Changes In Soil Parameters Research Articles

Large strain radial thermo-consolidation model for saturated soil foundation

Based on the piecewise-linear approach, a large strain nonlinear radial thermo-consolidation model for saturated soil foundation, called RTCS1, is established. The model uses the finite difference method to solve the governing equations of radial heat transfer in the soil layer and couples it with large strain radial consolidation. RTCS1 accounts for thermal effect, thermal expansion, time-dependent load increment and time-dependent heat source temperature, unload/reload effects, radial and vertical flows, equal strain and equal stress, and the nonlinear changes of soil parameters during thermo-consolidation process. Validation of the model is conducted through laboratory and field test of thermo-consolidation from existing literature, and the RTCS1 numerical solution for settlement is in good agreement with the test values. Computational examples are presented to explore the effect of strain condition, strain magnitude, and heating mode on the thermo-consolidation of saturated soil foundations. The findings indicate that the consolidation rate under equal strain condition is greater than that under equal stress condition, the lager strain leads to faster heat transfer. Under the cyclic heating modes, the excess pore pressure cannot be completely dissipated, and the soil settlement, temperature and excess pore pressure fluctuated with time.

Reproduction, growth and oxidative stress in earthworm Eisenia andrei exposed to conventional and biodegradable mulching film microplastics

Plastic contamination in agricultural soils has become increasingly evident. Plastic mulching films are widely used in agricultural practices. However, the increased use of biodegradable plastics has, to some extent, replaced their non-degradable counterparts. The fragmentation of plastics generates microplastics (MPs), posing risk to soil functions and organisms. In this study the effects of low-density polyethylene microplastics (PE-MP) and polybutylene adipate terephthalate biodegradable microplastics (PBAT-BD-MP) originating from mulching films on the earthworm Eisenia andrei were studied. The earthworms were exposed to seven concentrations (0, 0.005, 0.05, 0.1, 0.5, 1, and 5 % w/w) based on environmentally relevant levels and worst-case scenarios on soil contamination. Survival, growth, reproduction, and biomarkers for oxidative stress [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), and lipid peroxidation (LPO)] were analysed. Additionally, the Integrated Biomarker Response Index (IBR) was calculated to assess the overall oxidative stress status of the earthworms. Results showed that PE-MP exposure slightly decreased the biomass of the earthworms towards higher concentrations, whereas PBAT-BD-MPs induced growth at lower concentrations. MPs did not have a significant effect on Eisenia andrei reproduction; however, a slight negative trend was observed in juvenile production with increasing PE-MP concentrations. Both PE-MP and PBAT-BD-MP affected antioxidant system, PE-MPs with changes in CAT and GR levels and PBAT-BD-MPs inducing effects on SOD and LPO levels. Additionally, both MPs exhibited effects on soil parameters, resulting in increased soil pH and water-holding capacity at 5 % concentration. Changes in soil parameters can further affect soil organisms such as earthworms. This study provides understanding of the ecotoxicological effects of conventional and biodegradable microplastics on the earthworm Eisenia andrei. It also shows that MP particles of both conventional and biodegradable mulching films induce oxidative stress, considered as an early-warning indicator for adverse ecological effects, in environmentally relevant concentrations.

Examining the Effect of Agrochemicals on Soil Microbiological Activity, Micronutrient Availability, and Uptake by Maize (Zea mays L.) Plants

Agricultural practices profoundly influence soil microbial populations and physicochemical properties, vital for crop growth and quality. This study aims to explore the impact of diverse agrochemical applications on soil microbial dynamics, physicochemical properties, and maize yield and proximate properties. Topsoil samples, collected at depths of 1 to 15 cm, were transported to Jimma University for maize cultivation. Over 120 days, soil and maize samples were collected at specified intervals for analysis, including soil pH, microbial populations, and nutrient content. Statistical analysis using one-way ANOVA (p < 0.05) was conducted. Soil bacterial and fungal populations were measured on days 5, 10, 20, 40, 80, and 120. The highest total mesophilic bacterial count (TMBC) was in compost-treated pots (G) and the lowest in those receiving macronutrient fertilizers and glyphosates (B). The highest total mesophilic fungal count (TMFC) was in pots with glyphosates and compost (F), and the lowest was in pots treated with macronutrient fertilizers and glyphosates (B). Pots treated with macronutrient fertilizers and glyphosates (B), macronutrient fertilizers (A), and micronutrient fertilizers (C) showed the lowest Fe and Zn levels. Maize in pots treated with macronutrient fertilizer combined with glyphosate (B) exhibited the lowest protein, fats, and carbohydrates. Notably, compost-treated soils showed the highest bacterial and fungal counts, Fe, and Zn concentrations, while micro-mineral fertilizer combined with glyphosate (B) depleted the soil. Agrochemical treatments negatively affected maize yield quality, indicating complex treatment-related changes in soil parameters.

Modeling the impacts of extreme climate scenarios on soil acidity (pH and exchangeable aluminum) in Abbay River Basin, Ethiopia

The Abbay River Basin faces the looming threat of extreme climate events, including prolonged droughts and erratic rainfall patterns, which can significantly affect soil health and fertility. This study aimed to explore the influence of extreme climate conditions on soil pH and exchangeable aluminum, aiming to promote sustainable agricultural practices in Ethiopia. The Africa Soil Information Service (ASIS) provided datasets on soil pH and exchangeable aluminum. The European Copernicus Climate Change Data Store was used to download historical and future datasets of extreme climatic indices from 1980 to 2010 and 2015–2050, respectively. The Coupled Model Intercomparison Project Phase 6 model ensemble was used to predict future climate impacts under three shared socioeconomic scenarios: SSP1-2.6, SSP2-4.3, and SSP5-8.5. Data extraction, quality control, and clustering were conducted before analysis, and the model was validated for its accuracy and reliability in predicting soil parameter changes. An artificial neural network model was utilized to predict the effects of extreme climate indices on soil pH and exchangeable aluminum concentrations. The model was designed to accurately and reliably predict changes in soil parameters. This study compared the changes in soil pH and aluminum concentrations using paired t tests. The model's diagnostic results indicated a significant impact of extreme climate scenarios on soil pH and exchangeable aluminum. Extreme climate factors such as heavy precipitation and cooler night time temperatures significantly contribute to soil acidification and an increase in aluminum concentration. Under the SSP1-2.6 and SSP2-4.5 emission scenarios, soil pH levels are expected to increase by 8.38 % and 3.79 %, respectively. These changes in soil pH are expected to have significant impacts on the exchangeable aluminum content in the soil, with increases of 37 % and 5.38 %, respectively, under the same emission scenarios. However, the SSP5.8 scenario predicted a 45 % increase in exchangeable aluminum and a 9.36 % decrease in soil pH. Therefore, this study significantly enhances our understanding of the influence of climate change on soil health. The development of strategies to mitigate climate change impacts on agriculture in the region must consider the effects of extreme climate indices.

REGULATIONS OF THE FORMATION OF PROTECTIVE POTENTIAL OF UNDERGROUND STEEL PIPELINES UNDER CONDITIONS OF HETEROGENEOUS ENVIRONMENT

In the work, the modeling of the distribution of the protective potential of electrochemical protection stations is performed by revealed functional dependencies. The initial conditions are adopted for a typical assortment of rolled metal used for underground gas supply. At the initial stage of modeling, the stochastic nature of the change in soil parameters is not taken into account. The distribution of the protective potential of the underground pipeline as a function of two variables (time and distance) showed the mutual influence of neighboring stations on the formation of protective zone. New dependences of the operating parameters of the electrotechnical complex of electrochemical protection on the set of variables characterizing the power source, the physical dimensions of pipeline and the alternative arrangement of active cathodic protection stations (CPS) were obtained. Experimental studies of the modes of electrochemical protection stations at the objects of the gas transportation system of Ukraine confirmed the adequacy of the proposed analytical models. References 16, Figures 3.

Status of Soil Health Indicators after 18 Years of Systematic Tillage in a Long-Term Experiment

Long-term cultivation experiments are gaining more attention due to the possibility of following the changes in soil parameters (e.g., soil organic carbon (SOC), stock and soil health indicators, etc.). Our objective was to assess the status of soil in an 18-year-old tillage experiment after almost two decades of systematic tillage. In this research, soil physical (bulk density, moisture content), chemical (pH, SOC), and biological properties (soil microbial respiration, abundance, biomass, species composition of earthworms, yield) were used as indicators in three soil cultivation methods representing different degrees of disturbance (no-till—NT; shallow cultivation—SC; and ploughing—P). Based on our results, there were significant differences in bulk density (NT > SC, P) in 0–10 cm, and NT > P in deeper layers (10–20, 20–30, 30–40 cm), while the SOC content in 0–10 cm was the highest in NT (2.5%), followed by SC (2.4%) and P (2.0%). Soil microbial respiration was significantly greater in NT than in SC and P. The abundance and biomass of earthworms was the highest in NT (189 ind m−2, 41.26 g m−2), followed by SC (125 ind m−2, 36.9 g m−2) and P (48 ind m−2, 7.4 g m−2). We concluded that NT offered a beneficial habitat for earthworms and microorganisms and a high SOC storage capacity; however, bulk density was less convenient due to soil compaction in our experiment. Therefore, SC can be used as an alternative approach for sustainable soil tillage.

Effects of wild boar grubbing on the soil nematode community subject to seasonal variation in a broad-leaved Korean pine forest in Northeast China

Soil disturbances caused by large animals impact soil biodiversity and potentially alter forest ecosystem functioning and productivity. However, most studies have focused on the effects of wild boar infestations on above-ground vegetation and soil physical and chemical properties. Little is known about the influence of wild boar grubbing on the soil faunal community within forested ecosystems. To address this knowledge gap, we conducted a long-term (10-year) exclosure experiment to investigate the responses of soil nematode communities to wild boar grubbing and seasonal variations in a broad-leaved Korean pine forest in Changbai Mountain, China. The results indicated that wild boar grubbing did not significantly impact soil nematode abundance, genus richness, diversity indices (Shannon-Wiener diversity index, Simpson index, and evenness index), and ecological indices (enrichment index, channel index, structural index, and basal index). However, we observed that grubbing reduced the relative abundance of plant parasites while increased that of bacterivores and the maturity index (MI), leading to changes in nematode community composition. Notably, the influence of grubbing was more pronounced in the spring than in the autumn. Although season itself did not significantly affect soil nematode genus richness and diversity indices, it did affect soil nematode relative abundance, bacterivores, omnivores-predators, plant parasites, K-strategistis, r-strategistis, MI, enrichment index, and channel index. Long-term wild boar grubbing appeared to mitigate seasonal effects on soil nematode communities, resulting in higher MI and increased stability in nematode community abundance. Our findings suggest that changes in soil parameters, such as soil NH4+, soil pH, and soil NO3–, likely mediate the observed impact of wild boars on the soil nematode community. In summary, our study demonstrated that wild boar grubbing altered the structure of soil nematode communities, albeit with seasonal variations, indicating that the effects of wild boar activity on forest soil ecosystems influence biogeochemical cycles through changes in nematode community composition rather than nematode genera richness.

Spectrometry for better soil fertility management in Abbay River Basin

AbstractThe aim of this study was to determine how soil bunds affected important soil characteristics based on the soil's reflectance in Aba Gerima, an Ethiopian midland of the Abbay River Basin. Soil samples were collected from 0 to 30 cm of the soil depth in 48 plots for soil texture, pH, organic carbon (OC), total nitrogen (TN), available phosphorus (av. P), and available potassium (av. K). Using a spectroradiometer, we evaluated the reflectance of soils that had been air‐dried, pulverized, and sieved. To locate and forecast the change in soil parameters, we employed regression modeling. We identified and predicted soil properties using the models, which were evaluated by the coefficient of determination (R2) and root mean square error. Soils from bunded plots had less reflection. Higher amounts of clay (61%), OC (2.30%), av. P (13.72 ppm), and av. K (116.55 mg/kg) were found in bunded plots. For calibration data, R2 was 0.93, 0.83, and 0.82 for clay, sand, and OC contents, respectively. Spectroradiometry could therefore complement conventional soil analysis. More study is needed to enhance spectroscopy's prediction performance.

Temporal and spatial variation of temperature and displacement fields throughout cross-passage artificial ground freezing

The artificial ground freezing (AGF) method exhibits advantages of non-pollution, a good effect of reinforcement, and water sealing that are widely applied in underground engineering. However, the AGF method would disturb the original ground stress field and cause frost heave and thaw settlement. Therefore, it is significant to study the development of temperature and displacement fields for better and more efficient application of the AGF method. In this paper, a complex three-dimensional model, which considers the deflection arrangement of freezing pipes, the ice-water phase change, the thermal-mechanical coupling, and the nonlinear change of soil parameters comprehensively, has been created to study the temperature and displacement variations throughout the entire construction period of a representative AGF project. The findings demonstrate that the proposed sophisticated model corresponds well with the field monitoring results, which meet the limit value required by the specification. It is determined that each AGF construction period must be taken into account in order to more accurately estimate the freezing effects and environmental influences throughout the AGF project.

Microbiome of abandoned soils of former agricultural cryogenic ecosystems of central part of Yamal region

Microbial activity plays a crucial role in the development and formation of soil properties. The active and abandoned agricultural soils in the Arctic zone represent a valuable resource that can play a crucial role in providing food security in the northern regions. The reuse of abandoned land for agriculture will reduce environmental risks in the context of a changing climate. Therefore, there is a need for monitoring studies to assess changes in soil parameters after long-term abandonment (taxonomic diversity, agrochemical and physico-chemical qualities). In the study, we evaluated the taxonomic diversity of the microbiome in abandoned (postagrogenic) and pristine soils of the Central part of the Yamal region. In the process of taxonomic analysis, more than 30 different bacterial and archaeal phyla were identified. The formation of a specific microbiome associated with anthropogenic influence in post-agrogenic sites has been shown. Most common types of soil microorganisms in samples collected from pristine and postagrogenic soils were Firmicutes (average 26.86%), Proteobacteria (average 23.41%), and Actinobacteria (average 15.45%). Firmicutes phylum was found mainly in the agrocenoses soils, Proteobacteria were mainly described in the mature tundra soils, Actinobacteria in humid conditions. An increase in diversity indices in postagrogenic soils was shown.

Monitoring the efficiency of electro-kinetic soil remediation process with geophysical surveying method

Geoelectric surveying is a useful method of non-invasive investigation (e.g.: for the purpose of space delineation or time dependant monitoring) of subsurface contaminants. The measured onsite electrical resistivity values are a function of certain soil parameters and the electric properties of the contaminant. With executing time domain field surveys before and after the remediation process its efficiency on contamination removal can be valorized.In this study we present a field case to illustrate the applicability of the geoelectric method for monitoring the efficiency of hydrocarbon removal and highlighting the problems of interpretation due to change of soil parameters and various hydrocarbon composition. Due to the side effects of electro-kinetic soil remediation process some soil parameters affecting the electrical resistivity are also changed. Therefore, when interpreting the data the of field survey one must be able to separate the geoelectric response of the remnant contamination from the changed soil parameters. The paper presents a multilevel interpretation method when the measured electrical resistivity data were correlated with the time-domain results of detailed soil sample analytics including particle size distribution, physical properties, and chemical composition. As a result we were able to separate the time domain geoelectric effects of the soil from the geoelectric response of the hydrocarbon contamination and we could correlate the electrical resistivity anomalies with the integrated effects of hydrocarbon content and changes in the soil due to the remediation treatment.

Моделирование стационарных равновесных состояний почвы и их катастрофические изменения под влиянием антропогенных нагрузок

Several soil fertility models based on mathematical catastrophes theory are proposed. Models make it possible to calculate changes in soil parameters under the influenceof anthropogenic impact on it. Each model corresponds to one or another typical sprout ofcatastrophes and takes into account the required number of parameters characterizing soilproperties. This makes it possible to take into account the diversity of regional zones andclimatic conditions. Typicality of germs and their universal deformations gives us the opportunity to speak about the sufficient adequacy of the proposed models, since atypical germsrefer from the point of view of mathematics to exceptional phenomena that are rarely foundin nature.

Changes in soil chemical properties as affected by application of wastewater spiked with heavy metals

Wastewater was spiked with cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb) at various concentrations and applied in soil under gladiolus crop at research farm of Water Technology Center, ICAR-IARI, New Delhi during 2017. Changes in soil parameters were determined as per the standard methods. Results indicated that soil properties in-terms of pH, organic carbon, phosphorous, potassium and micronutrients (Cu, Fe, Mn, Zn) was not changed significantly, whereas significantly higher salt (EC 0.41 dS/m), nitrogen (161.50 kg/ha) as well as Ni (0.75 mg/kg), Cr (1.64 mg/kg), Cd (0.17 mg/kg) and Pb (2.75 mg/kg) in T5 treated soils were recorded, where highest concentration of metals, i.e. Cd (0.5 mg/L), Cr (5.0 mg/ L), Ni (10 mg/L), Pb (50 mg/L) were spiked in wastewater. It may be concluded that application of metals spiked wastewater irrigation may alter soil functioning by way of elevated levels of metal in soils under pot experiment.

Exploring the factors influencing the hydrological response of soil after low and high-severity fires with post-fire mulching in Mediterranean forests

Despite ample literature, the influence of the individual soil properties and covers on the hydrological response of burned soils of forests has not clearly identified. A clear understanding of the surface runoff and erosion rates altered by wildfires and prescribed fires is beneficial to identify the most suitable post-fire treatment. This study has carried out a combined analysis of the hydrological response of soil and its driving factors in burned forests of Central-Eastern Spain. The pine stands of these forests were subjected to both prescribed fire and wildfire, and, in the latter case, to post-fire treatment with mulching. Moreover, simple multi-regression models are proposed to predict runoff and erosion in the experimental conditions. In the case of the prescribed burning, the fire had a limited impact on runoff and erosion compared to the unburned areas, due to the limited changes in soil parameters. In contrast, the wildfire increased many-fold the runoff and erosion rates, but the mulching reduced the hydrological response of the burned soils, particularly for the first two-three rainfalls after the fire. The increase in runoff and erosion after the wildfire was associated to the removal of the vegetation cover, soil water repellency, and ash left by fire; the changes in water infiltration played a minor role on runoff and erosion. The multi-regression models developed for the prescribed fire were accurate to predict the post-fire runoff coefficients. However, these models were less reliable for predictions of the mean erosion rates. The predictions of erosion after wildfire and mulching were excellent, while those of runoff were not satisfactory (except for the mean values). These results are useful to better understand the relations among the hydrological effects of fire on one side and the main soil properties and covers on the other side. Moreover, the proposed prediction models are useful to support the planning activities of forest managers and hydrologists towards a more effective conservation of forest soils.

Combined intensive management of fertilization, tillage, and organic material mulching regulate soil bacterial communities and functional capacities by altering soil potassium and pH in a Moso bamboo forest.

Intensive management is a common practice in agricultural and forestry ecosystems to improve soil quality and crop yield by influencing nutrient supply and soil microbiota; however, the linkage between soil nutrients and bacterial community and functional capacities in intensively managed economic forests has not been well studied. In this study, we investigated the soil properties such as available potassium (AK), available nitrogen (AN), available phosphorus (AP), ammonium (NH), nitrate (NO), organic matter (OM), total nitrogen (TN), total phosphorus (TP), bacterial diversity and community composition, potential functions of rhizome roots, and soil microbiota across a chronosequence of intensively managed Moso bamboo (Phyllostachys edulis) forests. Our results demonstrated that the combined intensive management (deep tillage, fertilization, and organic material mulching) in this study caused a significant increase in the concentrations of AK, AN, AP, NH, NO, OM, TN, and TP (P < 0.05). However, they led to a remarkable decrease in pH (P < 0.05). Such changes lowered the Shannon diversity of the soil and rhizome root microbiota but did not significantly affect the community composition and functional capacity. Soil bacterial community variation was predominantly mediated by soil total potassium (TK) (15.02%), followed by pH (11.29%) and AK (11.13%). We further observed that Nitrospirae accounted for approximately 50% of the variation in soil pH, NO, NH, and AK, indicating its importance in soil nutrient cycling, especially nitrogen cycling. Accordingly, we propose that the management-induced changes in soil parameters reshaped the bacterial community structure and keystone bacterial assemblage, leading to the differentiation of microbial functions.

Seasonal Variation of Soil Quality in a Semi-deciduous Northern Tropical Forest of Nagaland, India.

To assess the seasonal changes in soil parameters and the soil quality of a semi-deciduous forest in Nagaland, tropical forest soil samples were tested for 10 physical and chemical variables. Apart from clay content, EC, and CEC, the rest of the parameters showed a seasonal mean significant difference at p < .05 level. Based on the principal component analysis, available nitrogen (Nav) and electrical conductivity (EC) were included in a minimum data set and are regarded to best represent the system attributes. In both additive and weighted soil quality method, maximum SQI was recorded in autumn season. The research summarized that seasonal variations can influence soil characteristics and soil quality through its aggregate effects. Considering the result obtained from the present study, the approach we have used in soil quality assessment would be suitable for primarily screening the tropical forest soil status. This would ultimately pave ways for future management and mitigation plans to facilitate the improvement of forest health and aid to biodiversity conservation.

BEHAVIOR OF NATURAL AND TREATED SOIL WITH MICROORGANISMS UPON VARIOUS WATER CONTENT DUE TO DYNAMIC LOAD

Liquefaction is a phenomenon where the saturated sandy soil experiences highly excess pore water pressure and loss of effective stress between soil particles simultaneously due to an earthquake. It will have an impact on building damage or failure which laid on sandy soil. Study location was selected at the New International Airport in Kulonprogo, Yogyakarta which was built on loose sandy soil and coincidentally categorized as highly earthquake zone. Based on this, an experiment model was carried out to analyze the behavior of sandy soil when stabilized with Aspergillus fungus as the microorganisms. The loads derived from dynamic loads (earthquake loads) and it will also analyze the changes of soil parameters after the soil stabilization. In a previous study using a fungus with the type of Rhizopus oligosporus, it resulted in a significant increase in soil consistency under certain conditions of water content. From the experiment, it is known that the appropriate percentage of soil mixture consists of ordinary sand with a percentage of 62% plus silt and clay with a percentage of 38%. Aspergillus fungus isolates at a concentration of 10-2 showed good tissue growth and without the presence of foreign substances.

Enduring legacy of coal mining on the fungal community in a High Arctic soil after five decades

Mineral extraction is known to affect soil fungi in polar environments, but it is unknown how long these effects persist. Here, by amplifying the internal transcribed spacer regions of rRNA genes in soil fungi, we compared soil fungal community in intact natural tundra with that in a nearby former coal mining area, abandoned 52 years previously, on Svalbard in the High Arctic. Compared with those in intact tundra, soils in the former mining area were more acidic and had lower plant coverage. Despite of similar diversity in the two areas, the fungal community was dominated by Basidiomycota in the intact tundra, but by Ascomycota in the former mining area. Ectomycorrhizal genera formed a major part of the tundra community, but were notably less abundant in the mining area. The principal variation among samples was soil pH. Surprisingly, network connectivity analysis indicated that the fungal community in the former mining area had greater network connectivity than that in the tundra area. Overall, the ecosystem in the former mining area has made only limited recovery towards the natural tundra state even after more than five decades. It is unclear whether the recovery of the fungal community is limited more by the low primary productivity, slow migration of fungi and plants, or slow changes in soil parameters. Our findings emphasize the susceptibility of polar ecosystems to disturbance, given their particularly slow recovery back towards the natural state.

Use of Impact Penetrometer to Determine Changes in Soil Compactness After Entracon Sioux EH30 Timber Harvesting

Wood harvesting with the use of wheeled harvesters is now common in Polish and Czech forests. While moving in the forest, the wheels of these machines affect the forest soil and the extent of this impact is interesting. The paper presents the results of measurements of the changes that occur in the soil on the operational trails after the timber harvesting using the Entracon Sioux EH30 thinning harvester. The measurements were taken on fragments of three operational trails, in and between the ruts and at a distance of 1.0 m off the trail. An impact penetrometer was used to measure the penetration resistance, soil samples were collected to determine the bulk density and moisture content, and soil deformations on the trail were measured with a profile meter. Unit pressures exerted by harvester wheels on the ground were determined. It was shown that in the places where the harvester wheels pass, even of a small weight (5.73 tons, 8 wheels) and with unit pressures of the wheels on the ground &amp;lt;50 kPa, changes in soil parameters occurred. A statistically significant increase in penetration resistance in relation to the control occurred at a depth of up to 35 cm, while at a depth of up to 5 cm the increase was more than 2-fold. There was also a slight decrease in soil moisture content (up to 7.9%) and an increase (up to 8.4%) in bulk density in the ruts, while rut depths were small and reached 4 cm. As it was shown, the impact penetrometer, simple in design, which was assumed to be used for measurements, and which is not used in this type of research in forestry, despite its limitations, can be used to determine the compactness of the soil and its changes resulting from machine work.

Variability of Potential Soil Nitrogen Cycling Rates in Stormwater Bioretention Facilities

Low-impact development (LID) is a common management practice used to infiltrate and filter stormwater through vegetated soil systems. The pollutant reduction potential of these systems is often characterized by a single pollutant removal rate; however, the biophysical properties of soils that regulate the removal of pollutants can be highly variable depending on environmental conditions. The goal of this study was to characterize the variability of soil properties and nitrogen (N) cycling rates in bioretention facilities (BRFs). Soil properties and potential N cycling processes were measured in nine curbside bioretention facilities (BRFs) in Portland, OR during summer and winter seasons, and a subset of six sites was sampled seasonally for two consecutive years to further assess temporal variability in soil N cycling. Potential N cycling rates varied markedly across sites, seasons, and years, and higher variability in N cycling rates was observed among sites with high infiltration rates. The observed seasonal and annual changes in soil parameters suggest that nutrient removal processes in BRFs may be highly variable across sites in an urban landscape. This variability has important implications for predicting the impacts of LID on water quality through time, particularly when estimated removal rates are used as a metric to assess compliance with water quality standards that are implemented to protect downstream ecosystems.