Soil carbon mineralization in response to nitrogen enrichment in surface and subsurface layers in two land use types

• Main Authors: Nazia Perveen, Mariam Ayub, Tanvir Shahzad, Muhammad Rashid Siddiq, Muhammad Sohail Memon, Sébastien Barot, Hamid Saeed, Ming Xu
• Format: Article
• Language: English
• Published: PeerJ Inc. 2019-07-01
• Series: PeerJ
• Subjects: Soil c mineralization; Nitrogen enrichment; Land use types; C sequestration; Subsurface soil C
• Online Access: https://peerj.com/articles/7130.pdf

Atmospheric nitrogen (N) deposition increases N availability in soils, with consequences affecting the decomposition of soil carbon (C). The impacts of increasing N availability on surface soil C dynamics are well studied. However, subsurface soils have been paid less attention although more than 50% soil C stock is present below this depth (below 20 cm). This study was designed to investigate the response of surface (0–20 cm) and subsurface (20–40 cm and 40–60 cm) C dynamics to 0 (0 kg N ha−1), low (70 kg N ha−1) and high (120 kg N ha−1) levels of N enrichment. The soils were sampled from a cropland and a grass lawn and incubated at 25 °C and 60% water holding capacity for 45 days. Results showed that N enrichment significantly decreased soil C mineralization (Rs) in all the three soil layers in the two studied sites (p < 0.05). The mineralization per unit soil organic carbon (SOC) increased with profile depth in both soils, indicating the higher decomposability of soil C down the soil profile. Moreover, high N level exhibited stronger suppression effect on Rs than low N level. Rs was significantly and positively correlated with microbial biomass carbon explaining 80% of variation in Rs. Overall; these results suggest that N enrichment may increase C sequestration both in surface and subsurface layers, by reducing C loss through mineralization.