Can Near or Mid‐Infrared Diffuse Reflectance Spectroscopy Be Used to Determine Soil Carbon Pools?

Abstract

The objective of this study was to compare mid‐infrared (MIR) an near‐infrared (NIR) spectroscopy (MIRS and NIRS, respectively) not only to measure soil carbon content, but also to measure key soil organic C (SOC) fractions and the δ¹³C in a highly diverse set of soils while also assessing the feasibility of establishing regional diffuse reflectance calibrations for these fractions. Two hundred and thirty‐seven soil samples were collected from 14 sites in 10 western states (CO, IA, MN, MO, MT, ND, NE, NM, OK, TX). Two subsets of these were examined for a variety of C measures by conventional assays and NIRS and MIRS. Biomass C and N, soil inorganic C (SIC), SOC, total C, identifiable plant material (IPM) (20× magnifying glass), the ratio of SOC to the silt+clay content, and total N were available for 185 samples. Mineral‐associated C fraction, δ¹³C of the mineral associated C, δ¹³C of SOC, percentage C in the mineral‐associated C fraction, particulate organic matter, and percentage C in the particulate organic matter were available for 114 samples. NIR spectra (64 co‐added scans) from 400 to 2498 nm (10‐nm resolution with data collected every 2 nm) were obtained using a rotating sample cup and an NIRSystems model 6500 scanning monochromator. MIR diffuse reflectance spectra from 4000 to 400 cm^?1 (2500 to 25,000 nm) were obtained on non‐KBr diluted samples using a custom‐made sample transport and a Digilab FTS‐60 Fourier transform spectrometer (4‐cm^?1 resolution with 64 co‐added scans). Partial least squares regression was used with a one‐out cross validation to develop calibrations for the various analytes using NIR and MIR spectra. Results demonstrated that accurate calibrations for a wide variety of soil C measures, including measures of δ¹³C, are feasible using MIR spectra. Similar efforts using NIR spectra indicated that although NIR spectrometers may be capable of scanning larger amounts of samples, the results are generally not as good as achieved using MIR spectra.     

Can the Activities of Acetylcholinesterase and Glutathione S-Transferases of Crangon crangon (L.) be Used as Biomarkers of Fuel Oil Exposure?

This work aimed to determine the sensitivity of acetylcholinesterase (AChE) and glutathione S-transferases (GST) activities of Crangon crangon (L.) to the water-accommodated fraction (WAF) of the fuel oil spilled by the oil tanker Prestige, in order to assess their usefulness as markers for this kind of pollution. Laboratory exposure of shrimps to WAF of weathered Prestige fuel oil showed no significant interference with AChE activity. Significant induction of GST activity was observed, potentially as a result of high concentrations of polycyclic aromatic hydrocarbons. However, these results were only obtained with the higher WAF concentrations tested. It was concluded that AChE and GST activities of C. crangon were not useful biomarkers for short-term exposure to the WAF of fuel oil spilled by the tanker Prestige and carried to the beaches of Galicia (NW Spain).     

Can soil moisture deficit be used to forecast when soils are at high risk of damage owing to grazing animals?

A potentially significant cause of damage to grassland soils is compaction of unsaturated soil and poaching of saturated or nearly saturated soil by animal hooves. Damage is caused when an applied stress is in excess of the bearing strength of the soil and results in a loss of soil structure, macroporosity and air or water conductivity. Severely damaged soils can cause reduced grassland productivity and make grazing management very difficult for the farmer. The actual amount of soil damage that can occur during grazing is dependent on the grass cover which acts as a protecting layer, the soil water content and the characteristics of the grazing animal (weight and hoof size). Assuming that the farmer is knowledgeable about the characteristics of the grazing animal and grass cover, it would be very useful for short‐term operational farm planning to be able to predict when soil water contents were likely to be in a critical range with respect to potential hoof damage. In this study soil moisture deficits (SMDs) which can be derived from meteorological forecasts are evaluated for predicting when soil water conditions are likely to lead to hoof damage. Two contrasting Irish grassland soils were analysed using a Hounsfield servo‐mechanical vertical testing machine to simulate static (285.4 N) and dynamic (571 N) hoof loads on the soil over a range of estimated SMDs (0, 5, 10 and 20 mm). The deficits were analysed with respect to the soil volumetric water content, compression (displacement) and change in dry bulk density. The SMDs imposed in the laboratory were similar to those under field conditions and thus the methods used in this study are applicable elsewhere. The change in dry bulk density following loading (0.2–0.7 g/cm³) was linearly related to SMD (R² ranged from 0.90 to 0.99), leading to the conclusion that a forecast of SMD can be used to predict when grassland soils are likely to be at risk of damage from grazing.     

Can differences in 15N natural abundance be used to quantify the transfer of nitrogen from legumes to neighbouring non-legume plant species?

Natural variations in the stable isotope ¹⁵N are often exploited in studies of N cycling in ecosystems. Lower ¹⁵N natural abundance in non-legume plants growing in association with legumes, compared with the non-legume grown alone in pure stands have been observed in cropping, forage, and agroforestry systems. Such observations have frequently been attributed to the transfer of biologically-fixed nitrogen (N) from the legume to the companion non-legume, and various methodologies have been employed to calculate the extent of the N transfer. While some of these ¹⁵N natural abundance-based estimates of N transfer were within the range previously reported using equivalent ¹⁵N-enriched techniques (<20% of non-legume plant N and <10 kg N ha⁻¹ derived from fixed N contributed by neighbouring legumes), many of the values obtained using natural abundance were much higher (30%–83% of the non-legume N derived from fixed N representing up to 30–40 kg N ha⁻¹) than generally measured by ¹⁵N-enriched methods; with even greater estimates being determined where data were available to allow N transfer to be re-calculated on the basis of total legume N rather than fixed N (42% to >100%, and up to 110 kg N ha⁻¹ per year). This review raises concerns about the assumptions behind the natural abundance approach, and provides some alternative interpretations for the observed differences in natural ¹⁵N abundance between plants grown in the presence and absence of legumes. It was concluded that simple comparative measures of non-legume δ¹⁵N alone cannot provide a quantitative estimate of N transfer between plant species if the dominant source and the isotopic identity of the transferred N cannot be validated, and if the extent of any isotopic fractionation associated with relevant N transformations occurring during transfer cannot be defined. To date this information is not forthcoming. There is a need to greatly improve our understanding of the transfer processes before the real value of the δ¹⁵N technology can be realized. In the first instance this will primarily be achieved by carefully executed experiments under controlled conditions, and in the field, employing both ¹⁵N natural abundance and enrichment approaches so estimates of transfer can be compared, and the data interrogated using modelling approaches to explore isotopic fractionation.     

Can the invasive earthworm,Amynthas agrestis,be controlled with prescribed fire?

Biological invasions are one of the most significant global-scale problems caused by human activities. Earthworms function as ecosystem engineers in soil ecosystems because their feeding and burrowing activities fundamentally change the physical and biological characteristics of the soils they inhabit. As a result of this “engineering,” earthworm invasions can have significant effects on soil physical, chemical and biological properties. The species Amynthas agrestis (family Megascolecidae) was introduced to the United States from Asia, and has expanded its distribution range to include relatively undisturbed forests. Here, to clarify life history traits, we reared individuals under seven different conditions of food provision using litter, fragmented litter and soil, and also analyzed the stable isotope ratios of field-collected specimens to investigate their food resources in the field. Second, we examined whether prescribed fire can be used to manage invasive earthworms. We constructed eight experimental plots, each with 100 individuals of A. agrestis each, and burned half of the plots. The feeding experiment showed that the earthworms in units containing soil and some form of organic matter (litter and/or fragmented litter) produced many cocoons, indicating that litter and fragmented litter are important food resources for them. Stable isotope analyses also supported this result. During the experimental fires, average soil temperature at 5 cm depth increased by only 7.7 °C (average maximum of 32.2 °C). Litter mass was significantly reduced by the fires. Although numbers of A. agrestis and cocoons recovered from burned and unburned plots were not different, the viability of cocoons was significantly lower in burned plots. Fire may also reduce the survival rate of juveniles in the next year by depriving them of their preferred food resource. Most native earthworms in the United States live in the soil, while many invasive ones live in the litter layer and soil surface. Therefore, prescribed fire could be a viable tool for control of invasive earthworms without negatively impacting native earthworm populations.     

Can nutritional status of apple trees be determined by leaf analysis in early vegetation?

In this study, whether the nutritional status of apple trees can be predicted in the early stages of vegetation was determined by leaf analysis. For this purpose, from different districts of Isparta province in Turkey where apples are cultivated extensively, 150 apple orchards were assessed according to the production potential of districts. The leaf samples were collected at six different stages of vegetation from these orchards, and nitrogen, phosphorus, potassium calcium, magnesium, iron, copper, zinc, manganese, and boron (N, P, K, Ca, Mg, Fe, Cu, Zn, Mn and B) amounts were determined. Correlations were examined between the sixth period and the previous periods. The presence of significant correlations was interpreted, as leaf analysis can be used to determine the nutritional status of apples in the early growth period. Consequently, it was determined that leaf analysis can be carried out at any time from the beginning of vegetation for all elements except Fe and Cu.     

How much oxygen is needed for acetylene to be consumed in soil?

Purpose  

Acetylene (C₂H₂) is employed for the quantification of important biological processes such as nitrogen fixation, nitrous oxide reduction, ammonium and methane oxidation, and methanogenesis. Although acetylene is not a natural product, the ability of bacteria to grow on C₂H₂ is a phenomenon common to soils and sediments. Our experiment was designed to study the modification of CO₂ production, O₂ uptake and microbial biomass (C_mic) in soil in response to the consumption of added acetylene.     

Can Polish wheat (Triticum polonicum L.) be an interesting gene source for breeding wheat cultivars with increased resistance to Fusarium head blight?

Nine spring lines of Polish wheat (Triticum polonicum) were compared with Kamut wheat and two common wheat cultivars. Plants were analyzed to determine morphometric parameters (plant height, spike length, spike density, grain weight per spike and single kernel weight) and some chemical properties of grain: content of protein, ash, fat, crude fiber, minerals and mycotoxins. The studied genotypes produced a relatively weak response to infection with Fusarium culmorum which was expressed by a decrease in grain weight per spike and single kernel weight by 13 % and over 6 %, respectively. The grain of T. polonicum was characterized by a significantly higher protein and ash content than the grain of common wheat (by 19.8 and 23.7 %, respectively) and considerably higher concentrations of fat and dietary fiber than Kamut wheat (by 30.2 and 17.4 %, respectively). In comparison with common wheat, the grain of the examined genotypes was significantly more abundant in sulfur, magnesium and potassium as well as zinc, iron, copper and molybdenum. It contained significantly less aluminum and strontium. The inoculation led to a significant increase in fusariotoxin levels in the grain of all studied genotypes, and the average concentrations of the above metabolites were lower in the grain of T. polonicum than in Triticum aestivum. Polish wheat may constitute valuable genetic material for breeding new wheat varieties characterized by a high nutritive value and satisfactory resistance to FHB.     

Can adverse effects of dietary fat intake be overestimated as a consequence of dietary fat underreporting?

OBJECTIVE: To describe the consequences of systematic reporting bias by the obese for diet-disease relationships. DESIGN: The present report used 24-hour urinary nitrogen and estimates of 24-hour energy expenditure to assess error in diet reporting, and examined the consequence of accounting for this error for associations between dietary fat intake and serum low-density lipoprotein (LDL)-cholesterol. SETTING: Sub-study to the Danish MONICA (Monitoring Trends and Determinants in Cardiovascular Disease) project, carried out in 1987-1988. SUBJECTS: A random sub-sample of the adult Danish male population (n = 152). RESULTS: Correcting dietary fat for underreporting error weakened, rather than strengthened, the association between dietary fat intake and LDL-cholesterol by reducing the slope of the regression from beta = 3.4, P = 0.02 to beta = 2.7, P = 0.04. CONCLUSION: This example illustrates that systematic underreporting of dietary fat by high-risk groups such as the obese may produce an overestimated association. These results imply that previous epidemiological studies showing a positive association between percentage of energy from fat and other health outcomes, e.g. cancer and heart disease, may have overestimated the negative effects of a high-fat diet. If we were able to correctly assess dietary fat intake in general populations, recommendations for fat intake may be more liberal than the 30% suggested today. Improved assessment of fat intake in epidemiological studies is necessary for future development of evidence-based recommendations for diet and health .     

Metal toxicity assessment in soils using enzymatic activity: Can water be used as a surrogate buffer?

Ecotoxicological tests based on soil enzyme activity are widely used to assess the terrestrial ecotoxicology of metals in soils. However, several standard enzymatic methods use buffers that may alter the chemical pseudoequilibrium of soils and affect metal speciation, and, in turn, the metal effects on enzymes and enzyme kinetics. Researchers have suggested the use of H₂O as a solvent rather than chemical buffers, but opponents are concerned about pH fluctuations during incubation and the resulting difficulty in comparing enzymatic studies. Enzyme assays were conducted on 10 pairs of Zn-contaminated soils to evaluate 1) the buffer effect on Zn lability 2) the pH fluctuation during enzymatic assays conducted in water and 3) the comparison of enzymatic results obtained using chemical buffers versus water. Four standard enzymatic methods covering the major biogeochemical cycles were targeted: arylsulfatase (acetate pH 5.8), urease (borate pH 10), acid phosphatase (modified universal buffer pH 6.5) and protease (THAM pH 8.1). Furthermore, deionized water was tested in parallel as a surrogate solvent for these four methods. With the exception of the acetate buffer, the tested solvents did not significantly change the labile Zn concentration in the soil samples. The pH slightly fluctuated by +0.57 pH unit, corresponding to the intrinsic variability of soils. Enzymatic methods using buffers showed similar results compared to those using water, except for urease. These observations suggest that enzymatic methods setting alkaline conditions should be used with caution and that H₂O could be used as surrogate solvent in this context.     

Can a mesotrophic grassland community be restored on a post-industrial sandy site with compost made from waste materials?

Restoration of sites degraded by industry to species-rich semi-natural vegetation communities is difficult; it usually involves the addition of soil ameliorants but excessive fertility may favour dominance by competitive species. In a field-experiment we tested the establishment of a biodiverse mesotrophic grassland community using different compost types (comprising of mixtures of waste materials), application rates and seeding (with species in the target community). Compost addition to the alkaline sandy substrate increased soil organic matter, nutrient content and water holding capacity (WHC), whilst decreasing pH. Over the first two growing seasons compost addition, (especially at a higher rate) increased total vegetation cover (from <20% to a maximum of 67%), although the cover of the target community remained below 20%. Seeding with target species greatly increased their establishment on compost-treated plots, demonstrating its value for restoration of mesotrophic grassland communities in such sites lacking a local seed source. Five soil properties accounted for 46% of the variation in target species density: negative correlations with soil pH and %N, and positive correlations with electrical conductivity (EC), %C, and WHC. For this mesotrophic grassland community, high EC and WHC and low pH were most important for forb species and high %C for grasses. Overall, %C was the soil property that best explained variation in the early restoration success of different compost types and application rates; pH and EC were also correlated with the rate of vegetation establishment and available-P was linked to plant community composition. While a longer time period is needed to judge the sustainability of the outcome, this demonstrates the potential to refine compost properties for restoration of biodiversity.     

Can small, isolated primate populations be effectively reinforced through the release of individuals from a captive population?

Since November 1997 the Madagascar Fauna Group (MFG) has released 13 captive-bred black and white ruffed lemurs (Varecia variegata variegata) into the Betampona reserve in eastern Madagascar. Five of the thirteen are currently surviving, including one male who has integrated into a wild group. Five of the released lemurs fell victim to predation by fossa (Cryptoprocta ferox), one died of malnutrition, one disappeared from the reserve and one was withdrawn from the release programme. Ten of the released lemurs survived for more than one year post release, although all required varying levels of supplementary feeding. One pair bred twice—the first time the infants did not survive, but on the second occasion triplets were successfully raised beyond weaning. One of the triplets (male) is still surviving. One male has integrated into a wild group and sired a single infant in 2002 and a female released in 2001 gave birth to twins sired by a wild male also in 2002. The release programme has thus achieved a major objective of reinforcing the existing wild population. To date there is no significant difference in survival rates between animals born and raised in free-ranging environments and those raised in cages, between animals greater than or less than 5 years old at time of release, or between males and females.     

Can field populations of the enchytraeid,Cognettia sphagnetorum,adapt to increased drought stress?

The ability to evolve increased drought tolerance in response to climate change was investigated in the enchytraeid, Cognettia sphagnetorum. Populations exposed to reduced precipitation or increased night time temperature for more than six years were collected in mixed Calluna/grass heathland at the Mols Laboratory, Denmark. The level of prolonged drought and increased temperature corresponded to a predicted climate change scenario and has been applied since 1999. In autumn 2005, enchytraeids were sampled in 3 cm intervals down to 9 cm depth and total number, biomass, diversity and soil organic matter were determined. The drought treatment resulted in a significant reduction of the density and biomass of enchytraeids, as well as changes in the species composition. In total, five different genera were found at the site in all three treatments (control, temperature and drought). C. sphagnetorum was the dominant species, especially in the upper 0–3 cm, and was clearly affected by the drought treatment. C. sphagnetorum from all plots were cultured in the laboratory to rear second or third generation adults. Results showed that populations of drought treated plots had not developed an increased drought resistance compared to populations of control or warming plots even after several years of a putative severe selection. Lack of adaptive potential in C. sphagnetorum suggests that more frequent periods with drought in the future will have a very strong negative influence on enchytraeid density, biomass and diversity.     

How Can Organic Amendments Help to Bind Sulfadiazine in the Soil? – An Iranian Soil Study

ABSTRACT

Veterinary antibiotics can enter the environment especially agricultural soils via animal manure application in which Sulfadiazine (SDZ) is considered as one of the most used antibiotic. After soil application, it may be transported into subsurface water. The sorption behavior of SDZ is not only influenced by the soil type but also by soil organic matters as well. Hence, an experiment was executed aimed to study sorption/desorption processes of SDZ under experimental conditions in three various soils treated by different bio fertilizers including rice husk compost (RHC), rice husk biochar (RHB) and Micrococcus yunnanensis (My) bacterium. Sorption/desorption data of soils with and without bio-fertilizers were well fitted with Freundlich model (R² = 0.97). Results showed that bio-amended soils had higher values of k_d sorption ranged from 1.16 to 52.4 without and with bio-fertilizers application respectively, proposing low sorption of SDZ with substantial risk of leaching without bio-fertilizers application. Also for the desorption cycle values of K_d increased from 1.03 to 39.1 without and with bio-fertilizers application, respectively. Furthermore, there was a hysteresis effect using organic matter. As a result of bio-fertilizers application, a significant value of SDZ was strongly adsorbed on the soil particles which was not desorb through desorption process.