气候变化正在引起更频繁和强烈的热浪。因此,了解热浪如何影响陆地碳循环是很重要的,尤其是在草原上,特别容易受到极端气候的影响。这项研究评估了自然发生的影响,蒙古高原三个生态系统中CO2通量的同时短期热浪:草甸草原(MDW),典型草原(TPL),和灌木草地(SHB)。在三次热浪中,净生态系统生产力(NEP)降低了86%,178%,MDW为172%,TPL,SHB,分别。生态系统呼吸的变化,初级生产总值,蒸散,水的利用效率是不同的,表明观察到的NEP在站点之间降低的潜在机制。高土壤含水量减轻了MDW热浪的影响,这增强了蒸散和随后的冷却效应。然而,在TPL,土壤水分不足导致热和干旱联合胁迫和低恢复力。在SHB,生态系统对8月热浪的低耐受性受到物种物候的严重影响,因为它与植物的关键物候生长阶段相吻合。NEP对热浪的不同响应的潜在关键机制在于环境因素的不同稳定性和不同的重要性,结合NEP对生态系统中每个因子的特定敏感性。此外,我们的发现表明土壤环境异常,而不是大气异常,是热浪期间NEP异常的主要决定因素。这挑战了将热浪作为高空气温度的离散和短暂时期的常规理解。相反,热浪应被视为按时间顺序变化,化合物,和时间敏感的环境压力源。热浪对生态系统的最终影响是由复杂的环境相互作用共同决定的,生物,和热浪特征。
Climate change is causing more frequent and intense heatwaves. Therefore, it is important to understand how heatwaves affect the terrestrial carbon cycle, especially in grasslands, which are especially susceptible to climate extremes. This study assessed the impact of naturally occurring, simultaneous short-term heatwaves on CO2 fluxes in three ecosystems on the Mongolia Plateau: meadow steppe (MDW), typical steppe (TPL), and shrub-grassland (SHB). During three heatwaves, net ecosystem productivity (NEP) was reduced by 86 %, 178 %, and 172 % at MDW, TPL, and SHB, respectively. The changes in ecosystem respiration, gross primary production, evapotranspiration, and water use efficiency were divergent, indicating the mechanisms underlying the observed NEP decreases among the sites. The impact of the heatwave in MDW was mitigated by the high soil water content, which enhanced evapotranspiration and subsequent cooling effects. However, at TPL, insufficient soil water led to combined thermal and drought stress and low resilience. At SHB, the ecosystem\'s low tolerance to an August heatwave was heavily influenced by species phenology, as it coincided with the key phenological growing phase of plants. The potential key mechanism of divergent NEP response to heatwaves lies in the divergent stability and varying importance of environmental factors, combined with the specific sensitivity of NEP to each factor in ecosystems. Furthermore, our findings suggest that anomalies in soil environment, rather than atmospheric anomalies, are the primary determinants of NEP anomalies during heatwaves. This challenges the conventional understanding of heatwaves as a discrete and ephemeral periods of high air temperatures. Instead, heatwaves should be viewed as chronologically variable, compound, and time-sensitive environmental stressors. The ultimate impact of heatwaves on ecosystems is co-determined by a complex interplay of environmental, biological, and heatwave features.