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Background and aims Intensification of savannah land-use is predicted to negatively influence soil biodiversity and functioning such as litter decomposition by detritivores. Loss of macrodetritivores, particularly termites, may be problematic in drier savannahs due to the capacity of macrodetritivores to sustain litter decomposition. Here we investigate how human land-use and spatiotemporal rainfall influence the contribution of macrodetritivores to plant litter decomposition. Methods We measured decomposition using globally standardized litter: labile green and recalcitrant rooibos tea litter. The contribution of macrodetritivores to litter decomposition was determined through exclusion using meshed litterbags. Litter decomposition was determined in agricultural land, pastureland and wildlife protected areas during both wet and dry seasons and in mesic and wet rainfall regions across the borders of the Serengeti National Park, Tanzania. Results Macrodetritivores consumed recalcitrant rooibos and mainly avoided labile green tea litter. On average macrodetritivores enhanced recalcitrant litter decomposition by 22%, but litter mass loss varied across land-uses, typically being higher on agricultural and pastureland compared to wildlife protected areas, and was sustained during periods of water scarcity. However, we observed instances of higher decomposition of recalcitrant litter by macrodetritivores in wildlife protected areas. In contrast, litter decomposition by microbes and microdetritivores was more constrained by seasonal and regional water availability with a minor influence of land-use. Conclusion We found that moderate human-modification of savannahs is compatible with macrodetritivore litter decomposition. As savannahs become more intensely used by humans, raising ecological awareness among agropastoralist is required to ensure continued contribution of macrodetritivores to litter decomposition. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Decomposition is a vital ecosystem process, increasingly modified by human activity. Theoretical frameworks and empirical studies that aim to understand the interplay between human land-use, macro-fauna and decomposition processes have primarily focused on leaf and wood litter. For a whole-plant understanding of how land-use and macro-fauna influence decomposition, investigating root litter is required. Using litterbags, we quantified rates of root decomposition across contrasting tropical savanna land-uses, namely wildlife and fire-dominated protected areas and livestock pastureland without fire. By scanning litterbags for termite intrusion, we differentiated termite and microbial driven decomposition. Root litter was buried underneath different tree canopies (leguminous and non-leguminous trees) and outside canopies to account for savanna landscape effects. Additionally, we established a termite cafeteria-style experiment and common garden to explore termite selectivity of root litter and root trait relationships, respectively. After one year, we found no significant differences in root litter mass loss between wildlife dominated areas and pastureland. Instead, we found consistent species differences in root litter mass loss across land-uses and additive and non-additive effects of termites on root decomposition across plant species. Termite selectivity for root litter species occurred for both root and leaf litter buried near termite mounds, but was not explained by root traits measured in the common garden. Termite foraging was greater under leguminous tree canopies than other canopies; however, this did not influence rates of root decomposition. Our study suggests that land-use has a weak direct effect on belowground processes in savannas. Instead, changes in herbaceous species composition and termite foraging have stronger impacts on belowground decomposition. Moreover, termites were not generalist decomposers of root litter, but their impact varies depending on plant species identity and likely associated root traits. This root litter selectivity by termites is likely to be an important contributor to spatial heterogeneity in savanna nutrient cycling. © 2018 The Authors. Oikos © 2018 Nordic Society Oikos.