Study reveals plant diversity and ultraviolet radiation jointly regulate grassland litter decomposition mechanism

Litter decomposition is a key process in the carbon cycle of terrestrial ecosystems. recently，中国科学院植物研究所依托区域紫外辐射联网控制实验平台，在那曲、海北、固原、锡林浩特和四子王旗5个站点开展了长期野外分解实验。

The researchers set up mixed litter containing 2-5 species according to the biomass ratio of dominant plants at each site to characterize the local natural litter input, and constructed natural ultraviolet radiation and ultraviolet attenuation treatments respectively, and conducted field decomposition observations for nearly 4 years. The study found that UV attenuation extended the average residence time of mixed litter at different sites by 3% to 35%, indicating that the promotion effect of UV radiation on litter decomposition has obvious regional differences. Mixed litter with higher species richness and phylogenetic diversity decomposed faster overall, with the promotion effect of diversity on decomposition mainly occurring in the early stages. Faster decomposition shortens the residence time of litter on the surface and reduces cumulative UV exposure, thus weakening the relative contribution of photodegradation. At the regional scale, diversity and UV radiation intensity jointly explained 59% of the differences in photodegradation effects between sites, of which the relative contribution of diversity was 61.2%, which was higher than 38.8% of UV radiation intensity.

The study incorporated the litter mixing effect mediated by plant diversity into the quantitative analysis framework of photodegradation with "radiation intensity × exposure time" as the core, revealing its dual regulatory path for decomposition: on the one hand, it directly drives the biological decomposition process, and on the other hand, it indirectly affects the actual contribution of abiotic photodegradation by regulating the residence time of litter on the surface.

这一发现从机制上阐明了生物多样性效应与紫外光降解过程之间的内在关联，为在自然群落尺度上评估混合凋落物光降解对碳周转的贡献提供了新的理论依据。

Relevant research results were published inGlobal Change Biologysuperior. The research work is supported by the National Natural Science Foundation of China.

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凋落物混合效应调控紫外光降解的机制概念图