This dataset contains the results of a field experiment assessing the combined effects of ultraviolet (UV) radiation (UV-A and UV-B) and reduced rainfall on litter decomposition in two Mediterranean evergreen shrub species: Arbutus unedo and Phillyrea angustifolia. The aim is to evaluate how these climate change-related factors influence initial litter quality, mass loss, and microbial activity during the first year of decomposition. The dataset includes: • Repeated measurements of remaining biomass (%AFDW), enzymatic activities (β-glucosidase, cellobiohydrolase, peroxidase), and relative abundance of fungi and bacteria at different time points (0, 33, 117, 237, and 347 days for A. unedo and 0, 117, and 347 days for P. angustifolia). • Litter quality variables (fiber, cellulose, lignin, carbon and nitrogen content, C:N ratio) at the beginning and end of the decomposition period. • Experimental factors: three UV radiation levels (UV0, UVA, UVBA) and two rainfall regimes (natural and reduced), applied in 9 m² plots over six years. • Additional data on decomposition rate (k) for pretreated litter. Scope and nature: The data are quantitative, derived from a factorial field experiment with repeated measures. They are relevant for studies on soil ecology, nutrient cycling, climate change impacts on Mediterranean ecosystems, and decomposition modeling. Relation to the publication: This dataset complements the article “UV radiation and reduced rainfall: Legacy effects on litter and first-year decomposition in two Mediterranean evergreen shrubs” (Rodríguez-Hidalgo et al., 2025, Environmental and Experimental Botany), but the description here focuses on the dataset content and structure rather than the study results or conclusions.

Data preprocessing was carried out between August 2011 and August 2017, and the field decomposition experiment took place from autumn 2017 to autumn 2018. The project, as well as the collection, analysis, and interpretation of these data, was supported by several funding sources acknowledged in the related publication. Specifically, Cl-R-H was the recipient of a PhD grant from the Senescyt-UdG co-financed program (Contract Nº AR2Q-000421–2016). This work was funded by the Spanish Government through the “Ministerio de Ciencia, Innovación y Universidades – MCIN” (Refs. CGL2014–55976-R, PID2021–123735OB16C2/MCIN/AEI/10.13039/501100011033/FEDER, UE; and PCI2020–120702–2/AEI/10.13039/501100011033), and by the University of Girona (Refs. ASING2011/3 and MPCUdG2016). The SOLIPLANT research group was recognized as a consolidated group by the Generalitat de Catalunya (Refs. 2017SGR0055 and 2021SGR0047). AMR acknowledges funding from the AGAUR-ICREA Academia award (Catalan Institution for Research and Advanced Studies, Ref. 2024 ICREA 00144). We also thank the Gavarres Consortium (Girona, Spain) for allowing us to conduct the experiment at the Can Vilallonga forest farm