Lithology modulates the response of litter decomposition to precipitation in Mediterranean forests

Background and aims Plant litter decomposition has a major influence on the global carbon cycle. While extensive research has examined the primary environmental drivers of decomposition, the influence of lithology remains poorly understood. Methods We investigated the combined effects of lithology and climate on needle litter decomposition through a field experiment along a decreasing precipitation gradient (1097 to 641 mm yr ^− 1 ) located in the province of Malaga (Andalucía, Spain) where maritime pine ( Pinus pinaster ) forests occur on three distinct soil types: calcareous, metapelite, and peridotite. Additionally, we conducted a reciprocal transplant experiment at the intermediate precipitation site to test the home-field advantage hypothesis, using litter from Pinus pinaster and Abies pinsapo on calcareous and peridotite soils. Results After 1.5 years of decomposition, under intermediate precipitation, litter mass loss was highest on calcareous soils, exceeding mass loss on metapelite soils by 24% and peridotite soils by 50%. Decreased precipitation reduced decomposition by 35% on calcareous soils but had minimal effects on metapelite and peridotite soils. On peridotite soils, labile carbon decomposition was delayed by one dry season, whereas lignin decomposition began immediately. A home-field advantage pattern was observed on calcareous soils, while an away-field advantage was detected on peridotite soils. Conclusion Lithology modulates litter decomposition by influencing litter quality. Since lithology affects both, decomposition rates and their sensitivity to precipitation, understanding these interactions is critical for predicting climate change impacts on nutrient cycling and carbon dynamics.