Variability in oxidative degradation of charcoal: influence of production variables and environmental exposure

<p>Charcoal is a key component of the Black Carbon (BC) continuum, where BC is characterized as a recalcitrant, fire-derived, polyaromatic material. Charcoal is an important source of palaeoenvironmental data, and of great interest as a potential carbon sink, due to its high apparent environmental stability. However, at least some forms of charcoal are clearly susceptible to environmental alteration and degradation over relatively short timescales. Although these processes have importance for the role of charcoal in global biogeochemistry, they remain poorly understood.</p> <p>Here we present results of an investigation into the susceptibility of a range of charcoal samples to oxidative degradation in acidified potassium dichromate. The study examines both freshly-produced charcoal, and charcoal exposed to environmental conditions for up to 50,000 years. We compare the proportion of carbon present in different forms between the samples, specifically with respect to the relative chemical resistance of these forms. This was undertaken in order to improve understanding of the post-depositional diagenetic changes affecting charcoal within environmental deposits.</p> <p>A wide range in chemical compositions are apparent both within and between the sample groups. In freshly-produced charcoal, material produced at 300 °C contains carbon with more labile forms than charcoal produced at ≥400 °C, signifying a key chemical change over the 300–400 °C temperature range. Charcoal exposed to environmental depositional conditions is frequently composed of a highly carboxylated aromatic structure and contains a range of carbon fractions of varying oxidative resistance. These findings suggest that a significant number of the environmental charcoals have undergone post-depositional diagenetic alteration. Further, the data highlight the potential for the use of controlled progressive oxidative degradation as a method to characterize chemical differences between individual charcoal samples.</p&gt

Utilisation of different carbon sources in a shallow estuary identified through stable isotope techniques

Organic carbon in estuarine sediments can have many different sources. Terrestrial, riverine, estuarine and marine C pools may all contribute to and influence the organic C (Corg) inventory of the estuarine sediments and the differing stable isotope signatures of the sources are reflected in the sediment's overall 13C content. Ecological interpretations of sedimentary isotope data may, however, be limited by the fact the total Corg inventory of a sediment may not be an accurate representation of the fraction that is labile and being actively turned over by the sedimentary community. To gain a better understanding of sedimentary Corg dynamics in estuaries and the relationship between the sedimentary C pool and the Corg undergoing mineralisation, we studied three components of an estuarine system: (1) the sedimentary Corg inventory on a transect from the mouth to the upper end of the estuary, (2) temporal changes of sedimentary Corg at one station throughout a year, and (3) the d13C of respired CO2 compared to the d13C of available source material and sedimentary Corg in a novel application of methods developed for soil science. Our experiments demonstrated that material of marine origin dominated the studied estuary. At the time-series station, material of marine origin dominated the sedimentary Corg throughout the 1-yr study period. d13C values of CO2 released from the sediment differed significantly from the sedimentary Corg inventory at all study sites, but also clearly reflected differences between the main sections of the estuary. These results suggest that d13C measurements of respired CO2 are promising as a tool to advance our understanding of C cycling in estuaries, and highlight that the sedimentary Corg pool alone may not be a satisfactory indicator of OM utilisation in estuarine sediments

Internal cycling of nitrogen, potassium and magnesium in young Sitka spruce

Potassium (K) and magnesium (Mg) are essential macro-nutrients, but little is known about how they are cycled within plants. Stable isotope studies have shown that the internal cycling of nitrogen (N) is independent of current nutrient supply in temperate tree species. This is ecologically significant because it allows trees to produce rapid shoot growth in spring independent of current soil N uptake. We used stable isotopes to quantify N, K and Mg in new shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings and to compare the relative contributions from current uptake and internal cycling. Two-year-old Sitka spruce seedlings were labeled with 15N, 41K and 26Mg in an abundant or a limited supply for one growing season. The trees were repotted in the subsequent dormant season to prevent further root uptake of enriched isotopes and provided with an abundant or a limited supply of unlabeled nutrients until they were harvested in early summer of the following year. The supply was switched for half the trees in the second year to create four nutrient regimes. Enrichment of 15N, 41K and 26Mg in current-year growth was attributed to internally cycled N, K and Mg uptake from the previous year. The internal cycling of N, K and Mg in new growth was significantly affected by the first-year nutrient treatments. The second-year nutrient supply affected the growth rates of the trees, but had no effect on the amounts of N, K or Mg contributed from internal cycling. Thus, internal cycling of K and Mg in Sitka spruce are, like that of N, independent of current nutrient supply

Tracing N, K, Mg and Ca released from decomposing biomass to new tree growth. Part I: A model system simulating harvest residue decomposition on conventionally harvested clearfell sites

It is necessary to assess the effects of removing nutrient-rich harvest residues (brash) from clearfell sites because there is a growing market for this brash as bioenergy. The aim of this study was to use stable isotope techniques in a model system to trace nutrients released by decomposing brash. Labelled biomass was obtained by growing Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings with a generous or poor nutrient supply containing elevated 15N, 41K, 26Mg, and 44Ca. This biomass was used in two subsequent studies. In this study (Part I of II), the above-ground biomass was harvested and placed on soil in a pot containing a newly planted seedling. Soils from two forests, Ae and Teindland, of contrasting nutritional status were used. A full destructive harvest was undertaken after one growing season. Enriched 15N, 41K, 26Mg, and 44Ca were recovered in the new seedlings. The percentage contribution from labelled biomass to new tree growth was small, but discernible. The N contribution from labelled biomass to new trees was greater in Ae soil, but the base cation contribution was greater in Teindland soil. Results are discussed with reference to the initial nutrient concentrations of each soil. The elevated 15N, 41K, 26Mg and 44Ca in new seedlings indicate that nutrients in brash can make a direct contribution to new tree growth. The success of this model system will provide guidance for the application of similar techniques in field experiments

Tracing N, K, Mg and Ca released from decomposing biomass to new tree growth. Part II: A model system simulating root decomposition on clearfell sites

The decomposing roots of harvested trees are a potential source of nutrients for new trees on both conventional and whole-tree harvested clearfell sites. Roots contain significant reservoirs of nutrients, but little is known about the magnitude and rate of their release. The aim of this study was to use stable isotope techniques in a model system to trace nutrients released by decomposing roots. Labelled biomass was obtained by growing Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings with a generous or poor nutrient supply containing elevated 15N, 41K, 26Mg and 44Ca. Labelled trees were re-potted in sand and in two contrasting soils types to remove them from the enriched isotope supply. After re-potting, the labelled above-ground biomass was harvested, removed and used in a separate study described previously (Part I of II). In the study described here (Part II of II), new Sitka spruce seedlings were planted alongside the labelled root systems. A full destructive harvest was undertaken after one growing season. Enriched 15N, 41K, 26Mg, and 44Ca were recovered in the new seedlings in both sand and soils. The elevated amounts of 15N, 41K, 26Mg and 44Ca recovered in new seedlings indicate that nutrients released from decomposing roots can make a direct contribution to the growth of new trees on restock sites. The success of this model system will provide guidance for the application of similar techniques in field experiments

Evidence of fish spillover from freshwater protected areas in lakes of eastern Ontario

Research has identified numerous conservation benefits attributed to the use of marine protected areas (MPAs), yet comparatively less is known about the effectiveness of freshwater protected areas (FPAs). This study assessed multiple long-standing (>70 years active) intra-lake FPAs in three lakes in eastern Ontario, Canada, to evaluate their potential conservation benefits. These FPAs were intended initially to protect exploited populations of largemouth bass (Micropterus salmoides (Lacépède, 1802)), but since their establishment no empirical data have been collected to evaluate the effectiveness of FPAs for protecting bass or the broader fish community. A comparative biological census of fish species abundance, biomass and species richness was conducted using snorkelling surveys within FPAs, along the bor

Spatiotemporal ecology of juvenile Muskellunge (Esox masquinongy) and Northern Pike (Esox lucius) in upper St. Lawrence River nursery bays during their inaugural fall and winter

Understanding the spatial ecology of juvenile freshwater fish beyond summer months is an essential component of their life history puzzle. To this end, declines in the natural populations of sympatric Muskellunge (Esox masquinongy) and Northern Pike (Esox lucius) in the upper St. Lawrence River prompted study of spatiotemporal patterns and habitat requirements associated with earlier life stages of these congeneric, freshwater predators in fall and overwinter periods. Over 75 age-0 esocids were tagged and passively monitored using acoustic telemetry in four nursery embayments in fall and winter months from 2015 and 2017 months to elucidate spatiotemporal ecology and test hypotheses related to emigration. Presence, residency, space and habitat use were assessed and modelled against key environmental (i.e. water temperature and level) and biological (total length) covariates using mixed effect models. Muskellunge were found to spend more time in deeper, littoral regions with canopy-forming, submerged aquatic vegetation while Northern Pike aggregated in the deepest, highly vegetated region of their nursery embayment. Results suggest fish may exhibit transitionary movements in fall months and may span outwards into nearshore regions along the main river channel. Studies informing coastal restoration initiatives to increase Muskellunge production are encouraged to assess sympatric habitat use relative to prominent embayment structures and further explore depth partitioning by these young predators. With a substantial influence from water-level regulation on use of nursery habitat, future studies must work in concert with management plans aimed at producing more natural riverine cycles and thus increased recruitment of Esox species

Efeito cicatrizante e atividade antibacteriana da Calendula officinalis L. cultivada no Brasil Healing effect and antibacterial activity of Calendula officinalis L. cultivated in Brazil

Desde a antiguidade propriedades medicinais são atribuídas às flores da Calendula officinalis L. (Asteraceae) destacando-se a atividade cicatrizante. Estudos sobre a atividade geral de plantas medicinais na cicatrização vêm sendo realizados, sem especificar sobre qual das fases da cicatrização a planta atua. Neste trabalho a atividade cicatrizante e antiinflamatória do extrato etanólico das flores da C. officinalis cultivada no Brasil foi avaliada em feridas cutâneas de ratos Wistar, por meio de avaliação macroscópica e histológica. A atividade antimicrobiana do extrato e das frações hexânica e diclorometano também foi avaliada. A atividade antiinflamatória do extrato etanólico da calêndula foi atribuída à diminuição da exsudação serosa, da hiperemia, da deposição de fibrina e da hiperplasia epidermal, além de resultar em crostas mais delgadas e umedecidas. Observaram-se também aumento de colágeno no tecido de granulação e efeito antibacteriano. Assim, o extrato etanólico da calêndula atuou de forma positiva sobre a atividade cicatricial em feridas cutâneas de ratos, bem como apresentou atividade antibacteriana in vitro.<br>Since ancient history medicinal properties are attributed to flowers of Calendula officinalis L. (Asteraceae), mainly concerning its healing activity. Studies about the general activity of medicinal plants in healing wounds have been conducted without specifying in which healing phase the plant acts. In this work, the anti-inflammatory and healing activity of the ethanolic extract of C. officinalis flowers cultured in Brazil was evaluated in cutaneous wounds of Wistar rats through macroscopic and histological evaluation. The antibacterial activity of the extract and dichloromethane and hexane fractions was also evaluated. The anti-inflammatory activity of calendula ethanolic extract led to a reduction in plasmatic exudation, hyperemia, fibrin deposition and epidermal hyperplasia, besides resulting in less edematous crusts. There was also an increase in collagen in the granulation tissue and an antibacterial effect. Therefore, calendula ethanolic extract positively acted on the healing process of cutaneous wounds of rats and presented in vitro antibacterial activity