Abstract
Urban forest soil is often disturbed by rapid urbanization. Organic mulching is effective for improving soil quality and aggregate stability. This study evaluated how soil binding agents changed aggregate stability through organic mulching in urban forest soils. Three treatments were applied in Jiufeng National Forest Park, Beijing: (1) no organic mulch (control); (2) wood chips alone (5 cm thickness); and, (3) wood chips + wood compost (This mulch was divided into two layers, the upper layer of wood chips (2.5 cm), the lower layer wood compost (2.5 cm)). Soil samples were collected from the surface 10- cm soil layer and fraction into four aggregates. Glomalin-related soil protein and soil organic carbon were measured in bulk soil and the four aggregates. The results show that wood chips + wood compost increased the proportion of large and small macroaggregates, mean weight diameter and geometric mean diameter. The total and easily extractable glomalin-related soil protein were higher in the wood chips + wood compost. However, soil organic carbon was lower in the wood chips alone application compared to the controls and wood chips + wood compost. Easily extractable / total glomalin-related soil protein and glomalin-related soil protein / soil organic carbon ratios of wood chips alone and wood chips + wood compost had increased trend compared to the controls but did not reach significant levels (p > 0.05). Mean weight diameter and geometric mean diameter correlated positively with total and easily extractable glomalin-related soil protein but were not positively correlated with soil organic carbon, the ratios of easily extractable and total glomalin-related soil protein, and the ratios of glomalin-related soil protein and soil organic carbon. Redundancy analysis revealed that total glomalin-related soil protein was the most important driver for soil aggregate stability, especially the total glomalin-related soil protein of small macroaggregates. The results suggest that wood chips + wood compost enhanced soil aggregate stability through the increase of glomalin-related soil protein. Wood chips alone cannot enhance soil aggregate stability in urban forests in the short term.
Highlights
Urban forest soils have important ecological and social functions in improving the quality of the urban environment (Yang et al 2005; Wang et al 2019a)
The results suggest that wood chips + wood compost enhanced soil aggregate stability through the increase of glomalin-related soil protein
Numerous studies have shown that glomalin-related soil protein (GRSP) and soil organic carbon (SOC) are the most important binding agents that accelerate aggregate formation (Zhang et al 2012; Chen et al 2019; Jing et al 2021)
Summary
Urban forest soils have important ecological and social functions in improving the quality of the urban environment (Yang et al 2005; Wang et al 2019a). The characteristics of urban forest soils, including compaction, low-nutrient levels, poor structure, and decreased aggregate stability have been reported in numerous studies (Wang et al 2014a; Sax et al 2017; Kranz et al 2020). These characteristics affect the sustainable supply of soil ecosystem services, and . Numerous studies have shown that glomalin-related soil protein (GRSP) and soil organic carbon (SOC) are the most important binding agents that accelerate aggregate formation (Zhang et al 2012; Chen et al 2019; Jing et al 2021). The increase in GRSP and SOC increases microbial biomass and activity and a higher rate of macro-aggregate formation to improve aggregate stability (Liu et al 2014)
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