Effects of Glomalin-Related Soil Protein Driven by Root on Forest Soil Aggregate Stability and Carbon Sequestration during Urbanization in Nanchang, China

Abstract

Glomalin-related soil protein (GRSP) is a hydrophobic protein released by arbuscular mycorrhizal fungi. It is an important component of the soil carbon pool, and it improves the soil aggregate structure; however, it remains unclear whether GRSP can enhance soil carbon sequestration and improve soil quality during rapid urbanization. The built-up area in Nanchang, China was the study area, and the proportion of impervious surface area was the parameter of urbanization intensity. A total of 184 plots (400 m2) were set up to collect soil samples (0–20 cm) for analysis. Aggregates of five particle sizes were sieved, and the percentage amounts of soil organic carbon (SOC) and GRSP for them were determined. The results showed that the easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) contents of the four aggregates of <2 mm were 22–46% higher in low urbanization areas than those in high urbanization areas (p < 0.05), indicating that the higher urbanization intensity was associated with the lower GRSP content of different aggregates. The GRSP was significantly positively correlated with SOC (p < 0.05). Moreover, the contribution of GRSP to the SOC pool in the <0.25 mm aggregate was significantly higher than that in other aggregates. In addition, the EE-GRSP content was significantly positively correlated with mean weight diameter (MWD) and geometric mean diameter (GMD) in the four aggregates of <2 mm, whereas it was negatively correlated with fractal dimension (D) in the >2 mm, 1–2 mm and <0.053 mm aggregates. The T-GRSP content showed significant correlations only with MWD, GMD, and D in the 1–2 mm aggregate. This study revealed that increasing urbanization intensity can significantly reduce the GRSP content of different sized aggregates. Moreover, the GRSP content significantly promoted SOC sequestration, and the EE-GRSP content more significantly promoted soil aggregate stability than that of the T-GRSP. These findings provide new ideas for exploring the improvement of soil quality during the process of urbanization.

Urbanization-induced soil organic carbon loss and microbial-enzymatic drivers: insights from aggregate size classes in Nanchang city, China

“…Similar to this study, Luo et al (2021) demonstrated that urbanization leads to SOC loss. During urbanization, land for construction purposes often undergoes large-scale land leveling and filling, which can disrupt the original soil structure and composition of soil aggregates ( Cai et al, 2023 ). At the same time, artificial surfaces such as buildings and roads in urban areas often lack organic matter accumulation, which hinders SOC sources.…”

“…The increase in impermeable surfaces leads to hotspot formation in urban areas where SOC content is lost as the sealed soil becomes unable to retain carbon. Additionally, factors, such as reduced litter input and increased urban temperatures, can accelerate the carbon decomposition rate, ultimately resulting in SOC content decrease ( Cai et al, 2023 ). Therefore, land-use change significantly alters the distribution of different soil aggregates, thereby affecting aggregate stability and the association between aggregates and SOC ( Yu et al, 2023 ).…”

“… Chen et al (2014) uncovered that the input of large amounts of exogenous phosphorus (e.g., phosphorus from urban household waste) into the urban soils in Nanchang exacerbated the mineralization of SOC and led to a decrease in SOC stability. This phenomenon leads to substantial carbon outflows and imposes significant constraints on the sequestration function of SOC ( Cai et al, 2023 ). Therefore, this study focused on Nanchang City as the research area to investigate the impacts of urbanization on SOC of greenspace soil and aggregates.…”

Construction of an Ecological Security Pattern in Rapidly Urbanizing Areas Based on Ecosystem Sustainability, Stability, and Integrity

“…Nevertheless, the accompanying ecological and environmental challenges cannot be ignored. Urban pollution and ecological degradation have become significant barriers to Nanchang's sustainable development [47,48]. Therefore, Nanchang must strengthen environmental protection, scientifically plan and manage ecological resources, and achieve sustainable urban development during urbanization.…”