Effects of tree diversity on oak litter VOC emissions

Abstract Leaf metabolites are important drivers of biotic interactions. Leaf metabolic profiles are changing over ontogeny and in response to biotic and abiotic conditions. Additionally, plant species diversity can influence leaf metabolomes. However, it is rarely considered how changes in leaf metabolomes might affect the leaf litter volatiles, which mediate interactions with the decomposer community. We designed an optimized and validated solid-phase microextraction (SPME) method coupled with a gas chromatography-mass spectrometry (GC-MS) analysis to analyze liter volatile organic compound (VOC) emissions. This method was applied to test the hypothesis that sessile oak ( Quercus petrea ) leaf litter VOC profiles are influenced by surrounding tree diversity. The results showed that plot diversity significantly affected oak litter VOC profiles by increasing the emissions of fatty acids. Tree diversity marginally modulated terpenoid emissions. Particularly, the emission rates of (-)-β-bourbonene and (E)-β-caryophyllene decreased with increasing species diversity. Also, ethanol emissions, likely due to microbial activity, decreased with increasing tree diversity. By detecting diversity- and C: N-related changes in terpenoids, and diversity effects on fatty acids and ethanol emissions of Q. petraea leaf litter, we provide new insights into how biodiversity shapes litter chemistry and potentially restructures decomposer interactions.