UCL Institute of Archaeology, University College London, London, United Kingdom.
Scottish Universities Environmental Research Centre, Glasgow, United Kingdom.
PLoS One. 2023 Feb 6;18(2):e0268607. doi: 10.1371/journal.pone.0268607. eCollection 2023.
Nitrogen isotope ratio analysis (δ15N) of animal tissue is widely used in archaeology and palaeoecology to investigate diet and ecological niche. Data interpretations require an understanding of nitrogen isotope compositions at the base of the food web (baseline δ15N). Significant variation in animal δ15N has been recognised at various spatiotemporal scales and related to changes both in baseline δ15N, linked to environmental and climatic influence on the terrestrial nitrogen cycle, and animal ecology. Isoscapes (models of isotope spatial variation) have proved a useful tool for investigating spatial variability in biogeochemical cycles in present-day marine and terrestrial ecosystems, but so far, their application to palaeo-data has been more limited. Here, we present time-sliced nitrogen isoscapes for late Pleistocene and early Holocene Europe (c. 50,000 to 10,000 years BP) using herbivore collagen δ15N data. This period covers the Last Glacial-Interglacial Transition, during which significant variation in the terrestrial nitrogen cycle occurred. We use generalized linear mixed modelling approaches for interpolation and test models which both include and exclude climate covariate data. Our results show clear changes in spatial gradients of δ15N through time. Prediction of the lowest faunal δ15N values in northern latitudes after, rather than during, the Last Glacial Maximum is consistent with the Late Glacial Nitrogen Excursion (LGNE). We find that including climatic covariate data does not significantly improve model performance. These findings have implications for investigating the drivers of the LGNE, which has been linked to increased landscape moisture and permafrost thaw, and for understanding changing isotopic baselines, which are fundamental for studies investigating diets, niche partitioning, and migration of higher trophic level animals.
动物组织的氮同位素比值分析（δ15N）广泛应用于考古学和古生态学，以研究饮食和生态位。数据解释需要了解食物网底部的氮同位素组成（基线 δ15N）。在不同的时空尺度上，动物 δ15N 已经被认识到存在显著的变化，与基线 δ15N 的变化有关，这与陆地氮循环的环境和气候影响以及动物生态学有关。同位素景观（同位素空间变化模型）已被证明是一种有用的工具，可用于研究现代海洋和陆地生态系统中生物地球化学循环的空间变异性，但迄今为止，它们在古数据中的应用更为有限。在这里，我们使用食草动物胶原 δ15N 数据为晚更新世和早全新世欧洲（约 50,000 至 10,000 年前）提供时间切片的氮同位素景观。这一时期涵盖了末次冰期-间冰期过渡时期，在此期间陆地氮循环发生了显著变化。我们使用广义线性混合模型方法进行插值，并测试了包含和不包含气候协变量数据的模型。我们的结果表明，δ15N 的空间梯度随时间发生了明显的变化。在末次冰期最大值之后而不是期间，预测北纬地区最低的动物 δ15N 值与晚冰期氮激扰（LGNE）一致。我们发现，包含气候协变量数据并不会显著提高模型性能。这些发现对于研究 LGNE 的驱动因素具有重要意义，LGNE 与增加的景观湿度和永久冻土解冻有关，并且对于理解不断变化的同位素基线也具有重要意义，因为这些基线对于研究饮食、生态位分割和更高营养级动物的迁移至关重要。
