The effects of global warming are most pronounced in winter. A reduction in snow cover due to warmer atmospheric temperature in formerly cold ecosystems, however, could counteract an increase in soil temperature by reduction of insulation. Thus, soil freeze–thaw cycles (FTCs) might increase in frequency and magnitude with warming, potentially leading to a disturbance of the soil biota and release of nutrients. Here, we assessed how soil freeze–thaw magnitude and frequency affect short-term release of nutrients in temperate deciduous forest soils by conducting a three-factorial gradient experiment with ex situ soil samples in climate chambers. The fully crossed experiment included soils from forests dominated by Fagus sylvatica (European beech) that originate from different winter climate (mean coldest month temperature range ΔT>4 K), a range of FTC magnitudes from no (T=4.0 ^∘C) to strong ($T=-\mathrm{11.3}$ ^∘C) soil frost, and a range of FTC frequencies (f=0–7). We hypothesized that higher FTC magnitude and frequency will increase the release of nutrients. Furthermore, soils from cold climates with historically stable winter soil temperatures due to deep snow cover will be more responsive to FTCs than soils from warmer, more fluctuating winter soil climates. FTC magnitude and, to a lesser extent, also FTC frequency resulted in increased nitrate, ammonium, and phosphate release almost exclusively in soils from cold, snow-rich sites. The hierarchical regression analyses of our three-factorial gradient experiment revealed that the effects of climatic origin (mean minimum winter temperature) followed a sigmoidal curve for all studied nutrients and was modulated either by FTC magnitude (phosphate) or by FTC magnitude and frequency (nitrate, ammonium) in complex twofold and, for all studied nutrients, in threefold interactions of the environmental drivers. Compared to initial concentrations, soluble nutrients were predicted to increase to 250 % for nitrate (up to 16 µg NO₃-N kg^−1DM), to 110 % for ammonium (up to 60 µg NH₄-N kg^−1DM), and to 400 % for phosphate (2.2 µg PO₄-P kg^−1DM) at the coldest site for the strongest magnitude and highest frequency. Soils from warmer sites showed little nutrient release and were largely unaffected by the FTC treatments except for above-average nitrate release at the warmest sites in response to extremely cold FTC magnitude. We suggest that currently warmer forest soils have historically already passed the point of high responsiveness to winter climate change, displaying some form of adaptation either in the soil biotic composition or in labile nutrient sources. Our data suggest that previously cold sites, which will lose their protective snow cover during climate change, are most vulnerable to increasing FTC frequency and magnitude, resulting in strong shifts in nitrogen and phosphorus release. In nutrient-poor European beech forests of the studied Pleistocene lowlands, nutrients released over winter may be leached out, inducing reduced plant growth rates in the following growing season.

中文翻译：

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在寒冷和多雪的温带落叶林中，土壤融化后的融解释放出的氮和磷要比温暖，积雪少的条件下的土壤释放更多。

冬季，全球变暖的影响最为明显。但是，在以前寒冷的生态系统中，由于气温升高导致积雪减少，但可以通过减少保温材料来抵消土壤温度的升高。因此，土壤冻结-解冻循环（FTCs）的频率和幅度可能随着变暖而增加，从而可能导致土壤生物区系紊乱和养分释放。在这里，我们通过对气候室内的非原位土壤样品进行三因素梯度实验，评估了土壤冻结，融化幅度和频率如何影响温带落叶林土壤中养分的短期释放。完全交叉的实验包括来自以金格斯（Fagus sylvatica）为主的森林的土壤（欧洲山毛榉），其从不同的冬季气候起源（平均冷月温度范围Î?? Ť > 4 â???? K），从一系列FTC幅度没有（Ť = 4.0 â???? ^{A 380 ？} C）变强（$Ť=--\mathrm{11.3}$一种？？？？^{一种？？？？}C）土壤霜冻和FTC频率范围（f = 0?? 7）。我们假设较高的FTC数量和频率将增加营养物质的释放。此外，与来自温暖，多变的冬季土壤气候的土壤相比，来自深冷积雪的，具有历史上稳定的冬季土壤温度的寒冷气候土壤将比FTC更敏感。FTC的大小以及FTC频率（在较小程度上）导致硝酸盐，铵和磷酸盐的释放量增加，几乎完全来自寒冷，富含雪地的土壤中。我们的三因素梯度实验的层次回归分析表明，所有研究的营养物的气候成因（平均最低冬季温度）的影响均呈S型曲线，并受FTC量（磷酸盐）或FTC量值和频率（硝酸盐）的调节，铵盐）以两倍的形式存在，对于所有研究的营养素，环境驱动因素的三重相互作用。与初始浓度相比，硝酸盐的可溶性营养素预计将增加至250％（最多16％）。Aμ Gâ???? NO ₃ -Na ????公斤^{â???? 1个}DM），以110A ????％为铵（高达60A ???? Aμ Gâ???? NH ₄ -Na ????公斤^{â???? 1个}DM），以及400A ????％磷酸盐（2.2A ???? Aμ Gâ???? PO ₄ -PA ????公斤^{â???? 1}DM），以最强的幅度和最高的频率出现在最冷的位置。来自温暖地区的土壤几乎没有养分释放，并且不受FTC处理的影响，除了在最温暖的地区，由于极冷的FTC幅度，硝酸盐的释放高于平均水平。我们建议，从历史上看，目前温度较高的森林土壤已经超过了对冬季气候变化的高度响应能力，在土壤生物成分或不稳定的养分来源方面都表现出某种形式的适应性。我们的数据表明，以前寒冷的地点（在气候变化期间将失去保护性的积雪）最容易受到FTC频率和强度增加的影响，从而导致氮和磷的释放发生强烈变化。在研究更新世低地的营养不良的欧洲山毛榉森林中，