Many regions around the world experienced abrupt climate change with far-reaching societal and environmental effects at ca. 4.2 cal. ka BP. As one of the most distinct climatic events of the last 11.7 ka, it has been used to establish the formal boundary between the mid- and late-Holocene. Although the 4.2 ka event was not pronounced in East-Central Europe, its exact impact on the area has yet to be evaluated. The aim of this paper is twofold: (1) to reconstruct the functioning of the selected lake and terrestrial ecosystems from northern Poland around the time of the 4.2 ka event, and (2) to disentangle the drivers of the recorded environmental changes (local factors vs. climate impact). We studied the sedimentary record of Lake Spore, focusing on the period between 3.8 and 4.5 cal. ka BP using numerous biotic and abiotic proxies, such as chironomids, cladocerans, pollen and spores, δ¹³C_org, δ¹⁵N_org, δ¹⁸O_carb, δ¹³C_carb, TOC/N, Fe, S, LOI₅₅₀, and LOI₉₅₀. The chironomid-derived reconstruction of mean July air temperature did not change during the 4.2 ka event. Pollen accumulation rate (PAR) data showed lower pollen production of some tree taxa during the period 4.0–4.25 cal. ka BP that is consistent with low PARs recorded for the corresponding period in the sediments of nearby (~75 km) Lake Suminko. This change might have occurred due to either regional-scale forest disturbance or cooler winters resulting from an exceptionally strong Siberian High during the 4.2 ka event. Distinct peaks of Fe and δ¹³C_carb at 4.2 cal. ka BP likely record a pulse of podzolization. Although soil transformation processes were common in East-Central Europe after ca. 5 cal. ka BP due to general climate cooling, they could have been enhanced at Lake Spore during the 4.2 ka event, if winters were more severe. The δ¹³C_org, δ¹⁵N_org, TOC/N and δ¹⁸O_carb records point to a water level rise after 4.2 cal. ka BP that most likely resulted from soil transformation in the catchment, not a change in effective precipitation. The composition of the terrestrial vegetation and the lake fauna and flora remained largely unaffected by the 4.2 ka event.

世界各地的许多地区都经历了突然的气候变化，大约在2000年对社会和环境产生了深远的影响。4.2卡路里 ka BP。作为最近11.7 ka的最明显的气候事件之一，它已被用来建立全新世中期和晚期之间的正式边界。尽管在东中欧没有宣布4.2 ka事件，但它对该地区的确切影响尚待评估。本文的目的是双重的：（1）在4.2 ka事件发生时重建波兰北部所选湖泊和陆地生态系统的功能，以及（2）弄清记录的环境变化的驱动因素（局部因素）与气候影响）。我们研究了孢子湖的沉积记录，重点是3.8至4.5 cal之间的时间段。ka BP使用了许多生物和非生物代理，¹³ Ç_组织，δ ¹⁵ Ñ_组织，δ ¹⁸ ö_{碳水化合物}，δ ¹³ Ç_{碳水化合物}，TOC / N，铁，S，LOI ₅₅₀和LOI ₉₅₀。在4.2 ka事件期间，由手足动物得出的平均七月气温重建没有变化。花粉积累率（PAR）数据显示，在4.0–4.25 cal期间，某些树木类群的花粉产量较低。ka BP与附近（〜75 km）苏明科湖沉积物中相应时期记录的低PARs一致。这种变化可能是由于4.2 ka事件期间西伯利亚高压异常强而引起的区域范围的森林干扰或冬季凉爽。的Fe的不同的峰和δ ¹³ C ^_{碳水化合物}在4.2卡路里 ka BP可能记录了过饱和脉冲。尽管土壤转化过程在约20世纪80年代后在中东欧很普遍。5卡路里 ka BP由于普遍的气候降温，如果冬季更为严峻，则在4.2 ka事件期间本可在Spore湖上将其增强。的δ ¹³ C ^_组织，δ ¹⁵ Ñ_组织，TOC / N和δ ¹⁸ ö_{碳水化合物}记录指向后4.2 CAL的水位上升。ka BP很有可能是由流域内的土壤转化引起的，而不是有效降水量的变化。4.2 ka事件未对陆地植被和湖泊动植物的组成造成很大影响。