Sustainability of Urban Soil Management: Analysis of Soil Physicochemical Properties and Bacterial Community Structure under Different Green Space Types

Soil bacterial communities play a key role in nutrient cycling and ecosystem functioning. This study aims to reveal how green space type impacts soil quality and the bacterial community, which finally contributes to suggesting strategies for managing sustainable environments in urban areas. For this purpose, urban green space soils in this study are divided into four different types; park green space (PARK), street green space (STREET), attached green space (ATTACH) and residential green space (RESID). Results showed that significant differences were observed for soil physicochemical properties. Soil organic matter, total nitrogen, soil moisture content and available nitrogen in the ATTACH and PARK soils were significantly higher than in the STREET and RESID soils. Across the four green space types, the structure of bacterial communities was dominated by Proteobacteria, Actinobacteria and Chloroflexi at the phylum level. The diversity and richness of bacteria were significantly higher in the PARK and ATTACH soils than in the RESID and STREET soils. Results of principal component analysis (PCoA) showed that soil bacterial communities could be clustered into four different groups according to different green space types. In addition, analysis of similarities (ANOSIM) also implied that soil samples differed significantly from others. Redundancy analysis (RDA) and Spearman correlation analysis both showed that the contents of soil organic matter, total nitrogen, soil moisture and pH had great influence on the structures of bacterial communities. In summary, these results suggest that soil physicochemical properties and bacterial communities can be strongly affected by green space types, and thus, objective assessment of a particular measure can be provided to land managers and policy makers for informed decision-making in urban development and sustainability

The Earthworm Eisenia fetida Can Help Desalinate a Coastal Saline Soil in Tianjin, North China.

A laboratory microcosm experiment was conducted to determine whether the earthworm Eisenia fetida could survive in a saline soil from a field site in North China, and an experiment using response surface methodology was conducted at that field site to quantify the effects of E. fetida and green waste compost (GWC) on the salt content of the soil. The microcosm results showed that E. fetida survived in GWC-amended saline soil and increased the contents of humic acid, available N, and available P in the GWC-amended soil. The data from the field experiment were described by the following second-order model: [Formula in text], where y is the decrease in soil salinity (g of salt per kg of dry soil) relative to the untreated control, x1 is the number of E. fetida added per m2, and x2 is the quantity of GWC added in kg per m2. The model predicted that the total salt content of the saline soil would decrease by > 2 g kg(-1) (p<0.05) when 29-90 individuals m-2 of E. fetida and 6.1-15.0 kg m(-2) of GWC were applied. We conclude that the use of E. fetida for soil desalination is promising and warrants additional investigation

Levels of factors used for factorial design for the laboratory experiment.

<p>GWC: green waste compost.</p><p>Levels of factors used for factorial design for the laboratory experiment.</p

Physico-chemical properties of GWC applied to saline soil.

<p>Values are the means of three samples, and standard errors are in parentheses.</p><p>^a Determined for a suspension consisting of 1:5 (W/V) compost:distilled water.</p><p>Physico-chemical properties of GWC applied to saline soil.</p

The daily multiplication rate of <i>E</i>. <i>fetida</i> as affected the quantity of GWC and number of <i>E</i>. <i>fetida</i> added in the laboratory experiment.

<p>GWC: green waste compost. Ef-<i>x</i> (<i>x</i> = 10, or 20) indicates the initial number of <i>E</i>. <i>fetida</i> added per microcosm, and GWC-<i>y</i> (<i>y</i> = 0, 60, or 120) indicates the quantity of GWC added per microcosm (g). Values are means ± SE (<i>n</i> = 3). Within each level of Ef, means followed by different letters are significantly different at <i>p</i>≤0.05 according to the SNK test.</p

Humic acid carbon content of the soil (g kg^-1) as affected by the number of <i>E</i>. <i>fetida</i> and the quantity of GWC added in the laboratory experiment.

<p>GWC: green waste compost. Ef-<i>x</i> (<i>x</i> = 0, 10, or 20) indicates the initial number of <i>E</i>. <i>fetida</i> added per microcosm, and GWC-<i>y</i> (<i>y</i> = 0, 60, or 120) indicates the quantity of GWC added per microcosm (g). Values are means ± SE (<i>n</i> = 3). Within each level of GWC, means followed by different letters are significantly different at <i>p</i>≤0.05 according to the SNK test.</p

Response surface for the decrease in total salt content of the soil as affected by the number of <i>E</i>. <i>fetida</i> and quantity of GWC added in the field experiment.

<p>GWC: green waste compost. The fitted model for the response surface was: <math><mrow><mi>y</mi><mo>^</mo> =-1.76+0<msub><mrow>.091x</mrow>1</msub>+0<msub><mrow>.48x</mrow>2</msub>-0<msub><mrow>.00083x</mrow>1</msub><msub>x<mrow>2</mrow></msub>-0<msubsup><mrow>.00078x</mrow>1<mrow>2</mrow></msubsup>-0<msubsup><mrow>.022x</mrow>2<mrow>2</mrow></msubsup></mrow></math></p

Available N content in soil (mg kg^-1) as affected by the number of <i>E</i>. <i>fetida</i> and the quantity of GWC added in the laboratory experiment.

<p>GWC: green waste compost. Ef-<i>x</i> (<i>x</i> = 0, 10, or 20) indicates the initial number of <i>E</i>. <i>fetida</i> added per microcosm, and GWC-<i>y</i> (<i>y</i> = 0, 60, or 120) indicates the quantity of GWC added per microcosm (g). Values are means ± SE (<i>n</i> = 3). Within each level of GWC, means followed by different letters are significantly different at <i>p</i>≤0.05 according to the SNK test.</p

A photo of adult <i>Eisenia fetida</i> used in the study.

<p>A photo of adult <i>Eisenia fetida</i> used in the study.</p