Land-Use Conversion Altered Topsoil Properties and Stoichiometry in a Reclaimed Coastal Agroforestry System

Reclaimed coastal areas were mostly used for agricultural purposes in the past, while land-use conversion was initiated in recent decades in eastern China. Elucidation of the effects of land-use conversion on soil properties and stoichiometry is essential for addressing climate change and ecological conservation. In this study, five land-use types in a reclaimed area were chosen to compare the differences of soil properties and stoichiometry, which comprised paddy, upland, upland-forest, forest, and vegetable garden, with a soil age of about 100 years. The results indicated that these land-use types significantly differed in soil water concentration, pH, bulk density, soil salt concentration, soil organic carbon content, total nitrogen content, and total phosphorus, as well as C:N, C:P, and N:P ratios. Positive correlations were found among soil organic carbon, total nitrogen, and total phosphorus; and among pH, bulk density, and soil salt concentration. Total phosphorus and soil organic carbon contents were the main factors shaping the topsoil among the land-use types. Contents of soil organic carbon, total nitrogen, and total phosphorus in paddy and vegetable garden soils were higher than that in upland and upland-forest soils, while bulk density, pH, and soil salt concentration showed the opposite trends. Forest soil demonstrated intermediate values for most properties. And the highest C:N occurred in the upland and vegetable garden, the highest C:P in paddy and vegetable garden, while the lowest C:N and C:P occurred in upland-forest. The highest and lowest N:P occurred in paddy and upland, respectively. The stoichiometric characteristics presented a narrow range of the ratio, and the C:N:P averaged 48:3:1 similar to the stoichiometry of average Chinese cropland soils. Rotations including legume, the use of organic fertilizers, and appropriate fertilization strategies were suggested for improving cropland management.

Automated summary

This study compared the differences in soil properties and stoichiometry among five different land-use types in a reclaimed coastal area. The results showed significant variation in soil properties and stoichiometry among the land-use types. Paddy and vegetable garden soils had higher organic carbon, total nitrogen, and total phosphorus contents, while upland and upland-forest soils had lower contents. The stoichiometric characteristics presented a narrow range of ratios, similar to the stoichiometry of average Chinese cropland soils.