Nitrogen addition increases the contents of glomalin-related soil protein and soil organic carbon but retains aggregate stability in a Pinus tabulaeformis forest

Abstract

BackgroundGlomalin-related soil protein (GRSP) and soil organic carbon (SOC) contribute to the formation and stability of soil aggregates, but the mechanism by which global atmospheric nitrogen (N) deposition changes soil aggregate stability by altering the distribution of GRSP and SOC in different aggregate fractions remains unknown.MethodsWe used a gradient N addition (0–9 g N m−2 y−1) in Pinus tabulaeformis forest for two years in northeast China and then examined the changes in SOC contents, total GRSP (T-GRSP), and easily extractable GRSP (EE-GRSP) contents in three soil aggregate fractions (macro-aggregate: >250 μm, micro-aggregate: 250–53 μm, and fine material: <53 μm) and their relationship with aggregate stability.Results(1) The soil was dominated by macro-aggregates. Short term N addition had no significant effect on mean weight diameter (MWD) and geometric mean diameter (GMD). (2) GRSP varied among aggregate fractions, and N addition had different effects on the distribution of GRSP in aggregate fractions. The EE-GRSP content in the macro-aggregates increased initially and then decreased with increasing N addition levels, having a peak value of 0.480 mg g−1 at 6 g N m−2 y−1. The micro-aggregates had the lowest EE-GRSP content (0.148 mg g−1) at 6 g N m−2 y−1. Furthermore, the T-GRSP content significantly increased in the aggregate fractions with the N addition levels. (3) The macro-aggregate had the highest SOC content, followed by the micro-aggregate and the fine material had the lowest SOC content. N addition significantly increased the SOC content in all the aggregate fractions. (4) GRSP and SOC contents were not significantly correlated with MWD.ConclusionGlomalin-related soil protein and SOC contents increased by N addition, but this increase did not enhance aggregate stability in short term, and the improvement of stability might depend on binding agents and incubation time.

Nitrogen addition stimulates soil aggregation and enhances carbon storage in terrestrial ecosystems of China: A meta‐analysis

“…Our meta-analysis revealed that exogenous N input increased the MWD (Figure 2), suggesting a positive effect of N addition on the soil structure stability (Tripathi et al, 2008). Similar results were reported in many field experiments (Chang et al, 2019;Liu et al, 2015;Zhong et al, 2017), but different results were also found in other studies (Chen et al, 2019;Sun et al, 2018;Wu et al, 2018). We found the effect of N addition on soil aggregation is complex.…”

“…Depending on wet or dry sieving, the resulting MWD better reflects the stability of soil structure (Tripathi et al, 2008). Some studies have shown that N deposition can help stabilize soil structure and reduce POC decomposition by increasing the formation of macroaggregates and MWD (Chang et al, 2019;Zak et al, 2017;Zhong et al, 2017), but other studies have found that N deposition increases POC decomposition (Chen et al, 2019;Luo et al, 2020;Sun et al, 2018). Similarly, the wide-ranging effects of N enrichment on MOC (i.e., positive, negative, and neutral) preclude broad consensus (Cusack et al, 2011;Riggs et al, 2015).…”

Formation of Common Mycorrhizal Networks Significantly Affects Plant Biomass and Soil Properties of the Neighboring Plants under Various Nitrogen Levels

“…The GRSPs' contents increased with the addition of N, and the maximum GRSP fractions were found at N2. However, after a certain increase in N, the GRSP contents decreased, and similar findings were observed by Sun et al (2018). This is because, in the beginning, the addition of N quickly relieves the N deficiency in the soil, thereby encouraging the microbial activities to stimulate the production of GRSPs.…”

“…However, N addition beyond a certain level decreases the GRSPs in the soil [92]. Interestingly, the addition of N significantly increased the SOC in the soil of mycorrhizal treatment as compared to non-mycorrhizal treatment [93]. SOC is considered an important component of soil fertility and therefore AM fungal inoculation and the subsequent formation of CMNs enhance the soil fertility and improve the growth of donor and recipient plants.…”

Effect of Tillage Treatment on the Diversity of Soil Arbuscular Mycorrhizal Fungal and Soil Aggregate-Associated Carbon Content

“…Firstly, the decomposition and transformation of SOC are affected by aggregation construction (Zhang et al, 2008; Zhao et al, 2015, 2018). It has been reported that stable aggregates can physically prevent SOC against rapid decomposition (Sun et al, 2018). Secondly, SOC is considered to be the main binding agent contributing to aggregate stability (Chenu et al, 2000; Bhattacharyya et al, 2011).…”