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  • 1
    Electronic Resource
    Electronic Resource
    Effects of aggregated classifications of forest composition on estimates of evapotranspiration in a northern Wisconsin forest (2002)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 8 (2002), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Forest management presents challenges to accurate prediction of water and carbon exchange between the land surface and atmosphere, due to its alteration of forest structure and composition. We examined how forest species types in northern Wisconsin affect landscape scale water fluxes predicted from models driven by remotely sensed forest classification. A site-specific classification was developed for the study site. Using this information and a digital soils database produced for the site we identified four key forest stand types: red pine, northern hardwoods, aspen, and forested wetland. Within these stand types, 64 trees representing 7 species were continuously monitored with sap flux sensors. Scaled stand-level transpiration from sap flux was combined with a two-source soil evaporation model and then applied over a 2.5 km × 3.0 km area around the WLEF AmeriFlux tower (Park Falls, Wisconsin) to estimate evapotranspiration. Water flux data at the tower was used as a check against these estimates. Then, experiments were conducted to determine the effects of aggregating vegetation types to International Geosphere– Biosphere Program (IGBP) level on water flux predictions. Taxonomic aggregation resulting in loss of species level information significantly altered landscape water flux predictions. However, daily water fluxes were not significantly affected by spatial aggregation when forested wetland evaporation was included. The results demonstrate the importance of aspen, which has a higher transpiration rate per unit leaf area than other forest species. However, more significant uncertainty results from not including forested wetland with its high rates of evaporation during wet summers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2002.00554.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of stand age and tree species on canopy transpiration and average stomatal conductance of boreal forests (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We quantified the effect of stand age and tree species composition on canopy transpiration (EC) by analysing transpiration per unit leaf area (EL) and canopy stomatal conductance (GS) for boreal trees comprising a five stand wildfire chronosequence. A total of 196 sap flux sensors were used on 90 trees consisting of Betula papyrifera Marsh (paper birch; present in the youngest stand), Populus tremuloides Michx (quaking aspen), Pinus banksiana Lamb. (jack pine), and Picea mariana (Mill.) (black spruce). While fine roots were positively correlated with stand EC; leaf area index, basal area, and sapwood area were not. Stands less than 70 years old were dominated by Populus tremuloides and Pinus banksiana and stands greater than 70 years old were composed almost entirely of Picea mariana. As Populus tremuloides and Pinus banksiana increased in size and age, they displayed an increasing sapwood to leaf area ratio (AS : AL), a constant minimum leaf water potential (ΨL), and a constant proportionality between GS at low vapour pressure deficit (Dj GSref) and the sensitivity of GS to D (–δ). In contrast, AS : AL, minimum ΨL, and the proportionally between –δ and GSref decreased with height and age in Picea mariana. A GS model that included the effects of D, AS : AL, tree height, and for Picea mariana an increasing soil to leaf water potential gradient with stand age, was able to capture the effects of contrasting hydraulic properties of Picea mariana, Populus tremuloides and Pinus banksiana during stand development after wildfire.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01312.x
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  • 3
    Electronic Resource
    Electronic Resource
    Survey and synthesis of intra- and interspecific variation in stomatal sensitivity to vapour pressure deficit (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Responses of stomatal conductance (gs) to increasing vapour pressure deficit (D) generally follow an exponential decrease described equally well by several empirical functions. However, the magnitude of the decrease – the stomatal sensitivity – varies considerably both within and between species. Here we analysed data from a variety of sources employing both porometric and sap flux estimates of gs to evaluate the hypothesis that stomatal sensitivity is proportional to the magnitude of gs at low D (≤ 1 kPa). To test this relationship we used the function gs=gsref–m· lnD where m is the stomatal sensitivity and gsref=gs at D= 1 kPa. Regardless of species or methodology, m was highly correlated with gsref (average r2= 0·75) with a slope of approximately 0·6. We demonstrate that this empirical slope is consistent with the theoretical slope derived from a simple hydraulic model that assumes stomatal regulation of leaf water potential. The theoretical slope is robust to deviations from underlying assumptions and variation in model parameters. The relationships within and among species are close to theoretical predictions, regardless of whether the analysis is based on porometric measurements of gs in relation to leaf-surface D (Ds), or on sap flux-based stomatal conductance of whole trees (GSi), or stand-level stomatal conductance (GS) in relation to D. Thus, individuals, species, and stands with high stomatal conductance at low D show a greater sensitivity to D, as required by the role of stomata in regulating leaf water potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00513.x
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of nutrient versus water supply on hydraulic architecture and water balance in Pinus taeda (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated the hydraulic consequences of a major decrease in root-to-leaf area ratio (AR:AL) caused by nutrient amendments to 15-year-old Pinus taeda L. stands on sandy soil. In theory, such a reduction in AR:AL should compromise the trees’ ability to extract water from drying sand. Under equally high soil moisture, canopy stomatal conductance (GS) of fertilized trees (F) was 50% that of irrigated/fertilized trees (IF), irrigated trees (I), and untreated control trees (C). As predicted from theory, F trees also decreased their stomatal sensitivity to vapour pressure deficit by 50%. The lower GS in F was associated with 50% reduction in leaf-specific hydraulic conductance (KL) compared with other treatments. The lower KL in F was in turn a result of a higher leaf area per sapwood area and a lower specific conductivity (conducting efficiency) of the plant and its root xylem. The root xylem of F trees was also 50% more resistant to cavitation than the other treatments. A transport model predicted that the lower AR:AL in IF trees resulted in a considerably restricted ability to extract water during drought. However, this deficiency was not exposed because irrigation minimized drought. In contrast, the lower AR:AL in F trees caused only a limited restriction in water extraction during drought owing to the more cavitation resistant root xylem in this treatment. In both fertilized treatments, approximate safety margins from predicted hydraulic failure were minimal suggesting increased vulnerability to drought-induced dieback compared with non-fertilized trees. However, IF trees are likely to be so affected even under a mild drought if irrigation is withheld.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00625.x
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of soil porosity on water use in Pinus taeda (2000)
    Springer
    Oecologia 124 (2000), S. 495-505 
    Details
    ISSN: 1432-1939
    Keywords: Key words  Pinus taeda ; Xylem cavitation ; Soil water transport ; Root-shoot relations ; Stomatal regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We analyzed the hydraulic constraints imposed on water uptake from soils of different porosities in loblolly pine (Pinus taeda L.) by comparing genetically related and even-aged plantations growing in loam versus sand soil. Water use was evaluated relative to the maximum transpiration rate (E crit) allowed by the soil-leaf continuum. We expected that trees on both soils would approach E crit during drought. Trees in sand, however, should face greater drought limitation because of steeply declining hydraulic conductivity in sand at high soil water potential (Ψ S). Transport considerations suggest that trees in sand should have higher root to leaf area ratios (A R:A L), less negative leaf xylem pressure (Ψ L), and be more vulnerable to xylem cavitation than trees in loam. The A R:A L was greater in sand versus loam (9.8 vs 1.7, respectively). This adjustment maintained about 86% of the water extraction potential for both soils. Trees in sand were more deeply rooted (〉1.9 m) than in loam (95% of roots 〈0.2 m), allowing them to shift water uptake to deeper layers during drought and avoid hydraulic failure. Midday Ψ L was constant for days of high evaporative demand, but was less negative in sand (–1.6 MPa) versus loam (–2.1 MPa). Xylem was more vulnerable to cavitation in sand versus loam trees. Roots in both soils were more vulnerable than stems, and experienced the greatest predicted loss of conductivity during drought. Trees on both soils approached E crit during drought, but at much higher Ψ S in sand (〈–0.4 MPa) than in loam (〈–1.0 MPa). Results suggest considerable phenotypic plasticity in water use traits for P. taeda which are adaptive to differences in soil porosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008875
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  • 6
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    Estimating maximum mean canopy stomatal conductance for use in models (2001)
    Canadian Science Publishing
    Details
    Publication Date: 2001-02-01
    Description: Fertilized (F) and irrigated and fertilized (IF) stands of Pinus taeda L. produced twice the leaf area index of irrigated (I) and control (C) stands. Based on sap flux-scaled mean stomatal conductance (GS), we found that stomatal conductance in F was half that in other treatments. During the growing season, GS was related to vapor pressure deficit (D) and soil moisture. During the cooler season, soil moisture was high and light accompanied D in controlling GS. Under all conditions and treatments, the rate of decrease in GS with D was proportional to GS at low D (= 1 kPa). We evaluated whether GS can be used as an input to growth models and used a simple growth model (3-PG), which also predicts stand transpiration (EC), to compare with direct EC measurements in the four stands. Model predictions of monthly EC based on Penman-Montieth equation parameterized with maximum GS (GSmax) estimated under highest "native" soil moisture (0.07 m3·m3) produced long-term values within 10% of measured EC. When the model was parameterized with GSmax estimated under experimentally raised soil moisture, or with porometrically measured conductance, EC values were consistently overpredicted from 12 to 33%. Thus, sap-flux scaled mean canopy stomatal conductance obtained under non limiting light conditions, low D, and highest native soil moisture, is the most appropriate parameter value for certain single-leaf type of models.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 7
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    Understanding stomatal conductance responses to long-term environmental changes: a Bayesian framework that combines patterns and processes (2013)
    Oxford University Press
    Details
    Publication Date: 2013-02-21
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 8
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    Natural variation in GI affects circadian period [Plant Biology] (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-03-25
    Description: GIGANTEA (GI) was originally identified by a late-flowering mutant in Arabidopsis, but subsequently has been shown to act in circadian period determination, light inhibition of hypocotyl elongation, and responses to multiple abiotic stresses, including tolerance to high salt and cold (freezing) temperature. Genetic mapping and analysis of families of heterogeneous...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Size-mediated tree transpiration along soil drainage gradients in a boreal black spruce forest wildfire chronosequence (2012)
    Oxford University Press
    Details
    Publication Date: 2012-05-23
    Description: Boreal forests are crucial to climate change predictions because of their large land area and ability to sequester and store carbon, which is controlled by water availability. Heterogeneity of these forests is predicted to increase with climate change through more frequent wildfires, warmer, longer growing seasons and potential drainage of forested wetlands. This study aims at quantifying controls over tree transpiration with drainage condition, stand age and species in a central Canadian black spruce boreal forest. Heat dissipation sensors were installed in 2007 and data were collected through 2008 on 118 trees (69 Picea mariana (Mill.) Britton, Sterns & Poggenb. (black spruce), 25 Populus tremuloides Michx. (trembling aspen), 19 Pinus banksiana Lamb. (jack pine), 3 Larix laricina (Du Roi) K. Koch (tamarack) and 2 Salix spp. (willow)) at four stand ages (18, 43, 77 and 157 years old) each containing a well- and poorly-drained stand. Transpiration estimates from sap flux were expressed per unit xylem area, J S , per unit ground area, E C and per unit leaf area, E L , using sapwood ( A S ) and leaf ( A L ) area calculated from stand- and species-specific allometry. Soil drainage differences in transpiration were variable; only the 43- and 157-year-old poorly-drained stands had ~ 50% higher total stand E C than well-drained locations. Total stand E C tended to decrease with stand age after an initial increase between the 18- and 43-year-old stands. Soil drainage differences in transpiration were controlled primarily by short-term physiological drivers such as vapor pressure deficit and soil moisture whereas stand age differences were controlled by successional species shifts and changes in tree size (i.e., A S ). Future predictions of boreal climate change must include stand age, species and soil drainage heterogeneity to avoid biased estimates of forest water loss and latent energy exchanges.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 10
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    Allocation to male vs female floral function varies by currency and responds differentially to density and moisture stress (2017)
    Springer Nature
    Details
    Publication Date: 2017-08-02
    Print ISSN: 0018-067X
    Electronic ISSN: 1365-2540
    Topics: Biology
    Published by Springer Nature
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