Spatial patterns in soil physicochemical and microbiological properties in a grassland adjacent to a newly built lake

Abstract

Soil water content (SWC) is an important determinant for nutrient cycling and microorganism activity in the grassland ecosystem. Lakes have a positive effect on the water supply of the neighboring ecosystem. However, information evaluating whether newly built lakes improve the physiochemical properties and microorganism activity of adjacent grassland soil is rare. A 15-hectare artificial lake with a 2 m depth was built on grazed grassland to determine whether the change of soil physiochemical properties and microorganism activity of the adjacent grassland depended on the distance from the lake. SWC and total nitrogen (TN) were greater within 150 m of the lake than at distances over 150 m from the lake. The total organic carbon (TOC) increased first at 100-150 m from the lake and then decreased. The soil microbial biomass and the bacterial and fungal contents increased with increasing years after the construction of the lake. Gram-negative bacteria and methanotrophic bacteria were greater within a 30 m distance of the lake. Over 60 m away from the lake, Actinobacteria, gram-positive bacteria, and anaerobic bacteria showed higher abundances. In the area near the lake (<250 m distance), microorganisms were strongly correlated with SWC, EC, TN, and TOC and greatly correlated with the changes of total phosphorous (TP) and pH when the distance from the lake was over 250 m. The results indicated that the newly built lake could be a driving factor for improving the physiochemical properties and microorganism activity of adjacent grassland soil within a certain range.

Keywords: bacteria; grazing grassland; soil property; soil water content; the newly built lake.

Figure 1

The variation of soil microbial mass within different soil layers at different distances from lake during 2015, 2016, and 2017

Figure 2

The variation of soil bacterial content within different soil layers at different distances from the lake during 2015, 2016, and 2017

Figure 3

The variation of soil fungal content within different soil layers at different distances from the lake during 2015, 2016, and 2017

Figure 4

Principal component analysis of soil microbial community within different soil layers at different distances from the lake during the years 2015, 2016, and 2017. Gp (gram‐positive bacteria), Ab (Actinobacteria), Gn (gram‐negative bacteria), Am (arbuscular mycorrhizal fungi), Ef (ectomycorrhizal fungi), Mb (methanotrophic bacteria), Ag (anaerobic bacteria), and Sf (saprotrophic fungi). 15‐s1 to 15‐s8 represents distance in 2015; 16‐s1 to 16‐s8 represents distance in 2016; 17‐s1 to 17‐s8 represents distance in 2017

Figure 5

RDA two‐dimensional sequencing diagram of microbial and soil physicochemical properties in different soil layers. The blue lines represent different soil physicochemical indexes, and the red dashed lines represent different microorganism indicators. SWC represents soil water content, EC represents electrical conductivity, TOC represents soil organic carbon, TP represents soil total phosphorus, and TN represents soil total nitrogen

Figure 6

The path analysis of the relationship of microorganisms and soil physicochemical properties in different soil layers. B represents bacteria, F represents fungi, the dashed line represents a negative correlation, the solid represents a positive correlation, and the thickness of the line represents the strength of the correlation