Land use change influences soil C, N, and P stoichiometry under ‘Grain-to-Green Program’ in China

Changes in land use might affect the combined C, N and P stoichiometry in soil. The Grain-to-Green Program (GTGP), which converts low-yield croplands or abandoned lands into forest, shrub, and/or grassland, was the largest land reforestation project in China. This study collected the reported C, N and P contents of soil in GTGP zones to achieve the factors driving the changes in the C:N, C:P, and N:P values. The results showed that the annual average precipitation exerted significant effects on the C:P value, and on the N:P value became significant 20 years after the change in land use. The annual average temperature was the main factor affecting the C:N value during the first 10 years, while the annual average precipitation strongly affected this value afterwards. In addition, "Redfield-like" interactions between C, N, and P in the soil may exist. A linear regression revealed significant positive correlations between the C:N, C:P, and N:P values and the restoration age, temperature, and precipitation after a change in land use. Therefore large-scale changes in land use under the 'GTGP' program might significantly affect the C:N, C:P and N:P ratios in soil.