Different sensitivities of litter decomposition and nutrient release to ultraviolet radiation

Abstract. Ultraviolet (UV) radiation plays an important role in litter decomposition. Despite years of research, it is still not fully understood that the role of UV radiation in litter decomposition and carbon (C) and nutrient release, as well as the direct (litter decay directly exposed to UV) and indirect (plants received UV during growth) effects. In this study, a meta-analysis that comprised 54 published studies concerning UV radiation experiments, including 598 observations, was performed to quantify the responses of litter decomposition and C and nutrient release to UV radiation. The direct and indirect effects of UV-B enhancement on litter decomposition did not differ, but the direct effects of litter weight loss were more sensitive than the indirect effects under UV attenuation. Changes in UV radiation did not affect litter decomposition under laboratory conditions, but litter type only affected the rate of decomposition. In addition, the weight loss under UV radiation exhibited three-stage temporal dynamics: UV enhancement accelerated litter decomposition but required UV accumulation, whereas the UV attenuation effect decreased with time. The litter decomposition rates increased with decreasing precipitation (< 450 mm), and the sensitivity increased as the precipitation decreased (< 700 mm). Overall, UV attenuation showed considerable effects on C and nitrogen (N) release. The findings of this meta-analysis suggested that photodecomposition effects on litter decomposition depend on many factors and can alter C and N cycling during decomposition.