Patterns and Driving Mechanism of C, N, P Ecological Stoichiometry in Plant-Litter-Soil Systems of Monoculture and Mixed Coastal Forests in Southern Zhejiang Province of China

Mixed forests are usually associated with higher resource utilization compared to the corresponding monocultures; however, the tree mixing effects of carbon (C), nitrogen (N), phosphorus (P) ecological stoichiometry in coastal forest ecosystems remains largely unknown. We compared the C, N, P stoichiometry in different ecosystem components (i.e., canopy layer, herb layer, litter layer, 0–20 cm and 20–40 cm soils) among two monocultures (Casuarina equisetifolia and Eucalyptus saligna) and their mixture in Taizhou, Zhejiang province, China. We also assessed the effects of the main microhabitat factors (wind speed, soil salinity, soil moisture and pH) on C, N, P stoichiometry. Two monocultures and their mixture showed the same elemental pattern of “low C and high P” for both the canopy and herb layers, and soil, indicating evident N limitations; however, the mixture intensified the N deficiency more. The mixture showed stronger correlations among the C, N, P stoichiometry than the monocultures. Redundancy and hierarchical partitioning analysis showed the overall and independent effects of the microhabitat factors on the C, N, P stoichiometry separately, in which soil moisture presented more effects on shallow soil (20–40 cm) C, N, and P, while soil salinity mainly affected the herb and litter layers; wind speed had greater effects on canopy layer C, N, P stoichiometry. These results are expected to provide a management reference for the regeneration of degraded plantations in the southern Zhejiang province of China.