Plant functional diversity influences water and carbon fluxes and their use efficiencies in native and disturbed dryland ecosystems

Authors: CASTELLANOS, A. - Universidad De Sonora; HINOJO-HINOJO, C. - University Of Arizona; RODRIGUEZ, J. - Universidad De Sonora; ROMO-LEON, J.R. - Universidad De Sonora; WILCOX, B.D. - West Texas A & M University; Biederman, Joel; PENUELAS, J. - University Of Barcelona

Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2022
Publication Date: 3/9/2022
Citation: Castellanos, A., Hinojo-Hinojo, C., Rodriguez, J., Romo-Leon, J., Wilcox, B., Biederman, J.A., Penuelas, J. 2022. Plant functional diversity influences water and carbon fluxes and their use efficiencies in native and disturbed dryland ecosystems. Ecohydrology. 15(5). Article e2415. https://doi.org/10.1002/eco.2415.
DOI: https://doi.org/10.1002/eco.2415

Interpretive Summary: Vegetation in dryland agroecosystems is underoing rapid change due to human management and climate change. Therefore it is critical to know how vegetation change alters the water and carbon cycling in drylands. Here we measured water and carbon exchanges between the atmosphere and two nearby sites in the Sonoran Desert: one was a native shrubland, and the other had been transformed into a shrub-grass savanna through shrub removal several decades prior. We found the two sites performed similarly during the rain summer season, but that the more diverse vegetation in the savanna allowed this site to take up more carbon and use water more efficiently during the relatively dry winter season. The savanna was always a net sink of atmospheric CO2, while the shrubland was sometimes a sink and sometimes a source. These results show how vegetation management can enhance ecosystem water use and productivity.

Technical Abstract: Vegetation is changing rapidly in dryland ecosystems, but critical gaps remain on the long-term fluxes of carbon (C) and water. We determined how changes in the functional types of vegetation influenced (1) water and C fluxes and (2) water-use (WUEe) and C-use efficiencies (CUEe) in these ecosystems by comparing two adjacent sites in the Sonoran Desert, a native shrubland and the other a disturbed shrubland transformed to buffelgrass savanna. We used six years of eddy-covariance flux data to quantify evapotranspiration (ET), net ecosystem productivity (NEP), ecosystem respiration (Reco), and gross ecosystem productivity (GPP). Although flux magnitudes were more significant during the rainy summers, the sites fluxes differed more over the drier winters and years. The dominant plant functional type (PFT), greater WUEe, longer C uptake, and lower Reco were the crucial drivers of change in the savanna, particularly during winter and annual drier conditions. As a result, annual NEP was always positive (C sink) in the savanna and smaller and more variable in the shrubland, which functioned as a source in some years and a sink in others. Yearly and seasonal WUEe and CUEe differences indicate the importance of the dominant functional type in the C dynamics. Also, they suggest that changes in the vegetation structure, their seasonal function, and complementary ecohydrological feedbacks were essential drivers in the water and C fluxes dynamics in these dryland ecosystems.