Effects of different grassland use patterns on soil bacterial communities in the karst desertification areas

Abstract

Soil bacteria are closely related to soil environmental factors, and their community structure is an important indicator of ecosystem health and sustainability. A large number of artificial grasslands have been established to control rocky desertification in the karst areas of southern China, but the influence of different use patterns on the soil bacterial community in artificial grasslands is not clear. In this study, three grassland use patterns [i.e., grazing (GG), mowing (MG), and enclosure (EG)] were used to investigate the effects of different use patterns on the soil bacterial community in artificial grassland by using 16S rDNA Illumina sequencing and 12 soil environmental indicators. It was found that, compared with EG, GG significantly changed soil pH, increased alkaline hydrolyzable nitrogen (AN) content (P < 0.05), and decreased soil total phosphorus (TP) content (P < 0.05). However, MG significantly decreased the contents of soil organic carbon (SOC), total phosphorus (TP), available nitrogen (AN), ammonium nitrogen (NH₄⁺-N), β-1,4-glucosidase (BG), and N-acetyl-β-D-glucamosonidase (NAG) (P < 0.05). The relative abundance of chemoheterotrophy was significantly decreased by GG and MG (P < 0.05). GG significantly increased the relative abundance of Acidobacteria and Gemmatimonadota (P < 0.05) and significantly decreased the relative abundance of Proteobacteria (P < 0.05), but the richness index (Chao 1) and diversity index (Shannon) of the bacterial community in GG, MG, and EG were not significantly different (P > 0.05). The pH (R² = 0.79, P = 0.029) was the main factor affecting the bacterial community structure. This finding can provide a scientific reference for ecological restoration and sustainable utilization of grasslands in the karst desertification areas.

Keywords: Illumina sequencing; artificial grassland; karst desertification; soil microorganism; sustainable utilization.

Figure 1

Soil chemical properties and soil enzyme activity under different grassland use patterns [different lowercase letters indicate the significant differences between different treatments (P < 0.05, n = 3)]. SOC, soil organic carbon; TN, total nitrogen; TP, total phosphorus; AN, available nitrogen; AP, available phosphorus; NO₃⁻-N, nitrate nitrogen; NH₄⁺-N, ammonium nitrogen; BG, β-1,4-glucosidase; NAG, N-acetyl-β -D-glucosaminidase; LCP, acid phosphatase; LAP, leucine aminopeptidase; GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 2

Venn diagram of unique and shared bacterial OTUs under different grassland use patterns (at the 3% evolutionary distance). GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 3

PCoA of bacterial community composition under different grassland use patterns. GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 4

ANOSIM of soil bacterial community composition under different grassland use patterns based on the Bray–Curtis distance metric. GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 5

Relative abundance of soil bacterial phylum under different grassland use patterns (relative abundance>1%). GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 6

Redundancy analysis of soil properties (gray arrows) and soil microbial structure (blue arrows) at the phylum level. SOC, soil organic carbon; TN, total nitrogen; AP, available phosphorus; NO₃, nitrate nitrogen; NH₄, ammonium nitrogen; LCP, acid phosphatase; LAP, leucine aminopeptidase; GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 7

(A, B) Heatmap of the correlation between environmental factors and soil bacterial community at the phylum level (relative abundance >1%). Spearman's correlation coefficients are shown in different colors, and the legend on the right shows the color range of the different correlation coefficients (P-values: ^* < 0.05). SOC, soil organic carbon; TN, total nitrogen; TP, total phosphorus; AN, available nitrogen; AP, available phosphorus; NO₃⁻-N, nitrate nitrogen; NH₄⁺-N, ammonium nitrogen; BG, β-1,4-glucosidase; NAG, N-acetyl-β -D-glucosaminidase; LCP, acid phosphatase; LAP, leucine aminopeptidase; GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.

Figure 8

Relative abundance of soil bacterial community for ecological function under different grassland use patterns. GG, grazing grassland; MG, mowing grassland; EG, enclosure grassland.