Shifts in the frequency and magnitude of rain events (precipitation patterns) associated with climate change may impact ecosystem nitrogen and carbon cycling through effects on plant physiology and soil microbial activity. Here, we determined how the combination of temporal irrigation distribution and N supply affects plant-microbial C and N dynamics in microcosms with winter wheat. First, we investigated legacy effect of 12 weeks of contrasting irrigation distribution (frequent and small versus infrequent and large water inputs) and N inputs (high versus low) on plant biomass, organic and inorganic N pools, and potential nitrification and denitrification rates. Second, we investigated legacy effects of these treatments on C and N fluxes in plants and microbes over 29 h after a rewetting event, using ¹³C-CO₂ and ¹⁵N-NH₄ labeling. We found that irrigation distribution and N input led to significant differences in plant responses and soil C input, setting the scene for the rewetting response. Immediately after rewetting, microorganisms outcompeted plants for soil mineral N. However, over time, the net outcome of competition improved for plants regardless of water or N input history. Further, we found that a history of frequent irrigation led to more productive plants (biomass and rate of photosynthesis) and increased their net competitiveness for N over microorganisms. This suggests that the shift toward more extreme fluctuations in soil moisture predicted by climate forecasts for most temperate zones may have negative implications for plant productivity due to altered N dynamics between plants and soil microorganisms.

与气候变化相关的降雨事件（降水模式）的频率和幅度的变化可能通过对植物生理学和土壤微生物活动的影响来影响生态系统的氮和碳循环。在这里，我们确定了时间灌溉分布和 N 供应的组合如何影响冬小麦微观世界中的植物微生物 C 和 N 动态。首先，我们调查了 12 周对比灌溉分布（频繁和少量与不频繁和大量水输入）和氮输入（高与低）对植物生物量、有机和无机氮库以及潜在硝化和反硝化速率的遗留影响。其次，我们使用¹³ C-CO研究了这些处理对再润湿事件后 29 小时内植物和微生物中 C 和 N 通量的遗留影响₂和¹⁵ N-NH ₄标签。我们发现灌溉分布和 N 输入导致植物响应和土壤 C 输入的显着差异，为再润湿响应奠定了基础。再润湿后，微生物立即在土壤矿物质 N 方面胜过植物。然而，随着时间的推移，无论水或 N 输入历史如何，植物的竞争净结果都得到改善。此外，我们发现频繁灌溉的历史导致了更高产的植物（生物量和光合作用速率），并增加了它们对 N 的净竞争力超过微生物。这表明，由于植物和土壤微生物之间的氮动态变化，大多数温带地区的气候预测所预测的土壤水分向更极端波动的转变可能对植物生产力产生负面影响。