Effects of Grazing Intensity on Microbial Diversity at Different Soil Depths in Desert Steppe Soils
Abstract
:1. Introduction
2. Materials and Methods
2.1. Experimental Design
2.2. Measurement of Soil Physicochemical Properties
- Soil pH measurement: Soil pH was measured using a pHS-3G digital pH meter (Starter3100, OHAUS, Parsippany, NJ, USA). Five grams of air-dried soil were placed in a 50 mL conical flask, mixed with 25 mL of ultrapure water (soil-to-water ratio of 1:5), shaken thoroughly, and left to stand for 30 min before measurement.
- Soil moisture (SM) and bulk density (SBD): Soil moisture content was determined by the drying method, and soil bulk density was measured using the ring knife method, each with three replicates.
- Total soil phosphorus (TP) measurement: Total phosphorus was measured using the HClO4-H2SO4 digestion method. Five grams of air-dried soil were weighed with an analytical balance (CP224C, Sartorius, Germany) accurate to 0.0001 g and placed in a digestion tube. Five milliliters of concentrated sulfuric acid and ten drops of perchloric acid were added. The mixture was digested at 150 °C for 1 h in a temperature-controlled far-infrared digestion furnace (LWY84B) and then at 360 °C for an additional hour. The digest was transferred to a 100 mL volumetric flask, diluted to volume with distilled water, and filtered through phosphorus-free filter paper into a 10 mL centrifuge tube. Total phosphorus content was determined using a flow analyzer (AUTO ANALYZER3-AA3, SEAL Analytical, Germany).
- Soil organic carbon (SOC) measurement: Soil organic carbon was determined using the external heating potassium dichromate oxidation method. A 0.2500 g sample of air-dried soil was weighed into a digestion tube. Five milliliters each of concentrated sulfuric acid and 0.8 mol·L⁻¹ potassium dichromate solution (prepared after drying the reagents at 130 °C for 1 h) were added. The mixture was heated at 180 °C for 10 min in a digital constant-temperature oil bath (HH-S8). The digest was transferred to a conical flask, diluted with distilled water to 60–70 mL, and 1,10-phenanthroline indicator was added. The solution was titrated with 0.2 mol·L⁻1 ferrous sulfate standard solution until it turned brick-red, and the reading was recorded.
- Soil total nitrogen (TN) and available phosphorus (AP) measurement: Soil total nitrogen (TN) was determined using an elemental analyzer (Vario TOC, Elemental Inc., Germany). Specifically, air-dried soil samples were ground, passed through a 100-mesh sieve, and precisely weighed (105 mg) on a high-precision balance. Each subsample was then wrapped in a tin capsule and analyzed for total nitrogen content. Available phosphorus (AP) was measured using a spectrophotometer following standard colorimetric procedures.
2.3. Soil DNA Extraction, PCR Amplification, and Bacterial 16S rRNA Gene Sequencing
2.4. Statistical Analysis
3. Results
3.1. Soil Properties and Vegetation Traits
3.2. Microbial Community Richness and Biodiversity
3.3. Bacterial Beta Diversity
3.4. Community Composition
3.5. Soil Properties and Relative Abundance
4. Discussion
5. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Functional Groups | CK | LG | MG | HG | ||||
---|---|---|---|---|---|---|---|---|
Density (Individuals/m²) | Relative Abundance (%) | Density (Individuals/m²) | Relative Abundance (%) | Density (Individuals/m²) | Relative Abundance (%) | Density (Individuals/m²) | Relative Abundance (%) | |
Perennial bunch grasses | 106.4 ± 8.59 a | 17% | 146.4 ± 11.01 ab | 22% | 169.6 ± 11.95 b | 24% | 238.0 ± 20.8 c | 37% |
Perennial forbs | 44.8 ± 19.8 | 48% | 15.9 ± 5.47 | 19% | 13.7 ± 3.89 | 18% | 25.3 ± 3.87 | 15% |
Perennial rhizome grasses | 15.9 ± 9.06 a | 33% | 2.00 ± 1.87 a | 17% | 16.5 ± 13.7 a | 46% | 1.07 ± 0.77 a | 4% |
Shrubs and semi-shrubs | 18.7 ± 4.07 a | 45% | 3.60 ± 1.12 b | 25% | 2.13 ± 0.71 b | 13% | 1.87 ± 0.68 b | 18% |
Annual and biennials | 12.6 ± 3.28 a | 49% | 2.80 ± 1.22 b | 18% | 1.33 ± 0.62 b | 15% | 0.66 ± 0.33 b | 17% |
Soil Properties | Vegetation Characteristics | ||||||||
---|---|---|---|---|---|---|---|---|---|
Factors | SM (%) | SBD (g/cm3) | pH | SOC (g/kg) | TN (g/kg) | TP (g/kg) | AP (mg/kg) | BGB (g/m2) | Coverage (%) |
CK | 2.68 ± 0.10 ab | 91.5 ± 3.20 a | 7.73 ± 0.20 a | 15.9 ± 0.20 a | 1.43 ± 0.10 ab | 0.27 ± 0.01 a | 0.49 ± 0.010 b | 665.7 ± 41.1 a | 17.3 ± 0.30 a |
LG | 2.94 ± 0.10 a | 94.3 ± 0.60 a | 8.23 ± 0.20 a | 17.0 ± 0.20 a | 1.55 ± 0.10 a | 0.27 ± 0.01 a | 0.51 ± 0.003 a | 511.2 ± 30.1 b | 14.6 ± 0.40 b |
MG | 2.77 ± 0.20 a | 96.0 ± 1.00 a | 8.20 ± 0.20 a | 14.4 ± 0.50 b | 1.31 ± 0.10 ab | 0.26 ± 0.01 ab | 0.48 ± 0.003 b | 403.8 ± 19.6 c | 9.57 ± 0.60 c |
HG | 2.25 ± 0.40 b | 96.4 ± 2.10 a | 8.06 ± 0.10 a | 14.3 ± 0.50 b | 1.18 ± 0.10 b | 0.23 ± 0.01 b | 0.46 ± 0.003 c | 279.6 ± 24.2 d | 8.73 ± 0.60 c |
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Wang, Y.; Ju, X.; Wu, Q.; Han, G. Effects of Grazing Intensity on Microbial Diversity at Different Soil Depths in Desert Steppe Soils. Agronomy 2025, 15, 124. https://doi.org/10.3390/agronomy15010124
Wang Y, Ju X, Wu Q, Han G. Effects of Grazing Intensity on Microbial Diversity at Different Soil Depths in Desert Steppe Soils. Agronomy. 2025; 15(1):124. https://doi.org/10.3390/agronomy15010124
Chicago/Turabian StyleWang, Yuxin, Xin Ju, Qian Wu, and Guodong Han. 2025. "Effects of Grazing Intensity on Microbial Diversity at Different Soil Depths in Desert Steppe Soils" Agronomy 15, no. 1: 124. https://doi.org/10.3390/agronomy15010124
APA StyleWang, Y., Ju, X., Wu, Q., & Han, G. (2025). Effects of Grazing Intensity on Microbial Diversity at Different Soil Depths in Desert Steppe Soils. Agronomy, 15(1), 124. https://doi.org/10.3390/agronomy15010124