Soil salinity determines the relative abundance of C₃/C₄ species in Argentinean grasslands

Abstract

Aim The C4 and crassulacean acid metabolism (CAM) pathways are adaptations to compensate for high rates of photorespiration and water and carbon deficiency. This is the first attempt to compare the relative abundance of C3 vs. C4 + CAM species in temperate and subtropical grasslands across a latitudinal gradient in central Argentina. We predict that under the same rainfall regime, C4 + CAM plants will have larger soil coverage in highly saline soils than in neighbouring non‐saline ones. Location Data were taken from three phytogeographical provinces in the Santa Fe province of Argentina: Chaquenian, Pampean and Espinal. Methods The salinity of the soil was estimated through aqueous solution conductivity. The proportions of species belonging to C3/C4 + CAM photosynthetic pathways were compared among halophyte and non‐halophyte communities with a χ2 homogeneity test. The sum of cover percentages corresponding to the C3 and C4 + CAM photosynthetic pathways were calculated and compared using analysis of variance (ANOVA). Results The soil conductivity values were higher in the halophyte than in the non‐halophyte communities for the same phytogeographical area. The C4 + CAM plants had much higher soil coverage values in halophyte than in non‐halophyte communities in the Pampean and Espinal phytogeographical provinces. The differences were not statistically significant in the Chaquenian province. Main conclusions Soil drought provoked by soil salinity results in a much higher soil cover by C4 + CAM plants in regions with positive to neutral water balance (i.e. Pampean and Espinal). This differential abundance pattern in C4 + CAM functional group is not observed in areas where a pronounced water deficit exists per se (Chaquenian region), and therefore C4 + CAM plants predominate in all environments regardless of soil salinity. Our results suggest that one of the main environmental forces driving the upsurge of C4 species in Argentinean grasslands might have been the strong local soil salinity gradient.

Salt tolerance variability among stress‐selected Panicum coloratum cv. Klein plants

“…He suggested stress‐adapted plants expressed a basic similarity in the mechanisms that allow them to adapt to different forms of severe stress. Salinity, among other stress factors, has been regarded as one of the main environmental forces driving the increased occurrence of C4 species in Argentinean grasslands (Feldman et al ., ). Varietal differences in salt tolerance have been known since the 1930s, and intraspecific selection for salt tolerance has been used to develop salt‐tolerant cultivars (Flowers, ).…”

Leaf anatomy and C₄ photosynthetic enzymes in three reed ecotypes

“…The C 4 photosynthetic pathway with CO 2 -concentrating mechanisms is regarded as a superior carbon assimilation mode for plants when limitations on carbon acquisition are imposed by a variety of stress conditions (Pyankov andMokronsov 1993, Sage 2002). Drought and salinity can induce the shift from C 3 to C 4 carbon metabolic pathway (Ueno et al 1988, Reiskind et al 1997, Feldman et al 2008. It is well known that classical C 4 pathway involves not only the special Kranz anatomy but also the higher activities of specific enzymes for releasing and then refixing CO 2 , i.e., NAD-and NADP-dependent malic enzymes, (NADP-ME, NAD-ME) and phosphoenolpyruvate carbokinase (PEP-CK).…”

Effects of High Impact Grazing on Species Diversity and Plant Functional Groups in Grasslands of Northern Argentina

“…However, regarding fodder quality, the C 4 grasses have lower digestibility than C 3 species [49]. Complementarily, C 3 species represent only 5-8% of the cover in sub-tropical Argentina [50]. After HIG we recorded a strong increase of C 3 species green biomass cover.…”

“…After HIG we recorded a strong increase of C 3 species green biomass cover. To date, there was no previous report of such a management-induced increase of grassland C 3 species [50], which will likely translate into increased fodder quality. Further analyses of HIG effects on fodder quality might therefore be highly interesting for the livestock production.…”