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

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 to 41 years old), employing primary forests as a reference. Live fine roots had higher P, but lower Ca concentrations in plantations than natural forests across all age classes. Dead roots contained higher N, P, Ca, and Mg in young plantations than in natural forests. Live and dead fine root elemental concentrations and C:N:P stoichiometry did not change with stand age in both forest types, except for a decrease in dead root P and Mg concentrations in 19-41-year-old plantations. 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 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. Consequently, we recommend reducing fertilization and increasing plant diversity in plantations to optimize the C:N:P of plants.