Fluxes of carbon dioxide and water vapour from a Sahelian savanna

doi:10.1016/0168-1923(95)02294-5

Agricultural and Forest Meteorology

Volume 80, Issues 2–4, July 1996, Pages 231-248

https://doi.org/10.1016/0168-1923(95)02294-5 Get rights and content

Abstract

Simultaneous measurements of atmospheric CO₂ flux, F_c, and latent heat flux, E, from a shrub savanna in Niger, West Africa, were made by eddy correlation. The vegetation at the study site consisted of scattered shrubs with an understorey of grasses and herbs. The measurements made available some of the first data on CO₂ and H₂O exchange for an semi-natural, mixed plant community, growing in the semi-arid tropics. Such data are necessary for the development of improved soil-vegetation-atmosphere models, able to describe the complex interplay between atmospheric CO₂, vegetation conductance and the surface energy balance of the Sahel in global climate models. In this framework, the effect of the extreme and highly variable environment, represented by the saturation deficit, D, and integrated water content of the upper soil layers, Φ, was discussed. F_c and E were measured throughout the transition from the wet to the dry season (September–October) during the HAPEX-Sahel Intensive Observation period, in 1992. At the same time, leaf stomatal conductances, g₁, of the shrubs and two understorey herb species was measured. Daily totals of F_c decreased by 50% (peak values declined from −10 to −5 μmol m⁻²s⁻¹) over 3 weeks following the last rainfall of the wet season. During the same period, g₁ decreased roughly four-fold for all sampled species. D appeared to be the main controlling parameter in the exchange of CO₂ and H₂O. g₁ and ‘water use efficiency’, | $F_{c} E$ |, were well correlated with D, which also considerably influenced the response of F_c to photosynthetically active radiation, Q_p. Simultaneously, a decreasing Φ caused lower values of g₁ and F_c. However, soil moisture had little effect on the empirical relationships found between atmospheric variables (D or Q_p) and g₁ or F_c.

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Citation Excerpt :
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Research paperFluxes of carbon dioxide and water vapour from a Sahelian savanna

Abstract

Agric. For. Meteorol.

Agric. For. Meteorol.

Agric. For. Meteorol.

Agric. For. Meteorol.

Agric. For. Meteorol.

Field Crops Res.

The Savannas: Biogeography and Geobotany

A biochemical model of photosynthetic assimilation in leaves of C3-species

Planta

Carbon storage by introduced deep-rooted grasses in the South American savannas

Nature

The global carbon cycle: a viewpoint on the missing sink

Aust. J. Plant Physiol.

Potential production processes

HAPEX-Sahel: a large scale study of land atmosphere interactions in the semi-arid tropics

Ann. Geophys.

Stomatal conductance of West Central Supersite vegetation in HAPEXSahel: measurements and empirical models

J. Hydrol.

Procedures for reliable eddy covariance measurements of atmospheric heat and CO2-fluxes

Modelling daily dry matter production of winter wheat

Agron. J.

An intercomparison of single and dual-source vegetation-atmosphere transfer models applied to transpiration from Sahelian savannah

Boundary-Layer Meteorol.

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Plants and Microclimate

Research paper
Fluxes of carbon dioxide and water vapour from a Sahelian savanna

A biochemical model of photosynthetic assimilation in leaves of C₃-species

Procedures for reliable eddy covariance measurements of atmospheric heat and CO₂-fluxes

Direct impact of atmospheric CO₂ enrichment on regional transpiration