13 Dec 2022
13 Dec 2022
Status: this preprint is currently under review for the journal BG.

Dynamics of short-term ecosystem carbon fluxes induced by precipitation events in a semiarid grassland

Josué Delgado-Balbuena1, Henry W. Loescher2,3, Carlos A. Aguirre-Gutiérrez1, Teresa Alfaro-Reyna1, Luis F. Pineda-Martínez4, Rodrigo Vargas5, and Tulio Arredondo6 Josué Delgado-Balbuena et al.
  • 1Centro Nacional de Investigación Disciplinaria Agricultura Familiar, INIFAP, km 8.5 Carr. Ojuelos – Lagos de Moreno, 47563, Ojuelos de Jalisco, Jal., México
  • 2Battelle, National Ecological Observatory Network (NEON), Boulder, CO USA 80301
  • 3Institute of Alpine and Arctic Research (INSTAAR), University of Colorado, Boulder, CO USA 80301
  • 4Universidad Autónoma de Zacatecas, 108 Calzada Universidad, 98066 Zacatecas, Zacatecas, Mexico
  • 5Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA
  • 6Division de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa de San José 2055, Lomas 4ta, 78216 San Luís Potosí, S.L.P., México

Abstract. Precipitation (PPT) patterns in semiarid grasslands are characterized by infrequency and small PPT events; however, plants and soil microorganisms are adapted to use the unpredictable small pulses of water. Several studies have shown short-term responses of carbon and nitrogen mineralization rates (called the priming effect or the Birch effect) stimulated by wet-dry cycles; however, dynamics, drivers, and the contribution of the “priming effect” to the annual C balance is poorly understood. Thus, we analysed six years of continuous net ecosystem exchange measurements to evaluate the effect of the PPT periodicity, magnitude of individual PPT events on the daily/annual ecosystem C balance (NEE) in a semiarid grassland. We included the period between PPT events, a priori daytime NEE rate and a priori soil moisture content as the main drivers of the priming effect. Ecosystem respiration (ER) responded within few hours following a PPT event whereas it took five-nine days for gross ecosystem exchange (GEE; such as –NEE = GEE + ER) to respond. Precipitation events as low as 0.25 mm increased ER, but cumulative PPT > 40 mm that infiltrated deep into the soil profile stimulated GEE. Overall, ER fluxes following PPT events were related to the change of soil water content at shallow depth and previous soil conditions (e.g. previous NEE rate, previous soil water content) and the size of the stimulus (e.g. PPT event size). Carbon effluxes from priming effect accounted for less than 5 % of ecosystem respiration bur were significatively high respect to the carbon balance. In the long-term, changes in PPT regimes to more intense and less frequent PPT events, as expected by the climate change effect, could turn the semiarid grassland out from a slight C sink to a C source.

Josué Delgado-Balbuena et al.

Status: open (until 20 Feb 2023)

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Josué Delgado-Balbuena et al.

Josué Delgado-Balbuena et al.


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Short summary
In the semiarid grassland, increase of soil moisture at shallow depths instantly enhance carbon release by respiration. In contrast, deeper soil water controls carbon uptake by vegetation but with a delay of several days. Previous soil conditions, biological activity and the size and timing of precipitation are important factors determining the amount of carbon released into the atmosphere. Thus, future changes in precipitation pattern could convert ecosystems from sinks to sources of carbon.