Effects of long-term vegetation cover changes on the organic carbon fractions in soil aggregates of mollisols

Abstract

Aims Soil aggregate is the main habitat for decomposition and transformation of soil organic carbon (SOC) and is important to regulate SOC sequestration. The mechanisms of the stability of SOC fractions may vary among different aggregate sizes. The aims of this study were to explore the characteristics of SOC "fractionation" in soil aggregates, and to reveal the mechanisms of carbon (C) sequestration in soil aggregates of mollisols after 31-year changes in vegetation cover. Methods A long-term field experiment with different vegetation cover (grassland, farmland and bareland) was established in National Observation Station of Hailun Agro-ecosystem System. Soil aggregate fractionation, the density and humus fractionation within different aggregate sizes were further carried out. Important findings The results showed that after 31 years of land cover change, the surface SOC and total nitrogen (TN) contents in grassland with higher C inputs increased significantly with time, while the SOC and TN contents decreased significantly in bareland, but with no statistical significance in farmland. The 2-0.25 mm (include 2 mm, the same below) aggregates was the excellent fraction for SOC sequestration under all three land cover. The stability of soil aggregate was in the order of: grassland > farmland > bareland. The mass proportion of

Interactive effects of conservation tillage on the aggregate stability and soil organic carbon

“…Likewise, conservation tillage had a significantly larger MWD and GMD and exhibited more M of water‐stable aggregates than traditional tillage practices (Y. Li et al., 2019). No‐tillage plus straw returning increased MWD and GMD of soil aggregates, decreased D, and increased the content of M. Additionally, both showed that no‐tillage and straw returning has significant effects on improving the stability of soil aggregates (Cai et al., 2011) and previous studies reported that SOC is correlated with the number of water‐stable aggregates (N. Li et al., 2019), SOC was significantly positively correlated with GMD ( R 2 = 0.31) (Wang, Qi et al., 2019). Also, there was a linear relationship between SOC and MWD ( R 2 = 0.93) (Ali, 2021).…”

Effects of land use and cover change on soil organic carbon and total nitrogen in southwest China Karst region: A Meta-analysis

“…The decreased SOC and TN are probably due to deforestation that destroyed soil structure (i.e., aggregation) leading to releasing the previously protected organic matter (Jiang et al, 2005;Xiao et al, 2009) and reduced terrestrial litter inputs (Xie et al, 2004;Luo et al, 2009). On the other hand, the changed vegetation types may influence soil moisture and temperature conditions and thus accelerate SOM decomposition (Luo et al, 2009;Fei et al, 2015). Besides, because of the fragile land scape and soil properties in the Karst areas, deforestation may greatly aggravate soil erosion, resulting in massive loss of soil nutrients (e.g., C, N).…”

“…On the contrary, shifting from cropland to perennial vegetation was reported to increase SOC accumulation by transforming more atmospheric C into the soil and simultaneously decrease C loss from decomposition and erosion (Post and Kwon, 2000;Guo and Gifford, 2002;Berthrong et al, 2009;Laganiere et al, 2010;Duan et al, 2018;Nave et al, 2018). As another key factor in maintaining soil quality, total nitrogen (TN) and SOC generally exhibit similar responses to LUCCs by changing the microbial conditions and litter inputs in ecosystems (Xie et al, 2004;Luo et al, 2009;Xu et al, 2019), hydrothermal conditions at the land surface (Luo et al, 2009;Jerome et al, 2010;Fei et al, 2015) and plant species (Nie et al, 2014;Pan et al, 2015), which, if considering the impact of human activities (Xiao et al, 2009;Deng and Shangguan, 2017), jointly determined the changes in TN storage. Thus, appropriate land-use management practices (e.g., reforestation and land restoration) have been considered as one of the major strategies for mitigating climate change (Richard et al, 2006;Song et al, 2014;Hu et al, 2018).…”