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Introduction: Modeling and mapping of soil organic carbon concentration and distribution at the pedon scale is a current knowledge gap that can be addressed by laboratory-based hyperspectral imaging and chemometric analysis of soil cores. Despite the advancements in soil organic carbon models based on hyperspectral images, it is not clear how these models will perform upon input with images at higher resolutions than those of their training sets. This study aims to measure the generalizability of a soil organic carbon model based on a test set with higher resolution hyperspectral images than that of its training set. Methods: Organic carbon contents were measured at 10 cm intervals on eight soil cores for use as the training set and at 1 cm intervals on a single core for use as the test set. Three regression models, namely, multilayer perceptron, partial least-squares, and support vector regressions, were trained and tested with the median of each hyperspectral image for each of these intervals as the training and test predictors. Permutation importance analysis was performed to explain the models. Results: The results show that although all three models had the same validation R2 of 0.92 for cross-validation on the 10 cm data, multilayer perceptron regression allowed the best generalization with a test R2 of 0.96 compared to the partial least-squares regression (0.81) and support vector regression (0.86). It was demonstrated that the multilayer perceptron model is more robust to soil surface anomalies and that it predicts soil organic carbon on the test set by learning the spectral features related to soil organic matter chromophore activity in the 950--1,150 nm region along with clay mineralogy derived from peaks at 1,400, 1,900, 2,200, 2,250, and 2,350 nm. Conclusions: This study shows that while the regression models based on hyperspectral images perform well at the 10-cm-resolution cross validation, multilayer perceptron regression shows superior generalization and robustness for a higher 1-cm-resolution test set without much loss of prediction power. [ABSTRACT FROM AUTHOR]

Introduction: Modeling and mapping of soil organic carbon concentration and distribution at the pedon scale is a current knowledge gap that can be addressed by laboratory-based hyperspectral imaging and chemometric analysis of soil cores. Despite the advancements in soil organic carbon models based on hyperspectral images, it is not clear how these models will perform upon input with images at higher resolutions than those of their training sets. This study aims to measure the generalizability of a soil organic carbon model based on a test set with higher resolution hyperspectral images than that of its training set.Methods: Organic carbon contents were measured at 10 cm intervals on eight soil cores for use as the training set and at 1 cm intervals on a single core for use as the test set. Three regression models, namely, multilayer perceptron, partial least-squares, and support vector regressions, were trained and tested with the median of each hyperspectral image for each of these intervals as the training and test predictors. Permutation importance analysis was performed to explain the models.Results: The results show that although all three models had the same validation R2 of 0.92 for cross-validation on the 10 cm data, multilayer perceptron regression allowed the best generalization with a test R2 of 0.96 compared to the partial least-squares regression (0.81) and support vector regression (0.86). It was demonstrated that the multilayer perceptron model is more robust to soil surface anomalies and that it predicts soil organic carbon on the test set by learning the spectral features related to soil organic matter chromophore activity in the 950–1,150 nm region along with clay mineralogy derived from peaks at 1,400, 1,900, 2,200, 2,250, and 2,350 nm.Conclusions: This study shows that while the regression models based on hyperspectral images perform well at the 10-cm-resolution cross validation, multilayer perceptron regression shows superior generalization and robustness for a higher 1-cm-resolution test set without much loss of prediction power.

Currently, loosening and separating machines that combine the operations of crumbling and separating of soil according to the treated layer depth have come to the forefront. Interaction of the rotor blade of these machines with the soil comprises three stages: soil core formation; steady movement; and dumping of soil from the separating grid. The article determined the direction and magnitude of soil displacement, parameters and shape of the furrow formed after the ripper passage. Based on theoretical research, a mathematical model of the interaction of working bodies with the soil was developed. The initial data were obtained experimentally, and the model was justified. As a result, it was found that the supplied soil layer thickness and the fracture angle of ripper have the greatest influence on the transporting capacity of rotor ripper. Reducing the rotor blade entry angle into the soil from 45° to 30° made it possible to raise the second soil feed of the loosening and separating machine by more than 40 times. The width of rotor ripper practically does not affect the transporting capacity. Changing the angle of ripper entry into the soil allowed obtaining of the required transporting capacity of ripping and separating machine without changing the rotor design. Practical significance of the study lies in the possibility of increasing the work productivity without increasing its energy indicators.

Estimation of whole root biomass including coarse and larger roots and root balls can provide better understanding of carbon and nitrogen stocks in floodplain forests. Whole root systems of nine ash trees (Fraxinus angustifolia Vahl.) and six alder trees (Alnus glutinosa L.) trees ranging in diameter breast height (dbh) from 29.1 to 72.0 cm for ash and from 29.1 to 44.3 cm for alder were excavated, and their small < 1 cm, medium 1–4 cm, larger > 4 cm and root-ball biomass, and root carbon and nitrogen stocks were determined in Karacabey floodplain forest in Bursa, Turkey. In addition, for the method comparison, small root biomass (< 1 cm) was also determined using soil-core method. The whole root biomass of ash trees varied from 167.7 to 186.8 Mg ha−1. Alder trees had lower whole root biomass than ash trees ranging from 49.0 to 63.6 Mg ha−1. The determination of small root biomass by soil excavation method was nearly two-fold higher than by soil core method. Both root carbon and nitrogen stocks showed an increase with increasing root diameter. Among the tree characteristics (dbh, age, height, and volume), the dbh showed the highest correlation with whole root biomass and root carbon and nitrogen stocks for both tree species. It is concluded that young trees can have higher small, medium, and large root biomass and store more C and N in those roots, whereas older trees can have higher root-ball biomass and root-ball carbon and nitrogen stocks in Karacabey floodplain forests. [ABSTRACT FROM AUTHOR]

Optimal sampling strategy is vital in root studies because of the high degree of variability found in the belowground ecosystems. To inform the appropriate sample size, ninety-six cores and minirhizotrons in a subtropical evergreen broadleaved forest were used to examine diameter-related variation in the distribution of root length and volume, and assess the effects of sample size on estimation accuracy and sample representativeness. The variation coefficients of root traits estimated by the minirhizotron method were much higher than those estimated by the soil core method. Furthermore, minirhizotrons observed higher proportions of root length and volume in small diameter classes, reflecting thinner roots than those estimated by the soil core method. The Monte Carlo simulation analysis shows that, for the 0–5 mm diameter class, under a confidence level of 90% and estimation accuracy of 80%, the sample size for soil cores required to estimate the root length and volume are 5 and 12, respectively, and for minirhizotrons being 54 and over 96, respectively. The cumulative root diameter class curve analysis shows that the sample sizes required to encounter 80%, 90% and 95% of all diameter classes for soil cores are 3, 6 and 10, respectively, and for minirhizotrons being 38, 61 and 77, respectively. We conclude that due to the fractal distribution of root diameter, and the difference in sampling volume between different methods, larger sample sizes are required for minirhizotrons or larger-diameter roots than for soil cores or smaller-diameter roots to achieve better estimation accuracy and sampling representativeness. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change. [ABSTRACT FROM AUTHOR]

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 roots 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. Highlights: Selected root traits for increased depth, density and diameter may increase SOC in grassland.The effect of two high‐yielding forage grass cultivars were assessed in a field trial.Fast‐growing, high‐yielding cultivars enhanced root and SOC stocks compared to typical pasture.Lipid biomarkers confirmed that root inputs were the predominant C input to soil. [ABSTRACT FROM AUTHOR]

Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change.

Study region: This study used intact soil cores collected at the Boulder Creek Critical Zone Observatory near Boulder, Colorado, USA to explore fire impacts on soil properties. Study focus: Three soil scenarios were considered: unburned control soils, and low- and high-temperature burned soils. We explored simulated fire impacts on field-saturated hydraulic conductivity, dry bulk density, total organic carbon, and infiltration processes during rainfall simulations. New hydrological insights for the region: Soils burned to high temperatures became more homogeneous with depth with respect to total organic carbon and bulk density, suggesting reductions in near-surface porosity. Organic matter decreased significantly with increasing soil temperature. Tension infiltration experiments suggested a decrease in infiltration rates from unburned to low-temperature burned soils, and an increase in infiltration rates in high-temperature burned soils. Non-parametric statistical tests showed that field-saturated hydraulic conductivity similarly decreased from unburned to low-temperature burned soils, and then increased with high-temperature burned soils. We interpret these changes result from the combustion of surface and near-surface organic materials, enabling water to infiltrate directly into soil instead of being stored in the litter and duff layer at the surface. Together, these results indicate that fire-induced changes in soil properties from low temperatures were not as drastic as high temperatures, but that reductions in surface soil water repellency in high temperatures may increase infiltration relative to low temperatures.

Biochars are widely applied to improve soil pore structures. However, the quantitative effects of biochars on soil macropore networks still remain unclear. In this study, the effects and possible mechanism of biochar application on soil macropore networks were investigated quantitatively by industrial X‐ray microtomography (CT), a pore network model and network analyses. Soil cores of 5 cm in diameter and 10 cm in height were collected from a paddy soil (Typic Haplustalf) without biochar application (CK), and amended with rice straw biochar (RSB), corn straw biochar (CSB) and bamboo biochar (BB) at a rate of 25 Mg ha−1 (w/w). Results revealed that the total and connected macroporosity of the biochar‐amended soil was reduced significantly compared with CK, whereas the reverse was true for the isolated porosity. The three types of biochars exhibited different effects on macropores of the soil, depending on their size and shape. The pore network model and network analyses showed that the physical and topological structures of macropore networks in biochar‐amended soil were clearly reconfigured. The accessibility of these macropore networks was markedly reduced. Our results indicated that the incorporation of biochar did not necessarily increase the soil's macroporosity. The combination of pore network model and network analyses was effective for quantifying key properties of soil macropore networks affected by the incorporation of biochar. The changes in these properties may be used to evaluate the effects of biochar on water, air and nutrient transport. Highlights: Effect of biochars on the soil macropore structure was studied by industrial CT.Macropore network structure was quantified by a pore network model and network analyses.Biochar incorporation markedly changed the accessibility of the soil macropore network.The macropore network of soil can be reconfigured following biochar addition. [ABSTRACT FROM AUTHOR]

Pattern of vertical distribution of plant roots determines plant water and nutrient uptake and influences various soil processes under field conditions. However, information of root distribution in the whole rooting profile is rarely available in practice. This paper documents a method to quickly quantify root vertical distribution pattern using limited root length density data obtained from soil cores under field conditions. It was implemented through the development of a Minitab macro and an R script, with sample calculations conducted on field collected root length density data from the winter wheat crop in Texas, USA. The method is potentially useful for quantifying plant root activities in natural soils where deep roots are difficult to access by physical means and data of root length density distribution are only available in the upper root zone. [ABSTRACT FROM AUTHOR]

Sampled soil volume is a main experimental factor which must be properly considered to obtain a reliable estimation of soil physical quality (SPQ) and, thus, to obtain credible evaluation of the impact of a conservative-conventional soil management system on the soil air–water relationship. In this investigation, two ring sizes were used to sample two fine textured soils and soil management for durum wheat cultivation, namely, conventional tillage (CT) and no-tillage (NT). The soil water retention was determined; soil bulk density (BD), macroporosity (MACpor), air capacity (AC), and relative field capacity (RFC) were estimated to assess the soil physical quality indicators, in agreement with the guidelines suggested in the literature. The main results showed that the sampling volume of the soil affected the soil water retention estimation (θ) and, consequently, affected the SPQ estimation, given that (i) higher θ values (by a factor 1.11 as mean) were generally obtained with a large diameter than a small one; these differences decreased (by a factor 1.20, 1.10 and 1.03) as the imposed pressure head value decreased (respectively, at h = 0, −10 and −100 cm); (ii) among SPQ indicators considered, soil volume samples seemed to impact the BD–RFC estimation more than AC–MACpor, as statistical differences were identified only in the former case; iii) NT soil was significantly more compact, and had lower macroporosity or air capacity, when compared with CT; at the time of sampling, the mean SPQ was always poor for AC–RFC, or optimal for BD, regardless of soil management, and it was intermediate or poor when the MACpor was evaluated under CT or NT. This study contributes toward understanding the impact of soil management on soil physical properties in Mediterranean agro-environments.

This research demonstrates the importance of “perches”, a hard, impermeable sub-surface layer, for ephemeral wetland development in a semi-arid area. Over 1700 wetlands were identified in the Nelson Mandela Bay Municipality (NMBM), Eastern Cape, South Africa. The average wetland density in the Municipality is approximately nine wetlands per 10 km 2 . This density is high considering the climate of the NMBM, where annual evapotranspiration rates are approximately three times higher (1800 mm) than the average annual rainfall (613 mm). The NMBM is diverse in terms of its climate, vegetation types, geomorphology and underlying geology. This environmental diversity has resulted in a range of wetland types. Previous research in the Municipality has indicated that the majority of these systems are precipitation driven, with minimal groundwater input. Therefore, other environmental processes facilitate the formation of wetlands. For this study, data from 46 wetland sites were used that were situated across the different environments in the NMBM (geology, climate etc.). Thirty-four wetlands were perched, and were from all three of the different wetland types studied: depressions, seeps and wetland flats. A dense clay layer was found at 14 sites, across different geological and sediment types. Calcrete lenses were recorded at seven sites that were associated with aeolian deposits. A shallow bedrock layer was also observed at nine sites on quartzitic sandstones of the Peninsula Formation. In conclusion, this study has highlighted that perches are key for wetland development in some semi-arid areas. [ABSTRACT FROM AUTHOR]

Estimation of belowground net primary production ( BNPP) is crucial for prediction of grassland soil organic carbon sequestration, but there are high coefficients of variation ( CV) among methods of estimation. We compared accuracy and precision of two variations of the traditional soil core method and three of the ingrowth core method, over 2 years on grass-white clover swards in Germany. The ingrowth core method (5- to 9-week ingrowth period) provided the most accurate BNPP estimate (471 g m−2) with the highest precision ( CV: 31%), whereas the two soil core approaches resulted in underestimation and high error. Comparing results with other grassland studies, we found that reliability of the ingrowth core method was influenced by ingrowth period and sward rooting pattern related to grass phenological stages, while the precision was determined by ingrowth period and grassland productivity. We therefore recommend using the ingrowth core method for managed grasslands where belowground productivity is relatively high and installation disturbance is likely to be negligible. Using a 6- to 8-week ingrowth period, the method delivers reliable and feasible BNPP estimates for temperate managed grasslands which can be applied to long-term soil carbon budget simulation. Results from our work and other studies also indicated that standing root biomass masks seasonal pattern of rooting due to synchrony between root birth and death. The soil core method is likely to lead to underestimates and higher errors than the ingrowth core methods and thus should be avoided. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) are highly hydrophobic compounds with low migration potential in soil–water. Nevertheless, they have been occasionally reported in subsurface soils hypothesised as the result of facilitated transport processes with colloids or surfactants, or yet unidentified in-situ formation processes. To date, however, the prevalence of deep soil contamination, involved processes and their kinetics remain poorly understood. This study investigated PCDD/F concentrations and isomer profiles through deep soil cores (to 20 m) from agricultural, industrial and urban sites in Queensland, Australia. Based on isomer profiles, a unique source common to all core soils (regardless of depth) was identified, dominated by octachlorodibenzo- p -dioxin (OCDD). The source was consistent with contamination resulting from pesticide impurities. Elevated PCDD concentrations (μg/kg range) to depths up to ∼4–17 m and a continuous increase of peri-chlorinated (1,4,6,9-substituted) isomers through the cores suggested that vertical transport and lateral dechlorination were key post-depositional processes at these sites. The mobility of PCDDs in the present study is far greater than previously reported in soils in general. High estimated mass transport rates for OCDD in four agricultural cores (3.0–6.2% year −1 ) likely reflect significant levels of facilitating species, including surfactants, and intensive rainfall at these sites. The implications of such extensive subsurface transport of PCDD/Fs for groundwater contamination and load estimates may be significant. If the cores of the present study are assumed representative of the region, a total PCDD/F load in the order of 800 tonnes (1.6 tonnes TEQ) could be present in subsurface Queensland coastal soils. [ABSTRACT FROM AUTHOR]

Large quantities of radiocesium were deposited across a 3000 km 2 area northwest of the Fukushima Dai-ichi nuclear power plant after the March 2011 accident. Although many studies have investigated the fate of 137 Cs in soil in the months following the accident, the depth distribution of this radioactive contaminant in rice paddy fields requires further examination after the typhoons that occurred in this region. Such investigations will help minimize potential human exposure in rice paddy fields. Radionuclide activity concentrations, organic content and particle size were analysed in 10 soil cores sampled from paddy fields in November 2013, 20 km north of the Fukushima power plant. Our results demonstrate limited depth migration of 137 Cs with the majority concentrated in the uppermost layers of soils (<5 cm). More than 30 months after the accident, between 46.8 and 98.7% of the total 137 Cs inventories was found within the top 5 cm of the soil surface, despite cumulative rainfall totalling 3300 mm. Furthermore, there were no significant correlations between 137 Cs depth distribution and the other parameters. We attributed the maximum depth penetration of 137 Cs to grass cutting (73.6–98.5% of 137 Cs in the upper 5 cm) and farming operations (tillage – 46.8–51.6% of 137 Cs in the upper 5 cm). As this area is exposed to erosive events, ongoing decontamination works may increase soil erodibility. We therefore recommend the rapid removal of the uppermost – contaminated – layer of the soil after removing the vegetation to avoid erosion of contaminated material during the subsequent rainfall events. Further analysis is required to thoroughly understand the impacts of erosion on the redistribution of radiocesium throughout the Fukushima Prefecture. [ABSTRACT FROM AUTHOR]

Estimation of whole root biomass including coarse and larger roots and root balls can provide better understanding of carbon and nitrogen stocks in floodplain forests. Whole root systems of nine ash trees (Fraxinus angustifolia Vahl.) and six alder trees (Alnus glutinosa L.) trees ranging in diameter breast height (dbh) from 29.1 to 72.0 cm for ash and from 29.1 to 44.3 cm for alder were excavated, and their small < 1 cm, medium 1-4 cm, larger > 4 cm and root-ball biomass, and root carbon and nitrogen stocks were determined in Karacabey floodplain forest in Bursa, Turkey. In addition, for the method comparison, small root biomass (< 1 cm) was also determined using soil-core method. The whole root biomass of ash trees varied from 167.7 to 186.8 Mg ha -1 . Alder trees had lower whole root biomass than ash trees ranging from 49.0 to 63.6 Mg ha -1 . The determination of small root biomass by soil excavation method was nearly two-fold higher than by soil core method. Both root carbon and nitrogen stocks showed an increase with increasing root diameter. Among the tree characteristics (dbh, age, height, and volume), the dbh showed the highest correlation with whole root biomass and root carbon and nitrogen stocks for both tree species. It is concluded that young trees can have higher small, medium, and large root biomass and store more C and N in those roots, whereas older trees can have higher root-ball biomass and root-ball carbon and nitrogen stocks in Karacabey floodplain forests., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The vertical distribution of polybrominated diphenyl ethers (PBDEs) in soil at four sites within an e-waste recycling region of South China was investigated. PBDE concentrations in soil ranged from 1.38 to 765 ng/g. There was a trend of decreasing PBDE concentration with soil depth, especially in the paddy field. However, high concentrations of BDE-209 were found in deeper soils indicating a highly preferential migration. There was a stronger correlation between PBDEs and total organic carbon (TOC), compared to dissolved organic carbon (DOC), which suggests that the association between non-dissolved organic carbon (NDOC) and PBDEs is stronger than for DOC. Different land use types, in particular differences in farming activities, significantly influenced the vertical distribution of PBDEs in soils. PBDEs displayed a higher leaching tendency in moist paddy soil than in drier soils. The frequent flooding condition in paddy field may facilitate the vertical transfer of PBDEs to the deeper soils. [Copyright &y& Elsevier]

Highlights: [•] Deficit irrigation increased root growth in cv. Mission (cantaloupe; reticulatus). [•] Deficit irrigation had no adverse impact on melon fruit quality. [•] Significant water savings were obtained with deficit irrigation in cvs. Mission and Da Vinci (tuscan; reticulatus). [•] Due to high yield reduction, deficit irrigation may not be applicable for cv. Super Nectar(honeydew;inodorus). [Copyright &y& Elsevier]

Abstract: Increasingly biologists and ecologists are becoming aware of the vital importance of soil to processes observed aboveground and are incorporating soil analyses into their research. Because of the dynamic and heterogeneous nature of soil, proper incorporation of soil analysis into ecological studies requires knowledge and planning. Unfortunately, many ecologists may not be current (or trained at all) in soil science. We provide this review, based on our cumulative >60 years of work in soil science, to help familiarize researchers with essential information to appropriately incorporate soil analyses into ecological studies. Specifically, we provide a brief introduction into soils and then discuss issues related to soil sterilization, choosing a soil for a greenhouse project, sampling soils, and soil analyses. [Copyright &y& Elsevier]

Root systems are important for global models of below-ground carbon and nutrient cycling. Notoriously difficult sampling methods and the fractal distribution of root diameters in the soil make data being used in these models especially susceptible to error resulting from under-sampling. We applied the concept of species accumulation curves to root data to quantify the extent of under-sampling inherent to minirhizotron and soil coring sampling for both root uptake and carbon content studies. Based on differences in sample size alone, minirhizotron sampling missed approximately one third of the root diameters observed by soil core sampling. Sample volumes needed to encounter 90% of root diameters averaged 2481 cm3 for uptake studies and 5878 cm3 for root carbon content studies. These results show that small sample volumes encounter a non-representative sample of the overall root pool, and provide future guidelines for determining optimal sample volumes in root studies. [ABSTRACT FROM AUTHOR]

The anaerobic ammonium-oxidizing (anammox) and nitrite-dependent anaerobic methane-oxidizing (n-damo) bacteria in a paddy soil core (0-100 cm) were investigated with newly designed primers targeting the hydrazine synthase β-subunit ( hzsB) of anammox bacteria and the recently published primers targeting the pmoA and 16 S rRNA genes of n-damo bacteria. The hzsB gene was identified as a proper biomarker to explore the anammox bacterial biodiversity and abundance in soil. The anammox bacteria were present throughout the soil core with the highest abundance of 2.7 × 106 hzs B copies g−1 dry soil at 40-50 cm and were not detectable below 70 cm. Sequences related to at least three species of known anammox bacteria, ' Brocadia anammoxidans', ' Brocadia fulgida', and ' Jettenia asiatica' were detected. By combining the analysis of pmoA and 16 S rRNA genes, the n-damo bacteria were observed to be present in 30-70 cm with abundance from 6.5 × 103 (60-70 cm) to 7.5 × 104 (30-40 cm) copies g−1 dry soil. The pmoA sequences retrieved from different depths closely related to each other and formed a unique clade. Our results showed that anammox and n-damo bacteria co-occurred in the paddy soil. Both of them were abundant in deep layers (30-60 cm) and the community structures changed along depths in the soil core. [ABSTRACT FROM AUTHOR]

Abstract: Dongjiang (East River) is the key resource of potable water for the Pearl River Delta region, South China. Although industrial activities are limited in the water conservation area along this river, agriculture is very intensive. The present study evaluated trace metals in four soils under different cultivation. The total concentrations of trace metals decreased in the order orchard soil>vegetable soil>paddy soil>natural soil, reflecting decreasing inputs of agrochemicals to soils. Relatively high concentrations of Cd were recorded in the 60-cm soil profiles. The 206Pb/207Pb ratio in the above-ground tissues of plant was significantly lower than their corresponding soils. In combination with the low transfer factor of Pb from soil to plant shoots, atmospheric deposition is probably a major pathway for Pb to enter plant leaves. Regular monitoring on the soil quality in this area is recommended for the safety of water resource and agricultural products. [Copyright &y& Elsevier]

37 PBDE congeners were analyzed at six different depths in two soil cores taken from a typical electronic waste polluted area in South China. The PBDEs were congregated in the surface layer (0–5 cm) of soil cores and were 29 times in MK and 18 times in NW higher than the second lower layers (5–10 cm). As a whole, the concentrations of PBDEs were decreased with the soil depth increased in two cores. Lower brominated PBDE had higher penetrability than the deca-BDE in soil. The deca-BDE could be detected in deeper soil layers (15–20 cm in MK and 20–30 cm in NW) and the percentage of deca-BDE decreased with the increase of depth. [ABSTRACT FROM AUTHOR]

To verify the possibility of developing a sampling method to accurately describe the Norway spruce ectomycorrhizal community at plant level, research was conducted in four comparable monospecific forests on healthy, mature and coeval Norway spruce trees. The results showed that the lowest number of tips per root core can characterize the community changes from site to site, with tree species, age and sampling design being constant. This highlights the importance of ectomycorrhizal species distribution, which is not an intrinsic character of ectomycorrhizal species, and probably changes with the environmental and fungal community features. The research demonstrated, in accordance with a theoretical ectomycorrhizal distribution, the effectiveness of an encoded geometrical sampling design consisting of the collection of 24 root samples from each of the four unrelated plants, along four perpendicular directions and at six fixed distances from the collar, and with the observation of 10 randomly selected ectomycorrhizal tips per sample. [ABSTRACT FROM AUTHOR]

Abstract: In a pear orchard, when leaf senescence occurs, nitrogen (N) is added to the soil by the fallen leaves and can be re-used by the tree after undergoing decomposition and mineralization processes. Studies on leaf decomposition and N mineralization in orchards are scarce but essential to understand the N balance in the tree–soil ecosystem in a sustainable or precision agriculture. This study aimed to quantify the contribution of pear tree senescent leaves to N cycling in the orchard and its re-cycling by the crop. ‘Rocha’ pear unlabelled leaves were incubated in situ using the litter-bag technique and 15N-enriched leaves were placed at the soil surface in undisturbed confined cores. One- to six-year-old pear trees returned to the soil between 1kgNha−1 year−1 and 6kgNha−1 year−1 from senescent leaves that decomposed at rates varying from 0.0025day−1 (d−1) to 0.0047d−1 (estimated by both techniques, respectively). In the litter-bags, after 506–641 days, only 18–35% of initial DW was recovered in the soil, whereas in the soil cores the weight loss was higher, resulting in only 30–6% of initial DW after 398–406d. After this period, between 36% and 110% of the initial N of the senescent leaves was recovered as organic 15N in the surface soil layer (0–7.5cm), depending on climatic conditions, and being more prone to be absorbed by weeds. [Copyright &y& Elsevier]

The ecotoxicology of a soil core collected from a disused industrial area near Naples (Italy), contaminated by hydrocarbons and heavy metals, was investigated and the relationships between toxicity and pollutant concentrations were considered. The ecotoxicological evaluation was performed by acute and chronic toxicity tests both on the whole soil and on aqueous and organic extracts, utilizing organisms belonging to different trophic levels: the bioluminescent bacterium Vibrio fischeri, the green microalga Selenastrum cap ricornutum, the plants Sinapis alba, Lepidium sativum and Sorghum saccharatum, the cladoceran Daphnia magna, and the ostracod Heterocypris incongruens. Toxicity measured with the whole soil was lower than those obtained with both soil organic and aqueous extracts and did not seem comparable with the vertical trend of organic and inorganic contamination. V. fischeri identified the toxic effects due to the chemical interaction and/or to the undetectable contaminants in the whole soil. Phytotoxicity tests revealed as the most sensitive ones. Particularly, S. cap ricornutum was able to evidence the long term effects of both organic and inorganic contaminants, while plant tests mainly identified the stimulating effects of trace elements. [ABSTRACT FROM AUTHOR]

1 Elucidation of the patterns and controls of forest net primary production at ecosystem scales has been hindered by a poor understanding of fine root production, due largely to technical limitations. 2 Fine root (≤ 0.5 mm diameter) production was assessed using minirhizotron, soil core, ingrowth core, nitrogen budget and carbon budget techniques in three longleaf pine-wiregrass forest ecosystem types (hydric, mesic and xeric) forming an edaphic resource availability and above-ground productivity gradient. 3 Fine root production estimates differed substantially in magnitude, e.g. values ranged from 0 to 4618 kg ha−1 year−1 for the soil core and minirhizotron techniques, respectively, in the hydric site. 4 Minirhizotron production estimates in the hydric, mesic and xeric sites were 4618, 1905 and 2295 kg ha−1 year−1, respectively. 5 Soil core and ingrowth core root production estimates were on average 81 and 54% lower, respectively, than corresponding minirhizotron production estimates, and minirhizotron estimates were negatively related to soil core and ingrowth core estimates across the resource gradient. 6 The N budget method yielded unreliable root production estimates, presumably due to the underestimation of N availability for plant assimilation. 7 C budget estimates of total below-ground C allocation (6773, 5646 and 4647 kg C ha−1 year−1) were positively related to minirhizotron production estimates, but negatively related to soil core and ingrowth core production estimates. 8 Critical evaluations of the assumptions, potential errors and results for each method suggest that the minirhizotron technique yielded the most reliable root production estimates, and that the negative relationship between minirhizotron and core-based estimates may be attributed to the inherent deficiency of the core techniques in assessing root production when mortality and production occur simultaneously. 9 Minirhizotron root production estimates were positively related to foliage production estimates, supporting the hypothesis of constant proportional allocation of production to foliage, wood and fine roots across resource availability gradients in temperate forests. 10 These results suggest that fine root production is not negatively correlated with soil resource availability and foliage production as is commonly perceived in the ecological community and represented in ecosystem computer models. [ABSTRACT FROM AUTHOR]

Abstract: Dilution of high-sodicity soil water by low-sodicity rainfall or irrigation water can cause declining soil hydraulic conductivity (K) by inducing swelling, aggregate slaking and clay particle dispersion. Investigations of sodicity-induced reduction in K are generally restricted to repacked laboratory cores of air-dried and sieved soil that are saturated and equilibrated with sodic solution before tests are conducted. This approach may not yield a complete picture of sodicity effects in the field, however, because of loss of antecedent soil structure, small sample size, detachment of the sample from the soil profile, reliance on chemical equilibrium, and differing time scales between laboratory and field processes. The objectives of this study were to: (i) compare the electrical conductivity (EC), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) in laboratory cores of intact field soil that had, or had not, undergone prior saturation and equilibration with sodic solution; (ii) compare the pressure infiltrometer (PI) field method with the intact laboratory soil core (SC) method for assessing sodicity effects on saturated soil hydraulic conductivity; and (iii) characterize hydraulic conductivity reduction in a salt-affected sandy loam soil and a salt-affected clay soil in Sicily as a result of diluting high-sodicity soil water with low-sodicity water. In terms of EC, ESP and SAR, quasi-equilibrium between soil and infiltrating solution was attainable in 0.08 m diameter by 0.05 m long laboratory cores of intact clay soil, regardless of whether or not the cores were previously saturated and equilibrated with solutions of SAR=0 or 30. In the sandy loam soil, the PI and SC methods produced statistically equivalent linear reductions in K as a result of diluting increasingly sodic soil water (SAR=0, 10, 20, 30) with deionised water. In the clay soil, the PI method produced no significant correlation between initial soil water SAR and K reduction, while the SC method produced a significant log-linear decline in K with increasing soil water SAR. Sodicity-induced reductions in K ranged from 3–8% (initial soil water SAR=0) to 85–94% (initial soil water SAR=30) in the sandy loam, and from 9–13% (initial soil water SAR=0) to 42–98% (initial soil water SAR=30) in the clay. The reductions in K were caused by aggregate slaking and partial blocking of soil pores by dispersed clay particles, as evidenced by the appearance of suspended clay in the SC effluent during infiltration of deionised water. As a result, maintenance of K in these two salt-affected soils will likely require procedures to prevent or control the build-up of sodicity. [Copyright &y& Elsevier]

Two approaches are set forth to explain the sense of the process of soil core self-discharging from a pipe under the action of impact load generating anomalously low friction and oncoming pressure on the core. Some objects are stated for further experimental investigations. [ABSTRACT FROM AUTHOR]