Microbial Resource Limitation in Aggregates in Karst and Non-Karst Soils

Abstract

Karst is a widespread ecosystem with properties that affect the microbial activity and storage and cycling of soil organic carbon. The mechanisms underlying microbial resource availability in karst, which limit the microbial growth and activity in soil aggregates, remain largely unknown. We assessed the microbial resource limitations using exoenzymatic stoichiometry and key extracellular enzyme activities in bulk soil and aggregates in karst and non-karst forest soils. Soil organic carbon, total nitrogen, and microbial biomass carbon and nitrogen were significantly higher in bulk soil and the aggregate fractions in karst forests. However, the microbial biomass accumulation was higher in finer aggregates than in macroaggregate fractions. This may be attributed to the surface area of finer aggregates that increase the microbial C accumulation. In karst forests, the activity of extracellular enzymes β-d-glucosidase, β-N-acetylglucosaminidase, α-glucosidase, and α-d-1,4-cellobiosidase was two to three times higher in microaggregates (0.053–0.25 mm) and mineral fractions (<0.053 mm) than in macroaggregates. This coincided with the distribution of microbial biomass carbon and phosphorus in finer aggregate fractions. The microorganisms in bulk soil and aggregates in karst forests were largely co-limited by carbon and phosphorus and rarely by nitrogen and only by phosphorus in non-karst soils. The microbial phosphorus limitation in non-karst soils was alleviated in finer soil aggregates, while these fractions reflected slightly higher. microbial C limitations than bulk and other aggregates in karst forests. The patterns of microbial resource limitations in the bulk and aggregate fractions in karst ecosystems reflected the regulation of enzyme activity and soil organic carbon accumulation in finer aggregate fractions but not in other aggregates.

Root exudates with low C/N ratios accelerate CO2 emissions from paddy soil

“…Subsequently, resource stoichiometry alters microbial community composition to gain the required elements and increase SOM mineralization (Zhu, Ge, Liu, et al, 2018; Zhu, Ge, Luo, et al, 2018; Yuan et al, 2019; Wei, 2020). Extracellular enzyme activities, such as C‐ and N‐acquiring enzymes, can also reflect the resource demands of microbial communities (Schimel, 2003; Hill et al, 2012; Liu, Ge, et al, 2021; Wang et al, 2021). For example, β‐1,4‐glucosidase (BG) and β‐1,4‐xylosidase (XYL) are the largest contributors to the degradation of cellulose and hemicellulose, respectively.…”

“…Extracellular enzyme activities, such as C-and N-acquiring enzymes, can also reflect the resource demands of microbial communities (Schimel, 2003;Hill et al, 2012;Liu, Ge, et al, 2021;Wang et al, 2021). For example, β-1,4-glucosidase (BG) and β-1,4-xylosidase (XYL) are the largest contributors to the degradation of cellulose and hemicellulose, respectively.…”

Karst tiankeng create a unique habitat for the survival of soil microbes: Evidence from ecoenzymatic stoichiometry

“…As plant roots, microorganisms, and soil organic matter increase, soil aggregate stability also increases. The restoration of soil aggregates, in turn, can improve soil aeration and water retention, thereby helping to increase microbial activity (Wang et al, 2021). In addition, the decomposition of soil organic matter is usually easier to decompose in a humid and hot environment, while NDT has a significant "cold well effect" (Shui et al, 2018), which may weaken the decomposition process of soil organic matter and promote the accumulation of soil nutrients.…”

Heterogeneity of Spatial-Temporal Distribution of Nitrogen in the Karst Rocky Desertification Soils and Its Implications for Ecosystem Service Support of the Desertification Control—A Literature Review

“…Nitrogen performs a major role in regulating plant nutrient uptake, root development, photosynthetic physiology, yield and quality formation and N transporter genes [81]. At present, many studies have been conducted on SN in rocky desertification, such as soil quality [82,83], soil nutrients [84,85], soil microorganisms [86,87] and plant communities [88]. Most studies discuss the response and influence of TN, ON or IN on geographical factors.…”