One of the key characteristics of peatland ecosystems is the low input of nutrients such as nitrogen (N) and phosphorus (P), particularly in bogs that receive all of their nutrients from precipitation. Primary production in peatlands has been found to be limited by N or P availability, or co-limited by both N and P. It was found that nutrient availability increased with warming in the SPRUCE warming plots. The increased nutrient availability could stimulate plant growth and lead to the indirect fertilization effect. Whether or not the peatland ecosystem carbon (C) storage will increase with warming depends on the balance between the nutrient induced indirect fertilization effect and carbon loss due to warming and drying. Here we try to explore this question through model-data integration using ELMv1-SPRUCE.
Results/Conclusions
We first used the pre-treatment observational data to evaluate model performance. Based on the observational data, we improved model representation and parameterization of several key processes, including soil carbon accumulation at depth and nutrient leaching. We then used the model to examine how the N and P cycling dynamics respond to warming and how the nutrient responses affect carbon cycle responses. We compared the model simulated responses with the experimental data from SPRUCE. Our simulation results show that warming increases nutrient availability and leads to the indirect fertilization effect for plant growth. This effect, however, is limited by increased drying associated with warming. Overall warming leads to a loss of carbon in peatland ecosystems. Our simulations also suggest that warming in peatland ecosystems leads to a more open N cycle – higher denitrification fluxes and N2O gas emissions.