Larix Decidua Mill Research Articles

Natural Conditions for Heliophilous Tree-Species Following Forest Dieback in Temperate Zone After Periglacial Habitats

Abstract Widespread forest dieback following a series of exceptionally dry seasons has made restoration by relic heliophilous tree-species uncertain. Using logistic regression, we identified conditions suitable for relic Norway spruce (Picea abies /L./Karst.), Scots pine (Pinus sylvestris L.), European larch (Larix decidua Mill.), birches (Betula sp.), poplars (Populus sp.) and willows (Salix sp.) by comparing the relief and bedrock under stands that died abruptly between 2018 and 2020 at temperate zone after periglacial habitats of the Czech Republic. Extent of forest dieback was determined through automated object analysis on the basis of vectorised Planet Scope and Sentinel-2 satellite images. The object analysis consisted of mainly spruce stands and dieback indicated by a deep inter-year decrease in the vegetation indices. The overall occurrence of tree-species in pure or mixed stands was determined from a polygon geodatabase of forest management plans, while growth condition types were determined by overlaying biogeographically subdivided polygons. Dead forests provided suitable conditions for mixed conifer, birch, and poplar stands on 64.4 % of the greywackes, acid metamorphites, and waterlogged sediments on broken plateaus, depressions, and slopes. In comparison, pure stands of relic tree-species can cover 35.6 % of dead forest area. Restoration of mixed forests differenting over a range of growth conditions seems to be suitable for adaptation to climate change impacts.

Temperature-induced germination pulses above the alpine tree line

ABSTRACT Subject to a long research tradition, the tree line is considered an important biogeographic indicator of climate changes and associated range shifts. Realized tree line positions and the potential tree line isotherm are, however, rarely in equilibrium because trees are unable to track rapid temperature variations. Often ignored in tree line research, this dilemma constrains the suitability of tree line trees for understanding alpine vegetation responses to anthropogenic warming. Here, we present combined dendrochronological and wood anatomical assessments of 1,351 seedlings and saplings from three subalpine forest species—larch (Larix decidua Mill.), pine (Pinus cembra L.), and spruce (Picea abies)—collected between ~2,200 and 2,600 m.a.s.l. in the Swiss Alps. We found evidence for temperature-induced, pulse-like seedling germination, rather than a continuous, long-term upward movement. Though the species spread across overlapping elevational ranges, larch was found at the highest elevations, followed by spruce and pine. Surprisingly, we found a varying age structure, with no sign of decreasing age toward higher elevations. Spring and summer temperatures promoted germination pulses, but postgermination survival was likely facilitated by species-specific plant traits. Our study demonstrates the importance of seedling and sapling data from above the tree line to understand prevailing vegetation dynamics at cold temperature extremes and also suggests future tree line advancement in the Swiss Alps.

Population dynamics, feeding strategies, and coccinellid predators of the larch woolly adelgid exules on the European larch

The larch woolly adelgid Adelges laricis Vallot (Hemiptera: Adelgidae) infests spruce Picea spp. and larch Larix spp. in the Northern Hemisphere. The present field and laboratory research embraced the hitherto unknown aspects of the biology and ecology of A. laricis on its secondary host, the European larch Larix decidua Mill. in Poland. The study showed that the A. laricis population on L. decidua was represented by exulis sistens females at dwarf stem bases, exulis progrediens mobile 1st instar nymphs (crawlers) on needles, exulis progrediens sessile “woolly” nymphs and “woolly” adults on needles, and winged sexupara females. The maximum abundance of the A. laricis population occurred from the end of April until mid-May, which coincided with the predomination of crawlers in the age structure of the population. The most important limiting weather component was high rainfall, affecting mainly the crawlers. Eight species of Coccinellidae were recorded on adelgid-infested larch trees and Exochomus quadripustulatus (L.) was the dominant species. The main differences in food consumption strategies among adelgid developmental stages were related to the duration of phloem sap ingestion. While the total duration of sap consumption at a given time was similar in all adelgid instars studied, the individual bouts of sap ingestion were much shorter in crawlers than in the sessile forms. The specific probing behavior of the mobile nymphs probably reflects the crawlers’ strategy to evaluate plant sap quality in different phloem vessels. It is likely that such strategy is a behavioral preadaptation for finding abundant food sources for permanent settling before crawlers develop into sessile nymphs and adult females. The feeding strategy of crawlers promotes the rapid dispersal of the population. Therefore, the control of A. laricis on L. decidua should focus on the early stages of the population development, which would most effectively reduce the final damage.

Изменения дерново-подзолистой почвы в лесных культурах лиственницы европейской за длительный период

The research has been carried out in European larch forest plantations (Larix decidua Mill.) with the recording of changes in their silvicultural effect and the properties of sodpodzolic soil under the canopy of plantations over a period of more than 40 years. The aim of this work is to determine the nature of changes in the morphological and physicochemical properties of soils under the canopy of European larch forest plantations over a long period (45 years) in the conditions of the north-eastern Moscow Region. The research has covered 2 sample plots located in the B2 type of site conditions (simple fresh subor), which corresponds to fresh blueberry pine forests. The first sample plot (permanent sample plot 46) is located in an artificial plantation created in 1871 by planting. As for the second one (permanent sample plot B-2), it is located in forest plantations created in 1870 by sowing. Throughout the entire period of the research, the forest plantations have been growing according to the Ia quality class and have significantly increased the stock of stem wood. In forest plantations of the sample plot 46, the stock increased by 470 m3/ha (the current increase over 42 years of observation has equaled to 11.2 m3/ha per year), and in forest plantations of the sample plot B-2 – by 417 m3/ha (the current increase over 41 years of observations has equaled to 10.2 m3/ha per year). This indicates that there is currently no decay in the cultivated stands: they function successfully up to a century and a half old. Over 45 years, there have been changes in the morphological and physicochemical properties of the soil. A decrease in the content of the clay fraction has been established, especially in the upper part of the soil profile. The actual, exchange and hydrolytic acidity of the soil have increased as indicators of the ongoing process of podzolization. At the same time, the thicknesses of the forest floor and the humus content in the humus-eluvial layer have risen. The absorption capacity, the content of the exchange bases and the degree of saturation with the bases have increased, especially in the upper horizons of the soil, and the hydrolytic acidity has risen. In general, over a 45-year period, there has been no significant deterioration in the properties of sod-podzolic soils under the canopy of European larch forest plantations, and there are even trends of improvement in some indicators.

Revising Alpine summer temperatures since 881 CE

Europe experienced severe heat waves during the last decade, which impacted ecological and societal systems and are likely to increase under projected global warming. A better understanding of pre-industrial warm-season changes is needed to contextualize these recent trends and extremes. Here, we introduce a network of 352 living and relict larch trees (Larix decidua Mill.) from the Matter and Simplon valleys in the Swiss Alps to develop a maximum latewood density (MXD) chronology calibrating at r = 0.8 (p > 0.05, 1901–2017 CE) against May–August temperatures over Western Europe. Machine learning is applied to identify historical wood samples aligning with growth characteristics of sites from elevations above 1900 m asl to extend the modern part of the chronology back to 881 CE. The new Alpine record reveals warmer conditions in the tenth century, followed by an extended cold period during the late Medieval times, a less-pronounced Little Ice Age culminating in the 1810s, and prolonged anthropogenic warming until present. The Samalas eruption likely triggered the coldest reconstructed summer in Western Europe in 1258 CE (-2.32 °C), which is in line with a recently published MXD-based reconstruction from the Spanish Pyrenees. Whereas the new Alpine reconstruction is potentially constrained in the lowest frequency, centennial timescale domain, it overcomes variance biases in existing state-of-the-art reconstructions and sets a new standard in site-control of historical samples and calibration/ verification statistics.

Distribution of exchangeable Ca2+ during the process of Larix decidua Mill. pollination and germination

The involvement of Ca2+ ions in angiosperms sexual processes is well established, while in gymnosperms, such knowledge remains limited and is still a topic of discussion. In this study, we focused on Larix decidua, using Alizarin-red S staining and the pyroantimonate method to examine the tissue and subcellular distribution of free and loosely bound Ca2+ ions at different stages of the male gametophyte's development and its interaction with the ovule. Our findings show that in larch, both the germination of pollen grains and the growth of pollen tubes occur in an environment rich in Ca2+. These ions play a crucial role in the adhesion of the pollen grain to the stigmatic tip and its subsequent movement to the micropylar canal. There is a significant presence of free and loosely bound Ca2+ ions in both the fluid of the micropylar canal and the extracellular matrix of the nucellus. As the pollen tube extends through the nucellus, we observed a notable accumulation of Ca2+ ions just above the entry to the mature archegonium, a region likely crucial for the male gametophyte's directional growth. Meanwhile, the localized presence of free and loosely bound Ca2+ ions within the egg cell cytoplasm may inhibit the pollen tubes growth and rupture, playing an important role in fertilization.

Monitoring of the phytosanitary condition of Larix decidua Mill. plants in the Modryna tract of the Zviahel Forestry branch of the State Enterprise Forests of Ukraine

Phytosanitary monitoring of forest stands is currently a relevant and important area of scientific research that ensures observation, assessment, and forecasting of the dynamics (changes) of the quantitative and qualitative (including sanitary) state of forests and underlies the development of an effective system of tree protection. The purpose of this study was to identify the species composition and distribution of dominant phytopathogen species in the Modryna tract of the Zvyagelske Forestry branch and to identify the primary factors of Larix decidua Mill. decline. This study employed phytopathological, entomological, forest inventory, and comparative methods. The study identified and registered typical symptoms of damage and the consequences of the harmful effects of pests of L. decidua trees in the Modryna tract, leading to a general weakening of their sanitary condition. Symptoms of larch needle cast (meria needle blight) and browning were recorded on the needles; on the trunks – typical manifestations of cankers and fruiting bodies of a unique basidiomycete – Lariciphomes officinalis. Apart from infectious pathologies, sporadic wind and storm damaged larch trees, as well as other negative effects of wind exposure, were recorded in the study areas. The species composition of the pests of the surveyed larch trees included the following insect species: Cephalcia lariciphila, Sacchiphantes viridis Ratz., Coleophora laricella, Zeiraphera diniana Gn., Lasiomma laricicola Karl. It was generalised that the main threat to the centuries-old larch trees is the complex effect of anthropogenic, abiotic, and biotic (including parasitic) environmental factors that constantly and to varying degrees affect the sanitary and physiological state of ancient larch trees. The findings of this study provide information for predicting the risks of spreading pathogens and pests, which allows managing these risks and preventing their further spread

Characterization of Larix decidua Mill. (Pinaceae) oleoresin's essential oils composition using GC-MS.

Larch oleoresin has been described regarding several biological activities and medicinal applications, such as wound healing and treatment of ulcers, but little is known about its chemical composition. Eight oleoresins from Larix decidua Mill. obtained from four companies and one adulterated control were therefore investigated to determine their content of essential oils and to verify possible differences in their composition in relation to the harvest and manufacturing processes. Essential oils (EOs) were isolated by distillation and the yield was analysed. The yield of EO varied among all samples. The yield of the pure larch samples covered a range of 7.8% to 15.5%. A higher yield (19.0%) was observed for adulterated control, which contained oleoresins from different Pinaceae trees. Age of samples had no impact on yield. However, there was a significant statistical variation (p<0.05) in the yields of the mid-summer oleoresins (>10%) compared to early or late summer (<10%), emphasising the importance of the time of collection. Samples were subsequently analysed by GC-MS. EO samples confirmed the presence of various chemical classes, such as monoterpenes, sesquiterpenes, and diterpenes. α-pinene was the compound with the highest concentrations (>50%), followed by β-pinene (>6%), D-limonene (>2.5%), α-terpineol (>0.9%), β-myrcene (>0.2%), and 3-carene (>0.05%). Samples were grouped using multivariate data analysis (MVDA) with respect to the chemical variation between the oleoresins' EOs. The resulting four clusters were named low (low yield obtained for the samples), mixed (mixed oleoresin from different Pinaceae species, adulteration control), old (old oleoresin kept in the institute), and normal (other oleoresins) samples, each presenting distinct chemical biomarkers. There were considerable differences between site and time of collection. Essential oil yield did not always meet requirements as defined by the German Homeopathic Pharmacopoeia. In addition, adulterated or aged samples could be identified as compared to pure and fresh larch oleoresins. We conclude that larch oleoresin used for pharmaceutical applications has to be carefully analysed and standardised to guarantee reproducible product quality.

Nová paleobotanická data prokazují původní status modřínu opadavého (Larix decidua Mill.) v severních Čechách

Using pollen analysis, phytolith analysis and radiocarbon dating of newly discovered sedimentary archives, here we prove the native status of European larch (Larix decidua Mill.) in two sandstone rocky areas of north Bohemia (Czech Republic). At the end of the Last Ice Age and at the beginning of the Holocene, European larch was relatively common in Central Europe. In most critical period of the Middle Holocene, it demonstrably retreated to exposed rocky habitats, but did not become completely extinct. In the form of relict populations, it survived locally until the modern era, when non-native larch types were artificially introduced into managed forest stands. Our findings call for a radical rethinking of the approach to larch by both foresters and nature conservation authorities. In the future, it is primarily necessary to search for and protect the remnants of its original gene pool.

Je modřín opadavý v Nízkém Jeseníku opravdu jesenický? Pohled molekulárních metod

European larch (Larix decidua Mill.) is an important tree species commonly used in managed forests of central Europe. However, its genetic structure, post-glacial range dynamics, and consequent nativity status are poorly understood. Here we provide the first study focusing on the genetic structure of in situ larch populations in the north-eastern Czech Republic using molecular genetics. Most of the studied area is traditionally considered to be a part of the autochthonous native range of the Jeseníky lineage of larch and some of the included populations are protected as belonging to this type. We confirm a common presence of the Jeseníky type and its close evolutionary relation with larch populations from both the Carpathians and Poland. However, we also found important levels of admixture of genetic material from the Alps in all of the analyzed populations. The highest amount of Alpine admixture was found in the populations of intensively managed forests, the proportion of non-native material in the protected areas was relatively lower but still significant. Our results show the importance of populationgenetic research for practical conservation of local populations and lineages even for common species.

Adaptation of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. to environmental stress caused by tailings waste highly contaminated by trace elements

The seedlings of some tree species can successfully develop in areas polluted by heavy metals. Research on such species is important in order to explore the possibility of introducing tree species for the permanent biological stabilization and reclamation of post-flotation tailings, especially after the final recycling of trace metals, but where concentrations remain much higher than in natural soils. To better understand the adaptation and reaction of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. seedlings to heavy metals pollution caused by tailings waste highly contaminated by trace elements: 1) the relationships between the concentration of heavy metals in the soil substrate, the efficiency of heavy metal ions accumulation in plant organs, and the biometric parameters of the seedlings; and 2) the threshold content of heavy metals in the roots above which the plant physiological response is triggered was determined. We assume that there are certain limit concentrations of heavy metals in the soil and fine roots, which depend on the tree species and beyond which the plant responds strongly to stressThe obtained results showed that Betula is a suitable species for the phytostabilization of post-flotation tailings due to its rapid growth rate and production of root biomass. The accumulation of metals in Betula roots was found to be much greater than in Pinus and Larix. Despite the high concentrations of heavy metals in the prepared substrates, there was only a slight transfer of these elements to the aboveground parts of the plant. At high soil concentrations, the heavy metals adversely affected the cellular and physiological processes of plants. In plants growing in such conditions, the activity of the antioxidant system depended both on the species and organ of the plant, as well as on the type and metal concentration.

Some aspects of the methodological approach in the progeny testing of European larch in Poland

Abstract In Poland, the tree improvement programme was initiated in 2004, but the trials for European larch (Larix decidua Mill.) did not start until 2021. Our aim is to present certain aspects of the methodological approach of progeny testing for this species. The European larch, known for its rapid growth among native coniferous trees in Europe, holds great promise for forest breeding. Unfortunately, its natural range in Poland is limited, with rare but well-known valuable provenances. In 2023, six progeny tests were established using the same 130 open-pollinated families, derived from plus trees originating from valuable seed regions (Md51, Md61, Md71) and areas below 52° N latitude. After a decade of growth, the results will be used to identify valuable genotypes and establish advanced-generation seed orchards.

European larch sapwood: A model for predicting the cambial age and for a more accurate dating

European larch (Larix decidua Mill.) holds significant importance as a forest tree species throughout the Alps and in certain regions of central Europe. Its extensive use as construction timber has made it a subject of substantial interest in dendroarchaeological studies aimed at understanding the long-term interactions between human societies and forests. Precise dating of felling phases, accurate estimation of the age of harvested wood, and information on the geographical origin of wood play a crucial role when it comes to characterize these interactions. In this study, we compiled a large dataset of L. decidua samples from across the European Alps to provide a robust statistical model that predicts the cambial age of L. decidua trees based on the number of heartwood rings. By extension, this model can be used to estimate the number of sapwood rings so as to approximate the felling date and to more precise date archaeological larch timber. The model requires almost complete heartwood sequences (<5 missing rings) to achieve accurate estimations. Our results also evidence that the ratio between the number of sapwood and heartwood rings varies across the Alps. At the same time, the indicator developed in this work is not suitable for a determination of wood origin, raising doubts about the effectiveness of attempts aimed at dendroprovenancing L. decidua based on sapwood.

Application of Additive Manufacturing Technology for Chair Parts Connections

Additive manufacturing (AM) is a potential technology to be applied for replacing wood joints in the furniture industry. Overall, 3D-printed connectors have a lot of advantages in chair construction: the possibility of improving the design by using colored materials and new concepts with no limits of shape and size, avoiding the use of synthetic materials such as adhesives and finishing materials. The present research shows the results of the research conducted on 3D-printed connectors for a chair leg-stretchers joint. Larch (Larix decidua Mill.) wood was used for chair components and selective laser sintering (SLS) technology was employed for the 3D-printing connector designed to assemble the chair elements. Diagonal tensile and compression tests were performed on the L-type joints with 3D-printed connectors and the bending moments were determined and compared to the results obtained after testing the leg-stretchers mortise–tenon joints made of larch wood, taken as a reference. Micrograph investigation was finally performed on the broken areas of the 3D-printed connectors as a result of mechanical testing failures. The results show that the SLS printing technology applied to build the connector does not ensure enough strength to the assembly, and changes in printing parameters are needed for further research, in terms of laser power and scan speed.

Representation of the genus Larix Mill. in the protected areas of Ukrainian Polissia

Larix decidua Mill. may become more important than Picea abies (L.) Karst for reforestation and restoration of the natural balance, and therefore it is necessary to investigate this species. Therefore, the purpose of this study was to conduct an inventory of Larix taxa in the protected areas of the mixed forest zone of Ukrainian Polissia, to analyse their distribution, age structure, and use. Research methods used: route, analytical, comparative analysis, systematisation. It was found that 5 species, one variety and two hybrids of larch grow in the protected areas of the mixed forest zone of Ukraine. It was established that L. decidua is the most widespread – it grows in parks-monuments of landscape art, natural monuments, protected tracts, reserves in pure mixed plantings, alleys, row plantings, groups and as a solitaire tree. L. sibirica, L. kaempferi grow as solitaire trees and in groups of 3 to 10 specimens in 9 and 10 protected objects, respectively. L. gmelinii is present in two arboretums, L. laricina – in one. Larix decidua var. polonica (Racib. ex Wóycicki) Ostenf. &amp; Syrach is not widespread, represented in groups in 6 parks-monuments of landscape art and Bereznivskyi denrorark. Larix × eurolepis A. Henry. is widespread in pure and mixed stands, grows in an alley in the Slavianskyi park-monument of landscape art, in groups – in the Lisova Aleia Botanical Reserve, Bereznivskyi denrorark, and in mixed stands of the Riznolissia General Zoological Reserve. The age structure is quite diverse, represented by L. decidua, L. sibirica, L. decidua var. polonica aged from 100 to 200 years. Other species, varieties, and hybrids are represented by specimens aged from 3 years (L.×eurolepis) to 80 years (L. kaempferi). 69.2% of larch stands are in good condition, 28.9% are in satisfactory condition, and only 1.9% are in poor condition. The results of the research can be used in the further creation of pure and mixed stands, alleys, etc. in the mixed forest zone

Genetic Characterisation and Core Collection Construction of European Larch (Larix decidua Mill.) from Seed Orchards in Romania

European larch (Larix decidua L.) is an important forest tree species, with a large range and genetic variability; however, little is known about the characterisation of its genetic structure and diversity based on molecular markers in seed orchards, and no core collection—an improved tool for managing germplasm—has been developed for this species to date. In the present study, we employed nSSR molecular markers to characterise the genetic diversity and structure of five seed orchards and to construct a core collection for further use in breeding programmes. The results indicate that the values of heterozygosity in the seed orchards were slightly higher than the averages obtained in natural populations. The seed orchards displayed heterozygote deficiency, similar to other studies in Larix decidua or other Larix spp., which can be associated with a strong selective pressure on populations in a highly fragmented area. The presence of clones of autochthonous origin increased the allelic richness in the seed orchards where they were found. The degree of differentiation between individuals within the seed orchards was similar to that of populations originating from the Tyrolean Alps and Southern Carpathians (11.03% vs. 13% in the present study). The assignment, which was based on clustering, did not always match with the passport data (i.e., provenance), and we found that clones originating from stands from the northern Romanian Carpathians are distinct from the stands of the southern region, and most probably originated from a centre other than the Tyrolean Alps. The final extracted core collection (50 entries, 28% sampling effort) increases the rate of allele preservation, incorporates every allele from the entire collection, and provides candidate resources for the enhanced breeding of larch. The genetic characterisation of these germplasms will be essential for future breeding tasks, as well as for the preservation of valuable genotypes or populations.

Динамика радиальных приростов лиственницы европейской (Larix decidua Mill.) в условиях антропогенной нагрузки

The results of a dendrochronological analysis of the European larch (Larix decidua Mill.) forest plantations growth in the zone of influence of motor transport pollution in the territory near the Moscow Ring Road at a distance of 8 and 18 m from the roadbed and in a recreational plantation in the third stage of digression are presented. The influence of these factors at the age of European larch from 5 to 65 years was revealed. It has been established that in plantations near the Moscow Ring Road, the annual radial growth of European larch wood is on average 45 %, in a plantation with a recreational load it makes up 62 % of the increase in the control plot, remote from highways and settlements. Differences in annual increments are statistically significant throughout the entire observation period. The average long-term growth of wood at a distance of 8 m from the Moscow Ring Road is 34 % lower than at a distance of 18 m. With an increase in the distance from the roadbed by 1 m, the annual growth of wood increases by 0,2 mm. In forest plantations of European larch, growths of early wood predominate: in areas near the Moscow Ring Road — an average of 68 % of the annual growth, in a plantation with a recreational load — 63 %, in the control plot — only 49 %.

Effects of the cascading translocations of larch (Larix decidua Mill.) on canker disease due to Lachnellula willkommii (R. Hartig) Dennis

Key messageAppropriate silvicultural practices combined with the use of resistant Central European provenances can reduce the prevalence of larch canker caused by Lachnellula willkommii (R. Hartig) Dennis, a major disease affecting larch plantations in France. However, cascading translocations have resulted in frequent admixture in European larch (Larix decidua Mill.) and subsequent certification errors regarding the origin of plant material. Our study highlights the urgent need to improve the certification process of seed orchards.ContextThe recent history of European larch has been marked by translocations of plant stock within and beyond its native range. In order to increase stand resistance to larch canker disease, it is strongly recommended by French authorities to plant Central European provenances. However, a recent disease outbreak questioned the resistance of Central European provenances and the origin of the forest material used in these plantations.AimsOur goal was to assess the effects of cascading translocations and mixing between larch gene pools on genetic composition of plantations and on their vulnerability to the disease.MethodsIn the outbreak area, we checked the genetic origin of the trees and we estimated the percentage of Central European trees, disease prevalence and severity.ResultsIntra-site genetic diversity was high. Genetic composition did not match with geographic origin certificates. A high proportion of trees could not be assigned to either the Alpine or Central European gene pools. These admixed trees were as resistant as Central European trees. Geographic origin turned out to be one of the main drivers of canker prevalence, along with abiotic factors.ConclusionWe need a precise knowledge of the origin of material used in seed orchards to mitigate canker disease and adapt forests through assisted migration.

Combining Tree-Ring Width and Density to Separate the Effects of Climate Variation and Insect Defoliation

Though frequently used in dendroclimatology, European larch (Larix decidua Mill.) is regularly defoliated by mass outbreaks of the larch budmoth (Zeiraphera griseana Hb., LBM). The near-cyclic growth depressions are unrelated to but possibly coincide with cold summers, which challenges signal detection on interannual timescales. LBM defoliation events cause sharp maximum latewood density declines and irregular earlywood/latewood ratios in the outbreak year, followed by one or two anomalously narrow rings. Here, we present a process-based method integrating these diverse response patterns to identify and distinguish LBM-related signals from climate-induced deviations. Application to larch sites along elevational transects in the Swiss Alps reveals the algorithm to perform better than existing extreme event detection methods, though our approach enables additional differentiation between insect- and climate-induced signatures. The new process-based multi-parameter algorithm is a suitable tool to identify different causes of growth disturbances and will therefore help to improve both tree-ring-based climate and insect defoliation reconstructions.

Competition-based mortality and tree losses. An essential component of net primary productivity

Even-aged stands can regenerate with many thousand seedlings per hectare before the density declines to just a few hundred trees per hectare 100 years later; management practices can lead to even lower tree numbers due to quality selection and thinning. In other words, during the development of unmanaged stands, the majority of individuals die naturally due to competition. Despite the far-reaching consequences for structural and genetic diversity, dead wood and fuel wood accumulation, we have only limited quantitative knowledge about the continuous mortality of trees and the wood volume loss over longer timespans.For this study, we used a unique set of 476 unmanaged, monospecific experimental plots of Norway spruce (Picea abies (L.) H. Karst.), silver fir (Abies alba Mill.), Scots pine (Pinus sylvestris L.), European larch (Larix decidua Mill.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)), European beech (Fagus sylvatica L.), and oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) throughout Europe to analyze the competition-based mortality of trees and its dependency on age and site conditions.First, we show that the total stem volume production, standing stock, and mortality were continuously increasing until an age of 100–150 years. The accumulated competition-caused stem volume loss at that age amounted to 500–1000 m3 ha−1.Second, the net growth of the stands (share of the growth that is accumulated in the standing stock) strongly decreased with increasing age even when the gross growth was still high. The proportion of the net growth versus gross growth continuously decreased with increasing age regardless of site quality.Third, we show a degressive decrease of the annual relative tree number mortality rates from 0.05 to 0.20 in young down to 0.01–0.02 in mature stands. For some species, we found these rates to be site dependent with different directions of the site effect. The interplay of decreasing mortality rates and increasing average volume of the dead trees resulted in unimodal mortality curves over time of the annual mortality, peaking at 3–12 m3 ha−1 yr−1 at ages of about 75–150 years.Over the whole rotation, the average annual biomass loss from mortality ranged between 0.8 and 2.1 t ha−1 yr−1 with a carbon content of 0.4–1.1 t C ha−1 yr−1. We discuss the relevance of the results for measuring, understanding, modelling, and managing forest stands. Our results reveal that the withdrawal of forest management and setting aside (previously managed) forests over a rotation time of 100–150 years means that about one third of the total production in monospecific stands would flow to the debris pool rather than being exploited for carbon sequestration and related emission savings in harvested wood products. The mortality related loss fractions of above ground biomass we quantified in this study indicate the trade-off between wood production and setting aside forest to allow deadwood accumulation and associate changes in biodiversity.