Early stage litterfall decomposition dynamics in Pinus halepensis and Pinus brutia stands: Disentangling the effect of climate, species identity and management practices

Background and aims Understanding the main drivers of decomposition, a fundamental ecosystem process, is crucial for predicting carbon dynamics in Mediterranean pine forests in the context of climate change. Litter decomposition is highly influenced by micro-environmental conditions, litter chemistry and forest management practices. Methods A multi-plot decomposition experiment was conducted in Pinus brutia and Pinus halepensis dominated forests at three regions in Greece. In each plot, different forest management practices have been implemented over the last decades (overstory thinning, understory removal and lack of management). The mass loss of pine needles and standardized material (cellulose papers, wood sticks) was systematically measured along with micro-environmental conditions. Nonlinear mixed-effect models were used to explore the influence of species, stand structure, and micro-climatic and soil conditions on the early decomposition rates. Results Needle litter in P. halepensis dominated stands decomposed approximately twice as fast as litter in P. brutia stands; however, these species-specific differences were probably masked by micro-environmental variation and therefore could not be attributed to differences in litter chemistry. The analysis of the decomposition rates of cellulose papers revealed an across-region positive effect of pH that interacts with variation in microclimate (air temperature and soil water content) and stand structure (total basal area and leaf area index). For wood sticks, pH was the single across-plot predictor of decomposition. Conclusion The process of early-stage decomposition across regions could be primarily controlled by variation in soil conditions and their microbial communities, with microclimate and stand structure operating at a smaller (plot-level) scale.