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The supply of nitrogen (N) to plants limits primary productivity in numerous ecosystems and these limitations in N concentrations in plants also limit herbivores, by limiting their productivity in relation to both plant nutritional quantity and quality. Carbon isotope ratio can provide insight about the photosynthetic pathways utilized by different plant species. Plant C and N isotope ratios were studied for different species growing in old arable lands in Kubedlana communal area, located at 32—¦11"²53 S and 28—¦14"²1 E and at 1020.8 m altitude in the Eastern Cape, South Africa. The vegetation type of the study area is the Foothill Moist Grassland. The area receives an annual rainfall between 600 mm and 750 mm. The study was aimed at testing whether there was seasonal shift amongst different plant species in relation to δ13C and δ15N isotopes. Leaf samples of L. cuneata (legume), forbs (weeds) and native grasses from the area were sampled to determine carbon and nitrogen isotope ratios. Plant samples were dried for 48 h at 70 °C and ground with a ball mill. All sampling was done once in spring (November) 2022, summer (February) 2023 and autumn (March) 2023 and winter (May 2023) seasons, respectively. Permutational multivariate analysis of variance (PERMANOVA) was used to test the effect of plant type (forbs, grass and legume) on δ13C and δ15N isotopes. There was a significant difference (P = 0.001) between the three plant species and seasonal change regarding δ15N ratios. δ13C ratios, plant type also significantly (P = 0.001) affected plant carbon ratios. These findings emphasize the importance of