Effects of Nitrogen and Phosphorus Fertilization on Soil Carbon Fractions in Alpine Meadows on the Qinghai-Tibetan Plateau

Authors

Jin Hua Li, Lanzhou UniversityFollow
Yu Jie Yang, Lanzhou University
Bo Wen Li, Lanzhou University
Wen Jin Li, Lanzhou University
Gang Wang, Lanzhou University
Johannes M. H. Knops, University of Nebraska-LincolnFollow

Date of this Version

2014

Citation

Li JH, Yang YJ, Li BW, Li WJ, Wang G, et al. (2014) Effects of Nitrogen and Phosphorus Fertilization on Soil Carbon Fractions in Alpine Meadows on the Qinghai-Tibetan Plateau. PLoS ONE 9(7): e103266. doi:10.1371/journal.pone.0103266.

Comments

Copyright 2014 Li et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License.

Abstract

In grassland ecosystems, N and P fertilization often increase plant productivity, but there is no concensus if fertilization affects soil C fractions. We tested effects of N, P and N+P fertilization at 5, 10, 15 g m^-2 yr^-1 (N₅, N₁₀, N₁₅, P₅, P₁₀, P₁₅, N₅P₅, N₁₀P₁₀, and N₁₅P₁₅) compared to unfertilized control on soil C, soil microbial biomass and functional diversity at the 0– 20 cm and 20–40 cm depth in an alpine meadow after 5 years of continuous fertilization. Fertilization increased total aboveground biomass of community and grass but decreased legume and forb biomass compared to no fertilization. All fertilization treatments decreased the C:N ratios of legumes and roots compared to control, however fertilization at rates of 5 and 15 g m^-2 yr^-1 decreased the C:N ratios of the grasses. Compared to the control, soil microbial biomass C increased in N₅, N₁₀, P₅, and P₁₀ in 0–20 cm, and increased in N₁₀ and P₅ while decreased in other treatments in 20–40 cm. Most of the fertilization treatments decreased the respiratory quotient (qCO₂) in 0–20 cm but increased qCO₂ in 20–40 cm. Fertilization increased soil microbial functional diversity (except N₁₅) but decreased cumulative C mineralization (except in N₁₅ in 0– 20 cm and N₅ in 20–40 cm). Soil organic C (SOC) decreased in P₅ and P₁₅ in 0–20 cm and for most of the fertilization treatments (except N₁₅P₁₅) in 20–40 cm. Overall, these results suggested that soils will not be a C sink (except N₁₅P₁₅). Nitrogen and phosphorus fertilization may lower the SOC pool by altering the plant biomass composition, especially the C:N ratios of different plant functional groups, and modifying C substrate utilization patterns of soil microbial communities. The N+P fertilization at 15 g m^-2 yr^-1 may be used in increasing plant aboveground biomass and soil C accumulation under these meadows.