Long‐term soil warming can decrease soil organic matter (SOM), resulting in self‐reinforcing feedback to the global climate system. We investigated additional consequences of SOM reduction for soil water holding capacity (WHC) and soil thermal and hydrological buffering. At a long‐term soil warming experiment in a temperate forest in the northeastern United States, we suspended the warming treatment for 104 days during the summer of 2017. The formerly heated plot remained warmer (+0.39 °C) and drier (−0.024 cm³ H₂O cm⁻³ soil) than the control plot throughout the suspension. We measured decreased SOM content (−0.184 g SOM g⁻¹ for O horizon soil, −0.010 g SOM g⁻¹ for A horizon soil) and WHC (−0.82 g H₂O g⁻¹ for O horizon soil, −0.18 g H₂O g⁻¹ for A horizon soil) in the formerly heated plot relative to the control plot. Reduced SOM content accounted for 62% of the WHC reduction in the O horizon and 22% in the A horizon. We investigated differences in SOM composition as a possible explanation for the remaining reductions with Fourier transform infrared (FTIR) spectra. We found FTIR spectra that correlated more strongly with WHC than SOM, but those particular spectra did not differ between the heated and control plots, suggesting that SOM composition affects WHC but does not explain treatment differences in this study. We conclude that SOM reductions due to soil warming can reduce WHC and hydrological and thermal buffering, further warming soil and decreasing SOM. This feedback may operate in parallel, and perhaps synergistically, with carbon cycle feedbacks to climate change.

中文翻译：

---

长期土壤增温实验中减少的土壤有机质降低了土壤持水能力并影响了土壤的热力和水文缓冲能力

长期的土壤变暖会减少土壤有机质（SOM），导致对全球气候系统的自我强化反馈。我们研究了降低SOM对土壤持水量（WHC）以及土壤热力和水文缓冲的其他后果。在美国东北部的温带森林中进行的长期土壤变暖实验中，我们在2017年夏季中止了104天的变暖处理。原先加热的地块仍较温暖（+0.39°C）和较干燥（−0.024 cm ³ H ₂ O cm ^-3土壤）比整个悬浮液的对照样地大。我们测量了降低的SOM含量（对于O层土壤为-0.184 g SOM g ^-1，对于A层土壤为-0.010 g SOM g ^-1）和WHC（-0.82 g HO层土壤为₂ O g ^-1，-0.18 g H ₂ O g ^-1相对于对照图，在先前加热的图中显示的是“地平线土壤”。降低的SOM含量在O层中占WHC减少量的62％，在A层中占22％。我们调查了SOM组成的差异，以作为傅立叶变换红外（FTIR）光谱剩余减少量的可能解释。我们发现FTIR光谱与WHC的相关性比SOM更强，但是加热和控制区之间的特定光谱没有差异，这表明SOM成分会影响WHC，但不能解释本研究中的治疗差异。我们得出结论，由于土壤变暖而导致的SOM降低可以减少WHC以及水文和热缓冲作用，从而进一步使土壤变暖并降低SOM。该反馈可以与对气候变化的碳循环反馈并行运行，也可以协同运行。