Temperature anomalies such as heat waves and cold spells are increasingly common, posing threats to ecosystem functioning and delivered services. Although temperature anomalies have been shown to limit broad-scale patterns of carbon sequestration, fine-scale studies on CO2 fluxes and temperature anomalies are limited and interactions between temperature anomalies and agricultural management remain poorly understood. Using long-term data on grassland CO2 fluxes and air temperature (2003-2021), we investigated the effects of temperature anomalies (cold, warm, extreme cold, extreme warm) on gross primary productivity and ecosystem respiration in adjacent upland mesic grasslands subjected to either extensive or intensive cattle grazing management treatments. Both warm and cold temperature anomalies occurred throughout the study period, with 40 days per year on average classed as colder or warmer compared to normal. Irrespective of management treatment and flux type, we found that temperature anomalies had a significant effect on the magnitude of CO2 fluxes, the relationship between air temperature and CO2 fluxes, and the occurrence of anomalous flux events. The magnitude of CO2 fluxes was most affected by temperature anomalies at the start of the growing season, and fluxes were generally more sensitive to warm rather than cold temperature anomalies. However, cold temperature anomalies promoted asynchrony between C uptake and loss. Temperature-CO2 flux relationships were upregulated by warm temperature anomalies in spring but down-regulated in summer and autumn, with greater reductions in flux process rates in the intensive management treatment. Nevertheless, temperature anomalies were not found to be a strong driver of flux anomalies in this study system. Collectively, our results show that grassland management interacts with the timing and nature of temperature anomalies on CO2 fluxes and suggest that low grassland management intensity may buffer CO2 fluxes against warm air temperature anomalies in cool temperate systems, with implications for adaptation strategies for grasslands under climate change.

中文翻译：

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管理和温度异常对温带高地草原系统18 年记录的 CO2 通量的交互影响


热浪和寒潮等温度异常越来越普遍，对生态系统功能和提供的服务构成威胁。尽管温度异常已被证明限制了碳封存的大规模模式，但对 CO2 通量和温度异常的精细研究是有限的，温度异常与农业管理之间的相互作用仍然知之甚少。利用草原 CO2 通量和气温（2003-2021 年）的长期数据，我们研究了温度异常（寒冷、温暖、极寒、极暖）对邻近高地中湿草原总初级生产力和生态系统呼吸的影响，这些草地受到粗放或集约化放牧管理处理。在整个研究期间，暖温和低温异常都发生了，与正常情况相比，平均每年有 40 天被归类为更冷或更暖。无论管理处理和通量类型如何，我们发现温度异常对 CO2 通量的大小、空气温度与 CO2 通量之间的关系以及异常通量事件的发生都有显著影响。在生长季节开始时，CO2 通量的大小受温度异常的影响最大，并且通量通常对温暖的温度异常比对寒冷的温度异常更敏感。然而，低温异常促进了 C 摄取和损失之间的异步。温度-CO2 通量关系在春季被温暖的温度异常上调，但在夏季和秋季下调，在精养处理中通量过程速率的降低幅度更大。然而，在该研究系统中，温度异常并未被发现是通量异常的强大驱动因素。 总的来说，我们的结果表明，草原管理与 CO2 通量温度异常的时间和性质相互作用，并表明低草原管理强度可能会缓冲 CO2 通量与冷温带系统中暖空气温度异常的影响，这对气候变化下草原的适应策略具有影响。