Wetting‐induced soil CO2 emission pulses are driven by interactions among soil temperature, carbon, and nitrogen limitation in the Colorado Desert

Warming-induced changes in precipitation regimes, coupled with anthropogenically-enhanced nitrogen (N) deposition, are likely to increase the prevalence, duration, and magnitude of soil respiration pulses following soil wetting via interactions among temperature and C and N availability. Quantifying the importance of these interactive controls on soil respiration is a key challenge as pulses can be large terrestrial sources of atmospheric CO2 over comparatively short timescales. Using an automated sensor system, we measured soil CO2 flux dynamics in the Colorado Desert—a system characterized by pronounced transitions from dry-to-wet soil conditions—through a multi-year series of experimental wetting campaigns. Experimental manipulations included combinations of C and N additions across a range of ambient temperatures and across five sites varying in atmospheric N deposition. We found soil CO2 pulses following wetting were highly predictable from peak instantaneous CO2 flux measurements...., Our eight field experiments, which varied in experimental manipu- lations of temperature and C and N substrates, all used the same  measurement system to capture soil temperature, moisture, and CO2 fluxes before and after soil wetting. Prior to each field campaign,  pairs of polyvinyl chloride (PVC) soil collars measuring 20-cm in diam- eter were installed to 5-cm depth and adjacent to each other under  L. tridentata canopies or in interspaces between shrubs. One collar  per pair was used for trace gas measurements and the other was used  for soil temperature, moisture, and ancillary soil measurements. This  secondary collar was necessary because temperature and moisture probes contained wiring attachments that would interfere with the chamber's ability to seal around the soil collar; however, we assumed that collar pairs would experience similar climate and edaphic conditions given their proximity to each other. Both collars in each pair received identical wetting treatments and collar..., Statistical analyses were conducted  in JMP 14 (2021) and data management and visualization were performed in R 4.1.3 (2021) and RStudio (RStudio Team, 2020).

气候变暖导致的降水格局变化，加之人为增强的氮（N）沉降，可能通过温度与碳（C）、氮有效性之间的相互作用，提高土壤湿润后土壤呼吸脉冲的发生率、持续时间及强度。量化这些交互作用对土壤呼吸的调控作用是一项关键挑战，因为在相对较短的时间尺度内，此类脉冲可能成为大气CO₂的重要陆地来源。我们采用自动化传感器系统，通过多年的实验性湿润处理，在科罗拉多沙漠（该系统以土壤干湿状态的显著转变为特征）中测定了土壤CO₂通量动态。实验处理包括在不同环境温度及大气氮沉降水平各异的五个站点，添加碳和氮的不同组合。研究发现，土壤湿润后的CO₂脉冲可通过峰值瞬时通量测量高度预测……我们开展的八项野外实验（涉及温度及碳、氮底物的实验处理）均采用相同的测量系统，以捕捉土壤湿润前后的温度、湿度及CO₂通量变化。每次野外实验前，在三齿拉瑞阿（L. tridentata）灌丛下或灌丛间隙，安装直径20厘米的聚氯乙烯（PVC）土壤环对。每对环中，一个用于痕量气体测量，另一个用于土壤温度、湿度及辅助土壤参数的测定。设置第二个环是因为温湿度探头的接线会干扰测量室与土壤环的密封；不过，鉴于环对间距较近，我们假设两者所处的气候及土壤条件相似。每对环均接受相同的湿润处理……统计分析使用JMP 14（2021）进行，数据管理与可视化则通过R 4.1.3（2021）及RStudio（RStudio Team，2020）完成。