The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Douglas G. Sprugel - One of the best experts on this subject based on the ideXlab platform.
-
Spatial aspects of tree mortality strongly differ between young and old‐growth forests
Ecology, 2015Co-Authors: Andrew J Larson, Douglas G. Sprugel, Janneke Hillerislambers, James A. Lutz, Daniel C. Donato, James A. Freund, Mark E. Swanson, Jerry F FranklinAbstract:Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially autocorrelated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a three-decade record of tree mortality from replicated mapped permanent plots located in young ( 300-year-old) Abies Amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strongly density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatial...
-
morphological acclimation to understory environments in Abies Amabilis a shade and snow tolerant conifer species of the cascade mountains washington usa
Tree Physiology, 2008Co-Authors: Akira Mori, Eri Mizumachi, Douglas G. SprugelAbstract:: Light-related plasticity in a variety of crown morphology and within-tree characteristics was examined in sun and shade saplings of Abies Amabilis Dougl. ex J. Forbes growing in two late-successional forests with different snow regimes in the Cascade Mountains of Washington, USA. Compared with sun saplings, shade saplings typically had broad flat crowns as a result of acclimation at several scales (needle, shoot, branch, crown and whole sapling). Shoots of shade saplings had a smaller needle mass per unit of stem length than shoots of sun saplings, a feature that enhances light-interception efficiency by reducing among-needle shading. The low annual rate of needle production by shade saplings was associated with a longer needle lifespan and slower needle turnover. Reduced needle production within a shoot was reflected at the branch level, with lateral branches of shade saplings having a smaller needle mass than branches of the same length of sun saplings. Reduced allocation to needles permits greater investment in branches and stems, which is necessary to support the horizontally expanding branch system characteristic of shade saplings. Mean branch age of shade saplings was significantly higher than that of sun saplings. Shade saplings had lower needle mass per unit of trunk biomass or total biomass, reflecting greater investment in the trunk as a support organ. Increased investment in support organs in shade was more evident in the snowier habitat. The observed morphological acclimation makes A. Amabilis highly shade and snow-tolerant and thus able to dominate in many late-successional forests in snowy coastal mountain regions.
-
control of transpiration in a 220 year old Abies Amabilis forest
Forest Ecology and Management, 2001Co-Authors: T A Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Thomas M HinckleyAbstract:Abstract We measured sap flow at the branch and tree levels, and calculated tree transpiration at the stand level, in a 220-year-old Abies Amabilis (Dougl.) Forbes forest. Temporal and spatial patterns of branch sap flow rate per unit leaf area reflected differences in canopy position and diurnal variation in radiation exposure. Average leaf area normalized branch conductance of upper canopy branches ranged from 0.50 to 1.01 mm s−1. Maximum leaf area normalized tree sap flow rates were similar to those previously measured in a younger A. Amabilis forest (about 80 g m−2 leaf area h−1), but dominant trees in the old growth stand transpired approximately three times more per day (up to 281 kg H2O per day) than dominant trees in the younger forest. This difference was attributed primarily to leaf area: dominant trees in the old growth stand had approximately three times more leaf area than those in the younger Abies stand. Crown conductance on a ground area basis varied by an order of magnitude between the smallest and largest trees measured (maximum 4.84 mm s−1 and mean 1.44 mm s−1 versus maximum 37.54 mm s−1 and average 12.16 mm s−1, respectively). There was considerable spatial and temporal variation in stomatal versus boundary layer control of transpiration as expressed by the Ω decoupling coefficient. Ω for the largest measured tree ranged from less than 0.1 to greater than 0.6, and remained above 0.3 for more than 9% of the daylight hours monitored. The degree of decoupling decreased with tree size, with Ω of the smallest tree sampled never exceeding 0.3. Daily stand transpiration ranged from less than 0.4 mm to greater than 3.3 mm depending on radiation and vapor pressure deficit.
-
boundary layer conductance leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:: We used three methods to measure boundary layer conductance to heat transfer (g(bH)) and water vapor transfer (g(bV)) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s(-1) at low wind speeds (< 0.1 m s(-1)) to over 150 mm s(-1) at wind speeds of 2.0 m s(-1). Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (r(sV)) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (g(sV)) is small compared with g(bV). Analysis of the relative magnitudes of g(sV) and g(bV) revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., g(sV) is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 degrees C. Leaf temperature exceeded air temperature by more than 2 degrees C on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
Boundary layer conductance, leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:We used three methods to measure boundary layer conductance to heat transfer (gbH) and water vapor transfer (gbV) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s竏・ at low wind speeds (< 0.1 m s竏・) to over 150 mm s竏・ at wind speeds of 2.0 m s竏・. Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (gsV) is small compared with gbV. Analysis of the relative magnitudes of gsV and gbV revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., gsV is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 ﾂｰC. Leaf temperature exceeded air temperature by more than 2 ﾂｰC on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
Thomas M Hinckley - One of the best experts on this subject based on the ideXlab platform.
-
control of transpiration in a 220 year old Abies Amabilis forest
Forest Ecology and Management, 2001Co-Authors: T A Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Thomas M HinckleyAbstract:Abstract We measured sap flow at the branch and tree levels, and calculated tree transpiration at the stand level, in a 220-year-old Abies Amabilis (Dougl.) Forbes forest. Temporal and spatial patterns of branch sap flow rate per unit leaf area reflected differences in canopy position and diurnal variation in radiation exposure. Average leaf area normalized branch conductance of upper canopy branches ranged from 0.50 to 1.01 mm s−1. Maximum leaf area normalized tree sap flow rates were similar to those previously measured in a younger A. Amabilis forest (about 80 g m−2 leaf area h−1), but dominant trees in the old growth stand transpired approximately three times more per day (up to 281 kg H2O per day) than dominant trees in the younger forest. This difference was attributed primarily to leaf area: dominant trees in the old growth stand had approximately three times more leaf area than those in the younger Abies stand. Crown conductance on a ground area basis varied by an order of magnitude between the smallest and largest trees measured (maximum 4.84 mm s−1 and mean 1.44 mm s−1 versus maximum 37.54 mm s−1 and average 12.16 mm s−1, respectively). There was considerable spatial and temporal variation in stomatal versus boundary layer control of transpiration as expressed by the Ω decoupling coefficient. Ω for the largest measured tree ranged from less than 0.1 to greater than 0.6, and remained above 0.3 for more than 9% of the daylight hours monitored. The degree of decoupling decreased with tree size, with Ω of the smallest tree sampled never exceeding 0.3. Daily stand transpiration ranged from less than 0.4 mm to greater than 3.3 mm depending on radiation and vapor pressure deficit.
-
boundary layer conductance leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:: We used three methods to measure boundary layer conductance to heat transfer (g(bH)) and water vapor transfer (g(bV)) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s(-1) at low wind speeds (< 0.1 m s(-1)) to over 150 mm s(-1) at wind speeds of 2.0 m s(-1). Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (r(sV)) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (g(sV)) is small compared with g(bV). Analysis of the relative magnitudes of g(sV) and g(bV) revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., g(sV) is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 degrees C. Leaf temperature exceeded air temperature by more than 2 degrees C on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
Boundary layer conductance, leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:We used three methods to measure boundary layer conductance to heat transfer (gbH) and water vapor transfer (gbV) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s竏・ at low wind speeds (< 0.1 m s竏・) to over 150 mm s竏・ at wind speeds of 2.0 m s竏・. Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (gsV) is small compared with gbV. Analysis of the relative magnitudes of gsV and gbV revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., gsV is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 ﾂｰC. Leaf temperature exceeded air temperature by more than 2 ﾂｰC on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
crown conductance and tree and stand transpiration in a second growth Abies Amabilis forest
Canadian Journal of Forest Research, 1997Co-Authors: Timothy A. Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Jan Cermak, R Ceulemans, J S Rombold, Thomas M HinckleyAbstract:We measured whole-tree sap flow in a 43-year-old Abies Amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes n Tsuga heterophylla (Raf.) Sarg. forest in western Washington, U.S.A. We calculated whole-tree crown conductance to water vapor (gcrown) by substituting the sap flow data and meteorological measurements into the inverted PenmannMonteith equation. Individual tree sap flow and crown conductance varied widely with tree size, with the smallest tree sampled having average gcrown (on a ground-area basis) of 0.57 mms n1 and transpiring up to 4.9 kgday n1 , while the largest tree measured had an average gcrown of 7.20 mms n1 and lost as much as 98 kgday n1 . Crown conductance responded linearly and positively to radiation, and had a negative exponential response to vapor pressure deficit. These response patterns were utilized to construct an empirical model of gcrown that explained from 52 to 73% (average 66%) of the variation in gcrown. The dominant and codominant trees in the stand transpired for longer periods during the day than trees in the smaller size classes, and contributed disproportionately to total stand transpiration. Daily total sap flow for individual trees was strongly correlated with tree basal area; we used the relationship between these variables to estimate daily stand transpiration. Stand transpiration calculated for 28 days between August 6 and October 12, 1993, ranged from 0.01 to 3.52 mmday n1 . Stand transpiration increased curvilinearly with increasing average daily vapor pressure deficit, reflecting the negative response of gcrown to vapor pressure deficit.
-
effects of light on shoot geometry and needle morphology in Abies Amabilis
Tree Physiology, 1996Co-Authors: Douglas G. Sprugel, J R Brooks, Thomas M HinckleyAbstract:: In some conifers, shoot geometry and needle morphology vary significantly in response to the light conditions under which they develop. We measured shoot length, silhouette area, total projected needle area, total needle weight and needle thickness on current shoots developed under a wide range of light conditions in a 36-year-old Abies Amabilis (Dougl.) Forbes stand. Current light was quantified by evaluating percent openness from hemispherical photographs taken before the growing season. Unweighted total openness was correlated with shoot geometry and needle morphology better than any weighted indices tested. Needle thickness and leaf mass/area were both closely correlated with total openness (R(2) = 0.86 and 0.82, respectively). The most exposed needles were 2.5 times thicker and had 3-4 times more leaf mass/area than the most shaded needles. Total projected leaf area/shoot silhouette area was also correlated with openness (R(2) = 0.74) and was about twice as high in sun shoots as in shaded shoots. As a result of greater leaf mass/leaf area and greater leaf area/shoot silhouette area, a unit of intercepted light was dispersed over about 6 times as much leaf mass in a sun shoot as in a shade shoot, which presumably permits more efficient utilization of the intercepted light under high illumination with less energy wastage to light saturation. Moreover, leaf mass per unit of silhouette area was almost exactly proportional to canopy openness, as predicted by resource optimization theory if nitrogen concentration and photosynthetic capacity per unit mass are constant in new leaves. The close correlation of needle thickness and leaf mass/area with openness suggests that either parameter could be used as an index of the distribution of light or light-driven processes in an A. Amabilis canopy.
Akira Mori - One of the best experts on this subject based on the ideXlab platform.
-
convergence of leaf display and photosynthetic characteristics of understory Abies Amabilis and tsuga heterophylla in an old growth forest in southwestern washington state usa
Tree Physiology, 2009Co-Authors: Hiroaki Ishii, Kenichi Yoshimura, Akira MoriAbstract:Summary We compared the morphological and physiological characteristics of understory trees of Abies Amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes and Tsuga heterophylla (Raf.) Sarg. growing adjacent to each other in an old-growth forest in southwestern Washington State, USA. We hypothesized that, despite contrasting branching patterns and crown architectures, the two species should exhibit convergence in leaf display and photosynthetic gain per light intercepting area, because these are important properties determining their survival in the light-limited understory. The branching pattern of A. Amabilis was regular (normal shoot-length distribution, less variable branching angle and bifurcation ratio), whereas that of T. heterophylla was more plastic (positively skewed shoot-length distribution, more variable branching angle and bifurcation ratio). The two species had similar shoot morphologies: number of leaves per unit shoot length and leaf to axis dry mass ratio. Leaf morphology, in contrast, was significantly different. Leaves of A. Amabilis were larger and heavier than those of T. heterophylla, which resulted in lower mass-based photosynthetic rate for A. Amabilis. Despite these differences, the two species had similar levels of leaf overlap and area-based photosynthetic characteristics. Needle longevity of A. Amabilis was nearly twice that of T. heterophylla. The leaf N contents of current and 1-year-old leaves were lower for A. Amabilis than for T. heterophylla. However, the leaf N content of A. Amabilis did not change from current leaves to 6-year-old leaves, whereas that of T. heterophylla decreased with increasing leaf age. Abies Amabilis had deeper crowns than T. heterophylla and retained branches with low relative growth rates. Longer branch retention may compensate for the lower branch-level assimilation rate of A. Amabilis. We inferred that the convergence of leaf display and photosynthetic characteristics between A. Amabilis and T. heterophylla may contribute to the persistence of both species in the understory of this forest.
-
morphological acclimation to understory environments in Abies Amabilis a shade and snow tolerant conifer species of the cascade mountains washington usa
Tree Physiology, 2008Co-Authors: Akira Mori, Eri Mizumachi, Douglas G. SprugelAbstract:: Light-related plasticity in a variety of crown morphology and within-tree characteristics was examined in sun and shade saplings of Abies Amabilis Dougl. ex J. Forbes growing in two late-successional forests with different snow regimes in the Cascade Mountains of Washington, USA. Compared with sun saplings, shade saplings typically had broad flat crowns as a result of acclimation at several scales (needle, shoot, branch, crown and whole sapling). Shoots of shade saplings had a smaller needle mass per unit of stem length than shoots of sun saplings, a feature that enhances light-interception efficiency by reducing among-needle shading. The low annual rate of needle production by shade saplings was associated with a longer needle lifespan and slower needle turnover. Reduced needle production within a shoot was reflected at the branch level, with lateral branches of shade saplings having a smaller needle mass than branches of the same length of sun saplings. Reduced allocation to needles permits greater investment in branches and stems, which is necessary to support the horizontally expanding branch system characteristic of shade saplings. Mean branch age of shade saplings was significantly higher than that of sun saplings. Shade saplings had lower needle mass per unit of trunk biomass or total biomass, reflecting greater investment in the trunk as a support organ. Increased investment in support organs in shade was more evident in the snowier habitat. The observed morphological acclimation makes A. Amabilis highly shade and snow-tolerant and thus able to dominate in many late-successional forests in snowy coastal mountain regions.
Frederick C Meinzer - One of the best experts on this subject based on the ideXlab platform.
-
control of transpiration in a 220 year old Abies Amabilis forest
Forest Ecology and Management, 2001Co-Authors: T A Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Thomas M HinckleyAbstract:Abstract We measured sap flow at the branch and tree levels, and calculated tree transpiration at the stand level, in a 220-year-old Abies Amabilis (Dougl.) Forbes forest. Temporal and spatial patterns of branch sap flow rate per unit leaf area reflected differences in canopy position and diurnal variation in radiation exposure. Average leaf area normalized branch conductance of upper canopy branches ranged from 0.50 to 1.01 mm s−1. Maximum leaf area normalized tree sap flow rates were similar to those previously measured in a younger A. Amabilis forest (about 80 g m−2 leaf area h−1), but dominant trees in the old growth stand transpired approximately three times more per day (up to 281 kg H2O per day) than dominant trees in the younger forest. This difference was attributed primarily to leaf area: dominant trees in the old growth stand had approximately three times more leaf area than those in the younger Abies stand. Crown conductance on a ground area basis varied by an order of magnitude between the smallest and largest trees measured (maximum 4.84 mm s−1 and mean 1.44 mm s−1 versus maximum 37.54 mm s−1 and average 12.16 mm s−1, respectively). There was considerable spatial and temporal variation in stomatal versus boundary layer control of transpiration as expressed by the Ω decoupling coefficient. Ω for the largest measured tree ranged from less than 0.1 to greater than 0.6, and remained above 0.3 for more than 9% of the daylight hours monitored. The degree of decoupling decreased with tree size, with Ω of the smallest tree sampled never exceeding 0.3. Daily stand transpiration ranged from less than 0.4 mm to greater than 3.3 mm depending on radiation and vapor pressure deficit.
-
boundary layer conductance leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:: We used three methods to measure boundary layer conductance to heat transfer (g(bH)) and water vapor transfer (g(bV)) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s(-1) at low wind speeds (< 0.1 m s(-1)) to over 150 mm s(-1) at wind speeds of 2.0 m s(-1). Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (r(sV)) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (g(sV)) is small compared with g(bV). Analysis of the relative magnitudes of g(sV) and g(bV) revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., g(sV) is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 degrees C. Leaf temperature exceeded air temperature by more than 2 degrees C on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
Boundary layer conductance, leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:We used three methods to measure boundary layer conductance to heat transfer (gbH) and water vapor transfer (gbV) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s竏・ at low wind speeds (< 0.1 m s竏・) to over 150 mm s竏・ at wind speeds of 2.0 m s竏・. Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (gsV) is small compared with gbV. Analysis of the relative magnitudes of gsV and gbV revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., gsV is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 ﾂｰC. Leaf temperature exceeded air temperature by more than 2 ﾂｰC on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
crown conductance and tree and stand transpiration in a second growth Abies Amabilis forest
Canadian Journal of Forest Research, 1997Co-Authors: Timothy A. Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Jan Cermak, R Ceulemans, J S Rombold, Thomas M HinckleyAbstract:We measured whole-tree sap flow in a 43-year-old Abies Amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes n Tsuga heterophylla (Raf.) Sarg. forest in western Washington, U.S.A. We calculated whole-tree crown conductance to water vapor (gcrown) by substituting the sap flow data and meteorological measurements into the inverted PenmannMonteith equation. Individual tree sap flow and crown conductance varied widely with tree size, with the smallest tree sampled having average gcrown (on a ground-area basis) of 0.57 mms n1 and transpiring up to 4.9 kgday n1 , while the largest tree measured had an average gcrown of 7.20 mms n1 and lost as much as 98 kgday n1 . Crown conductance responded linearly and positively to radiation, and had a negative exponential response to vapor pressure deficit. These response patterns were utilized to construct an empirical model of gcrown that explained from 52 to 73% (average 66%) of the variation in gcrown. The dominant and codominant trees in the stand transpired for longer periods during the day than trees in the smaller size classes, and contributed disproportionately to total stand transpiration. Daily total sap flow for individual trees was strongly correlated with tree basal area; we used the relationship between these variables to estimate daily stand transpiration. Stand transpiration calculated for 28 days between August 6 and October 12, 1993, ranged from 0.01 to 3.52 mmday n1 . Stand transpiration increased curvilinearly with increasing average daily vapor pressure deficit, reflecting the negative response of gcrown to vapor pressure deficit.
Timothy A. Martin - One of the best experts on this subject based on the ideXlab platform.
-
boundary layer conductance leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:: We used three methods to measure boundary layer conductance to heat transfer (g(bH)) and water vapor transfer (g(bV)) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s(-1) at low wind speeds (< 0.1 m s(-1)) to over 150 mm s(-1) at wind speeds of 2.0 m s(-1). Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (r(sV)) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (g(sV)) is small compared with g(bV). Analysis of the relative magnitudes of g(sV) and g(bV) revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., g(sV) is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 degrees C. Leaf temperature exceeded air temperature by more than 2 degrees C on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
Boundary layer conductance, leaf temperature and transpiration of Abies Amabilis branches
Tree Physiology, 1999Co-Authors: Timothy A. Martin, Frederick C Meinzer, Thomas M Hinckley, Douglas G. SprugelAbstract:We used three methods to measure boundary layer conductance to heat transfer (gbH) and water vapor transfer (gbV) in foliated branches of Abies Amabilis Dougl. ex J. Forbes, a subalpine forest tree that produces clumped shoot morphology on sun-formed branches. Boundary layer conductances estimated in the field from energy balance measurements increased linearly from approximately 10 mm s竏・ at low wind speeds (< 0.1 m s竏・) to over 150 mm s竏・ at wind speeds of 2.0 m s竏・. Boundary layer conductances measured on shoot models in a wind tunnel were consistently higher than field measurements. The difference between wind tunnel values and field measurements was attributable to variation in path length between the two experimental environments. Boundary layer conductance estimated by subtracting stomatal resistance (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small. Sensitivity analysis demonstrated that this method is not suitable for coniferous foliage or when stomatal conductance (gsV) is small compared with gbV. Analysis of the relative magnitudes of gsV and gbV revealed that, under most conditions, A. Amabilis branches are well coupled (i.e., gsV is the dominant controller of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become substantially higher than air temperature when radiation is high and wind speed is low. Over a two-month period, the maximum difference between leaf and air temperatures exceeded 6 ﾂｰC. Leaf temperature exceeded air temperature by more than 2 ﾂｰC on 10% of the daylight hours during this period. Consideration of both the photosynthetic temperature response of A. Amabilis foliage as well as the summer air temperature conditions in its habitat suggests that these elevated leaf temperatures do not have a significant impact on carbon gain during the growing season.
-
crown conductance and tree and stand transpiration in a second growth Abies Amabilis forest
Canadian Journal of Forest Research, 1997Co-Authors: Timothy A. Martin, Douglas G. Sprugel, Frederick C Meinzer, Kim J Brown, Jiři Kucera, Jan Cermak, R Ceulemans, J S Rombold, Thomas M HinckleyAbstract:We measured whole-tree sap flow in a 43-year-old Abies Amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes n Tsuga heterophylla (Raf.) Sarg. forest in western Washington, U.S.A. We calculated whole-tree crown conductance to water vapor (gcrown) by substituting the sap flow data and meteorological measurements into the inverted PenmannMonteith equation. Individual tree sap flow and crown conductance varied widely with tree size, with the smallest tree sampled having average gcrown (on a ground-area basis) of 0.57 mms n1 and transpiring up to 4.9 kgday n1 , while the largest tree measured had an average gcrown of 7.20 mms n1 and lost as much as 98 kgday n1 . Crown conductance responded linearly and positively to radiation, and had a negative exponential response to vapor pressure deficit. These response patterns were utilized to construct an empirical model of gcrown that explained from 52 to 73% (average 66%) of the variation in gcrown. The dominant and codominant trees in the stand transpired for longer periods during the day than trees in the smaller size classes, and contributed disproportionately to total stand transpiration. Daily total sap flow for individual trees was strongly correlated with tree basal area; we used the relationship between these variables to estimate daily stand transpiration. Stand transpiration calculated for 28 days between August 6 and October 12, 1993, ranged from 0.01 to 3.52 mmday n1 . Stand transpiration increased curvilinearly with increasing average daily vapor pressure deficit, reflecting the negative response of gcrown to vapor pressure deficit.
