Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Responses in the Coupling of Carbon and Water Vapor Exchanges of Irrigated and Rainfed Andean Potato (Solanum Tuberosum Subsp. Andigenum) Agroecosystems

Version 1 : Received: 17 January 2023 / Approved: 25 January 2023 / Online: 25 January 2023 (03:27:31 CET)

How to cite: Martinez Maldonado, F.E.; Castaño Marín, A.M.; Góez Vinasco, G.A.; Marin, F.R. Responses in the Coupling of Carbon and Water Vapor Exchanges of Irrigated and Rainfed Andean Potato (Solanum Tuberosum Subsp. Andigenum) Agroecosystems. Preprints 2023, 2023010437. https://doi.org/10.20944/preprints202301.0437.v1 Martinez Maldonado, F.E.; Castaño Marín, A.M.; Góez Vinasco, G.A.; Marin, F.R. Responses in the Coupling of Carbon and Water Vapor Exchanges of Irrigated and Rainfed Andean Potato (Solanum Tuberosum Subsp. Andigenum) Agroecosystems. Preprints 2023, 2023010437. https://doi.org/10.20944/preprints202301.0437.v1

Abstract

We studied the link between carbon and water fluxes to understand the response of net ecosystem carbon exchange (NEE) to water availability conditions of three different potato water regimes cropping systems [full irrigation (FI), deficit irrigation (DI) and rainfed (RF)]. Through the eddy covariance technique, we measured CO2 and water vapor exchanges and determined surface resistances, omega factor, and inherent water use efficiency (IWUE). Additionally, continuous plant growth determinations of leaf area index (LAI) and specific leaf area (SLA) were made over the three cropping systems. The RF potato was a net carbon source (NEE = 187.21 ± 3.84 g C m−2), while both, FI (NEE= −311.96 ± 12.82 g C m−2) and DI (−17.3 ± 4.6 g C m−2) were a net carbon sink. Greater sink activity is due to high fluxes of gross primary productivity (GPP) [where the GPP > ecosystem respiration (Reco)] and evapotranspiration (ET), and the high efficiency in the exchange of carbon and water. Without water limitations, the larger canopy, with greater photosynthetic activity (GPP/Reco > 2) as well as with low internal resistance offers a greater area for water and carbon exchange, and the highly coupled and synchronized ET – GPP fluxes are primarily controlled by the radiative environment. The lower sink capacity of the DI potato crop and the carbon source activity from the RF, are consequences of a smaller area for water and carbon exchange due to the smaller canopy, and a low IWUE from decoupled and desynchronized carbon and water exchange caused by unbalanced restrictions on ET and GPP fluxes. Specifically, at DI potato, ET remained at a high rate, while GPP was reduced by means of non-stomatal limitations. In the rainfed potato, vapor pressure deficit (VPD) played a significant role increasing midday canopy resistance (Rc) up to 13 times compared to irrigated sites, when VPD was around 0.8 kPa. In consequence, ET and GPP fluxes decreased together, but GPP decreased more than ET because of stomatal and non-stomatal limitations.

Keywords

NEE; IWUE; ET-GPP coupling; omega; potato

Subject

Environmental and Earth Sciences, Environmental Science

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