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Leader of the development of tree breeding program for main commercial tree species in Latvia, now being implemented in practice, producing seed material for regeneration of ⁓10000 ha annually. Currently main research topics are related to forest adaptation (natural disturbances: wind and fire) – development of forest wind resistance models and recommendations for establishment and management of resilient stands. Assessment and modelling of carbon balance in old-growth forest and forest originating from improved plant material. Associated professor in Forestry faculty, director of Forestry PhD program.
The productivity of forests has been linked to the sensitivity of tree growth to meteorological conditions and their fluctuations, hence moderation of tree sensitivity is one of the goals for climate-smart forest management. For this, tree breeding is among the most effective means, particularly if breeding populations are supplemented with genotypes (provenances) adapted to the expected climates. Nonetheless, heritability of traits is essential for their improvement by breeding. In this study, heritability of growth sensitivity of south-eastern Baltic provenances of Scots pine differing by field performance to meteorological conditions was assessed combining methods of quantitative genetics and dendrochronology. Five parallel provenance trials within the south-eastern Baltic region were investigated. The effects of regional weather drivers of growth (moisture regime in summer, temperature regime in preceding summer and in the dormancy period) were estimated, yet their strengths differed among the provenances, indicating local specialization of metapopulations of Scots pine. The heritability of growth sensitivity to these factors ranged from low to moderate, similarly as observed for the morphometric traits within the region; however, the provenance (genetic) variation appeared to be higher. The differences in heritability of responses, however, indicated uneven adaptive significance of weather conditions. Although the estimates were based on a limited set of genotypes implying caution in the extrapolation of results, the weather-growth relationships and their heritability indicate that sensitivity of growth is a complementary trait aiding breeding of forest reproductive material best suited for future climates. Heritable weather-growth relationships also imply a high potential for forest breeding to moderate the sensitivity of the trees.
Roberts Matisons; Volker Schneck; Diāna Jansone; Endijs Bāders; Stefānija Dubra; PaulS Zeltiņš; Āris Jansons. South-Eastern Baltic Provenances of Scots Pine Show Heritable Weather-Growth Relationships. Forests 2021, 12, 1101 .
AMA StyleRoberts Matisons, Volker Schneck, Diāna Jansone, Endijs Bāders, Stefānija Dubra, PaulS Zeltiņš, Āris Jansons. South-Eastern Baltic Provenances of Scots Pine Show Heritable Weather-Growth Relationships. Forests. 2021; 12 (8):1101.
Chicago/Turabian StyleRoberts Matisons; Volker Schneck; Diāna Jansone; Endijs Bāders; Stefānija Dubra; PaulS Zeltiņš; Āris Jansons. 2021. "South-Eastern Baltic Provenances of Scots Pine Show Heritable Weather-Growth Relationships." Forests 12, no. 8: 1101.
European aspen deadwood is extensively studied as a habitat for saproxylic species, while less is known of its dynamics and role in carbon sequestration. We studied unmanaged mature (41–60 years), moderately overmature (61–80 years), overmature (81–100 years), and old-growth (101–140 years) and managed mature and moderately overmature aspen stands on fertile mineral soils. In unmanaged stands, marginal mean CWD volume was from 67.3 ± 12.1 m3 ha−1 in moderately overmature to 92.4 ± 5.1 m3 ha−1 in old-growth stands, with corresponding marginal mean CWD carbon pool 8.2 ± 1.6 t ha−1 and 12.5 ± 0.7 t ha−1 (all p > 0.05), respectively. High CWD volume was present in most stands, by at least two-thirds of plots comprising more than 20 m3 ha−1, and about half of CWD was larger than 30 cm in diameter. Changes in CWD species composition toward a higher proportion of deciduous deadwood in old-growth stands, together with a high volume of recently dead trees, suggest early senescence of the dominant aspen cohort.
Silva Šēnhofa; Guntars Šņepsts; Kārlis Bičkovskis; Ieva Jaunslaviete; Līga Liepa; Inga Straupe; Āris Jansons. Availability and Structure of Coarse Woody Debris in Hemiboreal Mature to Old-Growth Aspen Stands and Its Implications for Forest Carbon Pool. Forests 2021, 12, 901 .
AMA StyleSilva Šēnhofa, Guntars Šņepsts, Kārlis Bičkovskis, Ieva Jaunslaviete, Līga Liepa, Inga Straupe, Āris Jansons. Availability and Structure of Coarse Woody Debris in Hemiboreal Mature to Old-Growth Aspen Stands and Its Implications for Forest Carbon Pool. Forests. 2021; 12 (7):901.
Chicago/Turabian StyleSilva Šēnhofa; Guntars Šņepsts; Kārlis Bičkovskis; Ieva Jaunslaviete; Līga Liepa; Inga Straupe; Āris Jansons. 2021. "Availability and Structure of Coarse Woody Debris in Hemiboreal Mature to Old-Growth Aspen Stands and Its Implications for Forest Carbon Pool." Forests 12, no. 7: 901.
The increased removal of forest-derived biomass with whole-tree harvesting (WTH) has raised concerns about the long-term productivity and sustainability of forest ecosystems. If true, this effect needs to be factored in the assessment of long-term feasibility to implement such a drastic forest management measure. Therefore, the economic performance of five experimental plantations in three different forest types, where in 1971 simulated WTH event occurred, was compared with pure, planted and conventionally managed (CH) Norway spruce stands of similar age and growing conditions. Potential incomes of CH and WTH stands were based on timber prices for period 2014–2020. However, regarding the economics of root and stump biomass utilization, they were not included in the estimates. In any given price level, the difference of internal rate of return between the forest types and selected managements were from 2.5% to 6.2%. Therefore, Norway spruce stands demonstrate good potential of independence regardless of stump removal at the previous rotation.
Iveta Desaine; Annija Kārkliņa; Roberts Matisons; Anna Pastare; Andis Adamovičs; Zane Lībiete; Āris Jansons. Imitated Whole Tree Harvesting Show Negligible Effect on Economic Value of Spruce Stands. Forests 2021, 12, 841 .
AMA StyleIveta Desaine, Annija Kārkliņa, Roberts Matisons, Anna Pastare, Andis Adamovičs, Zane Lībiete, Āris Jansons. Imitated Whole Tree Harvesting Show Negligible Effect on Economic Value of Spruce Stands. Forests. 2021; 12 (7):841.
Chicago/Turabian StyleIveta Desaine; Annija Kārkliņa; Roberts Matisons; Anna Pastare; Andis Adamovičs; Zane Lībiete; Āris Jansons. 2021. "Imitated Whole Tree Harvesting Show Negligible Effect on Economic Value of Spruce Stands." Forests 12, no. 7: 841.
To identify general patterns in the effect of climate-driven changes in the outbreak frequency of forest defoliating species, we examined 60 years of records (1950–2010) of outbreaks of five defoliating species. Data on Lymantria dispar, Lymantria monacha, Bupalus piniarius, Panolis flammea, and Operophtera brumata from five Central European countries (Slovakia, Czech Republic, Austria, Hungary, and Germany), where the current climate is comparable with the projections of climate for the Eastern Baltic region by the end of the 21st century, were analyzed. Time series approach was applied to estimate the linkage between outbreaks and climate warming. Mean annual, summer, and winter deviations for the period of 1850 to 1900 were assessed as proxies of warming. To estimate the legacy effect, warming proxies were lagged by one year. Among those tested, warming proxies showed a linkage with outbreaks. Three significant outbreaks occurred in the analyzed period (at the beginning and end of the period). During the middle part of the analyzed period, the frequency and magnitude of outbreaks were low, implicating a higher insect outbreak risk with warming in Central Europe. In the latter part of the analyzed period, more frequent yet smaller outbreaks occurred, which supports the outbreak linkage with one-year lag, summer, and annual temperatures.
Ingars Siliņš; Annija Kārkliņa; Olga Miezīte; Āris Jansons. Trends in Outbreaks of Defoliating Insects Highlight Growing Threats for Central European Forests, and Implications for Eastern Baltic Region. Forests 2021, 12, 799 .
AMA StyleIngars Siliņš, Annija Kārkliņa, Olga Miezīte, Āris Jansons. Trends in Outbreaks of Defoliating Insects Highlight Growing Threats for Central European Forests, and Implications for Eastern Baltic Region. Forests. 2021; 12 (6):799.
Chicago/Turabian StyleIngars Siliņš; Annija Kārkliņa; Olga Miezīte; Āris Jansons. 2021. "Trends in Outbreaks of Defoliating Insects Highlight Growing Threats for Central European Forests, and Implications for Eastern Baltic Region." Forests 12, no. 6: 799.
Norway spruce (Picea abies (L.) H. Karst.) is predicted to decrease its abundance in the Eastern Baltic region as a result of climatic changes, and this process is already explicit at the southern limit of species lowland distribution. Still, there are uncertainties about the growth potential of Norway spruce within the region due to the plasticity of local populations. In this regard, an assessment of regional weather–growth responses, assuming a nonlinearity of the ecological relationship, can aid in the clarification of uncertainties regarding growth. Nonlinear regional weather–growth relationships for Norway spruce were assessed based on tree-ring widths from 22 stands spreading from Southern Finland to Northern Germany using dendrochronological methods and a generalized additive mixed model. Temporal and spatial stationarity of local linear weather–growth relationships was evaluated. Considering the drought sensitivity of Norway spruce, meteorological variables related to the summer moisture regime were the main predictors of radial increment, though conditions in winter and spring had complementary effects. Generally, the linear weather–growth relationships were spatially and temporary nonstationary, with some exceptions in Poland and Northern Germany. Explicit local specifics in the linear weather–growth relationships, which are common in the marginal parts of species’ distribution, were observed in Estonia, Latvia, and Poland. The estimated regional weather–growth relationships were mostly nonlinear, implying disproportional responses to climatic changes, particularly to intensifying drought conditions across the studied climatic gradient. Still, the responses to winter temperature suggested that warming might contribute to growth. The estimated linear and nonlinear growth responses indicate strict limitation by drought conditions, implying reductions of increment due to climatic changes southward from Latvia, suggesting the necessity for proactive management. Nevertheless, in the northern part of the analyzed region, the projected climatic changes appear favorable for growth of Norway spruce in the near future.
Roberts Matisons; Didzis Elferts; Oskars Krišāns; Volker Schneck; Holger Gärtner; Tomasz Wojda; Jan Kowalczyk; Āris Jansons. Nonlinear Weather–Growth Relationships Suggest Disproportional Growth Changes of Norway Spruce in the Eastern Baltic Region. Forests 2021, 12, 661 .
AMA StyleRoberts Matisons, Didzis Elferts, Oskars Krišāns, Volker Schneck, Holger Gärtner, Tomasz Wojda, Jan Kowalczyk, Āris Jansons. Nonlinear Weather–Growth Relationships Suggest Disproportional Growth Changes of Norway Spruce in the Eastern Baltic Region. Forests. 2021; 12 (6):661.
Chicago/Turabian StyleRoberts Matisons; Didzis Elferts; Oskars Krišāns; Volker Schneck; Holger Gärtner; Tomasz Wojda; Jan Kowalczyk; Āris Jansons. 2021. "Nonlinear Weather–Growth Relationships Suggest Disproportional Growth Changes of Norway Spruce in the Eastern Baltic Region." Forests 12, no. 6: 661.
Forests are the dominant land cover in Nordic–Baltic countries, and forestry, the management of forests for improved ecosystem-service (ES) delivery, is an important contributor to sustainability. Forests and forestry support multiple United Nations Sustainability Goals (UN SDGs) and a number of EU policies, and can address conflicting environmental goals. Forests provide multiple ecosystem services and natural solutions, including wood and fibre production, food, clear and clean water and air, animal and plant habitats, soil formation, aesthetics, and cultural and social services. Carbon sequestered by growing trees is a key factor in the envisaged transition from a fossil-based to a biobased economy. Here, we highlight the possibilities of forest-based solutions to mitigate current and emerging societal challenges. We discuss forestry effects on forest ecosystems, focusing on the optimisation of ES delivery and the fulfilment of UN SDGs while counteracting unwanted effects. In particular, we highlight the trilemma of (i) increasing wood production to substitute raw fossil materials, (ii) increasing forest carbon storage capacity, and (iii) improving forest biodiversity and other ES delivery.
Lars Högbom; Dalia Abbas; Kęstutis Armolaitis; Endijs Baders; Martyn Futter; Aris Jansons; Kalev Jõgiste; Andis Lazdins; Diana Lukminė; Mika Mustonen; Knut Øistad; Anneli Poska; Pasi Rautio; Johan Svensson; Floor Vodde; Iveta Varnagirytė-Kabašinskienė; Jan Weslien; Lars Wilhelmsson; Daiga Zute. Trilemma of Nordic–Baltic Forestry—How to Implement UN Sustainable Development Goals. Sustainability 2021, 13, 5643 .
AMA StyleLars Högbom, Dalia Abbas, Kęstutis Armolaitis, Endijs Baders, Martyn Futter, Aris Jansons, Kalev Jõgiste, Andis Lazdins, Diana Lukminė, Mika Mustonen, Knut Øistad, Anneli Poska, Pasi Rautio, Johan Svensson, Floor Vodde, Iveta Varnagirytė-Kabašinskienė, Jan Weslien, Lars Wilhelmsson, Daiga Zute. Trilemma of Nordic–Baltic Forestry—How to Implement UN Sustainable Development Goals. Sustainability. 2021; 13 (10):5643.
Chicago/Turabian StyleLars Högbom; Dalia Abbas; Kęstutis Armolaitis; Endijs Baders; Martyn Futter; Aris Jansons; Kalev Jõgiste; Andis Lazdins; Diana Lukminė; Mika Mustonen; Knut Øistad; Anneli Poska; Pasi Rautio; Johan Svensson; Floor Vodde; Iveta Varnagirytė-Kabašinskienė; Jan Weslien; Lars Wilhelmsson; Daiga Zute. 2021. "Trilemma of Nordic–Baltic Forestry—How to Implement UN Sustainable Development Goals." Sustainability 13, no. 10: 5643.
The dieback of common ash (Fraxinus excelsior L.) has dramatically decreased the abundance of the species in Europe; however, tolerance of trees varies regionally. The tolerance of trees is considered to be a result of synergy of genetic and environmental factors, suggesting an uneven future potential of populations. This also implies that wide extrapolations would be biased and local information is needed. Survival of ash during 2005–2020, as well as stand- and tree-level variables affecting them was assessed based on four surveys of 15 permanent sampling plots from an eastern Baltic region (Latvia) using an additive model. Although at the beginning of dieback a relatively low mortality rate was observed, it increased during the 2015–2020 period, which was caused by dying of the most tolerant trees, though single trees have survived. In the studied stands, ash has been gradually replaced by other local tree species, though some recruitment of ash was locally observed, implying formation of mixed broadleaved stands with slight ash admixture. The survival of trees was related to tree height and position within a stand (relative height and local density), though the relationships were nonlinear, indicating presence of critical conditions. Regarding temporal changes, survival rapidly dropped during the first 16 years, stabilizing at a relatively low level. Although low recruitment of ash still implies plummeting economic importance of the species, the observed responses of survival, as well as the recruitment, imply potential to locally improve the survival of ash via management (tending), hopefully providing time for natural resistance to develop.
Ilze Matisone; Roberts Matisons; Āris Jansons. The Struggle of Ash—Insights from Long-Term Survey in Latvia. Forests 2021, 12, 340 .
AMA StyleIlze Matisone, Roberts Matisons, Āris Jansons. The Struggle of Ash—Insights from Long-Term Survey in Latvia. Forests. 2021; 12 (3):340.
Chicago/Turabian StyleIlze Matisone; Roberts Matisons; Āris Jansons. 2021. "The Struggle of Ash—Insights from Long-Term Survey in Latvia." Forests 12, no. 3: 340.
The anticipated increase in extreme disturbance events due to climate change is likely to expose Norway spruce (Picea abies (L.) Karst.) dominated forests in northern Europe to new conditions. Empirical data on the resilience of such natural (unmanaged) forests to disturbance and the long-term patterns of regeneration in its aftermath are currently scarce. We performed a quantitative assessment of natural forest stands in north–western Latvia to identify and characterise the patterns of stand structure 44 years after a stand-replacing disturbance and investigated the effects of legacies on regeneration. The spatial distribution of tree species and their dimensions were assessed in 71 circular sample plots (500 m2 each) in natural forest areas, where Norway spruce dominated prior to the windthrow and salvage logging was not carried out. Spatial indices (species mingling index, size differentiation index, and aggregation index) were used to characterise stand structure and diversity. The different initial states (age and coverage of surviving trees) of stands affected eventual tree species dominance, size differentiation, degree of mingling and aggregation. Our results demonstrate a close relationship between disturbance legacies and spatial indices. The pre-storm understory and canopy survivors decreased species mingling, whereas survivors increased size differentiation. The size differentiation increased also with a higher degree of species mingling. Leaving differential post-storm legacies untouched promotes a higher structural and species diversity and therefore supports the management approach of preserving canopy survivors.
Endijs Bāders; Kalev Jõgiste; Didzis Elferts; Floortje Vodde; Andres Kiviste; Solveiga Luguza; Āris Jansons. Storm legacies shaping post-windthrow forest regeneration: learnings from spatial indices in unmanaged Norway spruce stands. European Journal of Forest Research 2021, 140, 819 -833.
AMA StyleEndijs Bāders, Kalev Jõgiste, Didzis Elferts, Floortje Vodde, Andres Kiviste, Solveiga Luguza, Āris Jansons. Storm legacies shaping post-windthrow forest regeneration: learnings from spatial indices in unmanaged Norway spruce stands. European Journal of Forest Research. 2021; 140 (4):819-833.
Chicago/Turabian StyleEndijs Bāders; Kalev Jõgiste; Didzis Elferts; Floortje Vodde; Andres Kiviste; Solveiga Luguza; Āris Jansons. 2021. "Storm legacies shaping post-windthrow forest regeneration: learnings from spatial indices in unmanaged Norway spruce stands." European Journal of Forest Research 140, no. 4: 819-833.
Use of whole tree biomass becomes increasingly more important due to rising demand for renewable energy and materials to replace fossil resources. Therefore, assessment of influence of this approach on hemiboreal forest ecosystem is essential. The aim of our study was to assess the long-term influence of full biomass removal (FBR) on the ground vegetation and soil chemical composition in Scots pine stands. Study sites were located in Vacciniosa, Myrtillosa, and Myrtillosa mel. forest types. Almost half a century from the FBR, it had no notable or significant influence on number of ground vegetation species. Significant differences in overall vegetation composition between stands established after FBR and conventional harvesting (stem-wood removal) were not found by the detrended correspondence analysis (DCA) and analysis of similarities (ANOSIM). In addition, values of Ellenberg and Düll indicators were similar and, in most cases (determined by forest type and parameter), had no significant differences between FBR and the same age control stands. Similarly, no significant differences were found between these stands in soil carbon and nitrogen pools. Thus, there had not been a negative long-term effect of FBR on the hemiboreal Scots pine ecosystem as indicated by ground vegetation and soil.
Roberts Čakšs; Linda Čakša; Iveta Desaine; Zane Lībiete; Didzis Elferts; Aldis Butlers; Āris Jansons. Long-Term Influence of Stump-Removal on Components of Hemiboreal Pine Forest Ecosystem. Sustainability 2021, 13, 2095 .
AMA StyleRoberts Čakšs, Linda Čakša, Iveta Desaine, Zane Lībiete, Didzis Elferts, Aldis Butlers, Āris Jansons. Long-Term Influence of Stump-Removal on Components of Hemiboreal Pine Forest Ecosystem. Sustainability. 2021; 13 (4):2095.
Chicago/Turabian StyleRoberts Čakšs; Linda Čakša; Iveta Desaine; Zane Lībiete; Didzis Elferts; Aldis Butlers; Āris Jansons. 2021. "Long-Term Influence of Stump-Removal on Components of Hemiboreal Pine Forest Ecosystem." Sustainability 13, no. 4: 2095.
In Northern Europe, an increase in heterogeneity of summer precipitation regime will subject forests to water deficit and drought. This is particularly topical for Norway spruce (Picea abies Karst.), which is a drought sensitive, yet economically important species. Nevertheless, local populations still might be highly plastic and tolerant, supporting their commercial application. Accordingly, the tolerance of Norway spruce seedlings from an Eastern Baltic provenance (western part of Latvia) to artificial drought according to soil type was assessed in a shelter experiment. To simulate drought, seedlings were subjected to reduced amounts (0%, 25%, 50%, 75%, and 100%) of naturally occurring precipitation (irrigation intensity). Three soil types (oligotrophic mineral, mesotrophic mineral, and peat) were tested. Seedling height, chlorophyll a concentration, and fluorescence parameters were measured. Both growth and photochemical reactions were affected by the irrigation intensity, the effect of which experienced an interacted with soil type, implying complex controls of drought sensitivity. Seedlings were more sensitive to irrigation intensity on mesotrophic mineral soil, as suggested by growth and photosynthetic activity. However, the responses were nonlinear, as the highest performance (growth and fluorescence parameters) of seedlings occurred in response to intermediate drought. On peat soil, which had the highest water-bearing capacity, an inverse response to irrigation intensity was observed. In general, fluorescence parameters were more sensitive and showed more immediate reaction to soil water deficit than concentration of chlorophyll on mesotrophic mineral and peat soils, while the latter was a better indicator of seedling performance on oligotrophic soil. This indicated considerable plastic acclimation and hence tolerance of seedlings from the local Norway spruce population to drought, though drought sensitivity is age-dependent.
Roberts Matisons; Oskars Krišāns; Āris Jansons; Toms Kondratovičs; Didzis Elferts; Gederts Ievinsh. Norway Spruce Seedlings from an Eastern Baltic Provenance Show Tolerance to Simulated Drought. Forests 2021, 12, 82 .
AMA StyleRoberts Matisons, Oskars Krišāns, Āris Jansons, Toms Kondratovičs, Didzis Elferts, Gederts Ievinsh. Norway Spruce Seedlings from an Eastern Baltic Provenance Show Tolerance to Simulated Drought. Forests. 2021; 12 (1):82.
Chicago/Turabian StyleRoberts Matisons; Oskars Krišāns; Āris Jansons; Toms Kondratovičs; Didzis Elferts; Gederts Ievinsh. 2021. "Norway Spruce Seedlings from an Eastern Baltic Provenance Show Tolerance to Simulated Drought." Forests 12, no. 1: 82.
Tree species mixing of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) has been shown to have positive effects on ecosystem service provision. From a management perspective, however, it is still uncertain which thinning regime provides the highest possible productivity of mixed oak–pine forests in the long term. Because of a lack of empirical studies dealing with thinning and species mixing effects on oak–pine forests, we simulated forest growth in order to test which thinning type and intensity may provide the highest productivity in the long-term. To achieve this, we simulated the growth of pure and mixed stands of oak and pine for 100 years in 23 triplets located on an ecological gradient across Europe. For this purpose, we applied four different growth simulators and compared their results: the distance-independent single-tree simulator PROGNAUS, the distance-dependent single-tree simulator SILVA, the gap model ForCEEPS, and the process-based simulator 3D-CMCC-FEM. We investigated the effects of species mixing and thinning from the upper (thinning from above) and lower tail (thinning from below) of the diameter distribution by reducing the stand basal area to 50 and 80% of the maximum basal area. We compared simulated results of the relative volume productivity of mixed versus pure stands and of thinned versus unthinned stands to empirical results previously obtained on the same set of triplets. Simulated relative volume productivity ranged between 61 and 156%, although extremes of 10% and of 300% could be observed. We found the relative volume productivity to be influenced by stand age, but not by stand density, except for PROGNAUS. Relative volume productivity did not increase with the site water supply of the triplet location. Highest long-term productivity for oak, pine and oak–pine stands can be expected in consequence of thinning from above, but the effect of thinning intensity differed between simulators. Thinning effects were positively affected by stand density, but not by stand age, except for thinning from above predicted by PROGNAUS. Predicted thinning effects showed good approximation of results from thinning experiments for oak, but not for pine stands. We hypothesize the results might be caused by the insufficient simulator representation of climate and its interaction with other site variables and stand structure. Further work is needed to reduce the revealed limitations of the existing growth models, as we currently see no alternative to such kind of studies and simulators.
Markus Engel; Sonja Vospernik; Maude Toïgo; Xavier Morin; Antonio Tomao; Carlo Trotta; Mathias Steckel; Anna Barbati; Arne Nothdurft; Hans Pretzsch; Miren del Rio; Jerzy Skrzyszewski; Quentin Ponette; Magnus Löf; Āris Jansons; Gediminas Brazaitis. Simulating the effects of thinning and species mixing on stands of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) across Europe. Ecological Modelling 2021, 442, 109406 .
AMA StyleMarkus Engel, Sonja Vospernik, Maude Toïgo, Xavier Morin, Antonio Tomao, Carlo Trotta, Mathias Steckel, Anna Barbati, Arne Nothdurft, Hans Pretzsch, Miren del Rio, Jerzy Skrzyszewski, Quentin Ponette, Magnus Löf, Āris Jansons, Gediminas Brazaitis. Simulating the effects of thinning and species mixing on stands of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) across Europe. Ecological Modelling. 2021; 442 ():109406.
Chicago/Turabian StyleMarkus Engel; Sonja Vospernik; Maude Toïgo; Xavier Morin; Antonio Tomao; Carlo Trotta; Mathias Steckel; Anna Barbati; Arne Nothdurft; Hans Pretzsch; Miren del Rio; Jerzy Skrzyszewski; Quentin Ponette; Magnus Löf; Āris Jansons; Gediminas Brazaitis. 2021. "Simulating the effects of thinning and species mixing on stands of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) across Europe." Ecological Modelling 442, no. : 109406.
Micropropagation has several advantages over conventional vegetative propagation methods, but it is limited by genotype responsiveness. We assessed the effect of age of the mother-tree and the time of explant collection on culture initiation, as well as the multiplication ability and effect of different nutrient media and plant growth regulators on silver birch genotypes. Explants collected from 1‐year‐old trees (66%) and explants collected in spring (64–67%) developed a significantly (both p < 0.001) higher proportion of shoots than those from 15‐year‐old trees (39%) and those collected in mid-summer (31%) and autumn (29%), respectively. In a stabilised culture, the length of the main shoot varied from 1.3 to 7.8 cm between genotypes, and the multiplication rate ranged from 1.0 to 6.8 shoots per explant. Hyperhydrated shoots were present in 17 out of 50 clones, and, among the clones, ranged from 14 to 50%. Cultures on the Murashige and Skoog basal medium had a higher multiplication rate than cultures on a Woody Plant Medium, and the application of zeatin provided better results than 6‐benzylaminopurine. The difference between cytokinin types was 11–29% for the multiplication rate and 21–29% for the length of the main stem. The highest multiplication rate was obtained using a zeatin concentration of 0.5 mg L−1. However, better shoot growth and proliferation had a significant positive relation to shoot hyperhydration (all p < 0.001). Therefore, a medium with an optimal balance between the multiplication rate and the number of hyperhydrated shoots should be carefully selected.
Arnis Gailis; Ineta Samsone; Silva Šēnhofa; Elva Girgžde; Rolands Kāpostiņš; Āris Jansons. Silver birch (Betula pendula Roth.) culture initiation in vitro and genotype determined differences in micropropagation. New Forests 2021, 1 -16.
AMA StyleArnis Gailis, Ineta Samsone, Silva Šēnhofa, Elva Girgžde, Rolands Kāpostiņš, Āris Jansons. Silver birch (Betula pendula Roth.) culture initiation in vitro and genotype determined differences in micropropagation. New Forests. 2021; ():1-16.
Chicago/Turabian StyleArnis Gailis; Ineta Samsone; Silva Šēnhofa; Elva Girgžde; Rolands Kāpostiņš; Āris Jansons. 2021. "Silver birch (Betula pendula Roth.) culture initiation in vitro and genotype determined differences in micropropagation." New Forests , no. : 1-16.
Strong wind is the major natural disturbance in European forests, that periodically causes tremendous damages to forestry. Yet, factors that affect the probability of wind damage for birch ( Roth and Ehrh.), the most common deciduous tree species in hemiboreal forests, are studied scarcely. This study aimed to assess the effects of several tree- and stand-scale variables on the probability of wind damage to birch using data from the Latvian National Forest Inventory (2004â2018), and determine individual tree characteristics that affect the height of the stem breakage. The data analysis was done using the Bayesian binary logistic generalized linear mixed-effects model and a linear mixed-effects model. The probability of wind damage significantly increased by stand age, basal area, and slenderness ratio. Trees with prior damage had a significantly higher probability (odds ratio 4.32) for wind damage. For wind-damaged trees, the snapping height was significantly decreased by an increase in the slenderness ratio (â=â0.03) and prior damage (â=â0.003). Previously damaged trees were more frequently (73%) snapped in the lowest 40% of tree height than trees without prior damage (54%). The probability of wind damage is largely set by factors related to the selection of site, species composition, and rotation. The damage probability could be decreased by management measures that lower competition within the stand with particular regard to preserving intact remaining trees during these manipulations. Factors that reduce the probability of the damage simultaneously increase the snapping height, emphasizing their relevance for mitigation of the wind damages.Betula pendula B. pubescens p p
Māra Kitenberga; Guntars Šņepsts; Jānis Vuguls; Didzis Elferts; Ieva Jaunslaviete; Āris Jansons. Tree- and stand-scale factors shape the probability of wind damage to birch in hemiboreal forests. Silva Fennica 2021, 55, 1 .
AMA StyleMāra Kitenberga, Guntars Šņepsts, Jānis Vuguls, Didzis Elferts, Ieva Jaunslaviete, Āris Jansons. Tree- and stand-scale factors shape the probability of wind damage to birch in hemiboreal forests. Silva Fennica. 2021; 55 (2):1.
Chicago/Turabian StyleMāra Kitenberga; Guntars Šņepsts; Jānis Vuguls; Didzis Elferts; Ieva Jaunslaviete; Āris Jansons. 2021. "Tree- and stand-scale factors shape the probability of wind damage to birch in hemiboreal forests." Silva Fennica 55, no. 2: 1.
Populations of tree species with a wide geographic range, such as silver birch ( Roth), show genetic specialization to native environments, while maintaining high phenotypical plasticity. Accordingly, assessment of local specialization is essential for adaptive management. The aim of the study was to detect geographic patterns of local adaptation of growth and stem quality based on two open-pollinated progeny trials in Latvia testing local material. Two provenance regions differing by continentality were distinguished, which also differed in genetic control of growth traits, likely originating from the post-glacial recolonization of vegetation and subsequent natural adaptation. Heritability of the traits was estimated for each of the distinguished regions, indicating differing patterns of genetic adaptation and potential for future selection. Trees from the more continental inland showed superior growth and possessed higher heritability. The coastal provenance region showed slower growth and intermediate heritability of the respective traits. Moderate to high heritability for stem quality traits was estimated irrespectively of region. Overall, better growth and higher heritability suggests that anthropogenic selection within the best inland provenances may constitute better performing and adaptable breeding population compared to the coastal one. Still, overlapping phenotypical variation and heritability of quality traits implies improved stemwood quality for plywood regardless of the provenance region. High adaptive capacity of silver birch genotypes suggests ability to cope with climatic changes, highlighting its potential for climate-smart forestry.Betula pendula
Arnis Gailis; PaulS Zeltiņš; Roberts Matisons; Andis Purviņš; Juris Augustovs; Valts Vīndedzis; Āris Jansons. Local adaptation of phenotypic stem traits distinguishes two provenance regions of silver birch in Latvia. Silva Fennica 2021, 55, 1 .
AMA StyleArnis Gailis, PaulS Zeltiņš, Roberts Matisons, Andis Purviņš, Juris Augustovs, Valts Vīndedzis, Āris Jansons. Local adaptation of phenotypic stem traits distinguishes two provenance regions of silver birch in Latvia. Silva Fennica. 2021; 55 (2):1.
Chicago/Turabian StyleArnis Gailis; PaulS Zeltiņš; Roberts Matisons; Andis Purviņš; Juris Augustovs; Valts Vīndedzis; Āris Jansons. 2021. "Local adaptation of phenotypic stem traits distinguishes two provenance regions of silver birch in Latvia." Silva Fennica 55, no. 2: 1.
Climate change will cause winds to strengthen and storms to become more frequent in Northern Europe. Windstorms reduce the financial value of forests by bending, breaking, or uprooting trees, and wind-thrown trees cause additional economic losses. The resistance of trees to wind damage depends on tree species, tree- and stand-scale parameters, and root-soil plate characteristics such as root-plate size, weight, and rooting depth. The root-soil plate is a complex structure whose mechanical strength is dependent on root-plate width and depth, as the root system provides root attachment with soil and structural support. In Latvia, the common aspen (Populus tremula L.) root system has been studied to develop a belowground biomass model, because information about root system characteristics in relation to tree wind resistance is scarce. The aim of this study was to assess the root-plate dimensions of common aspen stands on fertile mineral soil (luvisol). Study material was collected in the central region of Latvia, where pure mature (41–60 years old) common aspen stands were randomly selected, and dominant trees within the stand were chosen. In total, ten sample trees from ten stands were uprooted. The diameter at breast height (DBH) and tree height (H) were measured for each sample tree, and their roots were excavated, divided into groups, washed, measured, and weighed. The highest naturally moist biomass values were observed for coarse roots, and fine root biomass was significantly lower compared to other root groups. All root group biomass values had a strong correlation with the tree DBH. The obtained results show that there is a close, negative relationship between the relative distance from the stem and the relative root-plate depth distribution.
Valters Samariks; Dace Brizga; Jeļena RŪBA; Andris Seipulis; Āris Jansons. Root-Plate Characteristics of Common Aspen in Hemiboreal Forests of Latvia: A Case Study. Forests 2020, 12, 32 .
AMA StyleValters Samariks, Dace Brizga, Jeļena RŪBA, Andris Seipulis, Āris Jansons. Root-Plate Characteristics of Common Aspen in Hemiboreal Forests of Latvia: A Case Study. Forests. 2020; 12 (1):32.
Chicago/Turabian StyleValters Samariks; Dace Brizga; Jeļena RŪBA; Andris Seipulis; Āris Jansons. 2020. "Root-Plate Characteristics of Common Aspen in Hemiboreal Forests of Latvia: A Case Study." Forests 12, no. 1: 32.
Post-disturbance salvage logging mitigates economic loss after windthrow, and the value of salvaged timber is strongly linked to its quality and dimensions. We studied the occurrence of wind-induced damage of aspen in the hemiboreal forests of Latvia based on data from the National Forest Inventory and additional measurements. Individual tree data from three re-measurement periods were linked to follow a tree condition (live, broken, uprooted) and to link tree characteristics to a respective snag. Three linear models were developed to assess factors affecting the snapping height. An assortment outcome was calculated for undamaged and salvaged trees using the bucking algorithm, and timber value was calculated at three price levels. Wind-induced damage occurred for 3.4–3.6% of aspen trees, and among these, 45.8–46.6% were broken. The mean height of the broken trees was 27.3 ± 0.9 m, and it was significantly higher (both p < 0.01) compared to the height of undamaged and uprooted trees. The tested models indicated tree height as the main explanatory variable for relative snapping height, with higher trees having a lower point of the stem breakage. The other significant factor was the forest type group, indicating that trees growing on dry mineral soils had lower relative snapping height than trees growing on drained mineral soils. Stem breakage significantly (p < 0.001) reduced the volume of assortments, as compared to the volume of undamaged trees. Relative volume loss of sawlogs showed a logarithmic trend with a steep increase up to snapping height of 6 m, and it correlated tightly (r = 0.83, p < 0.001) with relative value loss of the total stem. Timber value loss had a strong, positive relation to tree diameter at breast height and fluctuated by 0.4% among different price levels. The mean volume reduction was 37.7% for sawlogs, 11.0% for pallet blocks, and 8.9% for technological wood.
Linda Čakša; Silva Šēnhofa; Guntars Šņepsts; Didzis Elferts; Līga Liepa; Āris Jansons. Effect of Stem Snapping on Aspen Timber Assortment Recovery in Hemiboreal Forests. Forests 2020, 12, 28 .
AMA StyleLinda Čakša, Silva Šēnhofa, Guntars Šņepsts, Didzis Elferts, Līga Liepa, Āris Jansons. Effect of Stem Snapping on Aspen Timber Assortment Recovery in Hemiboreal Forests. Forests. 2020; 12 (1):28.
Chicago/Turabian StyleLinda Čakša; Silva Šēnhofa; Guntars Šņepsts; Didzis Elferts; Līga Liepa; Āris Jansons. 2020. "Effect of Stem Snapping on Aspen Timber Assortment Recovery in Hemiboreal Forests." Forests 12, no. 1: 28.
Climate change manifests itself as a change in the probability of extreme weather events, and it is projected that windstorms will become more frequent and intense in Northern Europe. Additionally, the frequency and length of warm periods with wet, unfrozen soil in winter will rise in this region. These factors will lead to an increased risk of storm damages in forests. Factors affecting trees’ resistance to wind uprooting have been well quantified for some species but not for a common and economically important tree, the silver birch (Betula pendula Roth.). Therefore, this study aimed to assess the root-soil plate characteristics of silver birch on wet and dry mineral soils in hemiboreal forests. The root-soil plate and aboveground parameters were measured for 56 canopy trees uprooted in destructive, static-pulling experiments. The shape of the root-soil plate corresponds to the elliptic paraboloid. A decreasing yet slightly different trend was observed in root depth distribution with increasing distance from the stem in both soils. The main factors determining root-soil plate volume were width, which was notably larger on wet mineral soils, and tree diameter at breast height. Consequently, the root-soil plate volume was significantly larger for trees growing on wet mineral soils than for trees growing on dry soils, indicating a wind adaptation.
Valters Samariks; Nauris Īstenais; Andris Seipulis; Olga Miezīte; Oskars Krišāns; Āris Jansons. Root-Soil Plate Characteristics of Silver Birch on Wet and Dry Mineral Soils in Latvia. Forests 2020, 12, 20 .
AMA StyleValters Samariks, Nauris Īstenais, Andris Seipulis, Olga Miezīte, Oskars Krišāns, Āris Jansons. Root-Soil Plate Characteristics of Silver Birch on Wet and Dry Mineral Soils in Latvia. Forests. 2020; 12 (1):20.
Chicago/Turabian StyleValters Samariks; Nauris Īstenais; Andris Seipulis; Olga Miezīte; Oskars Krišāns; Āris Jansons. 2020. "Root-Soil Plate Characteristics of Silver Birch on Wet and Dry Mineral Soils in Latvia." Forests 12, no. 1: 20.
Storms and wind damage are the main cause of biomass loss in forests of Northern Europe, as well as they are synergic with the disturbances causing intense water and temperature stress. This highlights the necessity for climate-smart management at landscape level coupling ecological demands of forestry species with their wind resistance. Silver birch (Betula pendula Roth.), which is highly plastic species, appears to be promising for a wider application under such conditions, as it is believed to tolerate wide range of weather conditions. Though silver birch can be sensitive to water deficit and windthrow, local information on its wind tolerance in sites with different moisture regimes is advantageous. Mechanical stability of 71 mid-aged silver birches (Betula pendula Roth.) growing in seven dry (Hylocomiosa) and five periodically waterlogged (Myrtilloso-sphagnosa) sites with mineral soils in Latvia (hemiboreal lowland conditions) were assessed by the destructive static pulling tests. Site type had a significant, yet intermediate effect on the stability of silver birch. As expected, trees under periodically waterlogged conditions were more prone to collapse under static loading, however, they showed a better resistance to primary failure (beginning of wood structure deformation). Uprooting was the most common form of tree collapse. Surprisingly, considering similar root depths, stem breakage was more frequent in the periodically waterlogged than dry sites (21.9 vs. 5.1%, respectively), indicating high loading resistance of roots, supporting high plasticity and wind resistance of the studied metapopulation of silver birch. Nevertheless, in the periodically waterlogged sites, the difference between forces needed to cause primary and secondary (collapse) failures of stem decreased with age/size, implying necessity for optimization of rotation length. Accordingly, quantification of wind resistance can aid climate-smart selection of species for forest regeneration depending on landscape, suggesting birch as wind resistant option under periodically waterlogged conditions.
Oskars Krišāns; Roberts Matisons; Māra Kitenberga; Jānis Donis; Steffen Rust; Didzis Elferts; Āris Jansons. Wind Resistance of Eastern Baltic Silver Birch (Betula pendula Roth.) Suggests Its Suitability for Periodically Waterlogged Sites. Forests 2020, 12, 21 .
AMA StyleOskars Krišāns, Roberts Matisons, Māra Kitenberga, Jānis Donis, Steffen Rust, Didzis Elferts, Āris Jansons. Wind Resistance of Eastern Baltic Silver Birch (Betula pendula Roth.) Suggests Its Suitability for Periodically Waterlogged Sites. Forests. 2020; 12 (1):21.
Chicago/Turabian StyleOskars Krišāns; Roberts Matisons; Māra Kitenberga; Jānis Donis; Steffen Rust; Didzis Elferts; Āris Jansons. 2020. "Wind Resistance of Eastern Baltic Silver Birch (Betula pendula Roth.) Suggests Its Suitability for Periodically Waterlogged Sites." Forests 12, no. 1: 21.
Mixed-species stands have been found to be more productive than would be expected from the performance of their component species in monocultures due to facilitation and complementarity between species, although these interactions depend on the combination of species present. Our study focuses on monospecific and mixed-species stands of Scots pine and Norway spruce using 20 triplets established in nine countries along a climatic gradient across Europe. Differences in mean tree and stand characteristics, productivity and stand structure were assessed. Basal area increment in mixed stands was 8% higher than expected while volume increment was only 2% greater. Scots pine trees growing in mixed-species stands showed 11% larger quadratic mean diameter, 7% larger dominant diameter, 17% higher basal area and 25% higher stand volume than trees growing in monospecific stands. Norway spruce showed only a non-significant tendency to lower mean values of diameters, heights, basal area, as well standing volume in mixtures than monocultures. Stand structure indices differed between mixed stands and monocultures of Scots pine showing a greater stratification in mixed-species stands. Furthermore, the studied morphological traits showed little variability for trees growing in monospecific stands, except for diameter at breast height, crown length and crown length ratio. For trees growing in mixed stands, all the morphological traits of the trees were identified as different. Some of these morphological traits were associated with relative productivity. Nevertheless, relative productivity in mixed-species stands was not related to site conditions.
Ricardo Ruiz-Peinado; Hans Pretzsch; Magnus Löf; Michael Heym; Kamil Bielak; Jorge Aldea; Ignacio Barbeito; Gediminas Brazaitis; Lars Drössler; Kšištof Godvod; Aksel Granhus; Stig-Olof Holm; Aris Jansons; Ekaterina Makrickienė; Marek Metslaid; Sandra Metslaid; Arne Nothdurft; Ditlev Otto Juel Reventlow; Roman Sitko; Gintarė Stankevičienė; Miren del Río. Mixing effects on Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) productivity along a climatic gradient across Europe. Forest Ecology and Management 2020, 482, 118834 .
AMA StyleRicardo Ruiz-Peinado, Hans Pretzsch, Magnus Löf, Michael Heym, Kamil Bielak, Jorge Aldea, Ignacio Barbeito, Gediminas Brazaitis, Lars Drössler, Kšištof Godvod, Aksel Granhus, Stig-Olof Holm, Aris Jansons, Ekaterina Makrickienė, Marek Metslaid, Sandra Metslaid, Arne Nothdurft, Ditlev Otto Juel Reventlow, Roman Sitko, Gintarė Stankevičienė, Miren del Río. Mixing effects on Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) productivity along a climatic gradient across Europe. Forest Ecology and Management. 2020; 482 ():118834.
Chicago/Turabian StyleRicardo Ruiz-Peinado; Hans Pretzsch; Magnus Löf; Michael Heym; Kamil Bielak; Jorge Aldea; Ignacio Barbeito; Gediminas Brazaitis; Lars Drössler; Kšištof Godvod; Aksel Granhus; Stig-Olof Holm; Aris Jansons; Ekaterina Makrickienė; Marek Metslaid; Sandra Metslaid; Arne Nothdurft; Ditlev Otto Juel Reventlow; Roman Sitko; Gintarė Stankevičienė; Miren del Río. 2020. "Mixing effects on Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) productivity along a climatic gradient across Europe." Forest Ecology and Management 482, no. : 118834.
The annual shoot elongation could be described by a non-linear growth model to characterize differences in its dynamics among spruce genotypes, the effect of each shoot elongation phase on the total shoot length, and the genetic differences for a particular growth phase. The terminal shoot length was measured in two open-pollinated progeny trials of Norway spruce on average once per week during the ninth growing season. For the analysis, 10% of families with the longest annual increment (shoot) and 10% with the shortest were selected for each trial. The Gompertz model was fitted to individual tree data, and the mean values of its coefficients for each group of families were obtained. Family significantly (p < 0.001) affected total shoot length and all growth rhythm parameters, with similar trends reported in both studied sites. Heritability of Gompertz model coefficients in most cases exceeded that of the tree height. The superior10% of families started shoot elongation slightly but non-significantly earlier (all p > 0.05) than the other groups of families and had more intense shoot elongation (mm per day) during the entire growing season. A strong negative relation was found between the slope coefficient of the cumulative shoot elongation lines and the total height increment. The group of families with the longest increment had flatter relative shoot elongation lines, indicating relatively more evenly distributed growth within the growing season. In contrast, families with the shortest increment tended to accumulate a higher proportion of height increment during the active growth phase and reduced relative growth intensity more rapidly. The 10% of families with the largest annual increment showed superior characteristics in all shoot elongation phases, resulting in 30–40% longer shoots compared to the 10% of families with the smallest annual increment. The significant differences in Gompertz model coefficients indicate that genotypes with favorable growth patterns might be selected.
Baiba Jansone; Una Neimane; Silva Šēnhofa; Roberts Matisons; Āris Jansons. Genetically Determined Differences in Annual Shoot Elongation of Young Norway Spruce. Forests 2020, 11, 1260 .
AMA StyleBaiba Jansone, Una Neimane, Silva Šēnhofa, Roberts Matisons, Āris Jansons. Genetically Determined Differences in Annual Shoot Elongation of Young Norway Spruce. Forests. 2020; 11 (12):1260.
Chicago/Turabian StyleBaiba Jansone; Una Neimane; Silva Šēnhofa; Roberts Matisons; Āris Jansons. 2020. "Genetically Determined Differences in Annual Shoot Elongation of Young Norway Spruce." Forests 11, no. 12: 1260.