Nitrogen addition reduces litter decomposition but does not affect litter production and chemistry in an alpine shrubland

Background and aims

Alpine shrublands are critical for global carbon dynamics due to their widespread occurrence in cold-climate regions and vulnerability to environmental shifts, including increased nitrogen deposition. Although nitrogen deposition affects litter turnover and accumulation, the precise mechanisms governing litter dynamics, including production, chemical composition, and decomposition rates, remain uncertain for these ecosystems.

Methods

To address this knowledge gap, our study investigated the effects of different nitrogen additions on litter production, chemistry, and decomposition rates in an alpine shrubland ecosystem on the eastern margin of the Qinghai–Tibetan Plateau of China over a four-year period.

Results

Our results showed that nitrogen addition did not significantly affect litter production or chemical properties, including carbon, nitrogen, phosphorus, lignin, and cellulose concentrations. Consequently, the annual input of litter-derived carbon and nutrients remained unchanged. However, we observed a significant reduction in litter decomposition rates at nitrogen additions of 50 and 100 kg ha⁻¹ yr⁻¹, whereas no such effect was observed at nitrogen additions of 20 kg ha⁻¹ yr⁻¹.

Conclusions

Our study revealed that high nitrogen deposition reduces litter decomposition in alpine shrublands, which coincides with increased litter accumulation, with consequences for carbon and nutrient cycling.