The production and nutrients in the fine roots of fertilized Pinus tabulaeformis plantation forests in the Loess Plateau in China

Abstract

ABSTRACT Fine roots (FRs; <2 mm in diameter) might act as substantial pools of underground carbon and nutrients in the forest ecosystem. Since nutrient availability directly impacts plant growth, any changes in soil fertilization and subsequent changes in nutrients would alter the production of FRs. Here, we investigated the impact of fertilization with nitrogen (N) and phosphorus (P) [control, N (200 kg/ha/y), P (100 kg/ha/y), and N + P (200 kg N/ha/y + 100 kg P/ha/y)] on the FR production, biomass, turnover rate, N:P ratio in young (10-year) and nearly mature (40-year) Pinus tabulaeformis forest stands in the Loess Plateau in China. The production and biomass of FRs were evaluated using the ingrowth core and the soil core methods, respectively. The results showed that during the first growing season after N or P fertilization, neither the production, biomass nor the turnover rate of FRs responded significantly to the treatments. A substantial increase in the TN content was observed after fertilization with N, P, and N + P in the FR of the young forest stand, but not in the mature forest stand. The ratio of N:P in FRs increased after N addition but did not respond to P addition significantly in either the young or mature forest stands, indicating that FR N:P ratio was affected more by N availability than by P availability in P. tabulaeformis forests on the Loess Plateau.