Degradation‐induced microbiome alterations may aggravate soil nutrient loss in subalpine meadows

Abstract

Grassland degradation has become a serious environmental problem worldwide. However, the link between grassland degradation and soil functional microorganisms remains unclear. Here, we investigated the effects of subalpine meadow degradation on the taxonomic and functional communities of the soil microbiome on Mount Wutai on the eastern margin of the Loess Plateau, China, using shotgun metagenomic sequencing. The results showed that vegetation degradation decreased most soil nutrients (e.g., soil organic carbon [SOC, −48.9%], total nitrogen [TN, −15.2%] and carbon [TC, −38.3%]), leading to significant changes in the taxonomic (r = 0.892, p < 0.001) and functional compositions (r = 0.972, p < 0.001) of the microbial communities (explaining 66.6% and 64.5% of the variance, respectively). The structural equation model (SEM) showed that variations in the soil nutrient status and plant parameters caused by degradation resulted in changes in the microbial community structure and function. The variations in the plant and microbial communities during degradation altered carbon (C) and nitrogen (N) cycling separately or interactively. Among the C degradation‐related genes, the relative abundances of cellulose degradation, sugar utilization and chitin degradation genes in moderately degraded (MD) and heavily degraded (HD) meadows were significantly higher than those in nondegraded (ND) meadows (p < 0.05). The abundance of denitrification genes (nirK, nirS, norB and norC) and nitrification genes (pmoA/amoA, pmoB/amoB, pmoC/amoC and hao) was higher in all degraded meadows, which increased the risk of soil N loss. Our findings revealed the negative feedback of microbes due to subalpine meadow degradation, during which metabolically active microbes tended to accelerate soil nutrient loss.

Soil degradation regulates the effects of litter decomposition on soil microbial nutrient limitation: Evidence from soil enzymatic activity and stoichiometry

“…In all three degraded soils, the extracellular enzyme vector angles were less than 45°, indicating that microorganisms in all degraded soils were Nlimited, and the N limitation of microorganisms was significantly enhanced in heavily degraded soils (Figure 2B). Severely degraded grasslands were generally in a nutrientdeficiency state, especially lacking in N-related nutrients (Luo et al, 2022). The total and available nitrogen contents of highly degraded soils (Tables S1, S3) were significantly lower than those of the other two degraded soils.…”

“…Although the initial litter N content of L. chinensis litter was significantly higher than that of C. virgata litter (Table S2), differences in litter N input did not change N-acquiring enzyme activity and the original nutrient limitation of grassland soil. Moderately and highly degraded grassland are nutrient-poor (Luo et al, 2022), and soil extracellular enzyme activities were weakened by litter and were more susceptible to degraded soils.…”

Effective microorganisms input efficiently improves the vegetation and microbial community of degraded alpine grassland

“…With grassland degradation progressing, the abundance of bacteria, fungi, and actinomycetes in the soil are gradually declining ( Che et al, 2019 ; Wang et al, 2021 ). The degradation of grassland soil also disrupts the microbial community structure, ultimately leading to a decline in the population of beneficial soil microorganisms ( Luo et al, 2022 ; Liao et al, 2023 ). As a chain reaction of microbial changes, soil fertility declines, plant productivity reduces, and ultimately a vicious cycle of degradation occurs ( Che et al, 2020 ; Wang et al, 2021 ).…”

Overgrazing on unmanaged grassland interfered with the restoration of adjacent grazing-banned grassland by affecting soil properties and microbial community

“…The interaction between plants and soil microorganisms is important for maintaining the stability and productivity of ecosystems ( van der Heijden et al, 2008 ; Bardgett and van der Putten, 2014 ). Plants serve as specific hosts for soil microorganisms ( Zhang et al, 2018 ), influence the microbial community structure through root exudates ( Meier et al, 2017 ; Canarini et al, 2019 ), and provide energy and nutrients for microbial metabolism ( van der Heijden et al, 2008 ; Luo et al, 2022 ). Soil microorganisms regulate nutrient cycling between plants and soil, aiding the formation of soil structures that are conducive to plant growth ( Bissett and Burke, 2007 ; Coban et al, 2022 ; Hartmann and Six, 2023 ; Li et al, 2023 ).…”