Sprecher
Beschreibung
The study investigated climatic and ecological stress of selected gymnosperms from the Upper Triassic (Norian) to the Upper Jurassic (Kimmeridgian), in samples collected from eight sites representing the Norian, Hettangian, Bathonian, and Kimmeridgian stages. Carbon (δ13C) and nitrogen (δ15N) isotope ratios were measured to evaluate environmental stress and nitrogen availability in different habitats, and stomatal indices and cell density were analyzed to study plant responses to changes in environmental conditions.
δ13C values served as indicators of environmental stress, because photosynthetic pathways discriminate differently against 13C under stressful conditions. More negative δ13C values indicate lower stress and greater environmental stability. Within the Norian two localities showed relatively less negative values (around −24‰), suggesting higher stress levels, whereas one Norian locality (−29.29‰) and the Hettangian locality (−30.76‰) reflected the most stable environmental conditions. Bathonian and Kimmeridgian values ranged from approximately −26‰ to −27‰, indicating moderate stability.
δ15N values provided information on nitrogen availability and competition within ecosystems. Norian samples showed relatively uniform values (~5‰), while samples from the Hettangian and one Bathonian locality showed lower values (~2‰), indicating improved nitrogen access. Exceptionally negative δ15N values registered at other Bathonian (−5.79‰) and Kimmeridgian localities (−5.09‰), suggesting unusually high nitrogen availability in these areas. The correlation was observed between the variation of SI and cell density values in different plant species and the differences in 13C and 15N values from the same localities.
This research was funded by the National Science Centre (2022/45/B/NZ8/02000) and the W. Szafer Institute of Botany, PAS.