Coupling Mechanism of C:N:P Stoichiometry Between Plant and Soil after Long-Term Reclamation in the Coastal Area, Eastern China

Human reclamation activity can significantly affect the balance of ecological processes and elements in the coastal wetland ecosystems. The coupling mechanism of C:N:P stoichiometry plays a vital role in exploring ecological processes and nutrient cycle in plant–soil systems which is still unclear in the coastal area after long-term reclamation. The carbon (C), nitrogen (N), and phosphorus (P) in plant and total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) content of the soil in a coastal reclamation area of Jiangsu Province, China were measured, and the coupling mechanism of plant and soil C:N:P stoichiometry were further analyzed with structural equation modeling (SEM). Results showed that the sediments in coastal wetland gradually transformed into arable soil and accumulated nutrition through the process of dehydration and desalination after reclamation. Soil TOC, TN, and TP content increased with the increasing reclamation time. Soil C:N ratio varied between 3.99 and 49.71, soil N:P ratios from a low of 0.11 to a high of 2.87, and soil C:P ratio fluctuated between 3.43 and 15.17. Plant C concentration decreased with the increasing reclamation time, while plant P and N content increased. Plant C:N ratios vary between 8.56 and 403.86, plant N:P ratios from a low of 0.72 to a high of 15.91, and plant C:P ratios vary between 65.60 and 1045.07. The growth of plants in the coastal reclamation area was supposed to be limited by the N element. Plant P element might be the medium between plant C and N. Soil WC significantly affected plant C:P, and soil EC had a significantly positive influence on plant N:P. This study highlighted that the coupling of C:N:P stoichiometry in plant and soil were tight and soil N:P could be a good predictor of plant C:P and N:P ratios.