Sandra Metslaid - Academia.edu (original) (raw)
Papers by Sandra Metslaid
Forests, 2022
Coastal dunes near the Baltic Sea are often stabilized by Scots pine forests and are characterize... more Coastal dunes near the Baltic Sea are often stabilized by Scots pine forests and are characterized by a mild climate. These ecosystems are affected by water shortages and might be influenced by climate extremes. Considering future climate change, utilizing tree rings could help assess the role of climate extremes on coastal forest growth. We used superposed epoch analysis to study Scots pine responses to droughts and cold winters, with focus on frequency, timing, and duration. We measured ring widths (RW) and latewood blue intensity (LBI) on samples extracted from trees growing at dune ridge and bottom microsites at the south Baltic Sea. At the regional scale, we observed some similarities in tree responses to both extremes between RW and LBI within the same microsite type and region. At the local scale, RW and LBI were more frequently influenced by cold winters than droughts. RW and LBI from dune ridges were more frequently influenced by droughts than RW and LBI from dune bottoms. ...
Forest Ecology and Management, 2021
Mixed-species stands have been found to be more productive than would be expected from the perfor... more 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 mixedspecies 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
Frontiers in Forests and Global Change, 2020
Climate Sensitivity of Scots Pine temperature-growth relationships in the north and south respect... more Climate Sensitivity of Scots Pine temperature-growth relationships in the north and south respectively. We conclude that coastal Scots pine forests are primarily limited by winter-spring temperature and winterspring/summer drought despite differing microsite conditions. We detected some spatial and temporal variability in climate-growth relationships that warrant further investigation.
Dendrochronologia, 2017
The European Dendroecologial Fieldweek (EDF) provides an intensive learning experience in tree-ri... more The European Dendroecologial Fieldweek (EDF) provides an intensive learning experience in tree-ring research that challenges any participant to explore new multidisciplinary dendro-sciences approaches within the context of field and laboratory settings. Here we present the 25 th EDF, held in Asturias, NW Spain, in summer 2014. The course, with 33 participants and 10 instructors from 18 countries included advanced training in dendrochronology skills, an overview of tree-ring broad fields and methodological basics to deal with specific research questions as well as applied advanced micro-projects in dendroarchaeology (DAR), dendroclimatology (DCL), dendrogeomorphology (DGM), forest dynamics (FD) and plant anatomy (PA). The results demonstrated the potential of tree-ring research in the Asturias region. The DAR group researched archaeological samples from different contexts (Oviedo cathedral choir stalls, Segovia cathedral roof timbers, Ribadeo shipwreck ship timbers and Bronze Age site charcoal) and explored the supply of wood in different periods. The DCL group established that the Quercus robur and Castanea sativa ring-width measurements show weak climate-growth correlations, where for many trees this is likely caused by management. The strength of the climatic signal could be enhanced using undisturbed settings. The DGM group found that Corylus avellana and Salix spp. are challenging species for dendrogeomorphological studies. Debris flow events were detected by the presence of tension wood, growth reduction and scars, and their incidences were also supported by local meteorological data. The FD group found that tree growth decreases with increasing competition, a pattern more pronounced in C. sativa than in Pinus sylvestris forest plantations. The results indicate that wood production could be increased by applying thinning treatments on C. sativa. The PA group showed that xylem conduits and phloem area are organized according to the common needs for water supply to leaves and obtain photosynthetic products, regardless site growing conditions for P. sylvestris and Tusilago farfara. In conclusion, this EDF has been a model for interdisciplinary research and international collaboration that has demonstrated that high-quality research and education can be conducted within one week. The EDFs provide an important service to the dendrochronological community and demonstrate the usefulness of this educational-scientific and multi-cultural experience.
Forest Ecology and Management
Forestry Studies, 2020
Global change-type droughts will become more frequent in the future and threaten forest ecosystem... more Global change-type droughts will become more frequent in the future and threaten forest ecosystems around the globe. A large proportion of the Estonian forest sector is currently subject to artificial drainage, which could probably lead to negative feedbacks when water supply falls short because of high temperatures and low precipitation during future drought periods. In this short article, we propose a novel research perspective that could make use of already gathered data resources, such as remote sensing, climate data, tree-ring research, soil information and hydrological modelling. We conclude that, when applied in concert, such an assembled dataset has the potential to contribute to mitigation of negative climate change consequences for the Estonian forest sector. In particular, smart-drainage systems are currently a rare phenomenon in forestry, although their implementation into existing drainage systems could help maintain the critical soil water content during periods of dro...
Forests, 2019
Fourteen tree-ring chronologies developed from 788 peatland Scots pines sampled at sites in Eston... more Fourteen tree-ring chronologies developed from 788 peatland Scots pines sampled at sites in Estonia, Belarus and Sweden were compared for common growth trends and possible links to regional climate dynamics. Several synchronous growth release events were detected, especially during the 1910s, 1930s, and around 1970 and 1990, indicating that hydrological shifts and associated tree growth responses have been governed by similar forcing mechanisms, at least during the 20th century. In general, the best agreements were observed between the tree populations from Estonia and Belarus, but synchronous growth changes could also be detected between the Swedish and Estonian material. Trends detected in single tree-ring chronologies may be linked to local peatland management or land-use changes, whereas common variations detected at multiple sites are more likely linked to hydrological changes in the peatlands associated with regional climate dynamics. Understanding the links between climate an...
Agricultural and Forest Meteorology, 2018
In this study, we used a comprehensive tree-ring network from Estonia and investigated Scots pine... more In this study, we used a comprehensive tree-ring network from Estonia and investigated Scots pine (Pinus sylvestris L.) radial growth responses to changing climate conditions, considering differences in site conditions and local climates. To assess whether climate influences Scots pine radial growth consistently across the country, we developed thirteen tree-ring width chronologies for pine populations growing in four forest site types-Cladonia, Calluna, Myrtillus, and Rhodococcumin four sub-regions of Estonia and compared these to climate data. A correlation analysis between ring-width indexes and monthly resolved temperature and precipitation applied over the period of 1955-2006 revealed significant positive correlations with winter/early spring temperatures and the total precipitation of late summer in the year prior to growth. High mean temperatures in August of the year prior to growth were negatively related to pine growth, particularly on islands and in the Northeast of Estonia. Scots pine growth on mesic and medium fertile Myrtillus and Rhodococcum sites in the Southeast exhibited greater sensitivity to mean February−April temperatures, while high temperatures and low precipitation at the end of the summer of the previous growing season limited radial growth of pine on the islands and in the Northeastern sub-region. A principal component analysis conducted on mean index chronologies and a hierarchical cluster analysis performed on bootstrapped correlation coefficients showed that local climate is the main driver of common growth, followed by ecological site conditions. A moving correlation analysis, performed over the period of 1955-2006, using 30-year windows shifted by one year showed that climate-growth relationships are not stable in changing climatic conditions. Associations between Scots pine tree-ring width and winter temperatures are getting weaker.
Forestry Studies, 2015
Forest research has long traditions in Estonia that can be traced back to the 19th century. Data ... more Forest research has long traditions in Estonia that can be traced back to the 19th century. Data from long-term forest experiments are available since 1921. The first studies mainly focused on silvicultural treatments and application of such data for understanding and modeling ecological processes was limited. The Department of Forest Management of the Estonian University of Life Sciences started to develop the Estonian Network of Forest Research Plots (ENFRP) in 1995. Since then, plots have been continuously re-measured with 5-year interval. Approximately 100-150 permanent sample plots were measured annually. In 2014, the long-term research network consisted of 729 permanent sample plots, of which 699 have been re-measured at least once, 667 plots - twice and 367 plots - three times. The total number of trees recorded in the network database amounts to 130,479. The plots are systematically distributed throughout the country. Detailed dendrometric measurements including tree spatial...
Environmental Science and Pollution Research, 2015
Afforestation on reclaimed mining areas has high ecological and economic importance. However, eco... more Afforestation on reclaimed mining areas has high ecological and economic importance. However, ecosystems established on post-mining substrate can become vulnerable due to climate variability. We used tree-ring data and dendrochronological techniques to study the relationship between climate variables and annual growth of Scots pine (Pinus sylvestris L.) growing on reclaimed open cast oil shale mining areas in Northeast Estonia. Chronologies for trees of different age classes (50, 40, 30) were developed. Pearson's correlation analysis between radial growth indices and monthly climate variables revealed that precipitation in June-July and higher mean temperatures in spring season enhanced radial growth of pine plantations, while higher than average temperatures in summer months inhibited wood production. Sensitivity of radial increment to climatic factors on post-mining soils was not homogenous among the studied populations. Older trees growing on more developed soils were more sensitive to precipitation deficit in summer, while growth indices of two other stand groups (young and middle-aged) were highly correlated to temperature. High mean temperatures in August were negatively related to annual wood production in all trees, while trees in the youngest stands benefited from warmer temperatures in January. As a response to thinning, mean annual basal area increment increased up to 50 %. By managing tree competition in the closed-canopy stands, through the thinning activities, tree sensitivity and response to climate could be manipulated.
Forest research has long tradition in Estonia that can be followed back to 19th century. Data fro... more Forest research has long tradition in Estonia that can be followed back to 19th century. Data from long-term forest experiments is available since 1921. These studies were focused mainly on silvicultural treatments and the data has limited application for understanding and modelling ecological processes. Department of Forest Management of the Estonian University of Life Sciences has started the Estonian Network of Forest Research Plots in 1995. Monitoring plots have been continuously re-measured with 5-year interval. Approximately 100-150 permanent sample plots have been measured per year. In 2013, the long-term research network consisted of 714 permanent sample plots, of which 699 have been re-measured at least once, 654 plots - twice and 242 plots - three times. The total number of trees recorded in the network database amounts to 121,042. The plots are systematically distributed throughout the country. Detailed measurements including tree locations are part of the survey protocol...
Trees
Key message An exceptionally high number of blue rings were formed within and between Scots pine ... more Key message An exceptionally high number of blue rings were formed within and between Scots pine trees from Estonia in 1976: a year that is well known for its outstanding summer heatwave over Western Europe, but its extreme autumnal cooling over Eastern Europe has so far been neglected in scientific literature. Abstract ‘Blue rings’ (BRs) are visual indicators of less lignified cell walls typically formed towards the end of a tree’s growing season. Though BRs have been associated with ephemeral surface cooling, often following large volcanic eruptions, the intensity of cold spells necessary to produce BRs, as well as the consistency of their formation within and between trees still remains uncertain. Here, we report an exceptionally high BR occurrence within and between Scots pine (Pinus sylvestris L.) trees at two sites in Estonia, including the first published whole-stem analysis for BRs. Daily meteorological measurements from a nearby station allowed us to investigate the role te...
Ecosphere, 2018
In the Baltic States region, anthropogenic disturbances at different temporal and spatial scales ... more In the Baltic States region, anthropogenic disturbances at different temporal and spatial scales mostly determine dynamics and development phases of forest ecosystems. We reviewed the state and condition of hemiboreal forests of the Baltic States region and analyzed species composition of recently established and permanent forest (PF). Agricultural deforestation and spontaneous or artificial conversion back to forest is a scenario leading to ecosystems designated as recent forest (RF, age up to two hundred years). Permanent forest (PF) was defined as areas with no records of agricultural activity during the last 200 yr, including mostly forests managed by traditional even-aged (clear-cut) silviculture and salvage after natural disturbances. We hypothesized that RF would have distinctive composition, with higher dominance by hardwoods (e.g., aspen and birch), compared to PF. Ordination revealed divergence in the RF stands; about half had the hypothesized composition distinct from PF, with a tight cluster of stands in the part of the ordination space with high hardwood dominance, while the remaining RF stands were scattered throughout the ordination space occupied by PF with highly variable species composition. Planting of conifers, variability in site quality, and variability in spatial proximity to PF with relatively natural ecosystem legacies likely explained the variable compositions of this latter group of RF. We positioned the observations of RF in a classic quantification of site type conditions (based on Estonian forest vegetation survey previously carried out by Lõhmus), which indicated that RF was more likely to occur on areas of higher soil fertility (in ordination space). Climatic and anthropogenic changes to RF create complex dynamic trends that are difficult to project into the future. Further research in tracing land use changes (using pollen analysis and documented evidence) should be utilized to refine the conceptual framework of ecosystem legacy and memory. Occurrence and frequency of deforestation and its characteristics as a novel disturbance regime are of particular interest.
Journal of Forest Research, 2011
There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, th... more There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, the analysis of ring measurements has been a common method to study growth changes. In this study, annual height growth data from dominant or co-dominant Scots pine (Pinus sylvestris L.) trees were used to develop a growth model for three forest generations. Stem analysis was applied and annual height growth was measured as the distance between whorls, as detected by branch knots of whorls on the split stem surface. Retrospective analysis of height growth produced comparative trends for three different age groups. Statistical analyses were used to estimate the impact of different factors on growth. Annual height growth was considered the best indicator for detecting possible trends in the growth potential of trees. Study results indicate that three generations (separated by time periods of 30–40 years) showed significant differences in growth patterns caused by shifts in climatic factors and management regimes (anthropogenic and natural disturbances).
Baltic Forestry
A classic approach to obtain stand height H Dq in advanced stands in Estonia has to use the regre... more A classic approach to obtain stand height H Dq in advanced stands in Estonia has to use the regression height at the quadratic mean diameter D q. In juvenile stands, where a considerable number of young trees have not reached breast height, the modelling of the height distribution instead of the breast height diameter dbh distribution is more practical. Also, the field assessment methodologies differ for juvenile and advanced stands. In younger stands the mean height and stem number are assessed. In advanced stands (dbh larger than 6 cm) these variables are replaced with the basal area, quadratic mean diameter and the regression height. This study evaluates the predictive abilities of different mean height calculation functions in various tree species in naturally regenerated stands. We analyze different young stand height calculation methods in comparison with the classical stand height H Dq calculation method. Two independent sets of empirical materials were employed in our study:...
DESCRIPTION The following research paper analyzes Scots pine (Pinus sylvestris L.) radial growth ... more DESCRIPTION The following research paper analyzes Scots pine (Pinus sylvestris L.) radial growth responses to climatic factors in mesotrophic and heath forest site types in Estonia. Increment cores from 889 trees from 119 plots of the network of research plots were used and chronologies for mesotrophic and heath forest site types of Scots pine were constructed. The relationship between climatic factors and the radial growth of Scots pine was characterized by correlation coefficient; also pointer year analysis, Cropper method was applied to single tree series. Cropper values were calculated; extreme negative and positive pointer years were identified. According to analyses, 1940 and 1985 were the most significant negative pointer years among different sites; and significant positive years were 1945, 1946, 1989, and 1990. Extreme Cropper values indicated significant positive correlation with the monthly mean temperature in winter (January, February) and early spring (March, April) bef...
Journal of Forest Research, 2011
There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, th... more There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, the analysis of ring measurements has been a common method to study growth changes. In this study, annual height growth data from dominant or co-dominant Scots pine (Pinus sylvestris L.) trees were used to develop a growth model for three forest generations. Stem analysis was applied and annual height growth was measured as the distance between whorls, as detected by branch knots of whorls on the split stem surface. Retrospective analysis of height growth produced comparative trends for three different age groups. Statistical analyses were used to estimate the impact of different factors on growth. Annual height growth was considered the best indicator for detecting possible trends in the growth potential of trees. Study results indicate that three generations (separated by time periods of 30–40 years) showed significant differences in growth patterns caused by shifts in climatic factors and management regimes (anthropogenic and natural disturbances).
Forests, 2022
Coastal dunes near the Baltic Sea are often stabilized by Scots pine forests and are characterize... more Coastal dunes near the Baltic Sea are often stabilized by Scots pine forests and are characterized by a mild climate. These ecosystems are affected by water shortages and might be influenced by climate extremes. Considering future climate change, utilizing tree rings could help assess the role of climate extremes on coastal forest growth. We used superposed epoch analysis to study Scots pine responses to droughts and cold winters, with focus on frequency, timing, and duration. We measured ring widths (RW) and latewood blue intensity (LBI) on samples extracted from trees growing at dune ridge and bottom microsites at the south Baltic Sea. At the regional scale, we observed some similarities in tree responses to both extremes between RW and LBI within the same microsite type and region. At the local scale, RW and LBI were more frequently influenced by cold winters than droughts. RW and LBI from dune ridges were more frequently influenced by droughts than RW and LBI from dune bottoms. ...
Forest Ecology and Management, 2021
Mixed-species stands have been found to be more productive than would be expected from the perfor... more 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 mixedspecies 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
Frontiers in Forests and Global Change, 2020
Climate Sensitivity of Scots Pine temperature-growth relationships in the north and south respect... more Climate Sensitivity of Scots Pine temperature-growth relationships in the north and south respectively. We conclude that coastal Scots pine forests are primarily limited by winter-spring temperature and winterspring/summer drought despite differing microsite conditions. We detected some spatial and temporal variability in climate-growth relationships that warrant further investigation.
Dendrochronologia, 2017
The European Dendroecologial Fieldweek (EDF) provides an intensive learning experience in tree-ri... more The European Dendroecologial Fieldweek (EDF) provides an intensive learning experience in tree-ring research that challenges any participant to explore new multidisciplinary dendro-sciences approaches within the context of field and laboratory settings. Here we present the 25 th EDF, held in Asturias, NW Spain, in summer 2014. The course, with 33 participants and 10 instructors from 18 countries included advanced training in dendrochronology skills, an overview of tree-ring broad fields and methodological basics to deal with specific research questions as well as applied advanced micro-projects in dendroarchaeology (DAR), dendroclimatology (DCL), dendrogeomorphology (DGM), forest dynamics (FD) and plant anatomy (PA). The results demonstrated the potential of tree-ring research in the Asturias region. The DAR group researched archaeological samples from different contexts (Oviedo cathedral choir stalls, Segovia cathedral roof timbers, Ribadeo shipwreck ship timbers and Bronze Age site charcoal) and explored the supply of wood in different periods. The DCL group established that the Quercus robur and Castanea sativa ring-width measurements show weak climate-growth correlations, where for many trees this is likely caused by management. The strength of the climatic signal could be enhanced using undisturbed settings. The DGM group found that Corylus avellana and Salix spp. are challenging species for dendrogeomorphological studies. Debris flow events were detected by the presence of tension wood, growth reduction and scars, and their incidences were also supported by local meteorological data. The FD group found that tree growth decreases with increasing competition, a pattern more pronounced in C. sativa than in Pinus sylvestris forest plantations. The results indicate that wood production could be increased by applying thinning treatments on C. sativa. The PA group showed that xylem conduits and phloem area are organized according to the common needs for water supply to leaves and obtain photosynthetic products, regardless site growing conditions for P. sylvestris and Tusilago farfara. In conclusion, this EDF has been a model for interdisciplinary research and international collaboration that has demonstrated that high-quality research and education can be conducted within one week. The EDFs provide an important service to the dendrochronological community and demonstrate the usefulness of this educational-scientific and multi-cultural experience.
Forest Ecology and Management
Forestry Studies, 2020
Global change-type droughts will become more frequent in the future and threaten forest ecosystem... more Global change-type droughts will become more frequent in the future and threaten forest ecosystems around the globe. A large proportion of the Estonian forest sector is currently subject to artificial drainage, which could probably lead to negative feedbacks when water supply falls short because of high temperatures and low precipitation during future drought periods. In this short article, we propose a novel research perspective that could make use of already gathered data resources, such as remote sensing, climate data, tree-ring research, soil information and hydrological modelling. We conclude that, when applied in concert, such an assembled dataset has the potential to contribute to mitigation of negative climate change consequences for the Estonian forest sector. In particular, smart-drainage systems are currently a rare phenomenon in forestry, although their implementation into existing drainage systems could help maintain the critical soil water content during periods of dro...
Forests, 2019
Fourteen tree-ring chronologies developed from 788 peatland Scots pines sampled at sites in Eston... more Fourteen tree-ring chronologies developed from 788 peatland Scots pines sampled at sites in Estonia, Belarus and Sweden were compared for common growth trends and possible links to regional climate dynamics. Several synchronous growth release events were detected, especially during the 1910s, 1930s, and around 1970 and 1990, indicating that hydrological shifts and associated tree growth responses have been governed by similar forcing mechanisms, at least during the 20th century. In general, the best agreements were observed between the tree populations from Estonia and Belarus, but synchronous growth changes could also be detected between the Swedish and Estonian material. Trends detected in single tree-ring chronologies may be linked to local peatland management or land-use changes, whereas common variations detected at multiple sites are more likely linked to hydrological changes in the peatlands associated with regional climate dynamics. Understanding the links between climate an...
Agricultural and Forest Meteorology, 2018
In this study, we used a comprehensive tree-ring network from Estonia and investigated Scots pine... more In this study, we used a comprehensive tree-ring network from Estonia and investigated Scots pine (Pinus sylvestris L.) radial growth responses to changing climate conditions, considering differences in site conditions and local climates. To assess whether climate influences Scots pine radial growth consistently across the country, we developed thirteen tree-ring width chronologies for pine populations growing in four forest site types-Cladonia, Calluna, Myrtillus, and Rhodococcumin four sub-regions of Estonia and compared these to climate data. A correlation analysis between ring-width indexes and monthly resolved temperature and precipitation applied over the period of 1955-2006 revealed significant positive correlations with winter/early spring temperatures and the total precipitation of late summer in the year prior to growth. High mean temperatures in August of the year prior to growth were negatively related to pine growth, particularly on islands and in the Northeast of Estonia. Scots pine growth on mesic and medium fertile Myrtillus and Rhodococcum sites in the Southeast exhibited greater sensitivity to mean February−April temperatures, while high temperatures and low precipitation at the end of the summer of the previous growing season limited radial growth of pine on the islands and in the Northeastern sub-region. A principal component analysis conducted on mean index chronologies and a hierarchical cluster analysis performed on bootstrapped correlation coefficients showed that local climate is the main driver of common growth, followed by ecological site conditions. A moving correlation analysis, performed over the period of 1955-2006, using 30-year windows shifted by one year showed that climate-growth relationships are not stable in changing climatic conditions. Associations between Scots pine tree-ring width and winter temperatures are getting weaker.
Forestry Studies, 2015
Forest research has long traditions in Estonia that can be traced back to the 19th century. Data ... more Forest research has long traditions in Estonia that can be traced back to the 19th century. Data from long-term forest experiments are available since 1921. The first studies mainly focused on silvicultural treatments and application of such data for understanding and modeling ecological processes was limited. The Department of Forest Management of the Estonian University of Life Sciences started to develop the Estonian Network of Forest Research Plots (ENFRP) in 1995. Since then, plots have been continuously re-measured with 5-year interval. Approximately 100-150 permanent sample plots were measured annually. In 2014, the long-term research network consisted of 729 permanent sample plots, of which 699 have been re-measured at least once, 667 plots - twice and 367 plots - three times. The total number of trees recorded in the network database amounts to 130,479. The plots are systematically distributed throughout the country. Detailed dendrometric measurements including tree spatial...
Environmental Science and Pollution Research, 2015
Afforestation on reclaimed mining areas has high ecological and economic importance. However, eco... more Afforestation on reclaimed mining areas has high ecological and economic importance. However, ecosystems established on post-mining substrate can become vulnerable due to climate variability. We used tree-ring data and dendrochronological techniques to study the relationship between climate variables and annual growth of Scots pine (Pinus sylvestris L.) growing on reclaimed open cast oil shale mining areas in Northeast Estonia. Chronologies for trees of different age classes (50, 40, 30) were developed. Pearson's correlation analysis between radial growth indices and monthly climate variables revealed that precipitation in June-July and higher mean temperatures in spring season enhanced radial growth of pine plantations, while higher than average temperatures in summer months inhibited wood production. Sensitivity of radial increment to climatic factors on post-mining soils was not homogenous among the studied populations. Older trees growing on more developed soils were more sensitive to precipitation deficit in summer, while growth indices of two other stand groups (young and middle-aged) were highly correlated to temperature. High mean temperatures in August were negatively related to annual wood production in all trees, while trees in the youngest stands benefited from warmer temperatures in January. As a response to thinning, mean annual basal area increment increased up to 50 %. By managing tree competition in the closed-canopy stands, through the thinning activities, tree sensitivity and response to climate could be manipulated.
Forest research has long tradition in Estonia that can be followed back to 19th century. Data fro... more Forest research has long tradition in Estonia that can be followed back to 19th century. Data from long-term forest experiments is available since 1921. These studies were focused mainly on silvicultural treatments and the data has limited application for understanding and modelling ecological processes. Department of Forest Management of the Estonian University of Life Sciences has started the Estonian Network of Forest Research Plots in 1995. Monitoring plots have been continuously re-measured with 5-year interval. Approximately 100-150 permanent sample plots have been measured per year. In 2013, the long-term research network consisted of 714 permanent sample plots, of which 699 have been re-measured at least once, 654 plots - twice and 242 plots - three times. The total number of trees recorded in the network database amounts to 121,042. The plots are systematically distributed throughout the country. Detailed measurements including tree locations are part of the survey protocol...
Trees
Key message An exceptionally high number of blue rings were formed within and between Scots pine ... more Key message An exceptionally high number of blue rings were formed within and between Scots pine trees from Estonia in 1976: a year that is well known for its outstanding summer heatwave over Western Europe, but its extreme autumnal cooling over Eastern Europe has so far been neglected in scientific literature. Abstract ‘Blue rings’ (BRs) are visual indicators of less lignified cell walls typically formed towards the end of a tree’s growing season. Though BRs have been associated with ephemeral surface cooling, often following large volcanic eruptions, the intensity of cold spells necessary to produce BRs, as well as the consistency of their formation within and between trees still remains uncertain. Here, we report an exceptionally high BR occurrence within and between Scots pine (Pinus sylvestris L.) trees at two sites in Estonia, including the first published whole-stem analysis for BRs. Daily meteorological measurements from a nearby station allowed us to investigate the role te...
Ecosphere, 2018
In the Baltic States region, anthropogenic disturbances at different temporal and spatial scales ... more In the Baltic States region, anthropogenic disturbances at different temporal and spatial scales mostly determine dynamics and development phases of forest ecosystems. We reviewed the state and condition of hemiboreal forests of the Baltic States region and analyzed species composition of recently established and permanent forest (PF). Agricultural deforestation and spontaneous or artificial conversion back to forest is a scenario leading to ecosystems designated as recent forest (RF, age up to two hundred years). Permanent forest (PF) was defined as areas with no records of agricultural activity during the last 200 yr, including mostly forests managed by traditional even-aged (clear-cut) silviculture and salvage after natural disturbances. We hypothesized that RF would have distinctive composition, with higher dominance by hardwoods (e.g., aspen and birch), compared to PF. Ordination revealed divergence in the RF stands; about half had the hypothesized composition distinct from PF, with a tight cluster of stands in the part of the ordination space with high hardwood dominance, while the remaining RF stands were scattered throughout the ordination space occupied by PF with highly variable species composition. Planting of conifers, variability in site quality, and variability in spatial proximity to PF with relatively natural ecosystem legacies likely explained the variable compositions of this latter group of RF. We positioned the observations of RF in a classic quantification of site type conditions (based on Estonian forest vegetation survey previously carried out by Lõhmus), which indicated that RF was more likely to occur on areas of higher soil fertility (in ordination space). Climatic and anthropogenic changes to RF create complex dynamic trends that are difficult to project into the future. Further research in tracing land use changes (using pollen analysis and documented evidence) should be utilized to refine the conceptual framework of ecosystem legacy and memory. Occurrence and frequency of deforestation and its characteristics as a novel disturbance regime are of particular interest.
Journal of Forest Research, 2011
There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, th... more There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, the analysis of ring measurements has been a common method to study growth changes. In this study, annual height growth data from dominant or co-dominant Scots pine (Pinus sylvestris L.) trees were used to develop a growth model for three forest generations. Stem analysis was applied and annual height growth was measured as the distance between whorls, as detected by branch knots of whorls on the split stem surface. Retrospective analysis of height growth produced comparative trends for three different age groups. Statistical analyses were used to estimate the impact of different factors on growth. Annual height growth was considered the best indicator for detecting possible trends in the growth potential of trees. Study results indicate that three generations (separated by time periods of 30–40 years) showed significant differences in growth patterns caused by shifts in climatic factors and management regimes (anthropogenic and natural disturbances).
Baltic Forestry
A classic approach to obtain stand height H Dq in advanced stands in Estonia has to use the regre... more A classic approach to obtain stand height H Dq in advanced stands in Estonia has to use the regression height at the quadratic mean diameter D q. In juvenile stands, where a considerable number of young trees have not reached breast height, the modelling of the height distribution instead of the breast height diameter dbh distribution is more practical. Also, the field assessment methodologies differ for juvenile and advanced stands. In younger stands the mean height and stem number are assessed. In advanced stands (dbh larger than 6 cm) these variables are replaced with the basal area, quadratic mean diameter and the regression height. This study evaluates the predictive abilities of different mean height calculation functions in various tree species in naturally regenerated stands. We analyze different young stand height calculation methods in comparison with the classical stand height H Dq calculation method. Two independent sets of empirical materials were employed in our study:...
DESCRIPTION The following research paper analyzes Scots pine (Pinus sylvestris L.) radial growth ... more DESCRIPTION The following research paper analyzes Scots pine (Pinus sylvestris L.) radial growth responses to climatic factors in mesotrophic and heath forest site types in Estonia. Increment cores from 889 trees from 119 plots of the network of research plots were used and chronologies for mesotrophic and heath forest site types of Scots pine were constructed. The relationship between climatic factors and the radial growth of Scots pine was characterized by correlation coefficient; also pointer year analysis, Cropper method was applied to single tree series. Cropper values were calculated; extreme negative and positive pointer years were identified. According to analyses, 1940 and 1985 were the most significant negative pointer years among different sites; and significant positive years were 1945, 1946, 1989, and 1990. Extreme Cropper values indicated significant positive correlation with the monthly mean temperature in winter (January, February) and early spring (March, April) bef...
Journal of Forest Research, 2011
There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, th... more There is strong evidence that climate change alters tree growth in boreal forests. In Estonia, the analysis of ring measurements has been a common method to study growth changes. In this study, annual height growth data from dominant or co-dominant Scots pine (Pinus sylvestris L.) trees were used to develop a growth model for three forest generations. Stem analysis was applied and annual height growth was measured as the distance between whorls, as detected by branch knots of whorls on the split stem surface. Retrospective analysis of height growth produced comparative trends for three different age groups. Statistical analyses were used to estimate the impact of different factors on growth. Annual height growth was considered the best indicator for detecting possible trends in the growth potential of trees. Study results indicate that three generations (separated by time periods of 30–40 years) showed significant differences in growth patterns caused by shifts in climatic factors and management regimes (anthropogenic and natural disturbances).