Extreme droughts have serious impacts on the pools, fluxes and processes of terrestrial carbon (C) and nitrogen (N) cycles. A deep understanding is necessary to explore the impacts of this extreme climate change events. To investigate how soil C and N pools and fluxes respond to drought and explore their mechanisms we conducted a meta-analysis synthesizing the responses of soil C and N cycles to droughts (precipitation reduction experiments) in three main natural ecosystems: forests, shrubs and grasslands. Data were collected from 148 recent publications (1815 sampling data at 134 sites) with the drought experiments from 1 to 13 years across the globe. Drought reduced soil organic C content (-3.3%) mainly because of decreased plant litter input (-8.7%) and reduced litter decomposition (-13.0%) across all the three ecosystem types in the world. Drought increased mineral N content (+31%) but reduced N mineralization rate (-5.7%) and nitrification rate (-13.8%), and thus left total N unchanged. Compared with the local precipitation, drought increased the accumulation of dissolved organic C and N contents by +59% and +33%, respectively, due to retarded mineralization and higher stability of dissolved organic matter. Among the three ecosystem types, forest soils strongly increased litter C (+64%, n=8) and N content (+33%, n=6) as well as microbial CO₂ (+16%, n=55), whereas total CO₂ emission remains unaffected. Drought decreased soil CO₂ emission (-15%, n=53) in shrubs due to reduction of microbial respiration and decreased root biomass. The 98% (n=39) increase of NH₄⁺ concentration in forest soils corresponds to 11% (n=37) decrease of NO₃^- and so, it reflected the increase of N mineralization rate, but the decrease of nitrification. For shrubs and grasslands, however, stabilized or decreased N mineralization and nitrification mean less N uptake by plants under drought. Overall, the effects of drought on soil C and N cycles were regulated by the ecosystem type, drought duration and intensity. The drought intensity and duration intensify all effects, especially on the decreasing total CO₂ emission. However, the most studies mainly focused on the short-term droughts, and there is a lack of comprehensive understanding of how drought effects in a long-term consequences. So, future studies should strengthen drought frequency impacts on ecosystem C and N dynamics in the long-term sequence (> 10 years) in order to face the impacts of global change.

极端干旱严重影响了陆地碳（C）和氮（N）循环的池，通量和过程。需要深入了解以探索这种极端气候变化事件的影响。为了研究土壤碳，氮库和通量对干旱的响应并探索其机理，我们进行了荟萃分析，综合了森林，灌木和草地三种主要自然生态系统中土壤碳和氮循环对干旱的响应（减少降水的实验）。 。数据是从148个最新出版物中收集的（1815个采样数据在134个站点）以及全球1到13年的干旱实验。干旱降低了土壤有机碳含量（-3.3％），这主要是因为世界上所有三种生态系统类型的植物凋落物投入减少（-8.7％）和凋落物分解减少（-13.0％）。干旱增加了矿质氮含量（+ 31％），但降低了氮矿化率（-5.7％）和硝化率（-13.8％），因​​此总氮保持不变。与局部降水相比，干旱由于矿化作用的延迟和可溶性有机物稳定性的提高，分别使可溶性有机碳和氮的积累量增加了59％和+ 33％。在这三种生态系统类型中，森林土壤中的凋落物碳（+ 64％，n = 8）和氮含量（+ 33％，n = 6）以及微生物CO均大大增加 由于矿化滞后和溶解有机物的更高稳定性。在这三种生态系统类型中，森林土壤中的凋落物碳（+ 64％，n = 8）和氮含量（+ 33％，n = 6）以及微生物CO均大大增加 由于矿化滞后和溶解有机物的更高稳定性。在这三种生态系统类型中，森林土壤的凋落物碳（+ 64％，n = 8）和氮含量（+ 33％，n = 6）以及微生物CO大大增加₂（+ 16％，n = 55），而总CO ₂排放量不受影响。由于减少了微生物的呼吸作用和减少了根系生物量，干旱减少了灌木丛中土壤CO _2的排放（-15％，n = 53）。森林土壤中NH ₄ ⁺浓度增加98％（n = 39），对应于NO _3-减少11％（n = 37）^。因此，这反映了氮矿化率的增加，但硝化作用的减少。但是，对于灌木和草地，氮矿化和硝化作用的稳定或降低意味着干旱条件下植物对氮的吸收减少。总体而言，干旱对土壤碳氮循环的影响受生态系统类型，干旱持续时间和强度的调节。干旱强度和持续时间加剧了所有影响，特别是对减少总CO ₂排放的影响。然而，大多数研究主要集中在短期干旱上，并且缺乏对干旱如何造成长期后果的全面了解。因此，为了应对全球变化的影响，未来的研究应在长期序列（> 10年）中加强干旱频率对生态系统碳氮动态的影响。