Water Balance Delineates the Soil Layer in Which Moisture Affects Canopy Conductance

Oren, Ram; Ewers, B. E.; Todd, Philip; Phillips, Nathan; Katul, Gabriel G.

doi:10.2307/2640956

Cited by 65 publications

(112 citation statements)

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“…The soil type at the experiment site was a low-fertility acidic Hapludalf (Ultic Alfisol in the Enon series) with clay loam texture (61,64). Soils were collected in 2006.…”

Section: Methodsmentioning

confidence: 99%

The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

Chen

et al. 2010

Appl Environ Microbiol

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The global atmospheric carbon dioxide (CO 2 ) concentration is expected to increase continuously over the next century. However, little is known about the responses of soil bacterial communities to elevated CO 2 in terrestrial ecosystems. This study aimed to partition the relative influences of CO 2 , nitrogen (N), and the spatial factor (different sampling plots) on soil bacterial communities at the free-air CO 2 enrichment research site in Duke Forest, North Carolina, by two independent techniques: an entirely sequencing-based approach and denaturing gradient gel electrophoresis. Multivariate regression tree analysis demonstrated that the spatial factor could explain more than 70% of the variation in soil bacterial diversity and 20% of the variation in community structure, while CO 2 or N treatment explains less than 3% of the variation. For the effects of soil environmental heterogeneity, the diversity estimates were distinguished mainly by the total soil N and C/N ratio. Bacterial diversity estimates were positively correlated with total soil N and negatively correlated with C/N ratio. There was no correlation between the overall bacterial community structures and the soil properties investigated. This study contributes to the information about the effects of elevated CO 2 and soil fertility on soil bacterial communities and the environmental factors shaping the distribution patterns of bacterial community diversity and structure in temperate forest soils.

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“…The soil type at the experiment site was a low-fertility acidic Hapludalf (Ultic Alfisol in the Enon series) with clay loam texture (61,64). Soils were collected in 2006.…”

Section: Methodsmentioning

confidence: 99%

The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

Chen

et al. 2010

Appl Environ Microbiol

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“…Measured sap flux (J S , kg H 2 O m -2 sapwood s -1 ) in the xylem of trees is increasingly used to estimate G S (Köstner et al 1992;Granier and Loustau 1994;Phillips and Oren 1998;Oren et al 1998aOren et al , 1998b, based on the assumption that J S scaled by A S :A L is equal to transpiration rate per unit of leaf area (E L ). Thus, G S for conifers or other species with small leaves (Landsberg 1986;Phillips and Oren 1998;Ewers and Oren 2000) can be calculated using the function (modified from Monteith and Unsworth 1990): (2) where G S is the canopy stomatal conductance for water vapour (m s -1 ), γ is the psychrometric constant (kPa·K -1 ), λ is the latent heat of vaporization (J·kg -1 ), ρ is the density of air (kg·m -3 ), c p is the specific heat of air at constant pressure (J·kg -1 K -1 ), and D is the vapor pressure deficit (kPa).…”

Section: Methodsmentioning

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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“…The latter quantity was calculated for 1996-99 using 30 min RH measurements conditionally averaged for Q exceeding 200 mmol m -2 s -1 . The instruments and setup used for the RH and Q measurements is reported in Oren et al (1998b). This weighted averaging scheme yielded an = 0·49, which, when combined with = 0·66 resulted in m = 6·0 (unitless).…”

Section: Ball-berry Modelmentioning

confidence: 99%

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Katul

Ellsworth

Lai

2000

Plant Cell & Environment

143

129

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A spectrum of models that estimate assimilation rate A from intercellular carbon dioxide concentration (Ci) and measured stomatal conductance to CO2 (gc) were investigated using leaf‐level gas exchange measurements. The gas exchange measurements were performed in a uniform loblolly pine stand (Pinus taeda L.) using the Free Air CO2 Enrichment (FACE) facility under ambient and elevated atmospheric CO2 for 3 years. These measurements were also used to test a newly proposed framework that combines basic properties of the A–Ci curve with a Fickian diffusion transport model to predict the relationship between Ci/Ca and gc, where Ca is atmospheric carbon dioxide concentration. The widely used Ball–Berry model and five other models as well as the biochemical model proposed by Farquhar et al. (1980) were also reformulated to express variations in Ci/Ca as a function of their corresponding driving mechanisms. To assess the predictive capabilities of these approaches, their respective parameters were estimated from independent measurements of long‐term stable carbon isotope determinations (δ13C), meteorological variables, and ensemble A–Ci curves. All eight approaches reproduced the measured A reasonably well, in an ensemble sense, from measured water vapour conductance and modeled Ci/Ca. However, the scatter in the instantaneous A estimates was sufficiently large for both ambient and elevated Ca to suggest that other transient processes were not explicitly resolved by all eight parameterizations. An important finding from our analysis is that added physiological complexity in modeling Ci/Ca (when gc is known) need not always translate to increased accuracy in predicting A. Finally, the broader utility of these approaches to estimate assimilation and net ecosystem exchange is discussed in relation to elevated atmospheric CO2.

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Water Balance Delineates the Soil Layer in Which Moisture Affects Canopy Conductance

Cited by 65 publications

References 0 publications

The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

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

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

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Water Balance Delineates the Soil Layer in Which Moisture Affects Canopy Conductance

Cited by 65 publications

References 0 publications

The Spatial Factor, Rather than Elevated CO 2 , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

The Spatial Factor, Rather than Elevated CO 2 , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

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

Modelling assimilation and intercellular CO2 from measured conductance: a synthesis of approaches

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Resources

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The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

The Spatial Factor, Rather than Elevated CO ₂ , Controls the Soil Bacterial Community in a Temperate Forest Ecosystem

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches