Data from: Differing climatic mechanisms control transient and accumulated vegetation novelty in Europe and eastern North America

Understanding the mechanisms that produce novel ecosystems is of joint interest to conservation biologists and paleoecologists. Here, we define and differentiate transient from accumulated novelty and evaluate four climatic mechanisms proposed to cause species to reshuffle into novel assemblages: high climatic novelty, high spatial rates of change (displacement), high variance among displacement rates for individual climate variables, and divergence among displacement vector bearings. We use climate simulations to quantify climate novelty, displacement, and divergence across Europe and eastern North America (ENA) from the last glacial maximum (LGM) to present and fossil pollen records to quantify vegetation novelty. Transient climate novelty is consistently the strongest predictor of transient vegetation novelty, while displacement rates (mean and variance) are equally important in Europe. However, transient vegetation novelty is lower in Europe and its relationship to climatic predictors is the opposite of expectation. For both continents, accumulated novelty is greater than transient novelty, and climate novelty is the strongest predictor of accumulated ecological novelty. These results suggest that controls on novel ecosystems vary with timescale and among continents, and that the 21st-century emergence of novel ecosystems will be driven by both rapid rates of climate change and the emergence of novel climate states.

解析新型生态系统的形成机制，是保护生物学家与古生态学家共同的研究关切。本文中，我们对瞬时新异性与累积新异性进行定义与区分，并评估了四类被认为可促使物种重新组合形成新型生物群落的气候驱动机制：高气候新异性、高空间变化速率（位移）、单个气候变量位移速率的高方差，以及位移矢量方位的离散性。我们利用气候模拟数据，量化了从末次盛冰期（last glacial maximum, LGM）至今欧洲与北美东部（eastern North America, ENA）区域内的气候新异性、位移速率与离散程度；同时借助化石花粉记录，量化了植被新异性。研究结果显示，瞬时气候新异性始终是瞬时植被新异性的最强预测因子，而在欧洲，位移速率（均值与方差）的重要性与之相当。不过欧洲的瞬时植被新异性水平更低，且其与气候预测因子的关联与预期恰好相反。就两大洲而言，累积新异性均高于瞬时新异性，且气候新异性是累积生态新异性的最强预测因子。本研究结果表明，新型生态系统的调控因素随时间尺度与大陆区域而异，且21世纪新型生态系统的出现，将由快速气候变化与新型气候状态的形成共同驱动。