Microbial life history strategies explain dissolved organic matter response to warming

Soil dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), as the main component of dissolved organic matter (DOM), play pivotal roles in regulating soil carbon and nitrogen cycles and environmental effect. Warming alter microbial life history strategies, but the extent to whether these changes account for the effects of warming on DOC and DON remains unclear. To explore the effect variation, this study reviewed updated datasets with 321 individual DOC and 187 DON independent experiments globally combined with soil microbial properties. Our results indicated that while warming does not significantly affect DOC concentrations, it led to a notable increase in DON (8.84%), consequently reducing the DOC/DON by 10.79%. Soil moisture emerged as the most influential factor (19.0%) driving DOC responses to warming, whereas soil nitrate nitrogen was the primary driver (33.2%) of DON responses to warming. Under conditions of warming-induced carbon or/and water limitation and environmental stress, microbial tend to shift their life history strategies from a focus on Y (yield) to prioritizing resource acquisition (A) or stress tolerance (S), manifesting by increased soil enzyme activity. The increased DON is a result of microbes intensifying their consumption of carbon to maintain stability under stress, which in turn reduces soil organic carbon (-3.2%) and increases CO2 emissions (48.8%). The reduced DOC/DON ratio under warming had implications for nitrogen cycling. Specifically, soil ammonium nitrogen exhibited a positive linear relationship with the DOC/DON ratio, while soil nitrate nitrogen responded negatively as the DOC/DON ratio increased. This studies highlights the sensitivity and adaptability of soil carbon and nitrogen cycles to warming due to microbial shift from Y- toward A- or S-strategies.