PNNL

Abstract

How organic matter responds to climate change is important for the global carbon cycle but is challenging to predict, as its extremely diverse molecules have disparate intrinsic traits. Here we assessed the thermal response of dissolved organic matter in 480 aquatic microcosms along nutrient gradients on Eurasian mountainsides in contrasting climates. Organic molecules consistently responded to temperature change within and 31 across climate zones. At a compositional-level, organic matter in warmer sites had 32 stronger thermal response and reorganized towards molecules with lower thermodynamic 33 favorability for microbial decomposition. Such thermal response of organic matter was 34 more sensitive to warming at higher nutrient levels, with increased sensitivity of up to 38% 35 for each additional 1 mg L-1 of nitrogen loading. Our findings can help to forecast the 36 functional reorganization and sensitivity of carbon pools in a changing world. 37 38