Combination of nitrogen deposition and ultraviolet-B radiation decreased litter decomposition in subtropical China

Abstract

The interactive effects of enhanced nitrogen (N) deposition and ultraviolet-B (UV-B) radiation on litter decomposition are still unknown. The aims are to test whether the interactive effects of the two environmental factors on litter decomposition and nutrient loss are stronger than that of each factor alone. Experiment included five treatments: elevated UV-B radiation (UV-B, 10 % enhancement), low N addition (N1, 30 kg N ha−1 year−1), high N addition (N2, 60 kg N ha−1 year−1), the two combined treatments of the two factors (UV-B+N1 and UV-B+N2), and an unmanipulated control. The annual decomposition rates under combination of UV-B and N addition significantly decreased compared with that under UV-B and N additions for Pinus massoniana, and did also compared with that under UV-B but did not significantly differ with N additions for Cyclobalanopsis glauca. Negative effects of N additions alone on lignin degradation and P loss were partly offset but negative effect on N loss was further amplified when was combined with UV-B. The combination of N deposition and UV-B radiation on litter decomposition and nutrient loss was significantly different from that of each factor alone without a general response pattern of decomposition, and was regulated by litter chemistry.