Heterotrophic respiration by soil microbes in a changing climate
摘要
Soil microbes strongly influence the soil organic carbon (SOC) pool, which globally stores ~2,000 PgC. Specifically, the balance between microbial heterotrophic respiration (RH), which degrades SOC, and plant–microbe interactions that stabilize SOC determines whether terrestrial ecosystems are a net source or sink of CO2 to the atmosphere. In this Review, we evaluate how climate change alters these competing processes. RH is approximately half of total soil respiration, at ~50 PgC yr−1, with 70% occurring in topsoils. Warming accelerates microbial metabolism, with a 10 °C temperature increase estimated to raise RH by ~50%, an effect that is particularly strong in Arctic soils. Warming also reduces soil moisture, further modulating RH, which responds nonlinearly to soil moisture, being limited by saturation and desiccation and meeting a maximum at intermediate levels. Consequently, RH is highly sensitive to future precipitation changes and drought. However, soil management strategies could enhance SOC stocks and persistence under climate change. Bacterial and fungal inoculants can promote SOC production and stabilization, while deep-rooting plants increase SOC inputs to deeper layers that experience lower RH. Agricultural practices and biochar amendments can also enhance SOC and reduce RH. Expanding field trials across regions, climates and soil types would improve empirical understanding of these responses and support better representation of RH in predictive models, enabling more accurate assessments of climate impacts on SOC storage.