Objectives This study explored the C, N, P stoichiometry characteristics of fine roots of Castanea mollissima to provide a theoretical basis about targeted cultivation and high yield.

Methods Investigation was carried out in the Chestnut (Castanea mollissima) Breeding and Cultivation Base of Department of Economic Forest, Beijing Forest University, located in Qianxi County, Hebei Province. The plantation was six-years-old. During the growing season (April to October), soil samples were collected at 0–20 cm, 20–40 cm and 40–60 cm depth, and 50 cm and 100 cm away from tree trunks at monthly frequency. The number of fine roots in different soil layers and the C, N and P contents of the fine roots were determined. The dynamics and spatial distribution characteristics of carbon (C), nitrogen (N) and phosphorus (P) stoichiometry characteristics were studied.

Results The annual mean values of C, N and P contents of the fine roots were 382.01 g/kg, 7.99 g/kg and 1.06 g/kg, respectively, with corresponding C/N, C/P, and N/P ratios of 50.48、377.35 and 7.62 respectively. The C contents, the C/N and C/P ratios were maintained high from June to September, especially in June. The contents of N and P were highest in April and lowest in June, the N/P ratio reached top in the end of growing season. The maximum C content was found at 20–40 cm depth, that in July was appeared at 50 cm away and in June at 100 cm away from chestnut tree trunk, with the season increment of 26.82 g/kg and 11.84 g/kg respectively. N and P were mainly concentrated in soil layer of 0–20 cm, the maximum N and P contents were all founded at the 50 cm away and appeared in April for N and in July for P. And the soil N and P contents were decreased by 1.39 g/kg and 0.60 g/kg respectively during the growing period. At soil 100 cm away from tree trunks, the highest soil N was appeared in April and the highest P content in August, and the seasonal decrement of soil N and P contents were 2.91 g/kg and 0.56 g/kg respectively. The N content and the C/N, C/P and N/P ratios were mainly depended on season, while the contents of C and P were mainly on soil depth. N was a restrictive factor for Castanea mollissima.

Conclusions The distribution characteristics of fine root C, N and P stoichiometry characteristics show significant monthly and spatial variations. Reasonable management of water and fertilizer should be carried out according to the variation of fine root, especially the limiting factor of N.