The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Heikki Roininen - One of the best experts on this subject based on the ideXlab platform.
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The influence of windthrow area and timber characteristics on colonization of wind-felled Spruces by Ips typographus (L.)
Forest Ecology and Management, 2005Co-Authors: Miikka Eriksson, Antti Pouttu, Heikki RoininenAbstract:Abstract Leaving wind-felled Norway Spruces in forests is one way to increase the amount of dead wood. Many forest species would benefit because of these actions but unfortunately also forest pests such as the Spruce bark beetle (Ips typographus) reproduce in newly wind-felled trees. To minimize the risk of subsequent attacks on living trees, the decisions of removing trees out of the forest in high risk areas should be done as early as possible. If fallen trees are not colonized or if there are only a few colonized trees the risk of subsequent attacks on living trees are also minor. For this reason, it is essential to estimate the windthrow area and timber characteristics influencing the colonization of wind-felled trees. We studied the colonization of Norway Spruce dominated windthrow areas by I. typographus (L.) in 65 stands in southern Finland on two consecutive summers after the storms in November 2001. The studied areas ranged from single tree gaps to large gaps with over 3000 wind-felled Spruces. Using generalized linear modelling, we evaluated the significance of windthrow area and timber characteristics for the probability of the windthrow area to be colonized by I. typographus, the percentage of colonized wind-felled Spruces, the number of egg galleries, and the colonization density. In the first summer (2002) after the wind-felling 71% of studied windthrow areas were colonized by I. typographus. Only 1 of the 19 areas not colonized in 2002 was colonized in 2003. The number and mean diameter of wind-felled Spruces and the basal area of recently dead standing Spruces were the most important windthrow characteristics influencing colonization. The models showed that an increase in these characteristics also increased the values of the response variables. This study shows that local population levels of I. typographus varied greatly within the study area (appox. 200 km × 200 km) and that this variation should be included in models predicting the colonization risks of windthrown areas.
Miikka Eriksson - One of the best experts on this subject based on the ideXlab platform.
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The influence of windthrow area and timber characteristics on colonization of wind-felled Spruces by Ips typographus (L.)
Forest Ecology and Management, 2005Co-Authors: Miikka Eriksson, Antti Pouttu, Heikki RoininenAbstract:Abstract Leaving wind-felled Norway Spruces in forests is one way to increase the amount of dead wood. Many forest species would benefit because of these actions but unfortunately also forest pests such as the Spruce bark beetle (Ips typographus) reproduce in newly wind-felled trees. To minimize the risk of subsequent attacks on living trees, the decisions of removing trees out of the forest in high risk areas should be done as early as possible. If fallen trees are not colonized or if there are only a few colonized trees the risk of subsequent attacks on living trees are also minor. For this reason, it is essential to estimate the windthrow area and timber characteristics influencing the colonization of wind-felled trees. We studied the colonization of Norway Spruce dominated windthrow areas by I. typographus (L.) in 65 stands in southern Finland on two consecutive summers after the storms in November 2001. The studied areas ranged from single tree gaps to large gaps with over 3000 wind-felled Spruces. Using generalized linear modelling, we evaluated the significance of windthrow area and timber characteristics for the probability of the windthrow area to be colonized by I. typographus, the percentage of colonized wind-felled Spruces, the number of egg galleries, and the colonization density. In the first summer (2002) after the wind-felling 71% of studied windthrow areas were colonized by I. typographus. Only 1 of the 19 areas not colonized in 2002 was colonized in 2003. The number and mean diameter of wind-felled Spruces and the basal area of recently dead standing Spruces were the most important windthrow characteristics influencing colonization. The models showed that an increase in these characteristics also increased the values of the response variables. This study shows that local population levels of I. typographus varied greatly within the study area (appox. 200 km × 200 km) and that this variation should be included in models predicting the colonization risks of windthrown areas.
Antti Pouttu - One of the best experts on this subject based on the ideXlab platform.
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The influence of windthrow area and timber characteristics on colonization of wind-felled Spruces by Ips typographus (L.)
Forest Ecology and Management, 2005Co-Authors: Miikka Eriksson, Antti Pouttu, Heikki RoininenAbstract:Abstract Leaving wind-felled Norway Spruces in forests is one way to increase the amount of dead wood. Many forest species would benefit because of these actions but unfortunately also forest pests such as the Spruce bark beetle (Ips typographus) reproduce in newly wind-felled trees. To minimize the risk of subsequent attacks on living trees, the decisions of removing trees out of the forest in high risk areas should be done as early as possible. If fallen trees are not colonized or if there are only a few colonized trees the risk of subsequent attacks on living trees are also minor. For this reason, it is essential to estimate the windthrow area and timber characteristics influencing the colonization of wind-felled trees. We studied the colonization of Norway Spruce dominated windthrow areas by I. typographus (L.) in 65 stands in southern Finland on two consecutive summers after the storms in November 2001. The studied areas ranged from single tree gaps to large gaps with over 3000 wind-felled Spruces. Using generalized linear modelling, we evaluated the significance of windthrow area and timber characteristics for the probability of the windthrow area to be colonized by I. typographus, the percentage of colonized wind-felled Spruces, the number of egg galleries, and the colonization density. In the first summer (2002) after the wind-felling 71% of studied windthrow areas were colonized by I. typographus. Only 1 of the 19 areas not colonized in 2002 was colonized in 2003. The number and mean diameter of wind-felled Spruces and the basal area of recently dead standing Spruces were the most important windthrow characteristics influencing colonization. The models showed that an increase in these characteristics also increased the values of the response variables. This study shows that local population levels of I. typographus varied greatly within the study area (appox. 200 km × 200 km) and that this variation should be included in models predicting the colonization risks of windthrown areas.
Werner Schmidt - One of the best experts on this subject based on the ideXlab platform.
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Time-Resolved Chlorophyll Fluorescence for Monitoring of Forest Decline
Laser in der Umweltmeßtechnik Laser in Remote Sensing, 1994Co-Authors: Herbert Schneckenburger, Werner SchmidtAbstract:Aiming at clues of forest decline we studied prompt and delayed luminescence of Spruce needles from the picosecond to the second time range using various custom made kinetic equipments. Both kinetics in the picosecond and in the seconds time range could be fitted by three exponentially decaying components yielding three amplitudes and three reaction constants each. Basically, all components showed a typical annual time course, independent of the degree of damage or air pollution. In addition, it turned out that on one hand the “slow” component of picosecond decay kinetics (decay time τ = 2.0–3.5 ns) reflects some damage of the photosynthetic apparatus, which is mainly located in photosystem II. Similarly, in long term delayed luminescence in the seconds time range the “fast” component (decay time τ = 0.13 s) obviously carries some information on the Spruces’ vitality. In general, healthy or declined Spruces showed the highest photosynthetic efficiencies but also the most pronounced stress symptoms during the summer period — probalby due to high irradiance, drought and increased ozone concentrations.
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Time-resolved chlorophyll fluorescence for early detection of forest decline
Laser Study of Macroscopic Biosystems, 1993Co-Authors: Herbert Schneckenburger, Werner SchmidtAbstract:Aiming to an early detection of forest decline, prompt and delayed luminescence of Spruce needles was studied from the picosecond to the second time range using novel laser diodes and highly sensitive detection systems. In particular, (1) subnanosecond fluorescence decay measurements showed a superposition of at least three exponentially decaying components, the largest of which (decay time (tau) equals 2.0 - 3.5 ns) represented some `dead' chlorophyll or closed reaction centers. This component is more pronounced in slightly damaged than in healthy Spruces and can be used to monitor the early steps of photosynthesis. (2) Delayed luminescence -- which is supposed to report on the electron transport chain as a whole -- could also be correlated with the physiological state of the individual Spruce. In general, healthy and declined Spruces showed the highest photosynthetic efficiencies during the summer period, but also the most pronounced stress symptoms -- probably due to high irradiance, drought, and increased ozone concentrations.
John Mackay - One of the best experts on this subject based on the ideXlab platform.
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insect herbivory choristoneura fumiferana tortricidea underlies tree population structure picea glauca pinaceae
Scientific Reports, 2017Co-Authors: Genevieve J Parent, Isabelle Giguere, Gaby Germanos, Mebarek Lamara, Eric Bauce, John MackayAbstract:Variation in insect herbivory can lead to population structure in plant hosts as indicated by defence traits. In annual herbaceous, defence traits may vary between geographic areas but evidence of such patterns is lacking for long-lived species. This may result from the variety of selection pressures from herbivores, long distance gene flow, genome properties, and lack of research. We investigated the antagonistic interaction between white Spruce (Picea glauca) and Spruce budworm (SBW, Choristoneura fumiferana) the most devastating forest insect of eastern North America in common garden experiments. White Spruces that are able to resist SBW attack were reported to accumulate the acetophenones piceol and pungenol constitutively in their foliage. We show that levels of these acetophenones and transcripts of the gene responsible for their release is highly heritable and that their accumulation is synchronized with the most devastating stage of SBW. Piceol and pungenol concentrations negatively correlate with rate of development in female SBW and follow a non-random geographic variation pattern that is partially explained by historical damage from SBW and temperature. Our results show that accumulation of acetophenones is an efficient resistance mechanism against SBW in white Spruce and that insects can affect population structure of a long-lived plant.
