Deicing agents cause soil salinization and degradation in urban areas. We assessed the capacity of urban lawns to maintain carbon sequestration and nutrient cycling with increasing soil salinity. The sensitivity to soil salinity of the main ecosystem players: plants and microorganisms were assessed considering their complex interactions between each other and environment. The effects of low and moderate soil salinization by common deicing agent (NaCl) were evaluated in mesocosms planted with two urban lawns: Lolium perenne and mixture of grasses. Mesocosm-, plant-, and soil-level gas exchange were assessed on a short-term (days) and long-term (months) scales. Microbial response was characterized by analyzing the microbial properties and activities of nine enzymes. Carbon balance remained independent on the salinity due to cancelling effect of lowered gross primary production (GPP, −20%), decreased C input by plants into the soil (−40% for mixture) balanced by slower microbial decomposition of organic matter (−20%) and so, lower soil respiration (−35%). GPP declined as a long-term response by a combination of stomatal constraint on photosynthesis with leaf respiration increase. Toxic effects of salinization on soil respiration were observed only for temperatures above 15 C. Microbial community with high C:N ratio (common for fungi) was the most sensitive to salinization. The death of microbial biomass (−31% for Lolium) and cell lysis increased soil enzyme activities (+38% for Lolium). We conclude that C balance of urban lawns remain homeostatic at secondary salinization. Temperature effects and plant-microbial interactions will determine C and nutrients cycling under salinity stress in urban lawns.
Several studies have reported the presence of smithsonite (ZnCO3) in soils polluted by zinc mining. The present study aimed to determine upper critical threshold values of Zn phytotoxicity in a substrate spiked with ZnCO3 and to compare them with those obtained in field‐collected soils. We studied Zn toxicity to perennial ryegrass (Lolium perenne L.) grown in pots with unpolluted peat treated with increasing concentrations of ZnCO3 that produced nominal total Zn concentrations of 0, 0.7, 1.3, 2.0, 2.6, and 3.3%. To keep constant near‐neutral pH value in all the treatments, we used decreasing concentrations of dolomitic lime. In the treatment with total soil Zn of 3.3% (pH 6.8), the foliar Zn concentration of L. perenne was 1914 ± 211 mg kg–1, falling into the range of 2400 ± 300 mg kg–1 reported for Lolium species grown under similar laboratory conditions in a polluted soil (total soil Zn 5.4%, pH 7.3) collected near a Zn smelter. The value of 92 ± 98 mg kg–1 was obtained for the median effective concentration (EC50) values of 0.01 M KNO3‐extractable Zn using the responses of shoot dry biomass, shoot length, and total pigments. This value falls within the range of 95 ± 46 mg kg–1 reported in other studies for the EC50 values of salt‐extractable Zn using field‐collected soils. The application of ZnCO3 for spiking was able to mimic foliar Zn concentrations of Lolium species observed in field‐collected soils. The effective concentrations of soil Zn obtained in the present study are comparable to those obtained in field‐collected soils. Future research should determine effective concentrations of metals using soils spiked with metal‐containing compounds that mimic a real source of contamination. Environ Toxicol Chem 2020;39:1790–1796. © 2020 SETAC
<p><span><span>&#1055;&#1086;&#1078;&#1072;&#1083;&#1091;&#1081;&#1089;&#1090;&#1072;, &#1074;&#1089;&#1090;&#1072;&#1074;&#1100;&#1090;&#1077; &#1089;&#1074;&#1086;&#1081; &#1072;&#1073;&#1089;&#1090;&#1088;&#1072;&#1082;&#1090;&#1085;&#1099;&#1081; HTHigh anthropogenic impact and the rate of urbanization result in a decrease of urban soils&#8217; capacity to perform ecosystem services. Carbon sequestration is an important soil-based ecosystem service, which can be assessed through quantity and quality soil carbon stocks. The stability of soil organic matter (SOM) is characterized by the resistance of its constituent components to biological, chemical and physical destruction. In the study, SOME stability in peat-sand mixture used for urban soils&#8217; construction; floodplain soil was analyzed in response to temperature-moisture conditions. The decomposition rate of various soils was assessed. Decomposition was assessed through studying microbial production of CO2. In the research the CO2 emissions were studied under following temperatures and moisture conditions: temperature &#8211; 7&#176;C, 22&#176;C, 30&#176;C and 40&#176;C and moisture &#8211; 0.2 WHC, 0.4 WHC, 0.6 WHC, 0.8 WHC, 1 WHC. Moisture affects the amount and activity of microbial biomass, controls the availability of oxygen to microorganisms, causes periods of water microbial stress and also can destabilize organic matter, resulting in increased availability of carbon to soil microorganisms. Different patterns of moisture and temperature impacts on the soil organic carbon (SOC) decomposition rates were observed. It was concluded that, depending on the qualitative composition of carbon, the impact of hydrothermal conditions on the emission of carbon dioxide changed.ML &#1079;&#1076;&#1077;&#1089;&#1100;.</span></span></p>
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