The ubiquity of urban brownfields presents not only a challenge for environmental managers but also an opportunity to study the functional aspects of degraded ecosystems that are in close contact ...with human habitation. In this study, we investigate the soil microbial community response to heavy metal contamination at Liberty State Park (LSP), an urban brownfield in Jersey City, NJ, USA. Heavy metal contamination of the soils at LSP is heterogeneous, varying widely across site and among metals. We collected soils along a previously mapped gradient of metal contamination at LSP and sampled soil from a local and uncontaminated reference site (Hutcheson Memorial Forest (HMF)) for comparison. For all soils, we measured soil heavy metal concentrations, soil organic carbon content, bacterial density, and extracellular phosphatase activity as a proxy of ecosystem functioning. Additionally, we analyzed the microbial community composition using high-throughput sequencing. Data show that some sites within LSP have significantly higher phosphatase activity compared to HMF, indicating that some heavily contaminated LSP soils are highly functional. We also found that soil organic carbon and bacterial density have a significant and positive relationship with phosphatase activity. The microbial community analyses showed that the bacterial communities were sensitive to heavy metals and that the composition was significantly affected in particular by copper, zinc, and lead. The fungal communities, however, did not vary significantly with heavy metals. Our results shed important light on the composition and functioning of urban brownfield soils. A deeper understanding of these unique ecosystems is required for successful remediation, restoration and urban sustainability.
•Bacterial community composition varies with soil metal load, but fungal does not.•Soil microbial community functioning can be high in spite of metal load.•Soil phosphatase activity correlate with factors like: pH, soil organic matter, and bacterial abundance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The legacy of industrialization has left many soils contaminated. However, soil organisms and plant communities can thrive in spite of metal contamination and, in some cases, metabolize and help in ...remediation. The responses of plants and soil organisms to contamination are mutually dependent and dynamic. Plant–soil feedbacks are central to the development of any terrestrial community; they are ongoing in both contaminated and healthy soils. However, the theory that governs plant–soil feedbacks in healthy soils needs to be studied in contaminated soils. In healthy soils, negative feedbacks (i.e. pathogens) play a central role in shaping plant community structure. However to our knowledge, the nature of feedback relationships has never been addressed in contaminated soils. Here we review literature that supports a plant–soil feedback approach to understanding the ecology of metal-contaminated soil. Further, we discuss the idea that within these soils, the role of positive as opposed to negative plant–soil feedbacks may be more important. Testing this idea in a rigorous way in any ecosystem is challenging, and metal contamination imposes an additional abiotic constraint. We discuss research goals and experimental approaches to study plant–soil interactions applicable to metal-contaminated soils; these insights can be extended to other contaminated environments and restoration efforts.
•Plants, soil organisms and metal contamination interact in dynamic ways.•Plant–soil feedback theory may be subject to challenge under contamination.•Generalized feedback theory in urban soils requires reference sites and meta-analysis.•We have technological tools to study feedback interactions in contaminated soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The food webs of terrestrial soils and of freshwater and marine sediments depend on adjacent aboveground or pelagic ecosystems for organic matter input that provides nutrients and energy. There are ...important similarities in the flow of organic matter through these food webs and how this flow feeds back to primary production. In both soils and sediments, trophic interactions occur in a cycle in which consumers stimulate nutrient cycling such that mineralized resources are made available to the primary producers. However, aquatic sediments and terrestrial soils differ greatly in the connectivity between the production and the consumption of organic matter. Terrestrial soils and shallow aquatic sediments can receive organic matter within hours of photosynthesis when roots leak carbon, whereas deep oceanic sediments receive organic matter possibly months after carbon assimilation by phytoplankton. This comparison has implications for the capacity of soils and sediments to affect the global carbon balance.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Anthropogenic metal contamination is a pervasive problem in many urban or industrial areas. The interaction of metals with native soil communities is an important area of research as scientists ...strive to understand effects of long-term metal contamination on soil properties. Measurements of free soil enzyme activities can serve as useful indicators of microbial metabolic potential. The goals of this study are to determine extracellular soil enzymatic activities with respect to corresponding metal concentrations within a site of long-term contamination. These data are examined to understand relationships between extracellular soil enzyme activities and persistent metal loads in situ. Here we present such results from a rare research opportunity at an un-remediated, urban brownfield in Jersey City, NJ, USA. The soils of the site developed over the last 150 years through the dumping of urban fill from New York City as well as industrial rail use. The site was abandoned and fenced in the late 1960s, and within it, there is a mapped gradient of metal concentration in the soils, including As, Pb, Cr, Cu, Zn, and V. We measured soil enzymatic potential (alkaline phosphatase, cellobiohydrolase, and l-leucine-amino-peptidase) across four plots within the site and at an uncontaminated reference site that is of the same successional age and geographic influence. We found the highest enzymatic activities for all three activities measured at the site with the greatest soil metal loads and a particularly strong relationship among enzyme activity and the metals V and Cr. Our results differ from many experimental studies that show decreased soil enzyme activity in soils experimentally treated with metals. The results may indicate the effects of long-term adaptation of soil communities within these metal contaminated soils.
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•High enzyme activities were found in metal laden as opposed to reference soils.•Two heavy metals (Cr, V) correlate significantly with enzyme activities.•In sterile controls, added metals did not affect enzyme activities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Restoring enzyme function in barren, brownfield soils using green strategies can improve microbial functioning and enable phytoremediation. It is known that adding simple, readily metabolized ...substrates secreted by growing plant roots (root exudates) or a laboratory prepared solution of root exudates (artificial root exudates) can stimulate soil microbial function. It is not known whether and how well this strategy works in a contaminated, low functioning soil from an industrial barren site because contaminants in the barren soil might inhibit microbial survival and functioning, or the microbial community might not be adapted to functionally benefit from root exudates. The objective of this study was to determine whether artificial root exudates stimulate microbial function in a barren soil. We collected soils from a barren brownfield (25R) site and an adjacent vegetated brownfield site (25F), with low and high enzyme activities, respectively. We subjected both soils to three treatments: switchgrass (native to the site), artificial root exudates, and a combination of switchgrass and artificial root exudates. We measured enzymatic activity, plant growth, soil moisture, organic matter content, and easily extractable glomalin content over 205 days. By day 157, artificial root exudates increased the phosphatase activity by 9-fold in previously vegetated brownfield soil and by 351-fold in barren brownfield soil. When exudates were added to the barren soil, the plant shoot mass was higher (52.2 ± 2.5 mg) than when they were not (35.4 ± 3.6 mg). In both soils, adding artificial root exudates significantly increased the percent moisture, organic matter, and glomalin content. Treating contaminated, barren soil with artificial root exudates resulted in increased soil microbial function and improved soil properties that might promote a hospitable habitat to support vegetation in such extreme environments.
Summary: We added artificial root exudates to stimulate enzymatic function in two contaminated soils. Plant shoot mass, soil percent moisture, glomalin content, and organic matter content significantly increased due to the addition of artificial root exudates to the study soils. Microbially-mediated phosphatase activity was established in a barren, previously inactive, polluted soil.
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•A barren, contaminated, and enzymatically inactive industrial soil was revitalized.•Artificial root exudates increased the barren soil's phosphatase activity >300-fold.•Activity increased 39-fold more in the barren soil than in a vegetated reference.•Plant biomass and glomalin content also significantly increased in the barren soil.•After treatment, the barren soil functionally resembled the vegetated reference soil.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Shifts in animal husbandry and landscape use have significantly changed ungulate grazing effects on ecosystem functioning. These changes are now the subject of extensive research with respect to ...plant and soil communities, but the results of these studies are highly varied and context dependent. The objective of this study is to address contextual variation by holding all sampling methods and analytical approaches constant and analyse the effect of the feral goat (Capra hircus) population of Mallorca Island, Spain, on soil physical, chemical and biological characteristics across five controlled sites. Specifically, vegetation cover and soil properties in fenced plots excluded from ungulates were compared with adjacent grazed plots in five independent mountain areas of Mallorca. Soil microbial activity measured as Community-Level Physiological Profiles (CLPP) using EcoPlate™ increased when ungulates were excluded. However, all other physical and chemical measures of the soils did not vary significantly when we considered ungulate exclusion across all plots, and this may be caused by a soil community that is simply robust to the effects of the herbivores. Or, it may be due to the high heterogeneity that was detected among pair plots comparisons within each of the five sites. Indeed, we find more variability within a site than among our independent sites leading us to hypothesize that grazing does influence biogeochemical cycles, but it does it by increasing variability of the system in general. Our well-controlled multilevel meta-analysis confirms the notion that ungulate effects are highly context dependent, and soil heterogeneity makes resolving clear patterns very challenging. Apparently, context persistently drives the soil response more than the grazing itself, and this is seen even at very small scales.
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•Ungulate land use is in transition, with global implications for grassland ecosystem stability.•We study ungulate effects on soils of 14 pair exclosure experiments in 5 independent areas.•Ungulate exclusion significantly affects plant community and soil microbial activity.•Physicochemical soil characteristics and OM degradation did not consistently change.•Ungulates exclusion effect was more heterogeneous within plots than among areas.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Once abandoned, urban and post-industrial lands can undergo a re-greening, the natural regeneration and succession that leads to surprisingly healthy plant communities, but this process is dependent ...upon microbial activity and the health of the parent soil. This study aimed to evaluate the effects of arbuscular mycorrhizal fungi (AMF) in facilitating plant production in post-industrial soils. In so doing, we helped to resolve the mechanism through which AMF ameliorate environmental stress in terrestrial plants. An experiment was established in which rye grass (
Lolium perenne
) was grown in two heavy metal-contaminated soils from an urban brownfield in New Jersey, USA, and one non-contaminated control soil. One set of the treatments received an AMF inoculum (four species in a commercial mix:
Glomus intraradices, G. mosseae, G. etunicatum and G. aggregatum
) and the other did not. Upon harvest, dried plant biomass, root/shoot ratio, AMF colonization, and extracellular soil phosphatase activity, a proxy for soil microbial functioning, were all measured. Plant biomass increased across all treatments inoculated with AMF, with a significantly higher average shoot and root mass compared to non-inoculated treatments. AMF colonization of the roots in contaminated soil was significantly higher than colonization in control soil, and the root/shoot ratio of plants in contaminated soils was also higher when colonized by AMF. Mycorrhizal infection may help plants to overcome the production limits of post-industrial soils as is seen here with increased infection and growth. The application of this mechanistic understanding to remediation and restoration strategies will improve soil health and plant production in urban environments.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Soil anthropogenic contaminants can limit enzymatic nutrient mineralization, either by direct regulation or via impacts on the microbial community, thus affecting plant growth in agricultural and ...non-agricultural soils. The impact on phosphatase activity of mixing two contaminated, post-industrial rail yard soils was investigated; one was vegetated and had high phosphatase function, the other was barren and had low enzymatic function. The two soils had different abiotic properties, including contaminant load, vegetation cover, soil aggregate size distribution, and phosphatase potential. An experimental gradient was established between the two soils to systematically vary the abiotic properties and microbial community composition of the two soils, creating a gradient of novel ecosystems. The time dependence of extracellular phosphatase activity, soil moisture, and organic matter content was assessed along this gradient in the presence and absence of plants. Initially, mixtures with higher percentages of functional, vegetated soil had higher phosphatase activities. Phosphatase activity remained unchanged through time (65 days) in all soil mixtures in unplanted pots, but it increased in planted pots. For example, in the presence of plants, phosphatase activity increased from 0.6 ± 0.1 to 2.4 ± 0.3 μmol•h−1•gdry soil−1 from day one to day 65 in the 1:1 functional:barren soil mixture. The presence of plants also promoted moisture retention. Inoculation of poorly functioning soil with 10% of the functional soil with its microbial community did not, over 65 days, revitalize the poorly functioning soil. The findings showed that abiotic limitations to enzymatic activity in barren brownfield soils could be mitigated by establishing primary production but not by the addition of enzymatically active microbial communities alone.
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•Vegetated and barren brownfield soils had high and low phosphatase activities.•An experimental gradient of the two brownfield soil environments was created.•Mixtures containing more vegetated soil had proportionally higher enzyme activities.•Inoculation with functional microbes did not increase soil function over 65 days.•Primary production increased soil enzymatic activity across entire soil gradient.
Summary: We mixed two contaminated soils, creating a gradient of abiotic and biotic properties. When planted, enzymatic function increased in all soil mixtures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We experimentally investigated the determinants (consumer vs environmental productivity) and functional consequences of bacterial diversity using a simple laboratory bacterial assemblage and the ...bacterivorous ciliated protist Colpidium striatum. A two-way factorial design was used, with two productivity levels crossed with the presence/absence of Colpidium striatum. The effects of productivity and predation on bacterial diversity were similar to those previously reported for plant diversity in systems characterized by high productivities, with increased productivity reducing diversity and predation increasing diversity. When Colpidium was present, changes in trophic level biomass and individual bacterial species abundance in response to increased productivity were largely consistent with the keystone predation model. Importantly, Colpidium predation also resulted in an increase in particulate organic matter decomposition, largely due to an increase in the abundance of one single bacterial species that appeared resistant to predation. These results suggest that changes in community structure as a result of trophic interactions and other factors may have profound consequences for important ecosystem functions. We suggest that future research should take an integrative approach and study causes and consequences of biodiversity simultaneously.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
From the 1850's until the 1960's, the Central Railroad of New Jersey was among several major railways shipping anthracite and bituminous coal to the New York City area, transferring coal from railcar ...to barge at its extensive rail yard and port facility in Jersey City. The 490 ha Liberty State Park was developed on the site after the rail yard closed, but a ca. 100 ha brownfield zone within the park remains off limits to visitors pending future remediation. As part of an environmental forensic and industrial archeological investigation of this zone, the present study characterizes anthracite and bituminous coal particles present in abundance in the soil by scanning electron microscopy (SEM) and pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). A simple pretreatment procedure employing density separation improved the analytical results. This detailed information about the nature of contaminants at the site will help to inform the remediation effort in the public interest.
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•Legacy coal contamination is widespread in the soils of an unremediated area of Liberty State Park, formerly a rail yard and coal shipment port.•The soil coal particles are mostly of anthracite rank, the low PAH content of which reduces the potential environmental hazard at this brownfield.•PAH-rich bituminous coal, while less abundant, may be of greater concern, although the degree of PAH bioavailability must be considered.•Analysis of soil components by Py-GC-MS after a preparative density separation procedure is shown to an effective environmental forensics tool.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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