Urban Grassland Research Articles

Home ranges of fossorial water voles (Arvicola amphibius) in urban grasslands.

Water voles (Arvicola amphibius) occur in urban areas in mainland Britain but relatively little is known about their ecology in these environments. In Scotland’s largest city Glasgow, fossorial water voles occupy areas of grassland, some of which may be faced with urban development. The aim of this study was to estimate the area of habitat required by water voles in these urban grasslands by determining their home range size and spatial overlap. Radio-tracking was undertaken at two grassland sites over 29 days during September to October 2018. The mean ± SD home range size of males was 881.4 ± 636.21 m2 (n=5, range 197.8 -1836.2) and 996.5 ± 643.45 m² (n=5, range=435.1 – 2044.6) for females. There was no difference in home range size between sexes or sites and no correlation with body mass. Where home ranges overlapped, the percentage area overlap was 37.4 ± 26.81%. These initial findings provide valuable information on spatial use of urban grasslands by water voles that will inform the management of habitats for this species.

High resolution modeling of vegetation reveals large summertime biogenic CO2 fluxes in New York City

Abstract Cities are beginning to monitor atmospheric carbon dioxide (CO2) to assess the efficacy of their climate policies. However, changes in anthropogenic CO2 emissions must be separated from biospheric CO2 fluxes which have a large seasonal cycle. Urban vegetation (e.g. lawns, trees along street and in parks, etc) in developed land covers is often omitted in regional biogenic CO2 flux models. We set up a biosphere model to estimate the regional biogenic CO2 fluxes in New York City (NYC) and assess the importance of vegetation within developed land covers. The model incorporates a high-resolution (30 m) land cover map which identifies the mixture of impervious surfaces and vegetation that is ubiquitous across developed land covers. We designed three model scenarios to evaluate the role of developed land covers in regional biogenic CO2 fluxes by assuming (a) there is no vegetation versus scenarios where all remotely sensed vegetation in developed land covers is either (b) grassland or (c) deciduous forest. Despite relatively low tree canopy cover in NYC, the regional biogenic CO2 fluxes are surprisingly large when vegetation within the developed land covers is included. Furthermore, the types of vegetation within the developed land covers are crucially important for estimating regional biogenic CO2 fluxes, demonstrated by a doubling in estimates of total biogenic CO2 flux when this vegetation is assumed to be grassland compared to forest. Using a Lagrangian atmospheric transport model, we find that the regional biogenic CO2 uptake offsets up to 40% of atmospheric CO2 enhancements attributed to anthropogenic emissions in summer afternoons and completely balances on-road traffic in one of the most congested cities in the United States. Accurate characterization of the vegetation and biogenic carbon fluxes in cities are essential to the development of effective atmospheric monitoring tools. Future measurements should focus on constraining CO2 fluxes in urban grasslands (i.e. lawns).

Wild bees are exposed to low levels of pesticides in urban grasslands and community gardens

Globally documented wild bee declines threaten sustainable food production and natural ecosystem functioning. Urban environments are often florally abundant, and consequently can contain high levels of pollinator diversity compared with agricultural environments. This has led to the suggestion that urban environments are an increasingly important habitat for pollinators. However, pesticides, such as commercial bug sprays, have a range of lethal and sub-lethal impacts on bees and are widely available for public use, with past work indicating that managed bees (honeybees and bumblebees) are exposed to a range of pesticides in urban environments. Despite this, we still have a poor understanding of (i) whether wild bees foraging in urban environments are exposed to pesticides and (ii) if exposure differs between genera. Here we assessed pesticide exposure in 8 bee genera foraging across multiple urban landscapes. We detected 13 different pesticides, some at concentrations known to have sub-lethal impacts on pollinators. Both the likelihood of pesticides being detected, and the concentrations observed, were higher for larger bees, likely due to their greater foraging ranges. Our results suggest that restricting agrochemical use in urban environments, where the economic benefits are limited, is a simple way to reduce anthropogenic stress on wild bees.

Investigating the influences of concave depths on stormwater runoff and pollution retention of urban grasslands.

In this study, scale-based runoff plots of concave grasslands were designed and simulated rainfall experiments were conducted to investigate their retention effectiveness for runoff volume and pollutant loads, and to analyze the influences of concave depths on runoff and pollution retention of grasslands. Results showed that mean time to runoff of concave grasslands was 88.5 minutes, which was 5.3 times than that of flat grassland. Average peak flow rate of concave grasslands was reduced by 36.2% compared with flat grassland. Concaved grasslands averagely retained 58.2% of stormwater runoff. Deeper concave depths significantly increased runoff detention and retention performance of grasslands. Total suspended solids (TSS) load reduction rates of concave grasslands were ranged from 50.8% to 97.3%. Total nitrogen (TN) load reduction rate was 49.8% for concave depth of 10 cm. Total phosphorus (TP) load reduction rates were 45.0% and 93.9% for grasslands with 5 cm and 10 cm concave depths, respectively. Pollution load reduction rates of TSS, TN and TP enhanced along with the increase in concave depths. The estimated minimum area ratios of upslope impervious surface to grasslands of 5 cm and 10 cm concave depths were approximately 1:1 under 20 mm rainfall events, and 38:1 under 5 mm rainfalls, respectively.

Endangered animals and plants are positively or neutrally related to wild boar (Sus scrofa) soil disturbance in urban grasslands

Wild boar is increasingly establishing populations in the outskirts of European cities, with the largest German urban population occurring in Berlin. Related soil disturbance in grasslands is common and often considered as damage to biodiversity. However, it is unknown how animal and plant species in urban grasslands respond to wild boar activity - an important limitation for conservation management. We sampled plants, grasshoppers and sand lizards in 22 dry grasslands and measured wild boar activity. We show that plant diversity decreased with rooting intensity, but not species richness, endangered or specialist species. Relationships with animals were mostly positive. Grasshopper diversity, total richness and richness of endangered and specialist species were positively related to rooting, as was sand lizard abundance. These relationships contrast to mostly negative effects in the wild boar’s non-native range. This first multi-taxa study in a large city suggests that soil disturbance by wild boars is not necessarily a threat to biodiversity. An implication for conservation is to consider the context-dependence of biodiversity responses to wild boar activity. For dry grasslands, disturbed patches should be accepted in management plans rather than re-vegetated by seeding.

Can Urban Grassland Plants Contribute to the Phytoremediation of Soils Contaminated with Heavy Metals.

The main objective of this study was to investigate whether the most common wild plant species of urban grassland can be used for phytoremediation of soils polluted with heavy metals. The study was conducted in the city of Varaždin, in northern Croatia. The content of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, Zn) was determined in soil samples as well as in unwashed and washed plant samples (Taraxacum officinale, Plantago lanceolata, Trifolium repens). The results show that the most polluted site is the railway station, while most sites are polluted by road traffic. The soils are most enriched with Pb, Cu, Zn and Cd. The bioconcentration factors for all three plant species are <1, indicating the relatively low capacity of phytoextraction. A considerable amount of heavy metals is found in the dust deposited on the plant surface, which is confirmed by a statistically significant difference between washed and unwashed plant samples. In addition, the biomass of each plant species that can be removed (in t/ha year), the mass of specific heavy metal that can be removed (in kg/ha), and the years required for phytoremediation are reported. In conclusion, phytoremediation with only common plant species of urban grassland is not possible within a reasonable period of time.

The imprint of hydroclimate, urbanization and catchment connectivity on the stable isotope dynamics of a large river in Berlin, Germany

• Isotope monitoring in Berlin during the 2018 – 2020 drought. • Large-scale hydroclimate dynamics determine isotope patterns in the Spree. • Berlin’s green spaces largely disconnected from surface waters. • Catchment- & city-scale measures needed to adapt water resources to climate change. Sustainably meeting the growing water demand of cities during a changing climate will be a major challenge in the near future. Adjusting water management strategies towards preserving urban water resources while best utilizing urban “blue” and “green” infrastructure will require precise knowledge of urban water cycling, storage and losses across large built-up areas. To gain this understanding, using stable isotopes of water as tracers in the hydrological cycle can provide valuable insights, but their application remains challenging in complex and heterogeneous metropolitan areas. This study used stable isotopes, combined with hydrometric and climatic data, to assess the imprint of the urban area and climate warming on a large urbanised river system, the River Spree in Berlin, Germany, during the exceptionally warm and dry 2018 – 2020 period. Isotope dynamics in the Spree reflected gradually varying seasonal patterns with more enriched values in summer and more depleted values in winter. Large-scale climate variability and evaporative losses in the upstream catchment, along with anthropogenic activities, impacted isotope and discharge dynamics in the Spree, especially during warm and dry summer and autumn periods. In local urban sub-catchments, variability of isotope dynamics and subsequent water ages and transit times were largely affected by engineered system components, i.e. catchment imperviousness, connectivity to storm drains and effluent discharge. Berlin’s green spaces were largely disconnected from surface waters. Urban trees in particular had high water demands during dry periods that may be hard to sustain, as trees showed slower replenishment of soil moisture during winter, resulting in shorter recharge periods under trees. More research will be needed on: (a) how planting design with alternations of urban grassland, shrub and trees can enhance infiltration and maintain water demands for trees during drought; and (b) on better quantifying open-water evaporation in the upstream catchment to fully account for catchment water losses. To sustainably manage and preserve not just Berlin’s but also similar cities’ water resources in the future, our results indicate that both integrated city- and catchment-scale measures will be necessary.

Seeds harvested during mowing from semi-natural grasslands as an ad hoc but effective solution for grassland restoration.

Species-rich grasslands formed by local ecotypes of native species provide numerous ecosystem services both in rural areas as well as urban grasslands. Nonetheless, their area is still too small, making grasslands one of the most frequently restored habitats. Successful restoration requires high-quality seed material, which is expensive and often not easy to acquire. In this study, we tested the potential of seeds accidentally collected during the mowing of a semi-natural grassland for grassland restoration. We tested seed purity, species composition, and germination capability in both laboratory and field conditions. Ninety percent of the collected material consisted of pure seeds of numerous species. Their germination capability was relatively low but still sufficient for successful grassland restoration under a typical seed density/mass per unit area seeding ratio. The germination capacity was the highest in the first two weeks after sowing and increased with overwintering seed storage. The results suggested that the seeds could be successfully used for species-rich grassland restoration. In terms of advantages, the seed mixture had a low cost and contained native species seeds representing local ecotypes. In terms of disadvantages, there was a relatively low amount of seed material and an inability to plan the time of seed harvesting. Thus, the use of the accidentally collected seeds can be considered an effective but rather ad hoc solution.

Patterns and determinants of plant, butterfly and beetle diversity reveal optimal city grassland management and green urban planning

Urban landscapes are places with high interaction between humans and nature, and the benefit of maintaining their biodiversity to enhance human wellbeing is becoming clear. There is, therefore, an urgent need for understanding what influences biodiversity in cities to inform and influence urban landscape planning. We used a multi-taxa approach (plants, butterflies, and beetles) to assess the influence of the fragmented landscape of a European city, Pardubice (Czech Republic), on the biodiversity of urban grasslands. We randomly selected 40 urban grasslands and were interested in the influences of site and land-use characteristics on biodiversity. The influence of the land-use around the grasslands was analyzed along a gradient of spatial scales (i.e., the cover of land-use types within circular buffer zones of 250, 500, and 750 m around the study grasslands). We found that species richness of the three study taxa was positively influenced by the size of the grassland (measured as grassland perimeter). Butterflies were also negatively affected by increasing management intensity. Plants and beetles were influenced by the land-use type, with plant species richness positively affected by the extent of urban greenings (i.e., green areas such as urban parks, gardens, and sport grounds), and beetle species richness negatively affected by the extent of built-up areas in the grassland surroundings. Biodiversity responses to urbanization partly differed among the studied taxa, indicating different demands of specific groups, but the demands were not conflicting and instead, often complemented each other. Consideration of the three key factors influencing biodiversity identified here (grassland extent, land-use in the surroundings, and management intensity) would provide the optimal options for maintaining city biodiversity. Protecting current urban grasslands from development and restricting construction in their surroundings, restoring city wilderness areas using urban spatial planning, and setting up butterfly-friendly management regimes (e.g., mowing in mosaic) could all be future options to help enhance biodiversity in cities.

Biodiversity maintains soil multifunctionality and soil organic carbon in novel urban ecosystems

Abstract Biodiversity in urban ecosystems has the potential to increase ecosystem functions and support a suite of services valued by society, including services provided by soils. Specifically, the sequestration of carbon in soils has often been advocated as a solution to mitigate the steady increase in CO2 concentration in the atmosphere as a key driver of climate change. However, urban ecosystems are also characterized by an often high level of ecological novelty due to profound human‐mediated changes, such as the presence of high numbers of non‐native species, impervious surfaces or other disturbances. Yet it is poorly understood whether and how biodiversity affects ecosystem functioning and services of urban soils under these novel conditions. In this study, we assessed the influence of above‐ and below‐ground diversity, as well as urbanization and plant invasions, on multifunctionality and organic carbon stocks of soils in non‐manipulated grasslands along an urbanization gradient in Berlin, Germany. We focused on plant diversity (measured as species richness and functional trait diversity) and, in addition, on soil organism diversity as a potential mediator for the relationship of plant species diversity and ecosystem functioning. Our results showed positive effects of plant diversity on soil multifunctionality and soil organic carbon stocks along the entire gradient. Structural equation models revealed that plant diversity enhanced soil multifunctionality and soil organic carbon by increasing the diversity of below‐ground organisms. These positive effects of plant diversity on soil multifunctionality and soil fauna were not restricted to native plant species only, but were also exerted by non‐native species, although to a lesser degree. Synthesis. We conclude that enhancing diversity in plants and soil fauna of urban grasslands can increase the multifunctionality of urban soils and also add to their often underestimated but very valuable role in mitigating effects of climate change.

Influence of land use on the microbiological properties of urban soils

Advancing towards sustainable cities needs a better understanding of all components of urban ecosystems, including soils, but the biological component of urban soils remains poorly studied compared to natural and agricultural soils. With the objective of advancing knowledge in this aspect, we studied the microbiological properties in 61 soils of the city of Santiago de Compostela (NW Spain), under several land uses (urban grassland, urban forest, urban garden, and periurban arable land). We determined thirteen extracellular enzymatic activities as a proxy of microbial community functioning, along with measures of microbial activity (basal respiration), microbial abundance (DNA extraction and real-time PCR), and the composition of microbial communities (Illumina MiSeq sequencing on 16S rRNA and ITS marker regions). Results showed a high variability in all of the microbiological variables among soils, reflecting the typical spatial heterogeneity of urban soils. Respiration and enzymatic activities were highly correlated to soil organic matter contents but not affected by land use within the city, with the exception of alkaline phosphomonoesterase activity, which was higher in urban garden soils and correlated positively to pH and availability of phosphorus and nitrogen. Unlike fungal abundance, we recorded a higher bacterial abundance in the urban grasslands than in the other land uses. While the composition of bacterial communities was structured in a more homogeneous, land use-dependent manner (33% variance, pAdonis = 0.001), the respective fungal communities were more heterogeneous and less influenced by group-dependent characteristics (18%, pAdonis = 0.001). Soil pH had a larger influence on the bacterial community composition (28% variance) compared to the fungal composition (8.5% variance). Overall, these findings provide evidence that the typically high soil heterogeneity of urban ecosystems is the main driving force for the urban soil microbiome, with soil organic matter determining largely microbial activity.

Gulls living in cities as overlooked seed dispersers within and outside urban environments

The yellow-legged gull is an opportunistic and generalist bird that has colonised urban areas, where it has found very favourable trophic resources but also causes disturbance to humans and damage to infrastructure. Here, we investigated the potential role that gulls play in the dispersal of plants in Barcelona, a highly populated city of north-eastern Spain. We analysed the stomach contents of 145 chicks collected in urban nests and reported the presence of seeds of 27 plant taxa. We then developed a plant dispersal model based on the movements of 20 GPS-tracked yellow-legged gulls breeding in the city of Barcelona. We estimated seed dispersal distances, seed shadows and percentage of seeds reaching habitats suitable for seeds regurgitated in pellets and those excreted in faeces. Seven of the 27 plant taxa found in the stomachs were alien taxa to Spain. Average dispersal distances of plant seeds by gulls were around 700 m, but maximum dispersal distances reached up to 35 km. Dispersal distances and seed spatial patterns did not differ between faeces and pellet models, as most strongly depended on gull movements. About 95% of the seeds were dispersed within urban environments and between 20 and 30% reached suitable habitats for seed deposition (urban woodlands, green urban parks and urban grasslands). Urban gulls frequently dispersed seeds (including alien species) within urban habitats, both via direct consumption or via secondary dispersal after consuming granivorous birds that had ingested the seeds, such as pigeons or parakeets. Urban planning for Barcelona is based on native plant species, and thus, special attention should be paid to alien plants dispersed by birds, which could pose a risk to native biodiversity in urban ecosystems.

HSPF-Based Assessment of Inland Nutrient Source Control Strategies to Reduce Algal Blooms in Streams in Response to Future Climate Changes

The HSPF model was modified to improve the growth-temperature formulation of phytoplankton and used to simulate Chl-a concentrations at the outlet of the Seom River watershed in Korea from 2025 to 2050 under four climate change scenarios: RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5. The mean and median Chl-a concentrations increased by 5–10% and 23–29%, respectively, and the number of algal outbreak cases per year (defined as a day with Chl-a concentration ≥100 µg/L) decreased by 31–88% relative to the current values (2011–2015). Among the climate change scenarios, RCP 2.6 (stringent) showed the largest number of algal outbreak cases, mainly because of the largest yearly variability of precipitation and TP load. For each climate change scenario, three nutrient load reduction scenarios were in the HSPF simulation, and their efficiencies in reducing algal blooms were determined. Nonpoint source reduction in TP and TN from urban land, agricultural land, and grassland by 50% (S1) and controlling the effluent TP concentration of wastewater treatment plants (WWTPs) to 0.1 mg/L (S2) decreased algal outbreaks by 20–58% and 44–100%, respectively. The combination of effluent TP control of WWTPs during summer and S1 was the most effective management scenario; it could almost completely prevent algal outbreaks. This study demonstrates the cost effectiveness of using a season-based pollutant management strategy for controlling algal blooms.

Vegetation changes in urban grasslands over 25 years in the city of Zurich, Switzerland

Vegetation changes in urban grasslands over 25 years in the city of Zurich, Switzerland

Level of urbanization and habitat type, and not patch size, influence predacious arthropod diversity patterns of urban grasslands in South Africa

Abstract. Greyvenstein B, Botha M, van den Berg J, Siebert SJ. 2021. Level of urbanization and habitat type, and not patch size, influence predacious arthropod diversity patterns of urban grasslands in South Africa. Biodiversitas 22: 4078-4094. Predacious arthropods provide a valuable ecosystem service within urban environments by suppressing pest numbers. However, urban ecological studies largely ignore this functional group and its diversity and species composition patterns. Some studies have been published regarding these patterns, however they were mostly done in Australia, Europe and America, thus an African perspective is lacking. Our aim was to address the gap in African literature by quantify the differences in predacious arthropod species richness and diversity within urban green space in varying urbanization intensities, habitat types of grassland and patch sizes in South Africa. Various indices were considered to examine the effect of urbanization on the diversity patterns of Chrysopidae (Neuroptera), Mantodea, Araneae and Coccinellidae (Coleoptera). Study sites included three levels of urbanization represented by population density, two types of urban grasslands (i.e., ruderal and fragmented grassland) and a peri-urban rangeland grassland as control, and a wide range of patch sizes. Our results indicated that an increase in urbanization intensities was associated with increased abundance of predacious arthropod taxa. Also, that urban and peri-urban grasslands had similar predacious arthropod species richness and diversity, but differed in species composition. No relationship was found between patch size and arthropod diversity or composition. Thus, predacious arthropod abundances are influenced by the level of urbanization and their species composition is influenced by the type of urban grassland (ruderal or fragmented), which are important considerations for future urban planning/management and conservation strategies. This study gives a South African perspective and indicates that despite the lack of assigned function of urban green spaces, they sustain diverse and distinct predacious arthropod communities, which in turn fulfill various roles in a functioning ecosystem.

Land cover matters to human well-being

People migrate from rural to urban areas. In the meantime, the benefits of staying in greener areas are also known. People’s preferences might be different by area that is composed of several land types. If so, the effect of particular land cover on human well-being is different spatially. The spatial analysis is required to formulate effective land-use policies. Here we show that urban land, water, and grassland are positively related to human well-being, whereas bare land is negatively associated in Japan. A 1 {mathrm{m}}^{2} increase in the area of urban land per capita in a city is equivalent to an about 346 USD increase in the individual annual income of all the people in the city. Additionally, monetary values of areas of water, crops, and bare land per capita are 102, − 30, and − 268 mathrm{USD}/mathrm{Capita }{mathrm{m}}^{2}. Furthermore, the spatial context matters to the relationship between land cover and human well-being. This paper investigates the monetary values of several land types and their spatial variability, which provides insights to make better usage for land cover.

Impacts of dogs on urban grassland ecosystems

Dog walking is a highly popular leisure activity in cities around the globe. It is also a controversial issue for urban conservation and green space management due to presumed ecological impacts of dogs. Yet regulations allowing or prohibiting the presence of dogs in areas of conservation concern are rarely based on demonstrated effects of dogs on urban nature. To unravel the relationships between the presence of dogs at a site and soil features and plant and animal diversity, we selected dry grassland as our study system since this type of ecosystem is of conservation concern in many cities and is frequently used for dog walking. We combined data on the number and movement patterns of dogs and their owners in 52 dry grassland patches in Berlin, Germany, to create a novel index of dog presence and activity. We then analysed the relationship between the index and soil features, species richness of plants and seven invertebrate taxa, and abundances of sand lizards, a species of particular conservation interest. Generalised linear models revealed significant relationships between the dog index and one soil parameter and some biodiversity measures. The dog index was positively related to phosphorus and non-native plant richness but negatively to spider diversity. While dogs may facilitate biological invasions, likely through a combination of eutrophication and disturbance, overall relationships with general species richness or richness of endangered plant or animal species were weak. These results indicate opportunities for reconciling urban nature conservation with moderate dog walking in urban grassland areas. Still, urban policies should consider remaining dog-related risks in other ecosystem types - a promising direction for further urban research.

Anthills: stressor or opportunity for plant assemblage diversity? Evidence from Mediterranean Dasypyretum grasslands

We explored the structure of plant assemblages that settles around the anthills of a guild of Hymenoptera Formicidae (Messor wasmanni Krausse 1910, Tapinoma nigerrimum Nylander 1856 and Aphaenogaster spinosa Emery 1878), observable in urban grasslands dominated by Dasypyrum villosum (Rome, Central Italy). Since it is known that ants act as a disturbing factor on plant assemblages of grasslands, our hypothesis was that vegetation structures suffer from some stressorsthat affect, in this plant association, the dominant plant structure. We compared the plant assemblages observed in the plots of the anthills with the control grassland assemblages using a diversity/dominance diagram. We recorded 63 plant taxa. The average number of plant species was found to be significantly lower in anthill plots than in control grassland plots. In anthill plots, dominant plant species (Polygonum romanum, Poa trivialis Vulpia myuros, Aira elegantissima and Vulpia ligustica) have been found to be different from control grassland plots (Convolvolus arvensis, Dasypyrum villosum, Poa trivialis and Sheradia arvensis). Anthill plant assemblages were found to be significantly different (One-way PERMANOVA) and poorer in terms of species richness, less diversified, and with a reduced species turnover than control grassland plots. Whittaker plot analysis seems to show that the plant assemblages of the control, with greater evenness, emphasize a stressed condition in anthill plant assemblages. Non-metric multidimensional scaling shows a set of species strictly linked to anthills. Our data seem to confirm the role of ants as a stressor in the plant assemblage structures of Mediterranean urban grasslands. However, our results also show that the peculiar ant nest conditions may favor plant species less represented in the Dasypyretum grasslands (i.e. Polygonum romanum) or even absent in this plant assemblage (i.e. Aira elegantissima, Cynodon dactylon and Poa annua), thus increasing the overall local plant diversity.

Potentially Toxic Trace Elements in the Urban Soils of Santiago de Compostela (Northwestern Spain)

With the objective of increasing information inorganic pollutants in urban soils in Spain, we studied the presence of Cu, Pb, Zn, Ni, Cr, and As in 55 soils in the city of Santiago de Compostela (northwestern Spain). The soils were developed over diverse parent materials (granites, gneiss, schists, and amphibolites) and present different land uses, urban grasslands, urban forests, urban allotment gardens, and peri-urban agricultural soils. Total trace element concentrations, analyzed by XRF of ground samples, were correlated to physicochemical properties of the soils, and the influence of land use, lithology, and location on the degree of pollution was explored. In most soils, trace element concentrations followed the sequence Zn (55–484 mg kg−1) &gt; Pb (20–566 mg kg−1) &gt; Cr (17–277 mg kg−1) &gt; Cu (17–188 mg kg−1) &gt; As (13–205 mg kg−1) &gt; Ni (11–91 mg kg−1). The concentrations were overall higher than regional backgrounds, but not high enough to class the soils as contaminated according to the Spanish regulation. Accordingly, the geoaccumulation index values indicate that most soils present low to moderate pollution levels. Among the elements studied, Cu, Pb, and Zn were correlated between them, with their highest concentrations happening in soils of the green areas in the city center; Cr and Ni concentrations were related to lithology of the parent material, with the highest concentrations in soils developed over amphibolite; finally, As concentrations are higher in two precise points without a clear connection to a known source of pollution.

Vacant lot plant establishment techniques alter urban soil ecosystem services

Vacant residential lots are ubiquitous in cities. While there is increasing interest in enhancing the aboveground habitat and biodiversity of vacant lots via restoration, vacant lot restoration may also affect the properties of and ecosystem services provided by soil. We assessed the effects of four vacant lot plant community establishment techniques (seed bombing, broadcast seeding, plug planting, and intensive gardening) and unaltered lawn on three critical ecosystem services provided by urban soils: carbon sequestration, nutrient retention, and water infiltration. We found that aboveground-focused treatments had belowground consequences. Consistent with other “urban grassland” studies, lawns exhibited the highest carbon storage among our treatments. However, soil carbon may increase in our other treatments over time – a common phenomenon in disturbed urban soils. We also found that nutrient retention – particularly nitrogen retention – increased with treatment intensity, likely due to increased plant uptake and microbial immobilization in our plots with prairie plantings. Finally, our most investment-intensive treatment, intensive gardening, resulted in decreased water infiltration, likely due to soil disturbance and increased bare soil resulting from frequent watering and weeding. Thus, treatments did not have consistent positive or negative effects on soil ecosystem services, emphasizing the multifunctionality and trade-offs associated with urban soil ecosystem processes. However, assuming low soil carbon and organic matter pools in our broadcast seeding and plug planting treatments recover over time, these two treatments may optimize aboveground plant community establishment and belowground ecosystem service provision in urban vacant lots.