Properties Of Urban Soils Research Articles

Trade-Offs in Plant Functional Traits Driven by Soil Changes under Urban Hardened Surfaces

The large-scale surface hardening has changed the urban environment and affected the normal growth of urban plants. However, it is still unclear how the urban hardened surface affects the functional urban plant traits. To explore whether the urban hardened surface affects the ecological strategies of plants by changing the urban soil properties and reflecting them on the plant traits, we studied the physical and chemical properties and plant functional traits of three different types of hardened surface in Shandong Province, China. Our results showed that the physical and chemical properties (soil bulk density, soil total porosity, capillary porosity, non-capillary porosity, soil moisture content, pH, organic carbon, total nitrogen, total phosphorus, total potassium, available phosphorus, and available potassium) of urban soils showed obvious differences with the increase of hardening strength. In this case, the plant functional traits (branch diameter, branch length, leaf thickness, branch weight, internode length, leaf dry weight, leafing intensity, leaf area, specific leaf area, and leaf dry matter content) were also differentiated to varying degrees. Meanwhile, there was a strong correlation among plant functional traits. Nevertheless, hardened surfaces break the quantitative relationship among functional traits of urban trees. They do not affect their stable correlation: as the hardening intensity gradually increases, its correlation weakens. In addition, plant functional traits have a significant response mechanism to soil physicochemical properties. There was a transformation of plant resource utilization strategy by changing plant functional traits to adapt to the hardened environment. Urban trees exhibit strong and rapid resource-allocation strategies. They are mainly reflected in the reduction of branch diameter, branch weight, leaf dry matter content, leaf area, mass ratio of branches and leaves, and the improvement of leafing intensity and leaf thickness. Overall, there were tight connections among urban soil properties, plant branches, and leaves functional properties. This finding reveals that urban trees can change their functional traits and the plasticity of their trait combinations under the background of hardened urban surface expansion, which is conducive to survival and growth.

Properties of Urban Soils after Decontamination Measures on the Radioactively Contaminated Territory of the City of Elektrostal

Properties of Urban Soils after Decontamination Measures on the Radioactively Contaminated Territory of the City of Elektrostal

Soil source, not the degree of urbanization determines soil physicochemical properties and bacterial composition in Ningbo urban green spaces

Urban green spaces provide multiple ecosystem services and have great influences on human health. However, the compositions and properties of urban soil are not well understood yet. In this study, soil samples were collected from 45 parks in Ningbo to investigate the relationships among soil physicochemical properties, heavy metals and bacterial communities. The results showed that soil dissolved organic matter (DOM) was of high molecular weight, high aromaticity, and low degree of humification. The contents of heavy metals were all below the China's national standard safety limit (GB 3660–2018). The bioavailability of heavy metals highly correlated with soil pH, the content of DOC, the fluorescent component, the degree of humification and the source of DOM. The most abundant genera were Gemmatimonadaceae_uncultured, Xanthobacteraceae_uncultured, and Acidothermus in all samples, which were related to nitrogen cycle and bioavailability of heavy metals. Soil pH, bioavailability of Zn, Cd, and Pb (CaCl2 extracted) were the main edaphic factors influencing bacterial community composition. It should be noted that there was no significant impact of urbanization on soil physicochemical properties and bacterial composition, but they were determined by the source of soil in urban green spaces. However, with the passage of time, the effect of urbanization on urban green spaces cannot be ignored. Overall, this study provided new insight for understanding the linkage among soil physicochemical properties, heavy metals, and bacterial communities in urban green spaces.

Comprehensive evaluation of soil characteristics and carbon stocks variability in different urban land use types

The terrestrial environment generally serves as an important carbon pool. This study mainly assessed the properties and carbon storage capabilities of soils from different urban land uses. Soil samples from roads/highways, parks, institutional areas, and constructed wetlands were collected to assess the effects of soil sealing on the characteristics and carbon content of urban soils. Soil sealing and compaction greatly influenced urban soil properties by altering the mass-balance, thereby resulting in a disproportionate amount of inflow and outflow of compounds in the soil strata. Using the Walkley-Black and loss-on-ignition (LOI) methods of soil organic carbon (SOC) analysis demonstrated that LOI-based analysis yielded up to 26 times higher SOC values than the wet-oxidation method due to the high weight losses prompted by the volatilization of hygroscopic and structural water and thermal decomposition of carbonate-containing minerals. Further analyses indicated that open soils contain 5% to 78% higher percentage of organic carbon as compared with their sealed counterparts and top soil layers tend to have higher amounts of SOC due to the continuous deposition of carbon-containing compounds from external sources. Generally, the results of this inquiry can serve as a baseline for formulating strategies to augment pedologic carbon stocks in urban environments.

Assessment of the soil buffer capacity in the green plantings of the megalopolis parks

Land degradation poses a serious challenge to food security, livelihood sustainability, ecosystem services and biodiversity conservation, while inefficient land management leads to widespread loss of soil biodiversity. The soil buffer capacity is actively involved in the mechanisms of implementing such an ecosystem service as the development and stabilization of soil fertility. Buffering determines the share of the soil potential that determines the processes of immobilization (deposition) and mobilization (release, loss) of a particular element of fertility – first of all, mineral nutrients required by plants, productive moisture, thermal energy of the soil, gas composition of soil air, acidity. The soils in parks on the territory of megacities are an integral component of them determining the conditions for the growth and development of green spaces. We assessed the acid-base (pH) buffer capacity of urban areas in a park area covered with tree stands of such introduced tree species as horse chestnut (Aesculus hippocastanum), sugar maple (Acer saccharum), small-leaved elm (Ulmus parvifolia), common hackberry (Celtis occidentalis), honey locust (Gleditsia triacanthos) and Japanese pagoda tree (Styphnolobium japonicum) growing on the territory of the T. G. Shevchenko Park (Dnipro city, Ukraine). Soil samples were collected under the crowns of these tree species. The acid-base buffering capacity of urban soils was determined by the Arrhenius method, which includes adding certain volumes of acid and alkaline components to the sample, and further calculating the buffering area within acid and base intervals. Buffering areas were calculated using the Simpson formula. The results were processed with statistical methods (arithmetic mean and standard deviation were calculated, and the difference in means was found according to the Tukey's comparison test). Initially the samples of the studied soils were found to have mostly a slightly alkaline reaction of the soil solution. Within the acid range of external influences, the buffer capacity of urban soils under introduced tree species was determined to establish the following descending series: horse chestnut, common hackberry, small-leaved elm, honey locust, Japanese pagoda tree, sugar maple. The same series was established for the total acid-base buffering capacity. The results show the greater acid-base buffer capacity of soils sampled under horse chestnut, common hackberry, small-leaved elm and honey locust trees, and therefore these soils were resistant to degradation compared to the soils sampled under Japanese pagoda tree and sweet maple. The environment-forming role of introduced tree species in the implementation of buffer properties of urban soils in the park on the megalopolis territory can be assumed.

Mineral magnetic properties of urban forest soils tailored to soil quality indicator

Ecosystem surveys reveal the benefits to society, provided by the natural environment, which in turn is chiefly regulated by the geodiversity. Thus, physico-chemical processes regulating the solid rock/sediment response to environmental changes comprise an important part in the assessment of natural ecosystems. Environmental magnetism provides a wide set of field and laboratory data able to discover natural and anthropogenic processes affecting different environmental compartments. Despite this, geosciences and environmental magnetism in particular, are under-represented in ecosystem assessment tools due to the lack of unified and clearly articulated application template. In this study, we propose a new mineral magnetic indicator of soil’s quality, based on detailed appraisal of field- and laboratory mineral magnetic characteristics of a collection of 453 urban topsoil samples. Field magnetic susceptibility (Kfield) and laboratory measurements of magnetic parameters revealed that soil magnetism reflects sensitively soils affected by vehicle traffic and park’s alleys foot load from semi-natural soil. Geochemical analyses of the content of Potentially Toxic Elements (PTEs) on a sub-set of samples was used for magnetic data validation. Correlation analysis showed strong positive link between magnetic parameters and the main PTEs, the strongest being obtained between magnetic susceptibility and the complex pollution load index (PLI). Factor analysis suggested that three factors account for the 74% of data variability. They were assigned to: 1) traffic emissions, 2) pedogenic contribution and 3) lithogenic input plus anthropogenic organic waste additions. Novel mineral magnetic Indicator (MAG) was defined, combining information on composition, concentration and grain size of ferrimagnetic iron oxides, using scored contributions from five magnetic parameters and grain size sensitive ratios. Evaluation of the spatial MAG map showed its suitability as a complex indicator of soils’ contamination with PTEs. Kfield reflected sensitively overall anthropogenic load not necessarily related to PTEs contamination but also to foot trampling and application of fertilizers.

Short-term impact of different doses of spent coffee grounds, salt, and sand on soil chemical and hydrological properties in an urban soil

Natural and human activities have deteriorated urban soil’s health and ecological functions as compared to forest soils. Therefore, we hypothesized that any intervention in poor quality soil in urban area will change their chemical and water retention properties. The experiment was conducted in Krakow (Poland) in completely randomized design (CRD). The soil amendments used in this experiment consisted of control, spent coffee grounds (SCGs), salt, and sand (1 and 2 t ha−1) in order to evaluate the impact of these soil amendments on the urban soil chemical and hydrological properties. Soil samples were collected after 3 months of soil application. The soil pH, soil acidity (me/100 g), electrical conductivity (mS/cm), total carbon (%), CO2 emission (g m−2 day−1), and total nitrogen (%) were measured in laboratory condition. The soil hydrological properties like volumetric water content (VWC), water drop penetration time (WDPT), current water storage capacity (Sa), water storage capacity after 4 and 24 h (S4 and S24), and capillary water Pk (mm) were also determined. We noted variations in soil chemical and water retention properties in urban soil after the application of SCGs, sand, and salt. It was observed that SCGs (2 t ha−1) has reduced soil pH and nitrogen (%) by 14 and 9%, while the incorporation of salt resulted in maximum soil EC, total acidity, and soil pH. The soil carbon (%) and CO2 emission (g m−2 day−1) were enhanced and declined by SCGs amendment. Furthermore, the soil hydrological properties were significantly influenced by the soil amendment (spent coffee grounds, salt, and sand) application. Our results showed that spent coffee grounds mixing in urban soil has considerably enhanced the soil VWC, Sa, S4, S24, and Pk, whereas it decreased the water drop penetration time. The analysis showed that the single dose of soil amendments had not improved soil chemical properties very well. Therefore, it is suggested that SCGs should be applied more than single dose. This is a good direction to look for ways to improve the retention properties of urban soil and you can consider combining SCGs with other organic materials like compost, farmyard manure, or biochar.

Spatial heterogeneity of soil properties of recreational areas of Volgograd

The article presents the developed soil maps and maps of spatial variability of soil properties (pH, total salt and carbonate content, organic carbon, density) in some recreational areas of Volgograd. The anthropogenic soils in the studied recreational areas include various urbostratozems (Urbic Technosols (Transportic)), Ekranic Technosols (Transportic), as well as quasizems (Phaeozems (Tehnic)), among the agrogenic ones – accumulation-carbonate agrozems (Cambisols (Aric, Protocalcic). Natural soils are represented by light and dark humus soils, chestnut soils, solonetz, as well as stratozems and psammozems. According to the data of isolinear mapping, it was found that acid-alkaline properties of soils of green zones vary from slightly alkaline to alkaline depending on the soil horizon and anthropogenic load. The mapping did not reveal salinization of the upper 0–30 cm layer. Values of organic carbon vary greatly (1–10%) and are conditioned by the presence or absence of meliorative artificial layers, as well as by the character of territory use. The content of calcium carbonates in the upper 30 cm is small and varies from 0.7 to 5%. It is established that the physical properties (density) directly depend on the level of anthropogenic load, increasing in footpaths and lawns. Spatial assessment of the properties of urban soils is important for identifying areas with an excess or on the contrary – low content of certain chemical and physical indicators for the planning of landscaping and gardening of urban areas.

Urban forest soil is becoming alkaline under rapid urbanization: A case study of Changchun, northeast China

Soil pH in natural ecosystems is experiencing outstanding changes because of acid deposition, especially in the background of global climate change, which significantly alters the ecological material cycle and affects ecosystem function. However, in urban ecosystems, the direction and pattern of forest soil pH variation affected by urbanization are still unclear. In this study, we obtained the level of urbanization by remote sensing and combined it with urban forest soil properties obtained from field sampling to ascertain the effects of urbanization on the soil in Changchun city, Northeast China. Our results showed that the urban soil pH of urban forests was significantly higher than that in suburban (+3%) and outside-city forests (+33 %, p < 0.001) and that it increased with an increasing level of urbanization (p < 0.001). The other soil physical–chemical properties of urban forests in urban areas, such as soil electrical conductivity and EC (+41 %, p < 0.001; +172 %, p < 0.001) and soil water content and SWC (-9%; p > 0.05; −27 %, p < 0.001), were also significantly different from those in suburban and outside-city forests, but there were no evident changes in soil bulk density. Urbanization has caused topsoil soil water deficits and serious soil alkalization. The expansion of total impervious surface coverage (TISC) is the main influencing factor that has both direct (TISC-pH) and indirect effects (TISC-BD-SWC-EC-pH chain) on urban forest soil alkalization. Our findings highlight that urbanization possibly reverses the urban forest soil acidification risk and that its significance should be considered in global biogeochemical cycling.

Urban soils. Principles and practice, by Andrew W. Rate (Editor)

<i>Urban soils. Principles and practice</i>, by Andrew W. Rate (Editor)

Urban forest soils harbour distinct and more diverse communities of bacteria and fungi compared to less disturbed forest soils.

Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of the soil microbiota. However, it is not clear how increasing intensity of human disturbance is reflected in the soil microbial communities. To address this issue, we used amplicon sequencing to quantify the microbiota (bacteria and fungi) in the soil of forests (n=312) experiencing four different land uses, national parks (set aside for nature conservation), managed (for forestry purposes), suburban (on the border of an urban area) and urban (fully within a town or city), which broadly represent a gradient of anthropogenic disturbance. Alpha diversity of bacteria and fungi increased with increasing levels of anthropogenic disturbance, and was thus highest in urban forest soils and lowest in the national parks. The forest soil microbial communities were structured according to the level of anthropogenic disturbance, with a clear urban signature evident in both bacteria and fungi. Despite notable differences in community composition, there was little change in the predicted functional traits of urban bacteria. By contrast, urban soils exhibited a marked loss of ectomycorrhizal fungi. Soil pH was positively correlated with the level of disturbance, and thus was the strongest predictor of variation in alpha and beta diversity of forest soil communities, indicating a role of soil alkalinity in structuring urban soil microbial communities. Hence, our study shows how the properties of urban forest soils promote an increase in microbial diversity and a change in forest soil microbiota composition.

Micrometeorological and Hydraulic Properties of an Urban Green Space on a Warm Summer Day in a Mediterranean City (Attica–Greece)

Urban Green Spaces (UGSs) are considered the most effective tool to mitigate Urban Heat Islands (UHIs). The optical properties of the materials and the vegetation types of the UGSs affect their surface temperatures, directly influencing their cooling ability. The hydraulic properties of urban soils are also affected by the vegetation coverage. The aim of this study is to investigate the temperature and reflected radiation (albedo) differences between UGS’s elements, around noon on a warm summer day, in Greece. The results indicate that green elements have smaller surface temperatures and higher reflectance compared to the artificial or the dry bare soil, presenting differences with the direct air temperature (measured above the surfaces with unshielded thermometers) −5.5 °C (shrubs), −3.8 °C (grass), +7.8 °C or +8.7 °C (paved surfaces inside or outside the UGS), +10.8 °C (dry bare soil), +12.2 °C (concrete) and +12.5 °C (asphalt), and albedo values 0.14 (grass and shrubs), 0.15 (dry bare soil), 0.27 (concrete), 0.21 (asphalt) and 0.20 (paved surfaces). The tree shades also produce great surface differences. The unsaturated hydraulic conductivity of the urban soil is greater than the surfaces covered with grass compared to the shrub-covered or bare soil, presenting values of 27.6, 10.8 and 11.4 mm h−1, respectively.

Editorial: Urban soil formation, properties, classification, management, and function

Editorial: Urban soil formation, properties, classification, management, and function

Geochemical fingerprinting and magnetic susceptibility to unravel the heterogeneous composition of urban soils

The typically high heterogeneity of urban soil properties challenges their characterization and interpretation. The objective of this study was to investigate if proximally sensed volume-specific magnetic susceptibility and/or geochemical soil properties can uncover differences in anthropogenic, lithogenic and pedological contributions in, and between, urban soils. We also tested if volume-specific magnetic susceptibility can predict heavy metal enrichment. Data on 29 soil properties of 103 soil horizons from 16 soils from Ghent, Belgium, were analyzed by factor analysis. A correlation analysis, and in-depth analysis of five contrasting urban soils supplemented insights gained from the factor analysis.The factor analysis extracted four factors: 29.2 % of the soil property variability was attributed to fossil fuel combustion and industrial processes, with high (>0.80) loadings for S, organic carbon, magnetic susceptibility, and Zn. Furthermore, 26.0 % of the variability was linked to parent material differences, with high loadings (>0.80) for K, Rb and Ti. In absence of geogenic carbonates, increased soil alkalinity due to anthropogenic input of CaCO3 explained 17.0 % of the variability. Lastly, 4.7 % of the variability resulted from variable Zr contents by local geology. Elemental analysis by XRF, possibly combined with magnetic susceptibility measurements, helped to explain lateral or vertical differences related to (1) the nature of anthropogenic influence, for instance burning (e.g., by the S and Zn content) or the incorporation of building rubble (e.g., by the Ca content); (2) the particle size distribution (e.g., by the K, Rb or Ti content); (3) lithology (e.g., by the Zr content); or (4) pedology, such as organic matter build-up (e.g., by the S content) or leaching of alkalis (e.g., by the Ca content). Even though artifacts and soil translocation were common in the studied soils, volume-specific soil magnetic susceptibility measured on fine earth predicted the total heavy metal pollution loading index well (Pearson correlation = 0.85).

Growth Response of Nine Tree Species to Water Supply in Planting Soils Representative for Urban Street Tree Sites

In urban environments, newly planted street trees suffer from poor site conditions and limited water availability. It is challenging to provide site conditions that allow the trees to thrive in the long term, particularly under climate change. Knowledge about the hydrological properties of artificial urban planting soils related to the response of tree species-specific growth is crucial, but still lacking. Therefore, we established a three-year experimental field setup to investigate the response of nine tree species (135 individuals) to two common urban planting soils and a loamy silt reference. We determined and measured soil hydrological parameters and monitored tree growth. Our results revealed low plant available water capacities (6% and 10% v/v) and hydraulic conductivity restrictions with the drying of the sandy-textured urban planting soils. Therefore, tree species that are investing in fine root growth to extract water from dry soils might be more successful than trees that are lowering their water potential. Tree growth was overall evidently lower in the urban planting soils compared with the reference and differed between and within the species. We showed that using unfavorable planting soils causes severe, species-specific growth deficits reflecting limited above-ground carbon uptake as a consequence of low water availability.

The human factor of pedogenesis described by historical trajectories of land use: The case of Paris

Characterizing the physico-chemical properties of urban soils on a large scale remains a significant challenge. The heterogeneity and difficulty of access to these soils lead to very localized studies that are difficult to transfer to a whole urban area. This heterogeneity is mainly explained by the human factor in the formation and evolution of soils, which is a major contributor to the pedogenesis in cities. Throughout their evolution, urban soils undergo contrasting human activities that modify their properties and thus determine the historical trajectories of land use. Characterizing this human pedogenesis factor seems to be an essential condition for a better understanding of the functioning of urban soils and for qualifying them on a large scale. The aim of this work is to describe this human factor by an analysis of the historical trajectories and an evaluation of their impacts on soil properties. . We focus on soils in the conurbation of Paris over the last 70 years. The different historical trajectories were identified thanks to a database provided by a local land use inventory. Results show that 80% of the total surface area is affected by 21 historical trajectories. More than 60% of this area is characterized by single use trajectories showing that most of the area has not changed land use over the last 70 years. The urbanisation of agricultural land, leading to residential areas is a representative trajectory of land use described in the paper that transforms original soils into Technosols.

PHYTOTOXICITY OF SOILS PARKS ODESSA CITY (UKRAINE)

The article presents the materials of the study of the phytotoxicity of soils in the park areas of the city of Odessa. The characteristic of some chemical and biological properties of urban soils is given. According to the content of humus, the soils of park areas are characterized as medium-low-humus. The study of soil phytotoxicity showed that the soils of all study areas slightly inhibited the growth of test crops, which indicates a favorable ecological situation. Based on the study of the phytotoxicity of soils in the park area of Odessa and the analysis of the results obtained, it is recommended to use Písum (pea) as a test object in studying the ecological situation in urban ecosystems.

Urban soil properties distinguished by parent material, land use, time since urbanization, and pre-urban geomorphology

The typically high lateral and vertical variation of urban soil properties challenges the interpretation and prediction of their spatial patterns. The aim of this study was to investigate physico-chemical properties of, and pedogenesis in urban soils with different parent materials, and to evaluate whether information on land use, time since urbanization, and pre-urban geomorphology can help to better understand and spatially predict urban soil properties in the historic city of Ghent, Belgium. Sixteen soils were collected from sites with various land uses in three quarters that were urbanized at different times. They were described and characterized by laboratory methods (soil pH, electrical conductivity, soil organic carbon content, black carbon content, equivalent calcium carbonate content, soil particle size distribution, coarse fragments content) and portable X-ray fluorescence (total Cr, Ni, Cu, Zn, and Pb content). Site history and pre-urban geomorphology were deducted from archeological reports and historical imagery. Our results revealed that human-transported materials (HTMs) are common in soils in Ghent. Decalcification, eluvation or illuvation in HTM were only evidenced in soils for which landfill occurred >100 years ago, which had not been disturbed recently. Hence, soil properties were strongly influenced by compositional differences (e.g., nature or type of artifacts) between (native or human-transported) parent material types. In contrast to land use, time since urbanization and pre-urban geomorphology were indicative of parent material type, soil properties, and human soil modifications. More specifically, soils in the old, medieval quarter Inner City consisted mainly of urbic or spolic parent material and had a lower sand content, and a higher content of silt, coarse fragments, and heavy metals (Ni, Cu, Zn, Pb) compared to the young quarter Wondelgem, where soils mainly developed in native parent material or lithic HTM. Furthermore, soils situated in raised, former floodplains had a higher soil pH, electrical conductivity, calcium carbonate content, silt content, and coarse fragments content, and a lower sand content compared to soils of the periglacial plain. Multidisciplinary data sources (e.g., historical maps) can be integrated to better comprehend the complex urban soilscape, where past and current human interventions, pre-urban geomorphology and hydrography are all at play.

Soil carbon sequestration in urban afforestation sites in New York City

There is great interest in the ability of afforestation programs to sequester carbon, improve soil health, and provide other ecological benefits to urban areas. However, the capacity of urban soils to support successful afforestation and sequester carbon is poorly understood. This study quantified soil carbon in a series of experimental restoration sites established between 2009 and 2011 as part of the MillionTreesNYC Afforestation Project in New York City. Soil cores (0–100 cm) were collected at 10 sites and analyzed for total carbon content. Data were analyzed with respect to depth (0–10, 10–30, 30–70, 70–90, 90–100 cm), high (six species) versus low (two species) diversity planting palettes, and afforestation success (high or low). Results were compared with data from regional reference forest, degraded urban sites in New York City, and disturbed and undisturbed sites in other cities. High success afforestation sites had significantly larger carbon pools than low success afforestation sites and degraded NYC sites. We suggest that these differences were created by interactions between initial site conditions that facilitated plant community establishment and growth, which in turn increased soil carbon accumulation. These initial site conditions include land use history that influences soil physical and chemical factors, as well as proximity to existing forest stands. Diversity treatments had no effect on soil carbon levels, but these may need a longer time period to emerge. These results suggest that afforestation may enhance the capacity of urban soils to store carbon compared to urban degraded soils, but that urban soil properties and site characteristics constrain this capacity.

Soil structure as a significant indirect factor affecting crop yields

Soil structure as a significant indirect factor affecting crop yields