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In the present study, we examined fine root production and soil available nutrients (N, P and K) across different soil depths in rubber monoculture and rubber–Flemingia macrophylla agroforestry of different stand ages. We used the ingrowth cores method and sampled 360 soil cores over four growth intervals, representing one year of growth for the present study. The results showed that root production and macronutrient concentrations generally decreased with increasing soil depth. Total fine root production was comparatively high in the youngest stand age (12 years) rubber monoculture; a similar trend was observed for the soil available P and K, but available N was greater in older than younger stand ages. Root growth and soil available P and K were all lower in the agroforestry system than the monoculture. Significant differences in fine root production with stand ages, management system and seasons suggest that fine root responses to the soil available nutrients are vital to understanding the precise response of above- and belowground biomass to environmental changes.

A total of 344 soil cores were taken in annually cropped fields of Alberta, Saskatchewan, Manitoba, and Ontario from 2011 to 2013 in areas where the field shapes, or obstacles within fields, required the driving pattern of farm operations to overlap. Soil nitrate-N concentrations in overlapping areas were 60% greater, soil Olsen-P concentrations were 23% greater, and pH was 0.5 units greater at 0–15 cm depth compared with non-overlapping areas, suggesting smaller nutrient use efficiency and potential for greater nutrient loss.

The 15N gas-flux method allows for the quantification of N2 flux and tracing soil N transformations. An important requirement for this method is a homogeneous distribution of the 15N tracer added to soil. This is usually achieved through soil homogenization and admixture of the 15N tracer solution or multipoint injection of tracer solution to intact soil. Both methods may create artefacts. We aimed at comparing the N2 flux determined by the gas-flux method using both tracer distribution approaches. Soil incubation experiments with silt loam soil using (i) intact soil cores injected with 15N label solution, (ii) homogenized soil with injected label solution, and (iii) homogenized soil with admixture of label solution were performed. Intact soil cores with injected 15N tracer solution show a larger variability of the results. Homogenized soil shows better agreement between repetitions, but significant differences in 15N enrichment measured in soil nitrate and in emitted gases were observed. For intact soil, the larger variability of measured values results rather from natural diversity of non-homogenized soil cores than from inhomogeneous label distribution. Generally, comparison of the results of intact cores and homogenized soil did not reveal statistically significant differences in N2 flux determination. In both cases, a pronounced dominance of N2 flux over N2O flux was noted. It can be concluded that both methods showed close agreement, and homogenized soil is not necessarily characterized by more homogenous 15N label distribution.

No information exists on the susceptibility of arbuscular mycorrhizal fungal (AMF) communities in Canadian prairie agriculture soils to climate change. An experiment was initiated in mid-May 2011 in which replicated soil cores were transplanted reciprocally from four cultivated prairie sites in Saskatchewan, Canada, representing different regional climatic zones ranging from semiarid to subhumid regional climates, such that replicated (n = 4) soil cores from each site were present at all sites. Field pea was grown in all cores and at harvest in early-September 2011; soil samples were collected to analyze the changes of AMF communities over the cropping season. A total of 82 operational taxonomic units belonging to eight AMF genera were identified using 18S rRNA gene pyrosequencing. When soils were transplanted to new environments, the relative abundance of AMF changed considerably. Typically, Shannon diversity declined when soil cores were transplanted to new environments. We present evidence that with the altered climatic conditions following transplantation of soil cores, the relative abundance of AMF was significantly altered, and some taxa were enhanced, suppressed, or disappeared in the home-away soils compared with home-site soils. This study implies that the future climate change effects on AMF may impact specific phylogenetic taxa differently, such that rare species or those with low abundance may increase or decrease with unknown consequences. Understanding the potential responses of AMF communities to soil–climate interactions is important when considering the impacts of climate change on soil microbial communities.

Continued reliance on chemical methods for controlling annual bluegrass has resulted in many populations evolving resistance to PRE and POST herbicides, particularly in warm-season turfgrass species such as zoysiagrass. Soil seedbank management is critically important when managing herbicide-resistant weeds. Fraise mowing (also spelled fraze, frase, and fraize) is a new turfgrass cultivation practice designed to remove aboveground biomass while allowing turf to regrow vegetatively. We hypothesized that this process would remove annual bluegrass seed and therefore be a mechanical means of controlling annual bluegrass in turfgrass. Zoysiagrass field plots were fraise-mowed in June 2015 only, June 2016 only, June 2015 and June 2016, or left untreated. The fraise mower was configured to remove the uppermost 25 mm of plot surface (i.e., 15-mm verdure and 10-mm soil). Annual bluegrass infestation was quantified in April following fraise mowing via grid count. Soil cores (10.8 cm diameter) were extracted from each plot after grid count data were collected to assess effects of fraise mowing on the soil seedbank. Moreover, replicated subsamples (7.6 L) of debris generated during fraise mowing were collected to better understand weed seed content removed during the fraise mowing process. Fraise mowing in June offered a slight reduction (24%) in annual bluegrass cover the following April. Whereas 28% of the seed in fraise-mowing debris consisted of annual bluegrass, there was no difference in the quantity of annual bluegrass seed remaining in the soil seedbank among fraise-mowed and non–fraise-mowed plots. Although fraise mowing may help to temporarily reduce existing annual bluegrass infestations via mechanical removal, the frequency and depth we studied did not effectively reduce the seedbank. Fraise mowing is a useful tool for providing mechanical suppression of annual bluegrass but it is not a replacement for properly timed herbicide applications.Nomenclature: Annual bluegrass (Poa annua L.); zoysiagrass (Zoysia japonica Steud.)

Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 EliteTM nuclear gauge method (radiation) for measuring bulk density (ρB) and volumetric moisture content (θv) in a clay loam soil. Soil ρB and θv measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil ρB obtained using the core method (1.454, 1.492 g·cm−3) were greater than those obtained using the radiation method (1.343, 1.476 g·cm−3) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean ρB and θv values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil ρB values measured by the core method were lower than the CV values of those measured by the radiation method at both depths; however, the CV’s of ρB values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil θv values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of ρB and θv, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring ρB for many agricultural, hydrological and environmental studies in most soils.

Abiotic reduction of contaminants in iron-based laboratory model systems has been studied extensively, but the resulting understanding is not sufficient to allow prediction of reaction rates under ...

Our analyses revealed the spatial variability of the vertical distribution of fallout radiocesium measured in small cylindrical soil cores taken in a non-disturbed paddy field contaminated by the F...

Agricultural grass cultivars bred for increased forage yield commonly have extensive root systems. As roots are an important input of organic matter into the soil, it follows that such cultivars could lead to important increases in soil organic carbon (SOC), but this, and the mechanisms involved, are poorly understood with little empirical field evidence. We assessed the effect of two cultivars, Lolium perenne L. cv. ‘AberMagic’ and L. perenne L. × Festuca pratensis Huds. cv. ‘Prior’, in comparison with mixed-species permanent pasture (‘Pasture’) in a field experiment on temperate alluvial soil in the southwest UK. Root and SOC stocks, and specific plant-derived lipids as mechanistic biomarkers for shoot and root inputs of C, were measured on intact 1-m volumetric soil cores collected on four dates in 2013-2015. Total grass yields were greater for both grass cultivars (40-43 Mg ha–1) than Pasture (39 Mg ha–1), and by 2015 root stocks in the upper 0.1 m were significantly greater by more than 4.7 Mg ha–1. At 0.1-0.3 m depth, SOC stocks (per 0.1-m depth) were significantly greater under the two grass cultivars (24-50 Mg ha–1) compared to Pasture (18-32 Mg ha–1). In the full 1-m profile, mean SOC stocks were 137, 133 and 110 Mg ha–1 for AberMagic, Prior and Pasture, respectively, matching root biomass distribution. Odd-chain n-alkane concentrations were significantly greater for shoots than roots (274 vs. 64 mg kg–1, respectively), and roots had significantly greater concentrations than shoots of even-chain hydroxy fatty acids (1829 vs. 305 mg kg–1, respectively) and diacids (317 vs. 93 mg kg–1, respectively). This confirmed lipids as candidate biomarkers for distinguishing shoot and root inputs into the soil, with the latter being the dominant source of SOC. Based on the observations of increased forage yield and SOC stock, high-yielding forage grass cultivars can contribute to future strategies for climate-smart agriculture in grassland-dominated temperate regions.

This research was funded by the Ministry of Business, Innovation and Employment's Endeavour Fund, through the Manaaki Whenua-led `Next Generation S-map' research programme, C09 x1612. We would like to thank from Manaaki Whenua - Landcare Research John Dando for the laboratory physical determinations, Veronica Penny for collecting soil cores and samples, and John Drewry for reviewing the manuscript. Mathieu Sellier from Civil Mechanical of the University of Canterbury (New Zealand) is also thanks for reviewing the manuscript., Hydraulic parameters define the water retention, theta( psi), and the unsaturated hydraulic conductivity, K(theta), functions. These functions are usually obtained by fitting experimental data using inverse modelling. The drawback of inverting the hydraulic parameters is that they suffer from non-uniqueness and the optimal hydraulic parameters may not be physical. To reduce the non-uniqueness, it is necessary to invert the hydraulic parameters simultaneously from observations of theta( psi) and K(theta), and ensure the measurements cover the full range of theta from saturated to oven dry. The challenge of using bimodal theta(psi) and K(theta) compared to unimodal functions is that it requires double the number of parameters, one set for the matrix and another set for the macropore domain. The objective of this paper is to address this shortcoming by deriving a procedure to reduce the number of parameters to be optimized to obtain a unique physical set of bimodal soil Kosugi hydraulic parameters from inverse modelling. To achieve this, we (1) derive residual volumetric soil water content from the Kosugi standard deviation parameter of the soil matrix, (2) derive macropore hydraulic parameters from the water pressure head threshold between macropore and matrix flow, and (3) dynamically constrain the Kosugi hydraulic parameters of the soil matrix. The procedure successfully reduces the number of optimized hydraulic parameters and dynamically constrains the hydraulic parameters without compromising the fit of the theta(psi) and K(theta) functions, and the derived hydraulic parameters are more physical. The robustness of the methodology is demonstrated by deriving the hydraulic parameters exclusively from theta(psi) and Ks data, enabling satisfactory prediction of K(theta) even when no additional K(theta) data are available., Ministry of Business, Innovation and Employment's Endeavour Fund C09 x1612

Three soil core samples were collected from a forest located about 1.1 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) boundary in 2017, and the vertical profiles of 129I from the FDNPP accident were determined by the combination of TMAH (tetramethyl ammonium hydroxide) extraction and ICP-MS/MS analysis. The humus layer above the soil layer was heavily contaminated with 134Cs (1983–5985 Bq g−1) and 137Cs (1947–5902 Bq g−1) (decay-corrected to March 11, 2011). The 129I activity concentrations decreased sharply with the soil depth, from 1894 to 34.1, from 9384 to 78.9, and from 2536 to 51.3 mBq kg−1, for the three sites. Downward migration of 129I was slightly faster than the one of 134Cs. In addition, the cumulative 129I inventories were observed to be 43.4 ± 1.0, 71.7 ± 1.8, and 56.5 ± 1.8 Bq m−2, respectively. Subsequently, the cumulative 131I inventories were estimated to be 1.76 ± 0.06, 2.90 ± 0.11, and 2.28 ± 0.10 GBq m−2 (decay-corrected to March 11, 2011), respectively. Finally, the total atmospheric deposition of 129I on the land of Japan due to the FDNPP accident was estimated to be around 1.09–1.71 kg (7.11–11.2 GBq).

espanolLa region de Yalahau al norte de Quintana Roo, Mexico, contiene abundantes humedales de agua dulce y una historia de ocupacion Maya que abarca casi 3000 anos. Los mayores niveles de poblacion regional ocurrieron durante el periodo Preclasico tardio, del 100 AC al 350/450 DC. Los Mayas construyeron alineamientos rocosos cruzando los pantanos, y se ha hipotetizado que estas caracteristicas funcionaron para atrapar suelos y agua para la produccion de alimento y para el uso de recursos biologicos como el perifiton. Los estudios paleoambientales de un humedal de la porcion oriental de la region sugieren que la ocupacion de la region de Yalahau y la manipulacion de los humedales, corresponden con un periodo cuando el manto freatico fue menor que en tiempos modernos, creando ecosistemas de humedal que eran mas productivos para el cultivo. Este trabajo presenta resultados que aplican este modelo a escala regional (en humedales en otras partes de la region). Treinta pequenos nucleos de suelo fueron colectados de 12 humedales a lo largo de la region. Para este Proyecto, 5 nucleos de 4 humedales fueron seleccionados para los analisis que incluyen micromorfologia y fechamiento por radiocarbono. Las laminas delgadas, estudiadas bajo el microscopio petrografico, fueron usadas para identificar los varios tipos de caracteristicas presentes en los nucleos, incluyendo carbonatos, materia organica, conchas, pirita, yeso y espacio poroso. En cada nucleo, distinguimos una unidad superior dominada por carbonato micritico biogenico y una unidad inferior caracterizada por una variedad de caracteristicas de suelo unicas, como cristales espariticos de calcita, pirita, yeso y propiedades gleycas. Basado en esto, se sugiere que mientras que los procesos formadores del suelo moderno son claramente uniformes a lo largo de la region y controlados por la inundacion anual regular (~7 meses de >1 m de profundidad de inundacion cada ano), en el pasado (periodo Preclasico), la inundacion era menos regular y los ambientes de humedal fueron mas pantanosos y variados. Ademas, se sugiere que las depresiones del Preclasico encontradas por los Mayas, fueron un recurso agricola de calidad que permitio el florecimiento de la region durante el Preclasico tardio. Sin embargo, como la inundacion se volvio mas regular al final del periodo Preclasico, la region fue abandonada, solo para ser re-ocupada en el Postclasico tardio, cuando los humedales fueron explotados para recursos acuaticos, mas que para la agricultura. EnglishThe Yalahau region of northern Quintana Roo, Mexico, contains abundant freshwater wetlands and a history of Maya occupation that spans nearly 3000 years. The highest regional population levels occurred during the Late Preclassic period, from ca. 100 BC to AD 350/450. The Maya constructed rock alignments crossing wetland swales, and these have been hypothesized as features used to trap soil and water for production of food and useful biological resources such as periphyton. Paleoenvironmental studies from a wetland in the eastern part of the region suggested that occupation of the Yalahau region, and manipulation of the wetlands, corresponded to a period when the water table was lower than in modern times, creating wetland ecosystems that were most productive for cultivation. This paper presents results that apply this model at the regional scale (in wetlands in other parts of the region). Thirty short soil cores were collected from 12 wetlands across the region. For this project, 5 cores from 4 wetlands were selected for analyses including micromorphology and radiocarbon dating. Thin sections studied under petrographic microscope were used to identify the various types of features present in the core sequences including carbonates, organic matter, shell, pyrite, gypsum, and pore space. In each core, it was possible to distinguish an upper unit dominated by biogenic-micritic carbonate and a lower unit characterized by a variety of unique soil features such as sparitic calcite crystals, pyrite, gypsum, and gleyic properties. Based on this, it is suggested that while modern soil forming processes are fairly uniform across the region and controlled by regular annual flooding (~7 months of >1m deep flooding each year), in the past (Preclassic period), flooding was less regular and wetland environments were more swampy and varied. Furthermore, it is suggested that the Preclassic depressions encountered by the Maya were a prime agricultural resource that allowed the region to flourish during the Late Preclassic period. However, as flooding became more regular at the end of the Preclassic period, the region was abandoned, only to be reoccupied in the Late Postclassic when wetlands were exploited for aquatic resources rather than for agriculture.

Implementation of winter cover crops (CC) is a conservation practice aimed at improving soil health and increasing water infiltration. Reduced tillage (e.g., no-till), another, more common conservation practice, shares these aims. While the literature concerning the main effects of CC and reduced tillage is rich, the additive effects of CC and reduced tillage are unclear and understudied—specifically, the adoption of reduced tillage long before (20+ years) CC implementation, which is common in the last half-century. This study assessed two of the potential short-term effects of CC when added in a long-term no-till system: reduction of soil compaction (SC) and addition of soil total carbon (STC). Four field plots in northeast Mississippi were planted with CC while two were utilized as controls having no CC. All plots were under no-till for the last 20+ years. Soil penetration resistance measurements (SC) and soil cores were collected in April of 2017, following two years of CC implementation, from 20 semirandomly selected locations in each plot. Model comparisons were used to explore variation in SC and STC between CC and control plots, and the contributions of covariates to the observed variation. Results of the selected models (model with highest Akaike9s weight) indicated there was no difference in SC between CC and control plots; however, slight variation in STC did exist between the two treatment levels (d ± 95% CI = 0.46 ± 0.39, p

The vertical distributions and downward migrations of the global fallout derived 239+240Pu and 241Am in diverse types of Chinese soils (forest, grassland and desert) were studied. The mean 239+240Pu and 241Am activity concentrations in the investigated soil cores were 0.28–0.69 mBq/g and 0.13–0.37 mBq/g, respectively, while the accumulative inventories were 61.53–138.99 Bq/m2 for 239+240Pu and 28.29–61.05 Bq/m2 for 241Am. The convection-dispersion equation (CDE) was used to calculate the migration parameters of 239+240Pu and higher apparent dispersion coefficients (D) were observed for the acidic forest soils compared with the alkaline grassland and desert soils; meanwhile a compartment model was employed to compare the migration of 239+240Pu and 241Am in successive soil layers which showed that the migration behaviors of 239+240Pu and 241Am were rather similar; both velocities were less than 0.3 cm/y in diverse types of soils and these findings were compatible with those of short-term laboratory simulation experiments in China.

Simple Summary The hunting billbug is the most dominant and damaging insect pest species of sod farms (where turfgrass is commercially produced) in Georgia (USA). The larvae feed within the turfgrass stem, and roots affect turfgrass growth. Hunting billbugs are usually managed using insecticides. However, the application of insecticides to entire sod fields is not an economically and practically feasible option. Thus, an improved sampling plan for larvae and adults is warranted to improve management decisions. The current study was aimed at understanding the spatial distributions of hunting billbug larvae and adults in sod farms using geospatial techniques. The larvae and adults were sampled using soil cores and pitfall traps, respectively. After evaluating two geospatial techniques, the distribution pattern of hunting billbug larvae and adults within the sod farms was aggregated. The presence of billbugs in samples collected at 4 m apart suggests active infestation. This information will help develop integrated pest management for hunting billbug in sod farms and reduce insecticide use, benefiting growers and the environment alike. Abstract The hunting billbug, Sphenophorus venatus vestitus Chittenden (Coleoptera: Curculionidae), is an important turfgrass pest, especially in sod farms. S. venatus vestitus larvae feed on the stems and roots of turfgrass. Damaged turfgrass is loosely held together and poses a challenge for machine harvesting. Additionally, the normal growth of turfgrass is affected, especially after winter dormancy. Because S. venatus vestitus larvae are hidden inside the stems or under the soil, larval management is challenging. To improve sampling and management, the spatial distribution patterns of S. venatus vestitus larvae and adults were assessed at four sod farm sites with a history of S. venatus vestitus infestation in central Georgia (USA). The larvae were sampled by soil cores using a hole cutter, whereas adults were collected using pitfall traps for 7 d. The spatial distributions of larvae and adults was analyzed using SADIE and variograms. The SADIE and variogram analyses revealed a significant aggregation pattern for adults, whereas aggregated distributions were detected for larvae with variogram analyses. The average ranges of spatial dependence for larval and adult samples were 3.9 m and 5.4 m, respectively. Interpolated distribution maps were created to visually depict S. venatus vestitus infestation hotspots within the sod farms.

Sequential harvests of cotton seedlings grown in soil cores enabled the quantification of the density of arbuscular mycorrhizal fungi to detect the effects of time, cultivation and periodic wetting of the soil. Cotton seedlings grown in soil cores from three locations formed arbuscular mycorrhizas at similar rates when cores were stored dry for up to 18 months. Disturbance of dry cores followed by dry storage for 18 months did not reduce the rate of establishment of mycorrhizas. Periodic wetting and drying of the cores, especially if the cores had first been disturbed, significantly reduced the rate of establishment of mycorrhizas. We suggest that long fallow disorder is possibly caused by falls of rain in clay soils of eastern Australia used to grow cotton. The proportion of the root with mycorrhizas at 3 wk was strongly correlated with the infection at 8 wk. We also suggest that it might be possible to predict maximum levels of infection and early uptake of phosphate of seedlings by determining the proportion of roots that are mycorrhizal 3 wk after emergence of cotton seedlings.

International audience; In a companion study, carried out in a fallow meadow close to a lead recycling factory, we showed that earthworms were absent in the first 20 m and then gradually increased in abundance from 30 to 110 m from the factory. Here we assessed in the same meadow whether these differences in earthworm abundance were associated with the loss of physical soil properties. Soil cores were sampled and infiltration measured in situ at five distances from the factory (10, 30, 50, 80 and 110 m). X-ray tomography was used to characterize the earthworm burrow systems within cores. The burrow systems were minimal at the first two distances, with the only macropores observed probably produced by insects such as ants. Typical earthworm burrows were seen at 50 m but most of their characteristics (volume, diameter, continuity) were similar to those observed at 10 or 30 m. Dense and well-developed burrow systems were observed at 80 and 110 m from the factory with significantly larger volume and continuity. Burrow diameter at 80 m was significantly higher than at closer distances but it significantly decreased at 110 m associated with the higher abundance of endogeics earthworm species. Water infiltration followed the same trend with significantly lower rates at the first two distances compared to those further from the factory, where rates increased from 70 to 250%. This study emphasizes the need to develop a more functional approach to study the spatial effects of contamination on soil ecological processes and fertility, beyond modifications in earthworm communities.

A possibility of using bottom sediments from dam reservoirs in earth structures was considered. Sediments from the Rzeszow reservoir (Poland) were used as research material, which, according to geotechnical standards, were classified as low permeable silt with high organic content. As fine, cohesive soil with a low coefficient of permeability, the sediments can be used in sealing elements of hydraulic engineering embankments. In order to verify the suitability of the sediments, stability and filtration calculations were carried out for embankments with a sealing in the form of a core made of the sediments. It was stated that by using a core made of sediments, the volume of seepage on the downstream side during continuous or variable backwater was significantly lower in relation to an embankment without a core, and the phreatic line did not extend to the downstream slope. It is estimated that, in the case of a planned dredging in Rzeszow Reservoir, the amount of dredged sediment would exceed 1.5 million m3, and therefore, the possibility of their economic use is essential. The search for materials that could replace natural soil in earthen structures is an important issue from both the ecological and economic points of view.

Researchers face a number of challenges in the construction of soil columns which can affect the outcome of their experiments. The use of intact soil cores closely mimics actual field conditions. However, the excavation of large intact soil cores is a time-consuming, labor-intensive process and may lead to soil compaction that would influence the solute transport behavior of the soil column. Repacked soil columns are used as an option to circumvent these challenges of intact soil cores. However, repacked soil columns also have their limitations and introduce other challenges. Here, we present a step by step procedure for the design of repacked soil columns to achieve a realistic bulk density, prevent preferential flow paths, and ensure hydraulic connectivity between soil layers. This protocol will be beneficial to Soil Scientists, Hydrologists and other Environmental Scientists utilizing repacked soil columns.

The 239+240Pu and 137Cs activities and 240Pu/239Pu atom ratios in surface soil and soil core collected from Qinghai-Tibet Plateau were investigated. The maximum of 239+240Pu and 137Cs activity concentrations in five soil cores were found in upper layers and have a same trend: the maximum followed by exponential decline. The 240Pu/239Pu atom ratio ranged from 0.160 ± 0.009 to 0.212 ± 0.012, clarified that the plutonium mainly came from the global fallout and the contribution of Lop Nor test sites was negligible. In addition, the vertical profiles of radionuclides (210Pb, 238U, 232Th, 226Ra, 40K) have been studied and a high correlation has been found between them. The correlations of Pu between organic matter (OM) and heavy metals were also studied. Person Correlation Coefficients revealed Pu had significant positive correlations with organic matter and Cd, Cu, Co, Zn, but negative correlation with Tl. The results have important implication for further understanding of the sources, records and environmental impacts of global and regional nuclear activities, which expanded the database of Pu activity level and atom ratio in Chinese soil and established a foundation for future environmental risk assessment.

Metode jatuhan radioisotop (Fallout Radio Nuclides) telah lama dimanfaatkan dan dikembangkan untuk mempelajari dan mengukur erosi tanah. Penelitian ini bertujuan menduga erosi/deposisi tanah di Sub DAS Ciesek, DAS Ciliwung Hulu menggunakan jatuhan radioisotop 137Cs dan 210Pb excess di alam. Pengambilan sampel tanah dilakukan menggunakan soil core pada empat transek penggunaan lahan yang berbeda. Sampel tanah dianalisis menggunakan Multi Channel Analyzer (MCA) untuk mendapatkan nilai inventori kedua radioisotop tersebut. Hasil penelitian menunjukkan perbedaan pola distribusi erosi/deposisi antara isotop 137Cs dan 210Pb excess. Penggunaan isotop 137Cs menunjukkan proses erosi tanah terjadi pada lahan kebun campuran dan tegalan, tapi proses deposisi terjadi di lahan terbuka. Penggunaan 210Pb excess menunjukkan erosi tanah terjadi di lahan terbuka, namun deposisi terjadi di lahan kebun campuran dan tegalan. Penggunaan 210Pb excess pada penelitian ini lebih dapat diandalkan dibandingkan dengan 137Cs, dalam hal pendugaan erosi tanah

Soil organic carbon (SOC) decomposition is inherently sensitive to temperature. As such, a big concerning is the potential SOC loss under climatic warming, but field empirical evidences are lacking, particularly in tropical forest soils in which ∼10% of global SOC is stored. Recently Nottingham et al. (2019) assessed the data collected from a novel experiment translocating soils across a 3000 m tropical forest elevation gradient to mimic temperature changes in situ, and concluded that warming caused considerable SOC loss. However, this conclusion was based on a metric with a strong assumption that soil cores translocated to other elevations on average had the same initial SOC content to control soil cores reinstalled at their original elevation. Because of limited replicates (n =3) in the data, an approach ignoring spatial heterogeneity of SOC content may undermine the credibility of the results. Here, we used a nonparametric bootstrap approach to re-analyze the data, explicitly taking data variability into account. Contrary to Nottingham et al. (2019), we found that SOC content did not show significant differences among translocated soils from the same elevation origin. Further looking into six chemical fractions determined by 13C NMR spectroscopy shown that they had similar, insignificant response to translocation-induced temperature changes, which also does not support the conclusion of Nottingham et al (2019) that labile SOC is more sensitive to warming. We concluded that temperature changes did not significantly alter either total SOC content or its six chemical fractions after five years of shift of temperature regimes in tropical forests. This may largely due to thermal adaptation of microbial decomposition and environmental constrains (e.g., low pH) which suppress the effect of temperature changes. Longer term experiment with more sampling replicates are required to maximize the value of soil translocation experiments to address the effect of warming on SOC dynamics.

Refereed/Peer-reviewed Despite the critical importance of roots within soils for supporting plant growth, the assessment of root distribution in soils remains difficult and much is unknown regarding their behaviour. In this review, we examine X-ray computed tomography (CT) as a non-invasive method for examining root distribution in soils. X-ray CT enables three-dimensional reconstruction of soil cores to accurately estimate a wide range of features within the soil, including roots, not only examining changes spatially but also temporally. With the development of high-end X-ray CT systems and image processing algorithms, this approach can now be used to examine a range of factors, including root system architecture, soil-root interactions, soil pore architecture, soil biophysical interactions, and soil microorganism behaviour. In addition, we examine the use of synchrotron-based X-ray CT which has been used to provide better resolution, larger sample analysis, faster scanning, and images with greater contrast compared to conventional systems.

In this study, we conducted an incubation experiment on a frozen soil core collected from a black spruce forest in Interior Alaska, in order to investigate potential changes in greenhouse gaseous (...

15N gas flux method allows for quantification of N2 flux and tracing soil N transformations. An important requirement for this method is a homogeneous distribution of the 15N tracer added to soil. This is usually achieved by soil homogenization and admixture of the 15N tracer solution or multipoint injection of tracer solution to intact soil. Both methods may create artefacts. We aimed at comparing the results of the gas flux method using both tracer distribution approaches. Intact soil cores with injected 15N tracer solution show wider range of the results obtained. Homogenized soil shows better agreement between repetitions, but significant differences in 15N enrichment measured in soil nitrate and in emitted gases were also observed. For intact soil the wider variability of measured values rather results from natural diversity of non-homogenized soil cores than from inhomogeneous label distribution. Generally, comparison of the results of intact cores and homogenized soil did not reveal statistically significant differences in N2 flux determination. In both cases, pronounced dominance of N2 flux over N2O flux was noted. It can be concluded that both methods showed close agreement and homogenized soil is not necessarily characterized by more homogenous 15N label distribution.

Understanding solute transport behaviors of deep soil profile in the Loess Plateau is helpful for ecological construction and agricultural production improvement. In this study, solute transport processes of a deep soil profile were measured by a conservative tracer experiment using 25 undisturbed soil cores (20 cm long and 7 cm diameter for each) continuously sampled from the surface downward to the depth of 500 cm in the Loess Plateau of China. The solute transport breakthrough curves (BTCs) were analyzed in terms of the convection-dispersion equation (CDE) and the mobile-immobile model (MIM). Average pore-water velocity and dispersion coefficient (or effective dispersion coefficient) were calculated using the CDE and MIM. Basic soil properties and water infiltration parameters were also determined to explore their influence on the solute transport parameters. Both pore-water velocity and dispersion coefficient (or effective dispersion coefficient) generally decreased with increasing depth, and the dispersivity fluctuated along the soil profile. There was a good linear correlation between log-transformed pore-water velocity and dispersion coefficient, with a slope of about 1.0 and an average dispersivity of 0.25 for the entire soil profile. Generally speaking, the soil was more homogeneous along the soil profile. Our results also show that hydrodynamic dispersion is the dominant mechanism of solute transport of loess soils in the study area.

Northeast Shark River Slough (NESS), lying at the northeastern perimeter of Everglades National Park (ENP), Florida, USA, has been subjected to years of hydrologic modifications. Construction of the Tamiami Trail (US 41) in 1928 connected the east and west coasts of SE Florida and essentially created a hydrological barrier to southern sheet flow into ENP. Recently, a series of bridges were constructed to elevate a portion of Tamiami Trail, allow more water to flow under the bridges, and attempt to restore the ecological balance in the NESS and ENP. This project was conducted to determine aspects of soil physiochemistry and microbial dynamics in the NESS. We evaluated microbial respiration and enzyme assays as indicators of nutrient dynamics in NESS soils. Soil cores were collected from sites at certain distances from the inflow (near canal, NC (0–150 m); midway, M (150–600 m); and far from canal, FC (600–1200 m)). Soil slurries were incubated and assayed for CO2 emission and β-glucoside (MUFC) or phosphatase (MUFP) activity in concert with physicochemical analysis. Significantly higher TP contents at NC (2.45 times) and M (1.52 times) sites than FC sites indicated an uneven P distribution downstream from the source canal. The highest soil organic matter content (84%) contents were observed at M sites, which was due to higher vegetation biomass observed at those sites. Consequently, CO2 efflux was greater at M sites (average 2.72 µmoles g dw−1 h−1) than the other two sites. We also found that amendments of glucose increased CO2 efflux from all soils, whereas the addition of phosphorus did not. The results indicate that microbial respiration downstream of inflows in the NESS is not limited by P, but more so by the availability of labile C.

Several studies have shown that the distribution of cation adsorption sites (CASs) is patchy at a millimetre to centimetre scale. Often, larger concentrations of CASs in biopores or aggregate coatings have been reported in the literature. This heterogeneity has implications on the accessibility of CASs and may influence the performance of soil system models that assume a spatially homogeneous distribution of CASs. In this study, we present a new method to quantify the abundance and 3-D distribution of CASs in undisturbed soil that allows for investigating CAS densities with distance to the soil macropores. We used X-ray imaging with Ba2+ as a contrast agent. Ba2+ has a high adsorption affinity to CASs and is widely used as an index cation to measure the cation exchange capacity (CEC). Eight soil cores (approx. 10 cm3) were sampled from three locations with contrasting texture and organic matter contents. The CASs of our samples were saturated with Ba2+ in the laboratory using BaCl2 (0.3 mol L−1). Afterwards, KCl (0.1 mol L−1) was used to rinse out Ba2+ ions that were not bound to CASs. Before and after this process the samples were scanned using an industrial X-ray scanner. Ba2+ bound to CASs was then visualized in 3-D by the difference image technique. The resulting difference images were interpreted as depicting the Ba2+ bound to CASs only. The X-ray image-derived CEC correlated significantly with results of the commonly used ammonium acetate method to determine CEC in well-mixed samples. The CEC of organic-matter-rich samples seemed to be systematically overestimated and in the case of the clay-rich samples with less organic matter the CEC seemed to be systematically underestimated. The results showed that the distribution of the CASs varied spatially within most of our samples down to a millimetre scale. There was no systematic relation between the location of CASs and the soil macropore structure. We are convinced that the approach proposed here will strongly aid the development of more realistic soil system models.

As a new type of bridge foundation, Lattice-Shaped Diaphragm Wall (hereinafter for LSDW) is highly concerned in relevant construction area but its research is far from achievement. Based on PFC2D, the soil arching effect of LSDWs is studied thoroughly in this paper and the special attention is given to its influencing factors. It turns out to be that a differential wall-soil settlement can be found at the lower location of soil core of an LSDW which is one of the trigger factors of soil arching; meanwhile, the differential settlement degree can reflect the exertion degree of soil arching; the shape of soil arching is basically a hemisphere which can be explained by the theory proposed by Hewlett and Randolph; normally, the chamber number is a negative factor for the development of soil arching; the soil arching effect is significantly influenced by the distance of two adjacent wall elements and the foundation depth, and a relatively large or small value of these factors is disadvantageous to the exertion of soil arching; in addition, the soil arching effect increase with the growth of stiffness and friction coefficient of particles and the friction coefficient of particles has insignificant influence on the development of soil arching effect compared with particle stiffness.

Waterfowl ingest residual lead or nontoxic shotshell pellets while foraging for food in agricultural and other habitats. The Chenier Plain of Louisiana and Texas and the Texas Mid-Coast provide important habitats for wintering waterfowl, yet these regions are characterized by long traditions of waterfowl and other game-bird hunting, which potentially exposes waterfowl to historical lead pellets remaining in the environment. Recent evidence suggests that migrant and resident waterfowl within the Chenier Plain and Texas Mid-Coast regions continue to ingest lead pellets despite strict shotshell regulations. Thus, we randomly collected and radiographed soil cores (10-cm diameter and depth) from production and idled ricelands (n = 500 from each type) in the Chenier Plain (n = 760) and Texas Mid-Coast (n = 240) during November 2013 to estimate density of lead and nontoxic pellets in important waterfowl habitats of these regions. Across all regions and field types, we detected only one lead pellet and zero nontoxic pellets, despite 100% detection of known numbers of pellets in test samples. The single lead pellet was recovered from a production rice field in the Chenier Plain, yielding an estimated density of 1,019 lead pellets/ha (95% CI: 0–3,034) in this sampling region. Failure to detect lead pellets in other regions and nontoxic pellets across all regions precluded estimation but suggested pellet densities < 3,000 pellets/ha. We speculate that regular soil tillage of ricelands helps incorporate pellets into the soil, rendering all or most unavailable to our sampling and foraging by waterfowl. We recommend that future research estimate densities of lead pellets in areas where they may be concentrated (e.g., near permanent hunting blinds), where dove hunting is prevalent, and in other heavily hunted waterfowl habitats along the Gulf Coast (e.g., coastal marsh).

Elevated atmospheric CO2 (eCO2) is anticipated to have marked effects on soil microbial populations. While there is experimental evidence to support this view there are also studies where changes in microbial populations, such as the abundance of bacteria, are suggested but cannot be statistically established. We conducted this study to identify whether the sampling and sample treatment methods used could influence the results obtained using bacterial abundance as the variable of interest. We tested three different sampling methods and two different DNA extraction kits. The first because microbes are distributed heterogeneously in soil so the sampling procedure might be expected to influence the accuracy and precision of the population estimate and the second because the quantity and quality of DNA extracted influences the microbial analyses that can be performed and can introduce bias. Samples were taken from a long-running FACE experiment on grassland from under plants ofAgrostis capillaris. We found that bacterial abundance was consistently lower under eCO2 but we were only able to establish a statistical difference where a more intense sampling regime was used and bulking of the soil sample was avoided. A reduction in bacterial abundance is a consistent outcome in eCO2 field experiments but the only other occasion where this reduction has been found to be significant was also where individual soil cores were analysed rather than the samples being bulked. We conclude that while there is extra work and cost attached to more detailed sampling this approach is highly desirable if we are to make robust conclusions about the impacts of eCO2 on soil microbes.