Intensive plantations decouple fine root C:N:P in subtropical forests

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Fine roots play key roles in carbon and nutrient cycling in terrestrial ecosystems. Despite the global conversion of natural forests to tree plantations, a quantitative evaluation of the dynamics of fine root nutrients and C:N:P stoichiometry in plantations and natural forests is lacking. This study examined the fine root elemental concentrations and C:N:P stoichiometry of Chinese fir plantations and natural secondary forests (5–41 years old), employing primary forests as a reference. Live fine root C, N, P and K concentrations did not differ with forest types, but live fine roots had lower Ca and Mg concentrations in plantations than natural secondary and primary forests. Dead roots contained higher N, P, and Mg in plantations than in natural forests. Live and dead fine root elemental concentrations and C:N:P stoichiometry did not change with stand age, except for a decrease in dead root Ca and Mg concentrations in 19–31-year-old stands. Live root C:N, C:P, and N:P ratios did not differ between forest types; however, dead root C:N, C:P, and N:P ratios were higher in natural forests than in plantations. Our findings suggest that intensively managed forest monoculture plantations have a negative impact on the resorption proficiency of fine root nutrients and decouple the C:N:P of fine roots in subtropical forests. We recommend reducing fertilization and increasing plant diversity in plantations to optimize the C:N:P of plants.