Aim Climate change is expected to modify growth trends of forests around the world. However, this... more Aim Climate change is expected to modify growth trends of forests around the world. However, this modification may vary in strength and intensity across a species' biogeographical range. Here, we study European populations of silver fir (Abies alba) across its southern distribution limits in Spain, Italy and Roma-nia. We hypothesized that growth trends of silver fir will differ across its distribution range, with a marked decline in growth in drought-prone regions near the species' southernmost biogeographical limits. Location Europe (Spain, Italy, Romania). Methods We collected tree-ring data from at least 1300 silver fir trees located in 111 sites. The dataset was used to assess and model growth trends, quantified as changes in basal area increment, and to determine how growth responds to climate. Results We found contrasting patterns of basal area increments among countries and sites. Populations of silver fir located outside the Mediterranean area (e.g. northern Italy, Romania) have shown a clear increase in growth over the last two decades, whereas most populations in Spain and southern Italy have displayed a marked decline in growth since the 1980s. The growth of silver fir forests at the southwestern distribution limit is severely constrained by low spring–summer water availability, whereas growth of silver fir forests in non-Mediterranean areas is limited by cold conditions in late winter to early spring. Main conclusions Climate warming is distinctly modifying growth patterns and responses to climate in silver fir across most of the species' European distribution area. In southwestern Europe the reduction in growth of many populations is related to an observed increase in aridity, whereas in more temperate areas warming is enhancing growth. Our results confirm a decline in the growth of silver fir at its southwestern distribution limits as a consequence of climate warming.
High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances.... more High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances. Nonetheless, even in this remote region, human pressure is often most important in influencing forest and landscape structure. In the last decades, fuelwood demand has risen due to increasing numbers of tourists and mountaineers. To understand human interactions with forest resources, stand structure and composition were examined at the landscape scale in the Sagarmatha National Park and its Buffer Zone in the Khumbu valley (Nepal). Using biological and historical data sources, a multi-scale approach revealed the influence of human activities on the distribution of tree species and forest structure. We sampled stand structure and environmental characteristics from 173 plots, and derived anthropogenic variables from thematic maps and satellite images for multivariate statistical analyses. Results suggest relationships among forest structure, anthropogenic influences, and topography. Low-density stands (100-150 tph) with sparse trees and rare big trees were in close proximity (0-36 m) to tracks and lodges. The wide variability in species diversity (0.67 at SNP and 0.58 at BZ) was strongly related to environmental factors, such as elevation, and human pressure. The frequent removal of green branches has adverse effects on tree growth, forest resistance, resilience, and regeneration capacity. We conclude that natural resources can adequately supply the local population needs, but current practices are not sustainable.
Sustainable forest management has to consider the long-term effects of climate change on species ... more Sustainable forest management has to consider the long-term effects of climate change on species growth to develop adaptation measures. In this perspective, dendrochronology provides valuable information on climate-growth relationships over long time periods. Tree-ring analyses in mixed stands can elucidate how different species respond to climate change within the same environmental conditions. However, few studies have investigated such stands, especially in South-Eastern Europe. In the forest reserve of Lom, in Bosnia and Herzegovina, we had the opportunity to study three co-occurring species (silver fir, Norway spruce, European beech) in an old-growth forest characterized by reduced human and natural disturbances, and a climate favourable to the tree species. We evaluated tree growth response to climate on inter-annual and decadal time scales over about 250 years. Response to inter-annual climate variability changed over the study period. Climate signal in beech was generally low, with a negative correlation to April temperature in the last decades. In fir and spruce, the positive effect of current year's spring temperature decreased, while the negative effect of the previous summer temperature considerably increased over the last century. At the decadal scale, different responses have been detected among species: spruce was mostly negatively affected by summer temperature whereas summer precipitation benefited fir growth, probably balancing high evapotranspiration. Beech showed a peculiar delayed response, and protracted drought periods led to severe growth reductions. Despite a temperature increase over the last three decades, fir did not experience any growth reduction, while a strong decline was evident in spruce and beech productivity. Mesic sites are commonly underrepresented in tree-ring research. In our analysis, covering about 250 years, we observed that climate also affects species-specific growth patterns in these areas. Within a global change perspective, specific divergent responses are likely to occur even where current environmental conditions appear to be not limiting for tree species. Future management strategies should consider these outcomes.
Proceedings of the National Academy of Sciences of the United States of America, Jan 27, 2010
Ecological communities exhibit pervasive patterns and interrelationships between size, abundance,... more Ecological communities exhibit pervasive patterns and interrelationships between size, abundance, and the availability of resources. We use scaling ideas to develop a unified, model-independent framework for understanding the distribution of tree sizes, their energy use, and spatial distribution in tropical forests. We demonstrate that the scaling of the tree crown at the individual level drives the forest structure when resources are fully used. Our predictions match perfectly with the scaling behavior of an exactly solvable self-similar model of a forest and are in good accord with empirical data. The range, over which pure power law behavior is observed, depends on the available amount of resources. The scaling framework can be used for assessing the effects of natural and anthropogenic disturbances on ecosystem structure and functionality.
High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances.... more High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances. Nonetheless, even in this remote region, human pressure is often most important in influencing forest and landscape structure. In the last decades, fuelwood demand has risen due to increasing numbers of tourists and mountaineers. To understand human interactions with forest resources, stand structure and composition were examined at the landscape scale in the Sagarmatha National Park and its Buffer Zone in the Khumbu valley (Nepal). Using biological and historical data sources, a multi-scale approach revealed the influence of human activities on the distribution of tree species and forest structure. We sampled stand structure and environmental characteristics from 173 plots, and derived anthropogenic variables from thematic maps and satellite images for multivariate statistical analyses. Results suggest relationships among forest structure, anthropogenic influences, and topography. Low-density stands (100-150 tph) with sparse trees and rare big trees were in close proximity (0-36 m) to tracks and lodges. The wide variability in species diversity (0.67 at SNP and 0.58 at BZ) was strongly related to environmental factors, such as elevation, and human pressure. The frequent removal of green branches has adverse effects on tree growth, forest resistance, resilience, and regeneration capacity. We conclude that natural resources can adequately supply the local population needs, but current practices are not sustainable.
Dicotyledons have evolved a strategy to compensate for the increase in hydraulic resistance to wa... more Dicotyledons have evolved a strategy to compensate for the increase in hydraulic resistance to water transport with height growth by widening xylem conduits downwards. In monocots, the accumulation of hydraulic resistance with height should be similar, but the absence of secondary growth represents a strong limitation for the maintenance of xylem hydraulic efficiency during ontogeny. The hydraulic architecture of monocots has been studied but it is unclear how monocots arrange their axial vascular structure during ontogeny to compensate for increases in height. We measured the vessel lumina and estimated the hydraulic diameter (Dh) at different heights along the stem of two arborescent monocots, Bactris gasipaes (Kunth) and Guadua angustifolia (Kunth). For the former, we also estimated the variation in Dh along the leaf rachis. Hydraulic diameter increased basally from the stem apex to the base with a scaling exponent (b) in the range of those reported for dicot trees (b = 0.22 in B. gasipaes; b = 0.31 and 0.23 in G. angustifolia). In B. gasipaes, vessels decrease in Dh from the stem's centre towards the periphery, an opposite pattern compared with dicot trees. Along the leaf rachis, a pattern of increasing Dh basally was also found (b = 0.13). The hydraulic design of the monocots studied revealed an axial pattern of xylem conduits similar to those evolved by dicots to compensate and minimize the negative effect of root-to-leaf length on hydrodynamic resistance to water flow.
Key message Double-stained microsections from high altitude Pinus nigra wood cores highlighted un... more Key message Double-stained microsections from high altitude Pinus nigra wood cores highlighted unlignified latewood cells possibly linked to abrupt temperature reduction at the end of the growing season. More consolidated detection could increase their role in dendroecology. Abstract Cambial activity and wood formation are influenced by environmental factors, primarily climate. During cell wall formation the lignification is mainly controlled by temperature. By staining with safranin and astra blue it is possible to distinguish cell walls richer in lignin (stained in red) from those richer in cellulose (stained in blue). Here we show an uncommon phenomenon observed in 41 transverse sections prepared for anatomical studies of young European black pine (Pinus nigra Arnold) individuals. We detected some layers of incompletely lignified cells that appear blue in safranin-astra blue-stained sections. Growth rings showing this anatomical feature were named ''blue rings''. The aims of this preliminary study are: (i) to describe the features of this peculiar anatomical trait, (ii) to enhance its visualization, and (iii) to suggest possible drivers of its formation. First results indicate the influence of low air temperature causing a lack of lignification in latewood cells. The added values provided by the identification of ''blue rings'' within tree-ring series could be (i) their possible use as pointer year, (ii) cross dating improvement, and (iii) finer assessment of tree sensitivity to environmental and climatic factors.
E nvironmental political action catalyzed about 35 years ago in Europe, with the widespread publi... more E nvironmental political action catalyzed about 35 years ago in Europe, with the widespread public perception that forests were dying as a result of air pollution and related acid deposition (Schütt and Cowling 1985; Innes 1987; Kandler and Innes 1995). This apparent decline, considered to be unprecedented in a broad spatiotemporal context, stimulated new pollution control legislation and promoted environmental awareness. However, scientific curiosity about this subject gradually waned after a decade of intensive research in conjunction with evidence of forest ecosystem recovery (Spiecker 1995).
In most mountain regions forests growing at high altitude have fundamental ecological roles and o... more In most mountain regions forests growing at high altitude have fundamental ecological roles and other benefits to humans. A key factor affecting the structure and evolution of these forest stands is the spatial and temporal dynamics of natural regeneration. Sound empirical knowledge is therefore important to support management prescriptions aimed at guaranteeing the space and time continuity of the forest cover through proper natural regeneration.
Climatic extreme events strongly affect forest growth and thus significantly influence the inter-... more Climatic extreme events strongly affect forest growth and thus significantly influence the inter-annual terrestrial carbon balance. As we are facing an increase in frequency and intensity of climate extremes, extensive empirical archives are required to assess continental scale impacts of temperature and precipitation anomalies. Here we divide a tree-ring network of approximately 1000 sites into fifteen groups of similar high-frequency growth variability to reconstruct regional positive and negative extreme events in different parts of Europe between 1500 and 2008. Synchronized growth maxima or minima within and among regions indicate eighteen years in the pre-instrumental period and two events in the 20th century (1948, 1976) with extensive radial growth fluctuations. Comparisons with instrumental data showed that the European tree-ring network mirrors the spatial extent of temperature and precipitation extremes, but the interpretation of pre-instrumental events is challenged by lagged responses to off-growing season climate extremes. We were able to attribute growth minima in subsequent years to unfavourable August-October conditions and to mild climate during winter months associated with respiratory carbon losses. Our results emphasize the importance of carry-over effects and species-specific growth characteristics for forest productivity. Furthermore, they promote the use of regional tree-ring chronologies in research related to climate variability and terrestrial carbon sink dynamics.
Evidence for reduced sensitivity of tree growth to temperature has been reported from multiple fo... more Evidence for reduced sensitivity of tree growth to temperature has been reported from multiple forests along the high northern latitudes. This alleged circumpolar phenomenon described the apparent inability of temperature-sensitive tree-ring width and density chronologies to parallel increasing instrumental temperature measurements since the mid-20th century. In addition to such low-frequency trend offset, the inability of formerly temperature-sensitive tree growth to reflect high-frequency temperature signals in a warming world is indicated at some boreal sites, mainly in Alaska, the Yukon and Siberia. Here, we refer to both of these findings as the 'divergence problem' (DP), with their causes and scale being debated. If DP is widespread and the result of climatic forcing, the overall reliability of tree-ring-based temperature reconstructions should be questioned. Testing for DP benefits from well-replicated tree-ring and instrumental data spanning from the 19th to the 21st century. Here, we present a network of 124 larch and spruce sites across the European Alpine arc. Tree-ring width chronologies from 40 larch and 24 spruce sites were selected based on their correlation with early instrumental temperatures to assess their ability of tracking recent temperature variations. After the tree-ring series of both species were detrended in a manner that allows low-frequency variations to be preserved and scaled against summer temperatures, no unusual late 20th century DP is found. Independent tree-ring width and density evidence for unprecedented late 20th century temperatures with respect to the past millennium further reinforces our results.
Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a cont... more Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a continental-scale tree-ring network.
Aim Climate change is expected to modify growth trends of forests around the world. However, this... more Aim Climate change is expected to modify growth trends of forests around the world. However, this modification may vary in strength and intensity across a species' biogeographical range. Here, we study European populations of silver fir (Abies alba) across its southern distribution limits in Spain, Italy and Roma-nia. We hypothesized that growth trends of silver fir will differ across its distribution range, with a marked decline in growth in drought-prone regions near the species' southernmost biogeographical limits. Location Europe (Spain, Italy, Romania). Methods We collected tree-ring data from at least 1300 silver fir trees located in 111 sites. The dataset was used to assess and model growth trends, quantified as changes in basal area increment, and to determine how growth responds to climate. Results We found contrasting patterns of basal area increments among countries and sites. Populations of silver fir located outside the Mediterranean area (e.g. northern Italy, Romania) have shown a clear increase in growth over the last two decades, whereas most populations in Spain and southern Italy have displayed a marked decline in growth since the 1980s. The growth of silver fir forests at the southwestern distribution limit is severely constrained by low spring–summer water availability, whereas growth of silver fir forests in non-Mediterranean areas is limited by cold conditions in late winter to early spring. Main conclusions Climate warming is distinctly modifying growth patterns and responses to climate in silver fir across most of the species' European distribution area. In southwestern Europe the reduction in growth of many populations is related to an observed increase in aridity, whereas in more temperate areas warming is enhancing growth. Our results confirm a decline in the growth of silver fir at its southwestern distribution limits as a consequence of climate warming.
High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances.... more High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances. Nonetheless, even in this remote region, human pressure is often most important in influencing forest and landscape structure. In the last decades, fuelwood demand has risen due to increasing numbers of tourists and mountaineers. To understand human interactions with forest resources, stand structure and composition were examined at the landscape scale in the Sagarmatha National Park and its Buffer Zone in the Khumbu valley (Nepal). Using biological and historical data sources, a multi-scale approach revealed the influence of human activities on the distribution of tree species and forest structure. We sampled stand structure and environmental characteristics from 173 plots, and derived anthropogenic variables from thematic maps and satellite images for multivariate statistical analyses. Results suggest relationships among forest structure, anthropogenic influences, and topography. Low-density stands (100-150 tph) with sparse trees and rare big trees were in close proximity (0-36 m) to tracks and lodges. The wide variability in species diversity (0.67 at SNP and 0.58 at BZ) was strongly related to environmental factors, such as elevation, and human pressure. The frequent removal of green branches has adverse effects on tree growth, forest resistance, resilience, and regeneration capacity. We conclude that natural resources can adequately supply the local population needs, but current practices are not sustainable.
Sustainable forest management has to consider the long-term effects of climate change on species ... more Sustainable forest management has to consider the long-term effects of climate change on species growth to develop adaptation measures. In this perspective, dendrochronology provides valuable information on climate-growth relationships over long time periods. Tree-ring analyses in mixed stands can elucidate how different species respond to climate change within the same environmental conditions. However, few studies have investigated such stands, especially in South-Eastern Europe. In the forest reserve of Lom, in Bosnia and Herzegovina, we had the opportunity to study three co-occurring species (silver fir, Norway spruce, European beech) in an old-growth forest characterized by reduced human and natural disturbances, and a climate favourable to the tree species. We evaluated tree growth response to climate on inter-annual and decadal time scales over about 250 years. Response to inter-annual climate variability changed over the study period. Climate signal in beech was generally low, with a negative correlation to April temperature in the last decades. In fir and spruce, the positive effect of current year's spring temperature decreased, while the negative effect of the previous summer temperature considerably increased over the last century. At the decadal scale, different responses have been detected among species: spruce was mostly negatively affected by summer temperature whereas summer precipitation benefited fir growth, probably balancing high evapotranspiration. Beech showed a peculiar delayed response, and protracted drought periods led to severe growth reductions. Despite a temperature increase over the last three decades, fir did not experience any growth reduction, while a strong decline was evident in spruce and beech productivity. Mesic sites are commonly underrepresented in tree-ring research. In our analysis, covering about 250 years, we observed that climate also affects species-specific growth patterns in these areas. Within a global change perspective, specific divergent responses are likely to occur even where current environmental conditions appear to be not limiting for tree species. Future management strategies should consider these outcomes.
Proceedings of the National Academy of Sciences of the United States of America, Jan 27, 2010
Ecological communities exhibit pervasive patterns and interrelationships between size, abundance,... more Ecological communities exhibit pervasive patterns and interrelationships between size, abundance, and the availability of resources. We use scaling ideas to develop a unified, model-independent framework for understanding the distribution of tree sizes, their energy use, and spatial distribution in tropical forests. We demonstrate that the scaling of the tree crown at the individual level drives the forest structure when resources are fully used. Our predictions match perfectly with the scaling behavior of an exactly solvable self-similar model of a forest and are in good accord with empirical data. The range, over which pure power law behavior is observed, depends on the available amount of resources. The scaling framework can be used for assessing the effects of natural and anthropogenic disturbances on ecosystem structure and functionality.
High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances.... more High altitude Himalayan regions are geo-dynamically active and sensitive to natural disturbances. Nonetheless, even in this remote region, human pressure is often most important in influencing forest and landscape structure. In the last decades, fuelwood demand has risen due to increasing numbers of tourists and mountaineers. To understand human interactions with forest resources, stand structure and composition were examined at the landscape scale in the Sagarmatha National Park and its Buffer Zone in the Khumbu valley (Nepal). Using biological and historical data sources, a multi-scale approach revealed the influence of human activities on the distribution of tree species and forest structure. We sampled stand structure and environmental characteristics from 173 plots, and derived anthropogenic variables from thematic maps and satellite images for multivariate statistical analyses. Results suggest relationships among forest structure, anthropogenic influences, and topography. Low-density stands (100-150 tph) with sparse trees and rare big trees were in close proximity (0-36 m) to tracks and lodges. The wide variability in species diversity (0.67 at SNP and 0.58 at BZ) was strongly related to environmental factors, such as elevation, and human pressure. The frequent removal of green branches has adverse effects on tree growth, forest resistance, resilience, and regeneration capacity. We conclude that natural resources can adequately supply the local population needs, but current practices are not sustainable.
Dicotyledons have evolved a strategy to compensate for the increase in hydraulic resistance to wa... more Dicotyledons have evolved a strategy to compensate for the increase in hydraulic resistance to water transport with height growth by widening xylem conduits downwards. In monocots, the accumulation of hydraulic resistance with height should be similar, but the absence of secondary growth represents a strong limitation for the maintenance of xylem hydraulic efficiency during ontogeny. The hydraulic architecture of monocots has been studied but it is unclear how monocots arrange their axial vascular structure during ontogeny to compensate for increases in height. We measured the vessel lumina and estimated the hydraulic diameter (Dh) at different heights along the stem of two arborescent monocots, Bactris gasipaes (Kunth) and Guadua angustifolia (Kunth). For the former, we also estimated the variation in Dh along the leaf rachis. Hydraulic diameter increased basally from the stem apex to the base with a scaling exponent (b) in the range of those reported for dicot trees (b = 0.22 in B. gasipaes; b = 0.31 and 0.23 in G. angustifolia). In B. gasipaes, vessels decrease in Dh from the stem's centre towards the periphery, an opposite pattern compared with dicot trees. Along the leaf rachis, a pattern of increasing Dh basally was also found (b = 0.13). The hydraulic design of the monocots studied revealed an axial pattern of xylem conduits similar to those evolved by dicots to compensate and minimize the negative effect of root-to-leaf length on hydrodynamic resistance to water flow.
Key message Double-stained microsections from high altitude Pinus nigra wood cores highlighted un... more Key message Double-stained microsections from high altitude Pinus nigra wood cores highlighted unlignified latewood cells possibly linked to abrupt temperature reduction at the end of the growing season. More consolidated detection could increase their role in dendroecology. Abstract Cambial activity and wood formation are influenced by environmental factors, primarily climate. During cell wall formation the lignification is mainly controlled by temperature. By staining with safranin and astra blue it is possible to distinguish cell walls richer in lignin (stained in red) from those richer in cellulose (stained in blue). Here we show an uncommon phenomenon observed in 41 transverse sections prepared for anatomical studies of young European black pine (Pinus nigra Arnold) individuals. We detected some layers of incompletely lignified cells that appear blue in safranin-astra blue-stained sections. Growth rings showing this anatomical feature were named ''blue rings''. The aims of this preliminary study are: (i) to describe the features of this peculiar anatomical trait, (ii) to enhance its visualization, and (iii) to suggest possible drivers of its formation. First results indicate the influence of low air temperature causing a lack of lignification in latewood cells. The added values provided by the identification of ''blue rings'' within tree-ring series could be (i) their possible use as pointer year, (ii) cross dating improvement, and (iii) finer assessment of tree sensitivity to environmental and climatic factors.
E nvironmental political action catalyzed about 35 years ago in Europe, with the widespread publi... more E nvironmental political action catalyzed about 35 years ago in Europe, with the widespread public perception that forests were dying as a result of air pollution and related acid deposition (Schütt and Cowling 1985; Innes 1987; Kandler and Innes 1995). This apparent decline, considered to be unprecedented in a broad spatiotemporal context, stimulated new pollution control legislation and promoted environmental awareness. However, scientific curiosity about this subject gradually waned after a decade of intensive research in conjunction with evidence of forest ecosystem recovery (Spiecker 1995).
In most mountain regions forests growing at high altitude have fundamental ecological roles and o... more In most mountain regions forests growing at high altitude have fundamental ecological roles and other benefits to humans. A key factor affecting the structure and evolution of these forest stands is the spatial and temporal dynamics of natural regeneration. Sound empirical knowledge is therefore important to support management prescriptions aimed at guaranteeing the space and time continuity of the forest cover through proper natural regeneration.
Climatic extreme events strongly affect forest growth and thus significantly influence the inter-... more Climatic extreme events strongly affect forest growth and thus significantly influence the inter-annual terrestrial carbon balance. As we are facing an increase in frequency and intensity of climate extremes, extensive empirical archives are required to assess continental scale impacts of temperature and precipitation anomalies. Here we divide a tree-ring network of approximately 1000 sites into fifteen groups of similar high-frequency growth variability to reconstruct regional positive and negative extreme events in different parts of Europe between 1500 and 2008. Synchronized growth maxima or minima within and among regions indicate eighteen years in the pre-instrumental period and two events in the 20th century (1948, 1976) with extensive radial growth fluctuations. Comparisons with instrumental data showed that the European tree-ring network mirrors the spatial extent of temperature and precipitation extremes, but the interpretation of pre-instrumental events is challenged by lagged responses to off-growing season climate extremes. We were able to attribute growth minima in subsequent years to unfavourable August-October conditions and to mild climate during winter months associated with respiratory carbon losses. Our results emphasize the importance of carry-over effects and species-specific growth characteristics for forest productivity. Furthermore, they promote the use of regional tree-ring chronologies in research related to climate variability and terrestrial carbon sink dynamics.
Evidence for reduced sensitivity of tree growth to temperature has been reported from multiple fo... more Evidence for reduced sensitivity of tree growth to temperature has been reported from multiple forests along the high northern latitudes. This alleged circumpolar phenomenon described the apparent inability of temperature-sensitive tree-ring width and density chronologies to parallel increasing instrumental temperature measurements since the mid-20th century. In addition to such low-frequency trend offset, the inability of formerly temperature-sensitive tree growth to reflect high-frequency temperature signals in a warming world is indicated at some boreal sites, mainly in Alaska, the Yukon and Siberia. Here, we refer to both of these findings as the 'divergence problem' (DP), with their causes and scale being debated. If DP is widespread and the result of climatic forcing, the overall reliability of tree-ring-based temperature reconstructions should be questioned. Testing for DP benefits from well-replicated tree-ring and instrumental data spanning from the 19th to the 21st century. Here, we present a network of 124 larch and spruce sites across the European Alpine arc. Tree-ring width chronologies from 40 larch and 24 spruce sites were selected based on their correlation with early instrumental temperatures to assess their ability of tracking recent temperature variations. After the tree-ring series of both species were detrended in a manner that allows low-frequency variations to be preserved and scaled against summer temperatures, no unusual late 20th century DP is found. Independent tree-ring width and density evidence for unprecedented late 20th century temperatures with respect to the past millennium further reinforces our results.
Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a cont... more Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a continental-scale tree-ring network.
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