The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Andreas Rigling - One of the best experts on this subject based on the ideXlab platform.
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drought induced adaptation of the xylem in Scots Pine and pubescent oak
Tree Physiology, 2009Co-Authors: Britta Eilmann, Roman Zweifel, Nina Buchmann, Patrick Fonti, Andreas RiglingAbstract:Summary Drought impairs tree growth in the innerAlPine valleys of Central Europe. We investigated species-specific responses to contrasting water supply, with Scots Pine (Pinus sylvestris L.), threatened by drought-induced mortality, and pubescent oak (Quercus pubescens Willd.), showing no connection between drought events and mortality. The two co-occurring tree species were compared, growing either along an open water channel or at a site with naturally dry conditions. In addition, the growth response of Scots Pine to a draining of a water channel was studied. We analysed the radial increment for the last 100 years and wood anatomical parameters for the last 45 years. Drought reduced the conduit area of pubescent oak, but increased the radial lumen diameter of the conduits in Scots Pine. Both species decreased their radial increment under drought. In Scots Pine, radial increment was generally more dependent on water availability than that in pubescent oak. Irrigated trees responded less negatively to high temperature as seen in the increase in the conduit area in pubescent oak and the removal of the limitation of cell division by high temperatures. After irrigation stopped, tree-ring width for Scots Pine decreased within 1-year delay, whereas lumen diameter and cell-wall thickness responded with a 4-year delay. Scots Pine seemed to optimize the carbon-perconduit-costs under drought by increasing conduits diameter while decreasing cell numbers. This strategy might lead to a complete loss of tree rings under severe drought and thus to an impairment of water transport. In contrast, in pubescent oak tree-ring width is less affected by summer drought because parts of the earlywood are built in early spring. Thus, pubescent oak might have gradual advantages over Pine in today’s climate of the inner-AlPine valley.
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drought as an inciting mortality factor in Scots Pine stands of the valais switzerland
Ecosystems, 2006Co-Authors: Matthias Dobbertin, Christof Bigler, Otto Ulrich Braker, Harald Bugmann, Andreas RiglingAbstract:During the 20th century, high mortality rates of Scots Pine (Pinus silvestris L.) have been observed over large areas in the Rhone valley (Valais, Switzerland) and in other dry valleys of the European Alps. In this study, we evaluated drought as a possible inciting factor of Scots Pine decline in the Valais. Averaged tree-ring widths, standardized tree-ring series, and estimated annual mortality risks were related to a drought index. Correlations between drought indices and standardized tree-ring series from 11 sites showed a moderate association. Several drought years and drought periods could be detected since 1864 that coincided with decreased growth. Although single, extreme drought years had generally a short-term, reversible effect on tree growth, multi-year drought initiated prolonged growth decreases that increased a tree’s long-term risk of death. Tree death occurred generally several years or even decades after the drought. In conclusion, drought has a limiting effect on tree growth and acts as a bottleneck event in triggering Scots Pine decline in the Valais.
Javier Retana - One of the best experts on this subject based on the ideXlab platform.
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patterns of forest decline and regeneration across Scots Pine populations
Ecosystems, 2013Co-Authors: Albert Vilacabrera, Jordi Martinezvilalta, Lucia Galiano, Javier RetanaAbstract:To predict future changes in forest ecosystems, it is crucial to understand the complex processes involved in decline of tree species populations and to evaluate the implications for potential vegetation shifts. Here, we study patterns of decline (canopy defoliation and mortality of adults) of four Scots Pine populations at the southern edge of its distribution and characterized by different combinations of climate dryness and intensity of past management. General linear and structural equation modeling were used to assess how biotic, abiotic, and management components interacted to explain the spatial variability of Scots Pine decline across and within populations. Regeneration patterns of Scots Pine and co-occurring oak species were analyzed to assess potential vegetation shifts. Decline trends were related to climatic dryness at the regional scale, but, ultimately, within-population forest structure, local site conditions, and past human legacies could be the main underlying drivers of Scots Pine decline. Overall, Scots Pine regeneration was negatively related to decline both within and between populations, whereas oak species responded to decline idiosyncratically across populations. Taken together, our results suggest that (1) patterns of decline are the result of processes acting at the plot level that modulate forest responses to local environmental stress and (2) decline of adult Scots Pine trees seems not to be compensated by self-recruitment so that the future dynamics of these forest ecosystems are uncertain.
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Lack of regeneration and climatic vulnerability to fire of Scots Pine may induce vegetation shifts at the southern edge of its distribution
Journal of Biogeography, 2011Co-Authors: Albert Vilà-cabrera, Anselm Rodrigo, Jordi Martínez-vilalta, Javier RetanaAbstract:Aim Forest ecosystems dominated by fire-sensitive species could suffer shifts in composition under altered crown fire regimes mediated by climate change. The aims of this study were to: (1) study the spatio-temporal patterns and the climatic distribution of fires in Scots Pine (Pinus sylvestris) forests during the last 31 years in north-eastern Spain, (2) evaluate the climatic vulnerability to fire of these forests in Spain, (3) analyse the regeneration of Scots Pine after fire, and (4) predict the mid-term maintenance or replacement of Scots Pine in burned areas. Location Catalonia (north-eastern Spain): the southern distribution limit of Scots Pine. Methods We characterized the spatio-temporal and the climatic distribution of fires that occurred in Catalonia between 1979 and 2009. We used a generalized linear model to characterize the climatic vulnerability to fire of Scots Pine in the whole of Spain. We assessed the regeneration of the species after crown fires in nine burned areas in Catalonia. The resulting data were integrated into a stochastic matrix model to predict the mid-term maintenance or replacement of Scots Pine in burned areas. Results During the last three decades, Scots Pine forests distributed in dry sites were most affected by fire. Our assessment of the vulnerability to fire of Scots Pine forests in Spain as a whole, based on climatic and topographical variables, showed that 32% of these forests are vulnerable to fire, and that this proportion could increase to 66% under a conservative climate change scenario. Field data showed almost no regeneration of Scots Pine after crown fires, and a limited capacity to recolonize from unburned edges, even in relatively old fires, with 90% of recruits located in the first 25 m from the edge. This process could be delayed by the elapsed time for new recruits to achieve reproductive maturity, which we estimated to be c. 15 years. Finally, our matrix model predicted the replacement of burned Scots Pine forests by oak (Quercus sp.) forests, shrublands or mixed resprouter forests. Main conclusions Increased vulnerability to fire of Scots Pine forests under future, warmer conditions may result in vegetation shifts at the southern edge of the distribution of the species.
Christof Bigler - One of the best experts on this subject based on the ideXlab platform.
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drought as an inciting mortality factor in Scots Pine stands of the valais switzerland
Ecosystems, 2006Co-Authors: Matthias Dobbertin, Christof Bigler, Otto Ulrich Braker, Harald Bugmann, Andreas RiglingAbstract:During the 20th century, high mortality rates of Scots Pine (Pinus silvestris L.) have been observed over large areas in the Rhone valley (Valais, Switzerland) and in other dry valleys of the European Alps. In this study, we evaluated drought as a possible inciting factor of Scots Pine decline in the Valais. Averaged tree-ring widths, standardized tree-ring series, and estimated annual mortality risks were related to a drought index. Correlations between drought indices and standardized tree-ring series from 11 sites showed a moderate association. Several drought years and drought periods could be detected since 1864 that coincided with decreased growth. Although single, extreme drought years had generally a short-term, reversible effect on tree growth, multi-year drought initiated prolonged growth decreases that increased a tree’s long-term risk of death. Tree death occurred generally several years or even decades after the drought. In conclusion, drought has a limiting effect on tree growth and acts as a bottleneck event in triggering Scots Pine decline in the Valais.
Harri Mäkinen - One of the best experts on this subject based on the ideXlab platform.
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Factors influencing the branchiness of young Scots Pine trees
Forestry, 2013Co-Authors: Saija Huuskonen, Sami Hakala, Harri Mäkinen, Jari Hynynen, Martti VarmolaAbstract:We studied the relationship between stand- and tree-level variables and branchiness of young Scots Pine (Pinus sylvestris L.) trees. Branchiness class (branchy‐not branchy) was visually determined based on the future saw timber quality. The study material consisted of tree-level inventory data for 140 young Scots Pine stands, which were repeatedly measured over 15 years, comprising 1976 trees in total. The plots covered the most common site types for Scots Pine in all the important wood production regions in Finland. The mean stand height was 3.4 and8.8 matthefirstandlastmeasurement,respectively.Thehighstanddensityandthepre-commercialthinning thatwasperformedwererelatedtothelowerprobabilityofbranchiness.Ontheotherhand,atree’slargediameter growth resulted in a higher probability of branchiness. The results indicated that the branchiness of young Scots Pinetreescanbeanticipatedbasedsolelyonthestand-levelinformationavailableattheinitialphaseofstanddevelopment. However, tree-level information will slightly improve the prognosis of future branchiness.
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predicting the decomposition of Scots Pine norway spruce and birch stems in finland
Ecological Applications, 2006Co-Authors: Harri Mäkinen, Jari Hynynen, Juha Siitonen, Risto SievänenAbstract:Models were developed for predicting the decomposition of dead wood for the main tree species in Finland, based on data collected from long-term thinning experiments in southern and central Finland. The decomposition rates were strongly related to the number of years after tree death. In contrast to previous studies, which have used the first-order exponential model, we found that the decomposition rate was not constant. Therefore, the Gompertz and Chapman-Richard's functions were fitted to the data. The slow initial decomposition period was mainly due to the fact that most dead trees remained standing as snags after their death. The initial period was followed by a period of rapid decomposition and, finally, by a period of moderately slow decomposition. Birch stems decomposed more rapidly than Scots Pine and Norway spruce stems. Decomposition rates of Norway spruce stems were somewhat lower than those of Scots Pine. Because the carbon concentration of decaying boles was relatively stable (about 50%) the rate of carbon loss follows that of mass loss. Models were also developed for the probability that a dead tree remains standing as a snag. During the first years after death, the probability was high. Thereafter, it decreased rapidly, the decrease being faster for birch stems than for Scots Pine and Norway spruce stems. Almost all stems had fallen down within 40 years after their death. In Scots Pine and Norway spruce, most snags remained hard and belonged to decay class 1. In birch, a higher proportion of snags belonged to the more advanced decay classes. The models provide a framework for predicting dead wood dynamics in managed as well as dense unthinned stands. The models can be incorporated into forest management planning systems, thereby facilitating estimates of carbon dynamics.
Jari Hynynen - One of the best experts on this subject based on the ideXlab platform.
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Factors influencing the branchiness of young Scots Pine trees
Forestry, 2013Co-Authors: Saija Huuskonen, Sami Hakala, Harri Mäkinen, Jari Hynynen, Martti VarmolaAbstract:We studied the relationship between stand- and tree-level variables and branchiness of young Scots Pine (Pinus sylvestris L.) trees. Branchiness class (branchy‐not branchy) was visually determined based on the future saw timber quality. The study material consisted of tree-level inventory data for 140 young Scots Pine stands, which were repeatedly measured over 15 years, comprising 1976 trees in total. The plots covered the most common site types for Scots Pine in all the important wood production regions in Finland. The mean stand height was 3.4 and8.8 matthefirstandlastmeasurement,respectively.Thehighstanddensityandthepre-commercialthinning thatwasperformedwererelatedtothelowerprobabilityofbranchiness.Ontheotherhand,atree’slargediameter growth resulted in a higher probability of branchiness. The results indicated that the branchiness of young Scots Pinetreescanbeanticipatedbasedsolelyonthestand-levelinformationavailableattheinitialphaseofstanddevelopment. However, tree-level information will slightly improve the prognosis of future branchiness.
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Energy wood thinning as a part of the stand management of Scots Pine and Norway spruce
Silva Fennica, 2009Co-Authors: Jani Heikkilä, Jari Hynynen, Matti Sirén, Anssi Ahtikoski, Tiina Sauvula, Mika LehtonenAbstract:2009. Energy wood thinning as a part of the stand management of Scots Pine and Norway spruce. Silva Fennica 43(1): 129–146.The effects of combined production of industrial and energy wood on yield and harvesting incomes, as well as the feasibility of energy wood procurement, were studied. Data for 22 Scots Pine (
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predicting the decomposition of Scots Pine norway spruce and birch stems in finland
Ecological Applications, 2006Co-Authors: Harri Mäkinen, Jari Hynynen, Juha Siitonen, Risto SievänenAbstract:Models were developed for predicting the decomposition of dead wood for the main tree species in Finland, based on data collected from long-term thinning experiments in southern and central Finland. The decomposition rates were strongly related to the number of years after tree death. In contrast to previous studies, which have used the first-order exponential model, we found that the decomposition rate was not constant. Therefore, the Gompertz and Chapman-Richard's functions were fitted to the data. The slow initial decomposition period was mainly due to the fact that most dead trees remained standing as snags after their death. The initial period was followed by a period of rapid decomposition and, finally, by a period of moderately slow decomposition. Birch stems decomposed more rapidly than Scots Pine and Norway spruce stems. Decomposition rates of Norway spruce stems were somewhat lower than those of Scots Pine. Because the carbon concentration of decaying boles was relatively stable (about 50%) the rate of carbon loss follows that of mass loss. Models were also developed for the probability that a dead tree remains standing as a snag. During the first years after death, the probability was high. Thereafter, it decreased rapidly, the decrease being faster for birch stems than for Scots Pine and Norway spruce stems. Almost all stems had fallen down within 40 years after their death. In Scots Pine and Norway spruce, most snags remained hard and belonged to decay class 1. In birch, a higher proportion of snags belonged to the more advanced decay classes. The models provide a framework for predicting dead wood dynamics in managed as well as dense unthinned stands. The models can be incorporated into forest management planning systems, thereby facilitating estimates of carbon dynamics.
