Climate warming and nitrogen deposition had no significant interaction effect on litter decomposition of subtropical mountain forest in Southwest China

Litter decomposition is essential for the global carbon cycle, which is affected by environmental factors. In the context of global warming and increasing nitrogen deposition, the responses of litter decomposition are unclear in subtropical forests.

Here, we carried out an interaction experiment of warming (3.3 °C) and nitrogen addition (50 kg ha⁻¹ yr⁻¹) and a recovery experiment (remove warming and nitrogen addition treatments) in a subtropical evergreen broad-leaved forest for four years in total.

The results showed that during the treatment period, warming, nitrogen addition, and their combination significantly decreased litter decomposition according to the k values by 35.8%, 23.0%, and 42.2%, respectively. However, there was no significant interaction effect between warming and nitrogen addition. Litter decomposition rates quickly returned to the same level during the two-year recovery period. Variance partitioning analysis (VPA) and covariance analysis (ANCOVA) simultaneously confirmed that warming and nitrogen addition significantly affected litter decomposition. VPA and ANCOVA also showed that soil temperature and water content significantly contributed to the decomposition rate during the treatment period.

This study suggests that warming and nitrogen addition significantly inhibit litter decomposition, but this effect is not sustainable.