Effects of shrub encroachment on soil aggregates and organic carbon vary in different grasslands in Inner Mongolia, China

Abstract

Widespread shrub encroachment in grasslands can lead to changes in soil aggregates and soil organic carbon (SOC), especially in deep soils. Soil aggregates physicochemically protect SOC and thus affect soil carbon sequestration. Characterizing the changes in soil aggregates and their organic carbon associated with shrub encroachment is critical for evaluating the ecological consequences of shrub encroachment in different grasslands. In this study, we investigated soil aggregates of various sizes and their associated organic carbon at maximum soil depths of 5 m in shrub patches and neighboring grass matrix in two types (desert and typical) of grasslands in Inner Mongolia, China. The mean weight diameter (MWD) of the soil aggregates was similar between the shrub patches and grass matrix in both grasslands. However, the proportion of each aggregate size fraction to whole soil in the shrub patches was significantly lower than that in the grass matrix in the desert grasslands, while there was no significant difference between the shrub patches and grass matrix in the typical grasslands. In addition, the organic carbon content of aggregates in the shrub patches was greater than that in the grass matrix in deep soil layers (>50 cm) but was lower in the topsoil (0-10 cm depth) in the desert grasslands. However, the organic carbon content of aggregates at all soil depths was greater in shrub patches than in the grass matrix in typical grasslands. Our results suggest that the effects of shrub encroachment on the soil aggregate proportion and associated organic carbon vary at different soil depths and in different grassland types. The results of this study also suggest that it is necessary to determine the size structure and its relation to carbon content for soil aggregates to accurately predict SOC dynamics with shrub encroachment.

Effects of Betula platyphylla invasion in North China on soil aggregate stability, soil organic carbon and active carbon composition of larch plantation

“…Zhibo et al (2020) showed that the contribution of aggregates > 0.25 mm to the organic carbon pool was signi cantly greater than that of aggregates < 0.25 mm. We found that the content of organic carbon and active carbon components of surface soil aggregates was slightly higher than that in deep soil, which was consistent with the research results of Zhu et al (2021). The content of SOC was the highest in the aggregates with > 2 mm particle size, and the aggregates with > 2 mm particle size also contributed the most to soil SOC.…”

“…The dynamic change in soil organic carbon is not only dependent on the input of organic matter, but also closely related to the structure of soil aggregates (Zhu et al, 2021). Considering the composition ratio of organic carbon and active carbon components in the same particle size aggregate and the content of this particle size aggregate in soil comprehensively, the contribution rate of organic carbon and active carbon components to soil carbon in the aggregate can be comprehensively re ected (Wang et al, 2014).…”

Impact of Integrated Rice-Crayfish Farming on Soil Aggregates and Organic Matter Distribution

“…The integrated rice-crayfish farming model affected the formation of soil aggregates compared to traditional paddy fields. Soil aggregates are a key factor affecting soil quality, and the content of aggregates at different grain sizes directly affects soil quality [24,25]. The present study showed that the integrated rice-crayfish farming model significantly increased the content of soil aggregates at >5 mm grain size.…”

Effects of shrub encroachment on grassland community and soil nutrients among three typical shrubby grasslands in the alpine subhumid region of the Qinghai-Tibet Plateau, China

“…ST, SA, LT, and other shrubs are widely distributed on the Zoige Plateau and are typical of the alpine shrub vegetation in the region, and they are the most influential of the shrubland types (Yang et al, 2017) and soil sampling depths (Chen et al, 2022). The effect of shrub invasion on soil is again determined by soil depth and grassland type, with deep soil organic carbon content showing higher levels in scrub than in grassland (Zhu et al, 2021). Most published studies have focused on the effects of climate (Gao et al, 2016) and grazing (Komac et al, 2013) on shrub encroachment, while the role of vegetation type and soil profile has rarely been considered (Yang et al, 2022).…”