Leaf litter quality is a stronger driver of decomposition in lawns than the microclimatic effect of trees

Lawns and wooded areas dominate urban green spaces (UGSs) and are known to store substantial amounts of carbon in soils, yet the role of lawn trees in litter decomposition dynamics remains poorly understood. This study assessed how trees influence litter decomposition through (i) microclimatic (temperature and moisture) and (ii) soil properties effects. Decomposition rates of 8 tree and shrub litters (Quercus robur, Quercus rubra, Fagus sylvatica, Platanus × acerifolia, Pinus radiata, Tilia × europaea, Cornus alba, Spiraea vanhouttei) frequently encountered in urban areas were measured using litterbags(5 mm and 2 mm mesh) in adjacent open and wooded lawns, allowing assessment of macrofauna contribution. Microclimatic conditions and soil physicochemical properties were monitored. Decomposition rates varied widely among litter types, with 5 tree litters decomposing slowly (0.29 < k < 0.85 y-1) and 3 litters—mostly shrubs—decomposing faster (3.06 < k < 6.23 y-1). Despite a higher average temperature in open lawns (+1.6 °C), the decomposition rates were similar between lawn types except for the two Quercus rubra and Q. robur, which decomposed 87% and 54% faster in wooded lawns, respectively.Macrofauna exclusion revealed a stronger contribution to the decomposition of labile litter in both lawn types. Overall, decomposition rates were primarily driven by litter quality, especially lignin and soluble compound content (R² = 0.59–0.92), while microclimate and soil properties had limited influence. These results indicate that litter quality outweighs microclimatic effects of trees on decomposition in UGSs and suggest that maintaining litter in wooded lawns could support soil carbon processes without impairing decomposition. Together, these findings offer UGS managers an initial framework to assess litter decomposition from various litter types when recycled on open and wooded lawn soils.