The effect of tree height on crown level stomatal conductance

Schäfer, Karina V. R.; Oren, Ram; Tenhunen, John

doi:10.1046/j.1365-3040.2000.00553.x

Cited by 297 publications

(283 citation statements)

References 55 publications

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“…Although transpiration accounting for~80% of LE in dry sites is not unheard of [Miller et al, 2010], we acknowledge that our lack of sap flux measurements over depth ranges within the sapwood and radial scaling of sap flux measurements contributed to errors in the sap flux data [Phillips et al, 1996;Schäfer et al, 2000]. Due to the increased number of large red maples and large bigtooth aspen trees in the control plot, these errors were likely greater in the control plot and would reduce the fraction of LE that is accounted for by E C in that plot.…”

Section: Red Oakmentioning

confidence: 97%

“…On this basis, we expected an overestimation of E C of roughly 11% in the control plot and 3.7% in the treatment plot. Due to the dependence of radial patterns in sap flow on species, tree age, and site history and, therefore, the large variability among reduction factors, we chose to disclose this limitation rather than to assume the applicability of a reduction factor from existing literature that was not specific to our plots [James et al, 2002;Nadezhdina et al, 2002;Phillips et al, 1996;Renninger et al, 2013;Schäfer et al, 2000;Shinohara et al, 2013]. Despite these errors, the roughly 15% difference in transpiration between the control and treatment plots remains significant.…”

Section: Red Oakmentioning

confidence: 99%

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Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

et al. 2014

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Intermediate disturbances shape forest structure and composition, which may in turn alter carbon, nitrogen, and water cycling. We used a large-scale experiment in a forest in northern lower Michigan where we prescribed an intermediate disturbance by stem girdling all canopy-dominant early successional trees to simulate an accelerated age-related senescence associated with natural succession. Using 3 years of eddy covariance and sap flux measurements in the disturbed area and an adjacent control plot, we analyzed disturbance-induced changes to plot level and species-specific transpiration and stomatal conductance. We found transpiration to be~15% lower in disturbed plots than in unmanipulated control plots. However, species-specific responses to changes in microclimate varied. While red oak and white pine showed increases in stomatal conductance during postdisturbance (62.5 and 132.2%, respectively), red maple reduced stomatal conductance by 36.8%. We used the hysteresis between sap flux and vapor pressure deficit to quantify diurnal hydraulic stress incurred by each species in both plots. Red oak, a ring porous anisohydric species, demonstrated the largest mean relative hysteresis, while red maple, bigtooth aspen, and paper birch, all diffuse porous species, had the lowest relative hysteresis. We employed the Penman-Monteith model for LE to demonstrate that these species-specific responses to disturbance are not well captured using current modeling strategies and that accounting for changes to leaf area index and plot microclimate are insufficient to fully describe the effects of disturbance on transpiration.

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Section: Red Oakmentioning

confidence: 97%

Section: Red Oakmentioning

confidence: 99%

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

et al. 2014

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“…To facilitate a comparison of G S response to D between the pre-and post-hurricane period, an evaluation of all predictions was made on data selected from scatterplots of G S versus D, based on a boundary line analysis (Martin et al 1997;Schäfer et al 2000). This was necessary because light measurements were not available for a conditional sampling of data in the posthurricane period.…”

Section: Daytime Responses Of G S To E L Q O and Dmentioning

confidence: 99%

Sensitivity of mean canopy stomatal conductance to vapor pressure deficit in a flooded Taxodium distichum L. forest: hydraulic and non-hydraulic effects

et al. 2001

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We measured the xylem sap flux in 64-yearold Taxodium distichum (L.) Richard trees growing in a flooded forest using Granier-type sensors to estimate mean canopy stomatal conductance of the stand (G S ). Temporal variations in G S were investigated in relation to variation in vapor pressure deficit (D), photosynthetic photon flux density (Q o ), and the transpiration rate per unit of leaf area (E L ), the latter variable serving as a proxy for plant water potential. We found that G S was only weakly related to Q o below 500 µmol m -2 s -1 (r 2 =0.29), but unrelated to Q o above this value. Above Q o =500 µmol m -2 s -1 and D=0.6 kPa, G S decreased linearly with increasing E L with a poor fit (r 2 =0.31), and linearly with lnD with a much better fit (r 2 =0.81). The decrease of G S with lnD was at a rate predicted based on a simple hydraulic model in which stomata regulate the minimum leaf water potential. Based on the hydraulic model, stomatal sensitivity to D is proportional to stomatal conductance at low D. A hurricane caused an ~41% reduction in leaf area. This resulted in a 28% increase in G S at D=1 kPa (G Sref ), indicating only partial compensation. As predicted, the increase in G Sref after the hurricane was accompanied by a similar increase in stomatal sensitivity to D (29%). At night, G Sref was 20% of the daytime value under non-limiting light (Q o >500 µmol m -2 s -1 ). However, stomatal sensitivity to D decreased only to ~46% (both reductions referenced to prehurricane daytime values), thus having more than twice the sensitivity expected based on hydraulic considerations alone. Therefore, non-hydraulic processes must cause heightened nighttime stomatal sensitivity to D.

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“…10.3 reduces to g c = c*1/h (where c is a constant), which takes the shape of a non-linear decline in g c with pathlength. Both hydraulic and stomatal conductances follow this relationship (Mencuccini and Grace 1996b;McDowell et al 2002a;Niinemets 2002;Schäfer et al 2000). Thus far it has been shown that many structural factors vary with increasing h to minimize its impact on g c as trees grow larger, but that these homeostatic adjustments fail to completely offset the negative impact of h on g c (McDowell et al 2002a, b;Mencuccini 2003), in part due to requirements to protect xylem from irreversible embolism (Domec et al 2008).…”

Section: Introductionmentioning

confidence: 97%

Relationships Between Tree Height and Carbon Isotope Discrimination

et al. 2011

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Understanding how tree size impacts leaf-and crown-level gas exchange is essential to predicting forest yields and carbon and water budgets. The stable carbon isotope ratio (d 13 C) of organic matter has been used to examine the relationship of gas exchange to tree size for a host of species because it carries a temporally integrated signature of foliar photosynthesis and stomatal conductance. The carbon isotope composition of leaves reflects discrimination against 13 C relative to 12 C during photosynthesis and is the net result of the balance of change in CO 2 supply and demand at the sites of photosynthesis within the leaf mesophyll. Interpreting the patterns of changes in d 13 C with tree size are not always clear, however, because multiple factors that regulate gas exchange and carbon isotope discrimination (D) co-vary with height, such as solar irradiance and hydraulic conductance. Here we review 36 carbon isotope datasets from 38 tree species and conclude that there is a consistent, linear decline of D with height. The most parsimonious explanation of this result is that gravitational constraints on maximum leaf water potential set an ultimate boundary on the shape and sign of the relationship. These hydraulic constraints are manifest both over the long term through impacts on leaf structure, and over diel periods via impacts on stomatal conductance, photosynthesis and leaf hydraulic conductance. Shading induces a positive offset to the linear decline, consistent with light limitations reducing carbon fixation and increasing partial pressures of CO 2 inside of the leaf, p c at a given height. Biome differences between tropical and temperate forests were more important in predicting D and its relationship to height than wood type associated with being an angiosperm or gymnosperm. It is not yet clear how leaf internal conductance varies with leaf mass area, but some data in particularly tall, temperate conifers suggest that photosynthetic capacity may not vary dramatically with height when compared between tree-tops, while stomatal and leaf internal conductances do decline in unison with height within canopy gradients. It is also clear that light is a critical variable low in the canopy, whereas hydrostatic constraints dominate the relationship between D and height in the upper canopy. The trend of increasing maximum height with decreasing minimum D suggests that trees that become particularly tall may be adapted to tolerate particularly low values of p c .

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The effect of tree height on crown level stomatal conductance

Cited by 297 publications

References 55 publications

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

Sensitivity of mean canopy stomatal conductance to vapor pressure deficit in a flooded Taxodium distichum L. forest: hydraulic and non-hydraulic effects

Relationships Between Tree Height and Carbon Isotope Discrimination

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