Variation in above-ground tissue multi-element concentrations among wild plant taxa in the Çapakçur microcatchment, Eastern Türkiye

Abstract

Wild plant taxa growing in semi-natural ecosystems may show marked variation in tissue concentrations of potentially toxic elements and trace metals. Such variation can provide useful preliminary information for understanding plant-based elemental patterns and for selecting taxa that warrant further validation in biomonitoring studies. However, integrated assessments combining family- and taxon-level comparisons, relative multi-element indices, and multivariate statistical approaches remain limited in heterogeneous microcatchment ecosystems characterized by forest–rangeland transitions and degraded forest conditions. In this study, above-ground or leaf tissue concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were evaluated in 123 composite wild plant samples representing 26 taxa from 14 botanical families in the Çapakçur microcatchment, eastern Türkiye. Significant differences were observed among both families and taxa for all investigated elements. PERMANOVA indicated that multi-element tissue concentration profiles differed significantly among family and taxon groups; however, these results were interpreted cautiously because of the unbalanced sampling design, the nested structure of taxa within families, and possible differences in environmental exposure among sampling locations. The Metal Pollution Index (MPI), interpreted here as a relative plant tissue multi-element index, and the Species Metal Accumulation Score (SMAS) provided complementary descriptive information on within-dataset variation. Globularia trichosantha showed the highest SMAS value, whereas Centaurea bingoelensis exhibited the highest MPI value. Family Metal Enrichment Ratio (FMER) analysis indicated element-specific enrichment tendencies within the present dataset, but these patterns should not be interpreted as general family-level traits because several families were represented by a single taxon. PCA, heatmap, clustering, and Spearman correlation analyses further showed that tissue element profiles were heterogeneous and largely element-specific, with limited evidence of strong co-association except for the positive Ni–Cu relationship. The results demonstrate that wild plant taxa in the Çapakçur microcatchment differ in their above-ground or leaf tissue multi-element concentration profiles. These differences may reflect a combination of taxon identity, tissue type, local environmental exposure, and microhabitat conditions rather than intrinsic tissue concentration profile alone. The taxa showing relatively high within-dataset scores may be prioritized for future biomonitoring validation, but paired soil–plant sampling, standardized plant organs, bioavailable soil fractions, spatially co-located sampling, and seasonal monitoring are required to confirm their indicator value and clarify soil–plant transfer mechanisms.