Why oaks should stay with their close relatives: growing in a distantly related neighbourhood delays and reorganizes nutrient recycling during litter decomposition

• Published in: Oikos Vol. 2025; no. 4
• Main Authors: Santonja, Mathieu, Pan, Xu, Courty, Pierre-Emmanuel, Butenschön, Olaf, Berg, Matty P., Murray, Phil, Yguel, Benjamin, Brulé, Daphnée, Zhang, Keliang, Prinzing, Andreas
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.2025; Nordic Ecological Society
• Subjects: Biodiversity and Ecology; Decomposition; Eco-evolutionary feedback; Ecosystems; Environmental Sciences; Feedback; Gymnosperms; herbivores; humidity; Leaf litter; leaf phenology; Leaves; litter decomposition; litter quality; microbial biomass; Microorganisms; Niches; Nutrients; phenolic compounds; phylogenetic neighbourhood; Phylogenetics; Phylogeny; plant litter; Plant species; plant-soil interaction; Quercus petraea; Recycling; species; Species richness; Transplantation; trees; litter quality; litter decomposition; leaf phenology; plant-soil interaction; Eco-evolutionary feedback; phylogenetic neighbourhood
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1111/oik.10567

Closely related species often conserve similar niches despite interacting negatively. We suggest that close relatives may interact positively via ecosystem feedbacks: leaf litter produced or exposed in a closely related neighbourhood (low phylogenetic isolation) may decompose more quickly, leading to more rapid nutrient recycling. We studied decomposition of leaf litter of oaks Quercus petraea across 8 and 14 months, reciprocally transplanting leaf litters between low and high phylogenetic isolation to distinguish between effects mediated by leaf litter quality and by decomposition environment. We found that, by affecting litter quality, phylogenetic isolation reduced decomposition across 14 months (loss of litter mass and C). Moreover, by affecting litter quality and decomposition environment, phylogenetic isolation reduced microbial biomass and extensively altered relationships between C and N losses and abundances/diversities of different soil organisms across 8 and 14 months. Phylogenetic isolation was to a large extant driven by percentage of gymnosperms, explaining the decomposition‐environment mediated effects. Such environment‐mediated effects reflected decreasing soil humidity and pH with phylogenetic isolation, while litter‐quality mediated effects reflected decreasing leaf phytophagy or increasing leaf phenolics. Tree‐species richness, in contrast, did not explain effects of phylogenetic isolation, and had little effect overall. To conclude, coexistence of oaks with distant relatives partly impedes recycling of leaf litter and re‐organizes the trajectories of this recycling. In contrast, oaks coexisting with close relatives may profit from a positive ecosystem feedback through increased nutrient recycling, possibly contributing to the conservation of the oak's niches. We suggest that such a positive ecosystem feedback among close relatives might exist in other late successional tree species.