pest attacks on the individual trees. The detail comparison of pixel values of the NDVI in the attacked and control sample plots was made on the base of images captured on 27.06.2020. The mean NDVI values in the three control plots (0.74-0.79) were much higher than the mean values in the sample plots attacked by the pest (0.57-0.65). These results showed that the values of NDVI based on satellite remote sensing data of Sentinel-2 can be used for early detection of I. typographus infestations in spruce stands around the windthrows. These data are important for rapid planning and implementing the sanitary feelings that reduce the pest population.

Testing the Efficiency of the Push-and-Pull Strategy during Severe Ips typographus Outbreak and Extreme Drought in Norway Spruce Stands

Protection of Norway spruce stands using anti-attractants was tested during an outbreak of bark beetles (Ips typographus) in their spring flight. The aims of this study were as follows: (1) to test the proposed experimental design for tree protection; (2) to evaluate height-specific alternatives for dispenser installation on trees; and (3) to evaluate the efficiency of tree protection measures using anti-attractants under bark beetle infestation and drought stress. The experiment was conducted at the forest edges adjacent to recent clearcuts on 10 blocks in the eastern Czech Republic. Each block had three adjacent experimental areas, with 20 trees growing in two rows at the recently cut forest edge (10 trees per row). In front of a block in each of the three areas, four pheromone traps were installed. The treatment area was protected by anti-attractants. The second area served as a so-called switch area, where beetles from the treatment area, as the outflux redirected from the anti-attractant, would start new attacks if not caught in nearby pheromone traps. The third area was a control. We attached anti-attractant tube dispensers on each tree trunk of the treated area at two heights. The results suggest a redirecting effect of anti-attractants, pushing beetles into the switch area and causing subsequent attacks, which was greater than in areas containing treated trees. There was no difference between two dispensers placed at 1 and 8 m height and both at 1 m. A switching effect of beetle attacks occurring outside of the treated areas was observed. Mounting anti-attractant dispensers on tree trunks at one low position above the ground can be substantially less labour-intensive and as efficient as positioning them at two different heights. For areas affected by severe drought and extremely dense bark beetle populations, the use of anti-attractants did not prove effective.

Ladin Meşcereleri Üst Topraklarında Derinliğe Göre Cmic ve Nmic 'in Değişimi

Bu çalışmada saf doğu ladini (Picea orientalis L.) ormanı altındaki toprakların özellikle organik C, toplam N, ayrışma oranı (Corg/Ntoplam), mikrobiyal biyokütle C (Cmic) ve N (Nmic) gibi karakteristiklerinin toprak derinliği ile değişimi araştırılmıştır. Araştırma sahası Trabzon ili Vakfıkebir ve Tonya İlçeleri sınırlarında bulunan Fol Deresi Mikro Havzası’nda yer almaktadır. Çalışma alanında alanı temsilen, rastgele 10 adet örnek nokta belirlenmiş ve bu noktalardan farklı iki derinlik kademesinden (0–15 cm ve 15–30 cm derinlik) toprak örneklemesi yapılmıştır. Alandan toprakların bazı fiziksel, kimyasal ve mikrobiyal analizleri için her derinlik kademesinden 10’ar örnek olacak şekilde toplamda 20 adet toprak örneği alınmıştır. Çalışma sonunda toprak derinliğine göre, % kum ve % toz içerikleri istatistiki olarak birbirinden farklılık (P<0,05) göstermiştir. Benzer olarak organik C, toplam N ve (Corg/Ntoplam) değerlerinin her iki derinlik kademesine göre istatistiksel olarak birbirinden farklı (P < 0,05) olduğu ortaya çıkmıştır. Toprakların Cmic içerikleri, 0-15 cm derinlik kademesinde 437,40–1315,20 μg g-1 ve 15-30 cm derinlik kademesinde 194,20–578,20 μg g-1 arasında değişim gösterdiği tespit edilmiştir. Toprakların Nmic içerikleri, 0–15 cm derinlik kademesinde ortalama 88,08  8,08 μg g-1 ve 15–30 cm derinlik kademesinde ortalama 41,17  4,32 μg g-1’dır. Toprakların hem Cmic hem de Nmic içeriklerinin toprak derinliğine göre istatistiksel farklılık (P<0,05) gösterdiği ortaya çıkmıştır. Ayrıca toprakların organik C ve toplam N içeriği ile Cmic ve Nmic arasında pozitif ve anlamlı bir korelasyonun olduğu belirlenmiştir. Çalışmada elde edilen sonuçlar, toprak derinliğine göre değişen toprak özelliklerinin Cmic ve Nmic içerikleri üzerinde etkili olduğunu göstermektedir.