Seasonal Evolution of Canopy Stomatal Conductance for a Prairie and Maize Field in the Midwestern United States from Continuous Carbonyl Sulfide Fluxes

Abstract. Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange of OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.

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Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

10.5194/bg-2016-365 ◽

2016 ◽

Author(s):

Richard Wehr ◽

Róisín Commane ◽

J. William Munger ◽

J. Barry McManus ◽

David D. Nelson ◽

...

Keyword(s):

Water Vapor ◽

Stomatal Conductance ◽

Eddy Covariance ◽

Deciduous Forest ◽

Carbonyl Sulfide ◽

Temperate Deciduous Forest ◽

Ecosystem Models ◽

Eddy Covariance Method ◽

Temperate Deciduous ◽

Canopy Stomatal Conductance

Abstract. Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface-atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly at the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly at the canopy scale via two independent approaches: (i) from heat and water vapor exchange, and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem-atmosphere exchange of OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases), and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 % to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counter-intuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning relies minimally on modeling and avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.

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Coping with depression and effects on parenting satisfaction for adolescent mothers in rural Midwestern United States

PsycEXTRA Dataset ◽

10.1037/e579192013-071 ◽

2012 ◽

Author(s):

L. Jensen

Keyword(s):

United States ◽

Adolescent Mothers ◽

Midwestern United States ◽

Parenting Satisfaction

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Inequality in the Promised Land

Journal of Interdisciplinary Studies in Education ◽

10.32674/jise.v9i1.1703 ◽

2020 ◽

Vol 9 (1) ◽

pp. 177-180

Author(s):

Muhammad Sharif Uddin

Keyword(s):

United States ◽

Minority Students ◽

Doctoral Dissertation ◽

Ethnographic Study ◽

Suburban Area ◽

Midwestern United States ◽

Minority Community ◽

Promised Land ◽

Land Race ◽

The Relationship

Inequality in the promised land: Race, resources, and suburban schooling is a well-written book by L’ Heureux Lewis-McCoy. The book is based on Lewis-McCoy’s doctoral dissertation, that included an ethnographic study in a suburban area named Rolling Acres in the Midwestern United States. Lewis-McCoy studied the relationship between families and those families’ relationships with schools. Through this study, the author explored how invisible inequality and racism in an affluent suburban area became the barrier for racial and economically minority students to grow up academically. Lewis-McCoy also discovered the hope of the minority community for raising their children for a better future.

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Stomatal conductance limited the CO2 response of grassland in the last century

BMC Biology ◽

10.1186/s12915-021-00988-4 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Juan C. Baca Cabrera ◽

Regina T. Hirl ◽

Rudi Schäufele ◽

Andy Macdonald ◽

Hans Schnyder

Keyword(s):

Climate Change ◽

Stomatal Conductance ◽

Nitrogen Nutrition ◽

Physiological Control ◽

Co2 Response ◽

Nitrogen Acquisition ◽

Wide Range ◽

Park Grass Experiment ◽

Conductance Changes ◽

Canopy Stomatal Conductance

Abstract Background The anthropogenic increase of atmospheric CO2 concentration (ca) is impacting carbon (C), water, and nitrogen (N) cycles in grassland and other terrestrial biomes. Plant canopy stomatal conductance is a key player in these coupled cycles: it is a physiological control of vegetation water use efficiency (the ratio of C gain by photosynthesis to water loss by transpiration), and it responds to photosynthetic activity, which is influenced by vegetation N status. It is unknown if the ca-increase and climate change over the last century have already affected canopy stomatal conductance and its links with C and N processes in grassland. Results Here, we assessed two independent proxies of (growing season-integrating canopy-scale) stomatal conductance changes over the last century: trends of δ18O in cellulose (δ18Ocellulose) in archived herbage from a wide range of grassland communities on the Park Grass Experiment at Rothamsted (U.K.) and changes of the ratio of yields to the CO2 concentration gradient between the atmosphere and the leaf internal gas space (ca – ci). The two proxies correlated closely (R2 = 0.70), in agreement with the hypothesis. In addition, the sensitivity of δ18Ocellulose changes to estimated stomatal conductance changes agreed broadly with published sensitivities across a range of contemporary field and controlled environment studies, further supporting the utility of δ18Ocellulose changes for historical reconstruction of stomatal conductance changes at Park Grass. Trends of δ18Ocellulose differed strongly between plots and indicated much greater reductions of stomatal conductance in grass-rich than dicot-rich communities. Reductions of stomatal conductance were connected with reductions of yield trends, nitrogen acquisition, and nitrogen nutrition index. Although all plots were nitrogen-limited or phosphorus- and nitrogen-co-limited to different degrees, long-term reductions of stomatal conductance were largely independent of fertilizer regimes and soil pH, except for nitrogen fertilizer supply which promoted the abundance of grasses. Conclusions Our data indicate that some types of temperate grassland may have attained saturation of C sink activity more than one century ago. Increasing N fertilizer supply may not be an effective climate change mitigation strategy in many grasslands, as it promotes the expansion of grasses at the disadvantage of the more CO2 responsive forbs and N-fixing legumes.

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