10-cm Layer Research Articles

Characteristics of soil organic carbon fractions under different land use patterns in a tropical area

To explore the effects of land use patterns on the accumulation of soil organic carbon (SOC) fractions in tropical areas, soil samples from paddy fields, abandoned croplands and vegetable-growing lands were collected at depths of 0–10, 10–20 and 20–30 cm in Hainan province, China. The particulate organic carbon (POC) and mineral-associated organic carbon (MOC) concentrations in soil samples were determined, and their distribution characteristics were analysed. The results showed that MOC is the main component of SOC, with an average MOC/SOC ratio of 0.65. The POC and MOC concentrations showed a trend of paddy field > abandoned cropland > vegetable-growing land and gradually decreased with an increase in soil depth. The POC concentrations in the 0–10-cm soil of the paddy field and abandoned cropland were significantly higher than those of the 20–30-cm layers, and the MOC concentration in the 0–10-cm soil layer of the paddy field was significantly higher than that of the 10–20 and 20–30 cm layers. Correlation analysis showed that POC and MOC had a significant positive correlation with SOC, a significant negative correlation with soil particulate diameter and a weak correlation with pH and Eh. Therefore, soil tillage and fertilisation under different land use patterns have a great influence on organic carbon fractions, and paddy fields have high carbon sequestration potential.

Liquid swine manure as a sidedressed nitrogen source for corn

AbstractSidedressing liquid swine (Sus scrofa) manure (LSM) on corn (Zea mays L.) may provide additional time to apply manure and help better match crop‐nutrient demand with nutrient supply. A 2‐yr, on‐farm study was conducted in Minnesota to assess three sidedress nutrient sources—injected LSM via dragline hose, anhydrous ammonia (AA), and urea ammonia nitrate (UAN)—against a non‐sidedressed control. At planting, all treatments (including the control) received 46 kg N ha−1 as starter fertilizer. At sidedressing, 157 kg N ha−1 of available N was targeted for application with the different N sources at the fourth leaf collar stage of corn (V4). Sidedressing did not affect plant population compared with the non‐sidedressed control in 2018, but sidedressed LSM reduced plant population by 6% relative to the control in 2019, likely due to wet soil conditions and manure injection settings that partially buried plants. In 2018, LSM produced comparable grain yield and net return to sidedressing costs as AA and UAN, despite lower soil ammonium and nitrate levels in the 0‐ to 15‐cm soil layer approximately 12 d after application. In 2019, LSM led to 18–25% lower grain yield than AA and UAN and lower net returns because of a combined plant population reduction and an application of 50 kg plant available N ha−1 less than expected. Sidedressing corn with LSM is a viable alternative to commercial fertilizers, although to realize consistent results, better fine‐tuning of application rate, depth, and speed under different soil moisture conditions may be needed.

Effects of manure on topsoil and subsoil organic carbon depend on irrigation regimes in a 9-year wheat-maize rotation

On the North China Plain, low soil organic carbon (SOC) content and a consistently dropping underground water level are seriously threatening food production security. To date, the interactive effect of fertilization types and irrigation regimes on surface and subsurface SOC contents has rarely been quantified. Here, we conducted a field study of three irrigation regimes with two fertilization types between 2009 and 2018. The three irrigation regimes included presowing irrigation (W0); presowing and jointing irrigation (W1); and presowing, jointing and anthesis irrigation (W2). The two fertilization types were mineral fertilizer only (CF) and mineral fertilizer plus composted chicken manure (CFM). Soil samples were collected from a depth of 0−100 cm in 20-cm increments to measure SOC and its composition, including labile pool I (LPI) (polysaccharides), labile pool Ⅱ (LPⅡ) (cellulose), and recalcitrant pool (RCP). Four SOC-related enzymes were determined, i.e., α-glucosidase, β-glucosidase, peroxidase and polyphenol oxidase. Stable carbon isotopic (13C) analysis was determined to distinguish the contributions of wheat- and maize-derived SOC in a wheat-maize rotation. The results showed that the 0−20-cm SOC content was highest in the W0 + CFM treatment. In the 0−20-cm layer, SOC decreased from W2 to W1 or W0 under CF, which is attributed to a reduction in the labile pool and maize-derived C and higher polyphenol oxidase. Conversely, under CFM, the 0−20-cm SOC content increased following decreased irrigation from W2 to W1 and from W1 to W0, mainly due to the increased LPⅡ and RCP. Compared with CF at W0 and W1, the 0−20-cm SOC content increased by 30.5 % and 21.8 % under CFM, respectively. Relative to the 0−20-cm soil layer, the SOC stock was larger in the 20−100-cm layer, which of the treatments had a variation manner similar to the 0−20-cm soil layer. Our results suggest that reduced irrigation regimes have significantly reduced the SOC stock and altered its composition in the 0−100-cm soil layer under CF and that CFM can increase the SOC stock in this layer when reducing the irrigation regime.

Impact of novel materials on alkalinity movement down acid soil profiles when combined with lime

Subsurface soil acidity in conjunction with aluminium (Al3+) toxicity is a major limitation to agricultural production globally. The conventional use of surface-applied lime is often insufficient at correcting subsurface acidity; therefore, new practices and ameliorants are required. This 3-month leaching experiment investigated whether animal wastes and other novel ameliorants in combination with lime could improve alkalinity movement, leading to greater amelioration of acid subsurface soil layers compared with lime alone. Five ameliorants (mature dairy compost, vegetable garden compost, poultry litter, potassium humate and gypsum) were added at a rate of 18 mg dry matter g−1 to the topsoil layer either without or with lime (target pH 5.5). All ameliorants with lime improved alkalinity movement below the amended layer (0–10 cm), with pH increases of 0.03–0.10 units at 1 month and 0.02–0.20 units at 3 months. In comparison, the Al3+ concentrations in 10–12-cm and 12–15-cm layers were significantly decreased by 2–5.5 μg g−1. With lime, the improvements in alkalinity movement with ameliorants were in the order of gypsum > vegetable garden compost > potassium humate > poultry litter > mature dairy compost. Without lime, each amendment increased soil pH in the subsoil, with their effectiveness decreasing in the order of poultry litter > vegetable garden compost > mature dairy compost > gypsum > potassium humate. Some organic amendments are effective in addressing subsoil acidity. When combined with lime, their additive effects are limited.

Simulating sulfosulfuron fate in soil under different weather scenarios to support weed management decisions.

Residual herbicides are an important component in many weed control strategies. Their herbicidal activity depends on their fate in soil, with respect to the required concentration for weed control in space and time. In this study, the effect of weather conditions on sulfosulfuron fate in soil, following pre-planting incorporation, and the predicted control efficacy of Egyptian broomrape in tomato, were analyzed for two sites using simulations in Hydrus-1D modeling software. Simulated concentration was compared to measured data from field experiments. Model evaluation against measured data from two fields, with weakly alkaline clay soils, showed high correlations between simulated and measured sulfosulfuron concentrations (r = 0.98 and 0.89). The ratio of measured to simulated concentration was relatively low (1.03) at the top 10-cm layer, in which the mean measured concentration was high (29.6 ng g-1 ). This ratio was higher (12.5) at the 30-60 cm depth, in which the mean measured concentration was lower (0.3 ng g-1 ). Simulations of sulfosulfuron fate in each site, using weather data from the years 2009 to 2019, revealed substantial variations in transport patterns. Thirty days after treatment, 16 out of the 22 years simulated for the two sites (11 at each site) resulted in concentrations lower than the critical value for Egyptian broomrape control throughout the soil profile. The data indicates that variation in sulfosulfuron fate is mainly due to differences in the cumulative precipitation. According to simulation results, cumulative precipitation above 20 or 10 mm during the first 10 or 20 days after treatment, respectively, is expected to reduce the efficiency of broomrape control. Considering weather effects when planning herbicide application could optimize herbicide use efficiency. A decision-support tool is presented, whose factors are the time gap and precipitation amount between sulfosulfuron application and tomato planting.

Distribution of organic carbon storage in different salt-marsh plant communities: A case study at the Yangtze Estuary

The high carbon (C) sequestration potentials of coastal wetlands play an important role in mitigating climate change associated with the greenhouse effect. In the present study, soil samples were collected from the 0–30-cm topsoil layers and from 0 to 100-cm cores for the analysis of the spatial dynamics and vertical distribution of organic carbon (OC) and biomass in different vegetation zones in a small tidal basin in Chongming Dongtan wetland. According to the results, sediments in the region were a mixture of terrestrial and marine sources and the proportions of terrestrial components decreased with an increase in depth. In addition, soil properties were quite similar in the top-soil layer. In the study area, the OC concentration was in the 0.7–10.93 g/kg range, which was positively correlated with halophyte biomass and negatively correlated with soil salinity and particle size. Furthermore, OC content decreased with an increase in depth. The OC content in different halophyte communities was in the order of Phragmites australis community > Mixed community > sedge community, and was consistent with the gross biomass. The total C sequestered of 100-cm depth in the area was 31,177 ton, with the P. australis community, mixed community, sedge community, and water sequestering 57.7, 49.2, 25.5 t/ha, and 8 t/tidal cycle, respectively. Tidal marshes in Chongming Dongtan exhibited a high C sequestration capacity, indicating that they play a major role in the C cycle in the Yangtze Estuary.

Forest carbon stock in Left-bank Forest-Steppe of Ukraine according to intensive forest monitoring data

The issues of carbon stock and dynamic in different carbon pools in forest stands of Left-bank Forest-steppe of Ukraine are considered. The aim of the study was to evaluate carbon stocks and their changes in main pools: trees biomass and mortmass. Data of two repeated observations on 19 permanent intensive forest monitoring plots in Kharkiv and Sumy regions were used. Conversion method was used. 
 Study of increment and mortality dynamics at monitoring plots showed, that two processes impact carbon balance: biotic damage which leads to trees dieback, and partial removal of dead wood from stands.
 Oak stands have, on average, higher carbon stock in trees biomass and mortmass (102.9 t С ha-1) than the pine stands (98.7 t С ha-1), which is associated with a higher representation of mature and overmature oak stands. While comparison by age classes showed that pine stands, in general, have higher values of C in trees biomass, due to higher productivity. The increase in carbon stocks with age is observed. 
 The annual change of C stock in trees biomass is the highest in younger stands, and it decreases with age; while in mortmass it increases. Mature and overmature oak stands have negative trees biomass and positive dead wood growth.
 At age 81-100 years oak forest stands have higher carbon storage capacity than pine (total carbon stock in main pools (biomass, mortmass, litter and soils (30-cm layer)) is 191.7 t C ha-1 for oak and 175.4 t C ha-1 for pine stands). Trees biomass carbon prevails among other pools (50.3 % in oak forests, and 57.6% in pine), the next is soil carbon pool (45.9 and 29.0%, respectively). 
 National forest inventory will provide data for assessments of carbon stocks and dynamics in trees biomass and mortmass pools. However, forest soil monitoring is necessary to evaluate carbon pools in soils and litter.

Spectral analysis as an extra method to soil type discrimination

Abstract. The purpose of the study was to test near infrared soil spectra as an extra method for three soil types (Fluvisols, Vertisols and Solonchaks) discrimination from different regions of South Bulgaria. The diffuse reflectance spectra of 177 soil samples (from the 0-20cm layers): 50 samples of Fluvisols soil type, 78 samples of Vertisols soil type and 48 samples of Solonchaks soil type were obtained using a Spectrum NIRQuest (OceanOptics, Inc.) working within the range from 900 to 1700 nm. Soft independent modelling of class analogy (SIMCA) was performed to classify samples according to their taxonomic classes. The results obtained showed that the soil samples are separated accurately according to their soil type based on their spectral information. All this could be used in the future studies related to the application of the NIRS method as a qualitative or quantitative method for soil analysis and also for the purposes of precision farming.

Viruses in the water column and the sediment of the eastern part of the Laptev Sea

The distribution of viruses and their impact on prokaryotes were studied using the epifluorescence and transmission electron microscopy along a transect, located at 130°E from the area adjacent to the Lena River delta next to the shelf area, the continental slope area and the deep-sea regions of the Laptev Sea in September 2015. The abundance of planktonic prokaryotes (NP) and free viral particles (NV), the frequency of visibly virus-infected prokaryotic cells (FVIC), and the viral-mediated prokaryotic mortality (VMP) varied within the following ranges: (0.1–3.1) × 106 cells mL−1, (0.1–4.4) × 106 viruses mL−1, 0.3–1.7% of NP, and 2.1–12.2% of the total mortality of prokaryotes, respectively, and reached maximum values at the inner shelf area. The percentage of viruses attached to prokaryotic cells varied from 2 to 6% of NV in the surface waters of the outer shelf and the deep-sea areas to 43–46% at the depth of 100–140 m in the continental slope area. The percentage of viruses that were attached to detrital or mineral microparticles varied from less than 1% in the waters of the deep-sea area to 27–50% in the waters of the inner shelf area adjacent to the Lena River delta. A negative correlation was found between the fraction of lysogenic prokaryotes and the FVIC values (r = – 0.60, p < 0.05).In the 20-cm bottom water layer above the sediment the NP, NV, FVIC and VMP values were (0.8–3.0) × 106 cells mL−1, (1.6–3.4) × 106 viruses mL−1, 0.5–1.2%, and 3.7–9.5%, respectively. In the surface 2-cm layer of the sediment these parameters were (1.8–4.4) × 109 cells cm−3, (0.8–2.3) × 109 viruses cm−3, 0.2–1.0%, and 1.4–7.8%, respectively. In the bottom water layer the percentage of viral particles attached to prokaryotes and to detrital and mineral particles was 10–29% and 20–79% of NV, respectively. In the surface sediments the percentage of viral particles attached to prokaryotes was considerably higher compared to the bottom water layer and ranged from 44 to 57% of NV. The capsid size of the viral particles from the pelagic zone, bottom water layer and surface sediments was on average 71 ± 14, 74 ± 7 and 63 ± 7 nm, respectively. In all these habitats, viruses from the size class of 60–100 nm prevailed.The relatively high abundance of prokaryotes and viruses, as well as the high FVIC values in the freshwater-seawater mixing zone (the highest values were recorded in the waters with a salinity of 9.6 psu) were apparently caused by the influx of considerable amounts of nutrients, and dissolved and particulate organic matter that come with the river runoff. At the same time, the high concentration of small detrital and mineral particles in the freshwaters lead to considerable adsorption of viruses by these particles and caused a decrease in the FVIC in the coastal areas adjacent to the Lena River delta.

In-Situ Monitoring and Characteristic Analysis of Freezing-Thawing Cycles in a Deep Vadose Zone

Freeze-thaw cycles play a critical role in affecting ecosystem services in arid regions. Monitoring studies of soil temperature and moisture during a freeze-thaw process can generate data for research on the coupled movement of water, vapor, and heat during the freezing-thawing period which can, in turn, provide theoretical guidance for rational irrigation practices and ecological protection. In this study, the soil temperature and moisture changes in the deep vadose zone were observed by in-situ monitoring from November 2017 to March 2018 in the Mu Us Desert. The results showed that changes in soil temperatures and temperature gradients were largest in soil layers above the 100-cm depth, and variations decreased with soil depth. The relationship between soil temperature and unfrozen water content can be depicted well by both theoretical and empirical models. Due to gradients of the matric potential and temperature, soil water flowed from deeper soil layers towards the frozen soil, increasing the total water content at the freezing front. The vapor flux, which was affected mainly by temperature, showed diurnal variations in the shallow 20-cm soil layer, and its rate and variations decreased gradually with increasing soil depths. The freeze-thaw process can be divided into three stages: the initial freezing stage, the downward freezing stage, and the thawing stage. The upward vapor flux contributed to the formation of the frozen layer during the freezing process.

Experimental investigation of shear performance of existing PC hollow slab

Prestressed concrete (PC) hollow slab is widely used in the construction of short and medium span highway bridges in China. With the increase in the highway load, the shear capacity of hollow slab bridges constructed before the 1990s can no longer meet the requirements of new safety regulations. Further research on the shear capacity of PC hollow slabs is necessary to ensure their safety, as these bridges continue to be operational. In this study, twelve hollow slabs with spans of 20 m, 16 m, and 10 m were tested to determine the shear performance of existing PC hollow slabs. Some hollow slabs were reinforced with a 15-cm thick concrete layer on the top surface to determine its effect on the shear capacity. The load-displacement curve, web strain, cracking and ultimate loads, and cracking and failure mode of the hollow slab were experimentally determined. The finite element method was used to simulate the shear process. The results show that the 10-m hollow slabs exhibited bending-shear failure, the 16-m hollow slabs exhibited shear compression failure, and the 20-m hollow slabs exhibited diagonal compression failure. Abdominal shear oblique cracks occurred on the webs of the hollow slabs with spans of 16 m and 20 m, whereas bending shear oblique cracks were formed in the 10-m hollow slabs. With post-casting of the 15-cm thick concrete layer, the cracking loads of the hollow slabs with spans of 10 m, 16 m, and 20 m increased by 47%, 32%, and 8%, whereas the ultimate loads increased by 41%, 22%, and 18%, respectively. A comparison of the results calculated based on design specifications and the test results shows that the design provisions for specifications related to the shear capacity are highly conservative. Finally, the conventional formula for the shear capacity was modified, and new formulas were proposed based on the test results and numerical simulation results to predict the shear capacities of the 10-m and 16-m/20-m PC hollow slabs. For these hollow slabs, the mean ratios of the calculated value to the experimental/simulated value obtained using the proposed formulas are 0.993 and 0.956, and the variances are 0.005 and 0.013, respectively.

Rapid peat development beneath created, maturing mangrove forests: ecosystem changes across a 25-yr chronosequence.

Mangrove forests are among the world's most productive and carbon-rich ecosystems. Despite growing understanding of factors controlling mangrove forest soil carbon stocks, there is a need to advance understanding of the speed of peat development beneath maturing mangrove forests, especially in created and restored mangrove forests that are intended to compensate for ecosystem functions lost during mangrove forest conversion to other land uses. To better quantify the rate of soil organic matter development beneath created, maturing mangrove forests, we measured ecosystem changes across a 25-yr chronosequence. We compared ecosystem properties in created, maturing mangrove forests to adjacent natural mangrove forests. We also quantified site-specific changes that occurred between 2010 and 2016. Soil organic matter accumulated rapidly beneath maturing mangrove forests as sandy soils transitioned to organic-rich soils (peat). Within 25yr, a 20-cm deep peat layer developed. The time required for created mangrove forests to reach equivalency with natural mangrove forests was estimated as (1) <15yr for herbaceous and juvenile vegetation, (2) ~55yr for adult trees, (3) ~25yr for the upper soil layer (0-10cm), and (4) ~45-80yr for the lower soil layer (10-30cm). For soil elevation change, the created mangrove forests were equivalent to or surpassed natural mangrove forests within the first 5 yr. A comparison to chronosequence studies from other ecosystems indicates that the rate of soil organic matter accumulation beneath maturing mangrove forests may be among the fastest globally. In most peatland ecosystems, soil organic matter formation occurs slowly (over centuries, millennia); however, these results show that mangrove peat formation can occur within decades. Peat development, primarily due to subsurface root accumulation, enables mangrove forests to sequester carbon, adjust their elevation relative to sea level, and adapt to changing conditions at the dynamic land-ocean interface. In the face of climate change and rising sea levels, coastal managers are increasingly concerned with the longevity and functionality of coastal restoration efforts. Our results advance understanding of the pace of ecosystem development in created, maturing mangrove forests, which can improve predictions of mangrove forest responses to global change and ecosystem restoration.

A 10-Yr Global Land Surface Reanalysis Interim Dataset (CRA-Interim/Land): Implementation and Preliminary Evaluation

A land surface reanalysis dataset covering the most recent decades is able to provide temporally consistent initial conditions for weather and climate models, and thus is crucial to verifying/improving numerical weather/climate forecasts/predictions. In this paper, we report the development of a 10-yr China Meteorological Administration (CMA) global Land surface ReAnalysis Interim dataset (CRA-Interim/Land; 2007–2016, 6-h intervals, approximately 34-km horizontal resolution). The dataset was produced and evaluated by using the Global Land Data Assimilation System (GLDAS) and NCEP Climate Forecast System Reanalysis (CFSR) global land surface reanalysis datasets, as well as in situ observations in China. The results show that the global spatial patterns and monthly variations of the CRA-Interim/Land, GLDAS, and CFSR climatology are highly consistent, while the soil moisture and temperature values of the CRA-Interim/Land dataset are in between those of the GLDAS and CFSR datasets. Compared with ground observations in China, CRA-Interim/Land soil moisture is comparable to or better than that of GLDAS and CFSR datasets for the 0–10-cm soil layer and has higher correlations and slightly lower root mean square errors (RMSE) for the 10–40-cm soil layer. However, CRA-Interim/Land shows negative biases in 10–40-cm soil moisture in Northeast China and north of central China. For ground temperature and the soil temperature in different layers, CRA-Interim/Land behaves better than the CFSR, especially in East and central China. CRA-Interim/Land has added value over the land components of CRA-Interim due to the introduction of global precipitation observations and improved soil/vegetation parameters. Therefore, this dataset is potentially a critical supplement to the CRA-Interim. Further evaluation of the CRA-Interim/Land, assimilation of near-surface atmospheric forcing variables, and extension of the current dataset to 40 yr (1979–2018) are in progress.

ЗАПАСИ ОРГАНІЧНОГО КАРБОНУ У БЛОЦІ "ПІДСТИЛКА – ҐРУНТ" СОСНОВОЇ ЕКОСИСТЕМИ ПОЛІСЬКОГО РЕГІОНУ

The results of studies of the content and stocks of organic carbon in the block "litter – soil" of pine ecosystems in Zhytomyr and Chernihiv Polissia are presented. The forest ecosystems are important stabilizers of the carbon cycle as well as stocks of carbon. The components of the forest ecosystem are interconnected by the flows of energy and substances. Binding ÑÎ2 in the block of "plant-soil", followed by the transformation of carbon into insoluble humus compounds is of particular importance. In the research area sod - light-podzolic and sod-medium-podzolic soils on fluvioglacial sands are mostly spread. These soils belong to the category of old arable ones. Present here are also peat – marsh soils. It is shown that the process of humus accumulation is characterized by low intensity, which is caused by a complex of reasons, in particular, the sandy composition of sod-podzolic soils (particle content &lt; 0,01 mm – 7,5 %).The thickness of the profile humus portion is 18 cm. The average content of humus is 0,97 %, and reserves – 28,3 t/ha in a 20-cm layer. Similar indicators of carbon are 0,56 % and 16,4 t/ha, respectively. Organic substance of sod-podzolic soils of pine habitats is resistant to mineralization and for a long time is removed from the cycle of substances of the pine ecosystem. The average carbon content in hydromorphic organogenic soils increases to 18,1 % and its stocks are 168,9 t/ha. The ability for mineralization peat soils is lower than that of sod-podzolic soils. So, they have a high carbon sequestration capacity. Pine litter reserves on the average are 30–33 t/ha, and carbon reserves on the average are – 12,6 t/ha, with its stable content – 40 %.The total carbon reserves in the block "litter – soil" of a typical pine ecosystem of Polissia are on average 29 t/ha, with the bulk of them being concentrated in the soil. Considering that highly productive pine forests are formed on the infertile soils of Polissia, their afforestation will not only stop the intensive degradation of soils of Ukraine, but also will increase the deposition of greenhouse gases, which will help to prevent further climate change at the regional level.

Lime and phosphate effects on atrazine sorption, leaching and runoff in soil

ABSTRACT Atrazine still is a widely used herbicide in tropical soils to control annual broad-leaved weeds and annual grasses mainly in maize and sorghum plantations. Sorption and desorption in such soils are important processes that affect transport, ending with soil and water contamination, not only in these soils, but in other soils around the world. Lime and phosphate are important amendments in tropical soils to mitigate low fertility. These treatments can affect interaction among soil particles and between soil and atrazine. The objectives here were to evaluate the effect of lime, phosphate, and lime + phosphate treatments on sorption and transport of atrazine in a Typic Hapludult, using soil-erosion-plots at field conditions in a 3%-slope landscape 20 m away from the floodplain. Water- and sediment-sampler devices were used to measure runoff during an entire rainy season. Soil, water and sediments were sampled and analyzed for atrazine. By increasing pH and changing soil organic matter interaction with mineral particles, lime and lime + phosphate decreased sorption in the upper 20-cm layer. This affected leaching and runoff of atrazine, showing that when lime and lime + phosphate were applied to soil, this herbicide had more potential to go deeper in the soil profile, towards the groundwater, or to runoff towards the lower part of the landscape. However, even with increasing leaching, the amount of rainfall, and water infiltration, were enough to dilute atrazine into levels below the maximum contaminant level (MCL) of atrazine in drinking water.

Long-term eutrophication affects vertical changes of Daphnia ephippia in the sediments of a subtropical Chinese lake.

Cladoceran remains (e.g., Daphnia ephippia) in sediments are usually able to accurately reflect the historical succession of cladoceran in lakes. However, mechanisms describing the interaction between density changes of empty ephippia and ephippia containing resting eggs in lake sediments and environmental factors remain unclear. The diversity and vertical changes of Daphnia ephippia in the 30-cm sedimentary layer (equivalent to about 90years) were investigated in a subtropical Chinese lake, Lake Chaohu. The ephippia of D. similoides sinensis, D. pulex, and D. galeata were identified in the lake sediments. The densities and accumulation rates of both empty ephippia and ephippia containing resting eggs of three Daphnia species showed similar patterns. The values in the surface sedimentary layers (after the 1970s) were notably higher than in the bottom sedimentary layers (before the 1970s). The densities and accumulation rates of both empty ephippia and ephippia containing resting eggs of D. similoides sinensis were higher than those of D. pulex and D. galeata. Highly significant relationships (P< 0.001) between the TN contents and the ephippial densities and accumulation rates of D. similoides sinensis and D. galeata. TP contents had also significant correlations with the ephippial densities and accumulation rates of D. similoides sinensis and D. galeata, whereas it was not significant correlations with those of D. pulex (P> 0.05). Our results suggested that long-term eutrophication and cyanobacterial blooms might significantly affect the production of Daphnia ephippia and their vertical distribution in the sediments in eutrophic lakes.

Nitrogen Accumulation and Root Distribution of Grafted Tomato Plants as Affected by Nitrogen Fertilization

Growth and yield typically increase when tomato plants are grafted to selected interspecific hybrid rootstocks from which distinctive root system morphologies are envisioned to aid nutrient uptake. We assessed these relationships using a range of exogenous nitrogen (N) supplies under field production conditions. This study analyzed the impact of N on growth, root distribution, N uptake, and N use of determinate ‘Florida 47’ tomato plants grafted onto vigorous, interspecific, hybrid tomato rootstocks ‘Multifort’ and ‘Beaufort’. Six N rates, 56, 112, 168, 224, 280, and 336 kg·ha−1, were applied to sandy soil in Live Oak, FL, during Spring 2010 and 2011. During both years, the leaf area index, aboveground biomass, and N accumulation (leaf blade, petiole, stem, and fruit) responded quadratically to the increase in N fertilizer rates. Averaged over the two seasons, the aboveground biomass, N accumulation, N use efficiency (NUE), and N uptake efficiency (NUpE) were ≈29%, 31%, 30%, and 33% greater in grafted plants than in nongrafted controls, respectively. More prominent increases occurred in the root length density (RLD) in the uppermost 15 cm of soil; for grafted plants, RLD values in this upper 15-cm layer were significantly greater than those of nongrafted plants during both years with an average increase of 69% over the two seasons. Across all the grafted and nongrafted plants, the RLD decreased along the soil profile, with ≈60% of the total RLD concentrated in the uppermost 0 to 15 cm of the soil layer. These results demonstrated a clear association between enhanced RLD, especially in the upper 15 cm of soil, and improvements in tomato plant growth, N uptake, and N accumulation with grafting onto vigorous rootstocks.

First demonstration of portable Compton camera to visualize 223-Ra concentration for radionuclide therapy

Radionuclide therapy (RNT) is an internal radiation therapy that can selectively damage cancer cells. Recently, the use of alpha-emitting radionuclides was initiated in RNT owing to its dose concentration and short range. In particular, 223Ra is widely used for bone metastasis of prostate cancer. Despite its potential for clinical applications, it is difficult to determine whether a drug has been properly delivered to the target lesion. As such, we propose a new method of monitoring nuclear gamma rays promptly and simultaneously emitted from 223Ra as alpha decay using a high-sensitivity Compton camera. We first observed a small bottle of 223Ra solution with a total radioactivity of 0.56 MBq. The reconstructed image converged at the correct position with a position resolution of ∼20 mm at a plane 10 cm in front of the camera. Next, we observed a phantom consisting of three spheres with diameters ranging from 13 to 37 mm filled with 223Ra solution (9 kBq/mL) and then surrounded by a ∼20-cm layer of water. A three-dimensional (3D) image was constructed by rotating the Compton camera around the phantom. Images were then acquired from eight directions at 30-min intervals, respectively. Although the image resolution remained limited at 351 keV, three spheres were resolved at the correct position in the 3D image with their relative intensities. Thirdly, we observed the body of a patient for 10 min and reconstructed almost the same accumulation as the image acquired by a single-photon emission computed tomography (SPECT) system for 30 min. While the spatial resolution of the Compton camera was worse, DOI-CC obtained a wider image in a shorter time. Finally, we discuss current problems and plans for improving sensitivity and angular resolution for future clinical applications.

Effect of Large Inputs of Manure and Fertilizer on Nitrogen Mineralization in the Newly Built Solar Greenhouse Soils

In China, greenhouse soils often receive large rates of different manures and have a high content of soil organic matter (SOM). Understanding changes in nitrogen (N) mineralization in soils of newly built greenhouses after their construction is important for managing N. Soil samples were obtained from solar greenhouses of different ages (0, 1, 2, and 3 years) located in the south edge of the Loess Plateau, China, at 0- to 20- and 20- to 40-cm depth. N mineralization in the soils was measured with the Stanford and Smith long-term aerobic incubation method over 30 weeks. SOM, total N, and the mineralized N in the 0- to 20-cm and 20- to 40-cm soil layers were significantly increased in the older greenhouses. The cumulative mineralized N in the 0- to 20-cm soil layer in different cultivation years was increased in each year since the greenhouses were established. For the greenhouses with the same age, the cumulative mineralized N in the 0- to 20-cm soil layer was greater than that in the 20- to 40-cm layer. The potentially mineralizable N (N0) both in the 0- to 20-cm and the 20- to 40-cm soil layers increased with the greenhouses’ age. Regression analysis indicated that when SOM increased 1 g·kg−1, N0 in the 0- to 20-cm and 20- to 40-cm depth increased 22.6 and 8.4 mg·kg−1, respectively. Therefore, as the N supply in soil increases with the age of the solar greenhouse, we suggest that the application rates of manure and synthetic fertilizer be reduced.

Investigating the Relationship Between Satellite-Based Freeze/Thaw Products and Land Surface Temperature

This paper investigates surface temperature variables as they relate to passive microwave-derived surface freeze/thaw (FT) state and assesses the accuracy of such FT products relative to surface temperature. Utilizing retrievals from the soil moisture active/passive (SMAP), advanced microwave scanning radiometer, and special sensor microwave imager instruments, surface FT records have previously been derived globally. Moderate Resolution Imaging Spectroradiometer skin temperature, North American Land Data Assimilation System (NLDAS) skin, 0–10-cm soil layer, and 2-m air temperatures are compared to the various FT state products (FTSPs) by defining the threshold for FT state transitions at 0 °C. This paper utilizes the 2015–2016 overlap period in FT records within the NLDAS domain. Spatial variability of classification accuracy (CA) is then investigated over the study area. A proportional differencing method also enables the identification of biases between FTSPs and surface temperature variables. Additionally, by analyzing probability distribution functions of FTSPs associated with temperature values, we assess the distribution of temperature variables as they relate to FT classifications. Classification agreement is shown to vary with sensor configuration, seasonality, and retrieval time. Air temperature is found to have the highest CAs across FTSPs (81%–91%), while NLDAS soil exhibits a close relationship to FTSPs, especially in regard to SMAP products. Finally, ascending ( p.m. ) retrievals are shown to be increasingly linked to the selected temperature parameters as compared to descending ( a.m. ) observations. This paper contributes to an improved understanding of current FTSPs and will benefit efforts to enhance future FT products.