Nitrogen budgets of urban lawns under three different management regimes in southern California

We constructed nitrogen (N) budgets for the lawns of three simulated residences built to test the environmental impacts of three different residential landscape designs in southern California. The three designs included: a “Typical” lawn planted with cool season tall fescue (Schedonorus phoenix), fertilized at the recommended rate for this species (192 kg^?1 ha^?1 year^?1) and irrigated with an automatic timer; a design intended to lower N and water requirements (“Low Input”) with the warm season seashore paspalum (Paspalum vaginatum) fertilized at 123 kg^?1 ha^?1 year^?1 and irrigated with a soil moisture-based system; and a design incorporating local best practices (“Low Impact” lawn) that included the native sedge species Carex, fertilized at 48 kg^?1 ha^?1 year^?1 and irrigated by a weather station-based system. Plant N uptake accounted for 33.2 ± 0.5 (tall fescue), 53.7 ± 0.7 (seashore paspalum), and 12.2 ± 1.3 % (Carex) of annual N inputs, while estimated N retention in soil was relatively large and similar in the three lawns (41–46 %). At lower N and water inputs than Typical, Low Input showed the highest annual clipping yield and N uptake, although it also had higher denitrification rates. Leaching inorganic N losses remained low even from the Typical lawn (2 %), while gaseous N losses were highly variable. The Low Input lawn was most efficient in retaining N with relatively low water and N costs, although its fertilization rates could be further reduced to lower gaseous N losses. Our results suggest that the choice of a warm-season, C₄ turf species with reduced rates of irrigation and fertilization is effective in this semi-arid region to maintain high productivity and N retention in plants and soils at low N and water inputs.     

The role of hydrodynamic sorting on the accumulation and distribution of organic carbon in an impoundment: Englebright Lake,California, USA

The global proliferation of dams is one of the most significant anthropogenic impacts on the environment, resulting in the trapping of massive loads of sediment and nutrients in impoundments. Few studies, however, have examined these impounded sediments to understand patterns of organic carbon (OC) accumulation and the effects of watershed processes on carbon delivery. This study measured total organic carbon (TOC) and stable isotopes of carbon and nitrogen (δ¹³C and δ¹⁵N) in Englebright Lake, CA to relate changes in OC sources and TOC accumulation to natural and anthropogenic events in the watershed and to depositional processes in the lake. Englebright Lake is a representative system for impoundments in small, mountainous rivers, and anthropogenic disturbances in the watershed caused high sediment accumulation rates in the lake. Throughout its 60-year history, 0.35 Tg OC has been trapped behind Englebright Dam and δ¹³C signatures indicate that more than 50% of the OC in Englebright Lake was derived from terrigenous sources. TOC content ranged from 0.03 to 30.24% of dry weight, and differed across depositional regimes; TOC content in topset deposits (0.35 ± 0.58%) was less than in foreset (2.64 ± 5.95%) and bottomset (1.51 ± 1.41%) deposits (p < 0.001) and TOC accumulation associated with flood events was higher (up to 231 kg_OC m^?2 year^?1) than during non-event periods (0.2 to 39 kg_OC m^?2 year^?1). TOC accumulation rates in Englebright Lake were up to an order of magnitude higher than previous estimates of OC burial in California impoundments. As the number and size of dams continues to expand worldwide, the storage of TOC in impoundments will likely add to the growing number of anthropogenic modifications to the global carbon cycle.     

Stable isotopic composition of carbon and nitrogen and nitrogen content in vascular epiphytes along an altitudinal transect*

The foliar content of nitrogen and the relative abundances of ¹³C and ¹⁵N were analysed in vascular epiphytes collected from six sites along an altitudinal gradient from tropical dry forests to humid montane forests in eastern Mexico. The proportion of epiphyte species showing crassulacean acid metabolism (CAM) (atmospheric bromeliads, thick-leaved orchids, Cactaceae, and Crassulaceae) decreased with increasing elevation and precipitation from 58 to 6%. Atmospheric bromeliads, almost all of which had δ ¹³C values indicating CAM, were more depleted in ¹⁵N (x = ? 10·9‰ ± 2·11) than the C₃ bromeliads which form water-storing tanks ( ? 6·05‰ ± 2·26). As there was no difference in δ ¹⁵N values between C₃ and CAM orchids, the difference in bromeliads was not related to photosynthetic pathways but to different nitrogen sources. While epiphytes with strong ¹⁵N depletion appear to obtain their nitrogen mainly from direct atmospheric deposition, others have access to nitrogen in intercepted water and from organic matter decomposing on branches and in their phytotelmata. Bromeliads and succulent orchids had a lower foliar nitrogen content than thin-leaved orchids, ferns and Piperaceae. Ground-rooted hemi-epiphytes exhibited the highest nitrogen contents and δ ¹⁵N values.     

Impact of nutritional conditions on yields,germination rate and shelf-life of Plectosporium alismatis conidia and chlamydospores as potential candidates for the development of a mycoherbicide of weeds in rice crops

The effect of nutritional conditions on spore qualities was investigated in order to select which propagules, conidia or chlamydospores, would be most suitable for mycoherbicide development. Plectosporium alismatis was grown in a liquid basal medium supplemented with glucose and a mineral nitrogen source (sodium nitrate) or an organic nitrogen source (casamino acids). Conidial and chlamydospore yields, germination rate and shelf-life were compared. Two growth models were developed: on one hand, sodium nitrate added as the sole nitrogen source was partially utilised (8%), resulting in poor growth (1.77±0.02 mg mL^?1; 6±1.7×10⁵ conidia mL^?1). Under these conditions, P. alismatis produced dense, melanised-like aggregates that contained chlamydospores (12.4±0.7×10⁴ chlamydospores mL^?1). Germination rates of chlamydospores and conidia produced under these conditions was high (80%). Twenty percent of chlamydospores were able to germinate after 4 months storage at 25°C, while survival of conidia declined rapidly (<2%). When casamino acids were added to the liquid medium as the sole nitrogen source, P. alismatis produced sparser pellets resulting in high dry weights (5.37±0.09 mg mL^?1 and high conidia numbers (9.6±1.5×10⁶ conidia mL^?1), while no chlamydospore were observed. The germination rate of conidia produced in casamino acids was low (33±13%) after 8 h incubation and microcycle conidiation occurred. Five percent of these conidia germinated after 4 months storage. These data indicate that chlamydospores may be suitable for mycoherbicide development, provided further optimisation of yields is achieved.     

Seasonal dynamics and bioavailability of dissolved organic matter in two contrasting temperate estuaries

Production and bioavailability of dissolved organic matter (DOM) were followed during a year in the nutrient-rich estuary, Roskilde Fjord (RF), and the more oligotrophic strait, Great Belt (GB), in Denmark. Bioavailability of dissolved organic carbon (DOC), nitrogen (DON), and phosphorous (DOP) was determined during incubations over six months. Overall, RF had three to five times larger pools of total nitrogen (TN) and total phosphorous (TP) and five to eight times higher concentrations of inorganic nutrients compared to GB. However, the allocation of carbon, nitrogen, and phosphorous into different pools were remarkably similar between the two systems. DON and DOP contributed with about equal relative fractions in the two systems: 72 ± 13% of total nitrogen and 21 ± 12% of total phosphorous. The average bioavailability of DOM was 25 ± 15, 17 ± 5.5, and 49 ± 29% for carbon, nitrogen, and phosphorous, respectively. The observed release of DIN from degradation of DON amounted to between 0.1 (RF winter) and 14 times (GB summer) the loadings from land and contributed with half of the total input of bioavailable nitrogen during summer. Hence, this study shows that nitrogen in DOM is important for the nitrogen cycling, especially during summer. The sum of inorganic nutrients, particulate organic matter, and bioavailable DOM (the dynamic pools of nutrients) accounted for 42 and 92% of nitrogen, and phosphorous, respectively, and was remarkably similar between the two systems compared to the difference in nutrient richness. It is hypothesized that the pelagic metabolism of nutrients in marine systems dictates a rather uniform distribution of the different fractions of nitrogen and phosphorous containing compounds regardless of eutrophication level.     

Plastic ingestion in Asian elephants in the forested landscapes of Uttarakhand,India

Ecological impacts of plastic contamination on marine environment have been documented extensively, however its spread and impacts on terrestrial and freshwater fauna are still poorly understood. In the present study, we investigated diet of Asian elephant (Elephas maximus indicus) for plastic ingestion around forested habitats of Uttarakhand state in India. We quantified plastic particles and other anthropogenic waste from elephant dung samples collected from edges and interiors of forest areas, confirming plastic ingestion by this endangered mammal species. Each human-derived item was identified, measured, and sub-categorized into plastic or other anthropogenic waste. About one-third (32%) of the elephant dung samples showed presence of anthropogenic waste. Plastic particles ranging from size 1–355 mm, comprised of 85% of the waste recovered from elephant dung samples (47.08 ± 12.85 particles per sample). We found twice as many plastic particles (85.27 ± 33.7/ 100 g) in samples collected from inside forest as compared to forest edge (35.34 ± 11.14 plastic particles/100 g). A higher count (34.79 ± 28.41 items/100 g sample) of non-biodegradable anthropogenic waste (glass, metal, rubber bands, clay pottery and tile pieces) was obtained from samples collected inside the forest area samples as compared to forest edge samples (9.44 ± 1.91items/100 g). There were higher proportion of macroplastic (>5 mm) retrieved than microplastic (1–5 mm) in the elephant dung. The present study is the first systematic documentation of non-biodegradable waste ingestion by Asian elephants. High plastic presence in elephant dung highlights its widespread use near protected habitats and lack of waste segregation practices underlining the vulnerability of wild animals to plastic ingestion risk. We provide recommendations for developing a comprehensive solid waste management strategy to mitigate the threat of plastic pollution around critical elephant habitats in India.     

Improved cryopreservation of domestic cat sperm in a chemically defined medium

The objective was to compare a proprietary egg yolk-based cryopreservation medium with a chemically defined soy-based medium, as well as to examine effects of temperature of glycerol addition on sperm parameters and IVF after freezing and thawing of domestic cat sperm. Semen was collected from adult cats (four males and three ejaculates per male), divided in four equal aliquots, and extended in either egg yolk with 4% glycerol added before (EYG) or after (EY) cooling to 5 °C, or soy-lecithin with 4% glycerol added before (SLG) or after (SL) cooling to 5 °C. Extended sperm were frozen in straws over liquid nitrogen vapor. Sperm progressive motility (%) and rate of progressive movement (scale of 0–5) were evaluated at 0, 1, 3, 6, and 24 h post-thaw. Sperm capacitation, acrosome integrity, and DNA integrity were assessed at 15 min post-thaw. Effects of media (EY or SL) on IVF success was also examined (three males and three ejaculates per male). Sperm motility was greater (P < 0.05) in soy-based compared with egg yolk-based media at 3, 6, and 24 h post-thaw. A higher (P < 0.05) percentage of noncapacitated sperm (pattern F) were present in soy-based (SLG, 63.7 ± 9.2%; and SL, 64.1 ± 9.2%) compared with egg yolk-based (EYG, 49.9 ± 7.9%; and EY, 52.4 ± 18.6%) cryopreservation media, regardless of temperature of glycerol addition. Addition of glycerol at 5 °C increased (P < 0.05) percentage of sperm motility at 6 h (EYG 16.3 ± 8.3% vs. EY, 24.0 ± 11.7%; SLG, 36.7 ± 6.5% vs. SL, 42.9 ± 10.1%) and 24 h (EYG, 2.1 ± 3.3% vs. EY, 8.3 ± 3.9%; SLG, 11.3 ± 8.3% vs. SL, 18.8 ± 7.4%) post-thaw in both media. There were no differences (P > 0.05) between cryodiluents in embryo cleavage, percentage of embryos reaching blastocyst, or cell number per blastocyst. The chemically defined, soy-based medium resulted in better preservation of long-term motility and capacitation status of frozen-thawed domestic cat sperm compared with a commercial egg yolk-based extender, without compromising fertilizing ability.     

The effect of nitrogen fertilization on the release of soil nitrogen

Summary The effect of fertilizer nitrogen on the available amount of soil nitrogen was investigated in a greenhouse experiment. To 9 different soils, 0, 50, 100 and 200 kg N/ha were applied, resp., as (N¹⁵H₄)₂SO₄ with an atom excess N-15 of 1%.No priming effect could be found for any of the treatments. The available amount of soil N, expressed as A_N value, was not affected by rate of N-fertilizer application.     

The fate of nitrogen from winter-frozen rapeseed leaves: mineralization,fluxes to the environment and uptake by rapeseed crop in spring

For environmental purposes, very early sowing of winter rapeseed may reduce winter nitrate leaching thanks to the high N uptake capacities of rapeseed in autumn. However, freezing could lead to high losses of leaf nitrogen, amounting to more than 100 kg N ha^-1 (Dejoux et al., 1999). Here we investigated the agronomic and environmental consequences of the decomposition of fallen leaves, based on field and laboratory studies with ¹⁵N labeled leaves (C:N=9). The potential kinetics of decomposition of leaves were measured by incubation in the laboratory. In the field, all leaves were removed at beginning of winter and replaced by labeled leaves, artificially frozen at −15°C , which were laid on the soil surface. Compared on a thermal time basis, decomposition proceeded as quickly in the field as in the incubations and was complete after 116 normalized days at 15 °C. The proportion of ¹⁵N derived from labeled leaves, absorbed again by the rape plants, was 28% at flowering and 24% at harvest. This high N recovery is assumed to result from the synchronization of leaves decomposition and active N absorption by rape in spring. Leaf N mineralization did not increase soil N mineral content at flowering or at harvest, but we observed a 40% loss of ¹⁵N. As no leaching was simulated, this loss was supposed to be gaseous. Such a high percentage could be explained by the fact that the decomposing leaves lay on the soil surface, and by climatic conditions conducive to such emissions. For environmental purposes, the quantity and nature of these gaseous N emissions have to be studied for other climatic conditions and types of leaves. As a proportion of N is reabsorbed, N fertilizer application rates could be reduced accordingly. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of fixation on freshwater invertebrate carbon and nitrogen isotope composition and its arithmetic correction

Retrospective investigations using carbon and nitrogen stable isotope composition of archived material have a great potential for describing past effects of anthropogenic ecosystem alterations or natural shifts in ecosystems. In this study, we examined the effects of two commonly used preservation substances of freshwater invertebrates, ethanol and lugol, on δ¹³C and δ¹⁵N of various planktonic and benthic taxa. For both isotopes, the average effect of fixation in ethanol was stronger than in lugol, and the effects on δ¹³C were stronger than on δ¹⁵N (average ± SD: 1.18 ± 0.94 and −0.47 ± 0.99 for δ¹³C ethanol and lugol fixed samples, respectively, and 0.39 ± 0.68 and 0.17 ± 0.77 for δ¹⁵N, respectively). The changes in the isotopic composition were not dependent on the initial isotopic composition of each taxon, but were related with concomitant changes in the carbon or nitrogen content. Application of a mass balance correction equation to the fixed samples resulted in a significantly lower average effect of fixation in ethanol (0.01 ± 0.59 and 0.44 ± 0.65 for δ¹⁵N and δ¹³C, respectively), while corrections had little effect for lugol fixed samples (0.24 ± 0.53 and −0.39 ± 0.85, respectively). For both isotopes and fixatives, corrections resulted in linear relationships between fixed vs. control samples, with slopes and intercepts not significantly different from 1 and 0, respectively. Therefore, mass balance correction of stable isotopes in fixed invertebrates is recommended for minimising the effects of fixation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: M. Power     

Comparison of the trophic niches between two planktivorous fishes in two large lakes using stable isotope analysis

This paper studied the sources of food and the trophic levels of silver and bighead carps using stable isotopes (δ¹³C and δ¹⁵N) analysis in Lake Qiandao and Lake Taihu. The δ¹³C values of POM and phytoplankton indicated that Particulate Organic Matter (POM) is of terrestrial origin in LQ and phytoplankton origin in LT. The different signature of δ¹⁵N of phytoplankton and POM also showed the different extent of anthropogenic impacts on the two lakes, with higher impacts in LT than in LQ. In LQ the trophic levels of silver and bighead carps were significantly different (2.48 ± 0.19 and 2.66 ± 0.19, respectively), while in LT the difference was not significant (2.15 ± 1.54 and 2.36 ± 0.38, respectively). Using a mixing model, we found that silver and bighead carps consumed a major proportion on phytoplankton and/or POM in both lakes with higher contribution of phytoplankton in more eutrophic lake. Silver and bighead carps had clear differentiation in food resources with silver carp more on POM and bighead more on zooplankton in deep and mesotrophic lakes. Contrary to this, both carps fed primarily on phytoplankton (and POM) and may have more niche overlaps in shallow and eutrophic lakes.     

Roads as nitrogen deposition hot spots

Mobile sources are the single largest source of nitrogen emissions to the atmosphere in the US. It is likely that a portion of mobile-source emissions are deposited adjacent to roads and thus not measured by traditional monitoring networks, which were designed to measure long-term and regional trends in deposition well away from emission sources. To estimate the magnitude of near-source nitrogen deposition, we measured concentrations of both dissolved inorganic nitrogen (DIN) and total dissolved nitrogen (inorganic + organic) (TDN) in throughfall (i.e., the nitrogen that comes through the forest canopy) along transects perpendicular to two moderately trafficked roads on Cape Cod in Falmouth MA, coupled with measurements of both DIN and TDN in bulk precipitation made in adjacent open fields at the same transect distances. We used the TDN throughfall data to estimate total nitrogen deposition, including dry gaseous nitrogen deposition in addition to wet deposition and dry particle deposition. There was no difference in TDN in the bulk collectors along the transects at either site; however TDN in the throughfall collectors was always higher closest to the road and decreased with distance. These patterns were driven primarily by differences in the inorganic N and not the organic N. Annual throughfall deposition was 8.7 (±0.4) and 6.8 (±0.5) TDN kg N ha^?1 year^?1 at sites 10 and 150 m away from the road respectively. We also characterized throughfall away from a non-road edge (power line right-of-way) to test whether the increased deposition observed near road edges was due to deposition near emission sources or due to a physical, edge effect causing higher deposition. The increased deposition we observed near roads was due to increases in inorganic N especially NH₄ ⁺. This increased deposition was not the result of an edge effect; rather it is due to near source deposition of mobile source emissions. We scaled these results to the entire watershed and estimate that by not taking into account the effects of increased gaseous N deposition from mobile sources we are underestimating the amount of N deposition to the watershed by 13–25 %.     

Contribution of allochthonous resources to breeding in a high-arctic avian predator

Allochthonous input of resources (i.e., originating from a place other than where they are found) can have a significant impact on food availability for consumers. We assessed the impact of an allochthonous source of food (the sewage outfall stream of a military base) on an avian predator breeding in a low-productivity, high-arctic site (Alert, 83°N, 62°W, Ellesmere Island), the long-tailed skua (Stercorarius longicaudus). We collected blood samples throughout the breeding season during two contrasting years of lemming abundance to characterize diet composition of skuas and evaluated the contribution of the anthropogenic and lemming food sources using stable isotopes (carbon ¹³C and nitrogen ¹⁵N). The isotopic signature of skuas changed seasonally because they switch from a marine to a terrestrial diet when they come ashore to breed but also differed between the 2 years of the study. Anthropogenic food source accounted for 33 % of the summer diet but this proportion varied between years, from 41 % (5–95 ‰: 13–59 %) in a year of low lemming abundance to 16 % (5–95 ‰: 10–21 %) in a high year. Skua nest density recorded in years of low lemming abundance at Alert (0.15 nests/km²) was higher than at any other comparable arctic sites (0–0.02 nests/km²). Overall, the use of an anthropogenic food sources apparently subsidizes skua reproduction at this site, which could affect the food web of this low-productivity ecosystem.     

Riverine nitrogen export in Swedish catchments dominated by atmospheric inputs

We present the first estimates of net anthropogenic nitrogen input (NANI) in European boreal catchments. In Swedish catchments, nitrogen (N) deposition is a major N input (31–94%). Hence, we used two different N deposition inputs to calculate NANI for 36 major Swedish catchments. The relationship between riverine N export and NANI was strongest when using only oxidized deposition (NO_y) as atmospheric input (r² = 0.70) rather than total deposition (i.e., both oxidized and reduced nitrogen, NO_y + NH_x deposition, r² = 0.62). The y-intercept (NANI = 0) for the NANI calculated with NO_y is significantly different from zero (p = 0.0042*) and indicates a background flux from the catchment of some 100 kg N km^?2 year^?1 in addition to anthropogenic inputs. This agrees with similar results from North American boreal catchments. The slope of the linear regressions was 0.25 for both N deposition inputs (NO_y and NO_y + NH_x), suggesting that on average, 25% of the anthropogenic N inputs is exported by rivers to the Baltic Sea. Agricultural catchments in central and southern Sweden have increased their riverine N export up to tenfold compared to the inferred background flux. Although the relatively unperturbed northernmost catchments receive significant N loads from atmospheric deposition, these catchments do not show significantly elevated riverine N export. The fact that nitrogen export in Swedish catchments appears to be higher in proportion to NANI at higher loads suggests that N retention may be saturating as loading rates increase. In northern and western Sweden the export of nitrogen is largely controlled by the hydraulic load, i.e., the riverine discharge normalized by water surface area, which has units of distance time^?1. Besides hydraulic load the percent total forest cover also affects the nitrogen export primarily in the northern and western catchments.     

A δ<Superscript>15</Superscript>N assessment of nitrogen deposition for the endangered epiphytic orchid <Emphasis Type="Italic">Laelia speciosa</Emphasis> from a city and an oak forest in Mexico

Atmospheric nitrogen deposition poses a major threat to global biodiversity. Tropical epiphytic plants are especially at risk given their reliance on atmospheric sources of nutrients. The leaf, pseudobulb, and root carbon and nitrogen content, C:N ratio, as well as the nitrogen isotopic composition were studied for individuals of Laelia speciosa from a city and from an oak forest in Mexico. The nitrogen content of leaves was similar between the city and the oak forest, reaching 1.3 ± 0.2 % (dry mass). The δ¹⁵N of leaves, pseudobulbs, and roots reached 5.6 ± 0.2 ‰ in the city, values found in sites exposed to industrial and vehicular activities. The δ¹⁵N for plant from the oak forest amounted to –3.1 ± 0.3 ‰, which is similar to values measured from sites with low industrial activities. Some orchids such as Laelia speciosa produce a single pseudobulb per year, i.e., a water and nutrient storage organ, so the interannual nitrogen deposition was studied by considering the ten most recent pseudobulbs for plants from either site formed between 2003 and 2012. The C:N ratio of the ten most recent pseudobulbs from the oak forest, as well as that of the pseudobulbs formed before 2010 for plants in the city were indistinguishable from each other, averaging 132.4 ± 6.5, while it was lower for the two most recent pseudobulbs in the city. The δ¹⁵N values of pseudobulbs from the oak forest averaged ?4.4 ± 0.1 ‰ for the entire series. The δ¹⁵N ranged from 0.1 ± 1.6 ‰ for the oldest pseudobulb to 4.7 ± 0.2 ‰ for the pseudobulb formed in the city from 2008 onwards. Isotopic analysis and the C:N ratio for L. speciosa revealed that rates of nitrogen deposition were higher in the city than in the forest. The δ¹⁵N values of series of pseudobulbs showed that it is possible to track nitrogen deposition over multiple years.     

Long-term changes of the δ15N natural abundance of plants and soil in a temperate grassland

Tracing back the N use efficiency of long-term fertilizer trials is important for future management recommendations. Here we tested the changes in natural N-isotope composition as an indicator for N- management within a long-term fertilization lysimeter experiment in a low mountain range pasture ecosystem at Rengen (Eifel Mountains), Germany. Cattle slurry (δ¹⁵N?=?8.9?±?0.5‰) and mineral fertilizers (calcium ammonium nitrate; δ¹⁵N?=??1.0?±?0.2‰) were applied at a rate between 0 and 480 kg N ha^?1?yr^?1 throughout 20 years from 1985 onwards. In 2006, samples were taken from different grass species, coarse and fine particulate soil organic matter, bulk soil and leachates. Total soil N content hardly changed during fertilization experiment. As also N leaching has been small within the stagnant water regime, most N was lost through the gaseous phase beside plant uptake and cutting. Unlike N uptake by plants, the process of N volatilization resulted in strong discrimination against the ¹⁵N isotope. As a consequence, the δ¹⁵N values of top soil samples increased from 1.8?±?0.4‰ to 6.0?±?0.4‰ and that of the plants from ?1.2?±?1.3‰ to 4.8?±?1.2‰ with increasing N fertilizer rate. Samples receiving organic fertilizer were most enriched in δ¹⁵N. The results suggest that parts of the fertilizer N signal was preserved in soils and even discovered in soil organic matter pools with slow N turnover. However, a ¹⁵N/¹⁴N isotope fractionation of up to 1.5‰ added to the δ¹⁵N values recovered in soils and plants, rendering the increase in δ¹⁵N value a powerful indicator to long-term inefficient N usage and past N management in the terrestrial environment.     

Seasonal dynamics of N in two Sphagnum moss species and the underlying peat treated with 15NH415NO3

Uptake of 15N labelled NH4NO3 by two Sphagnum mosses on a raised bog in north east Scotland was measured at different times of the year. In a field experiment, fortnightly additions of NH4NO3 at natural abundance, equivalent to 3 g N m-2 yr-1, were made over 14 months to cores of Sphagnum capillifolium occupying hummocks and S. recurvum colonizing hollows. Pre-harvested cores were treated with 15NH415NO3 two weeks before harvesting and 15N abundance determined for the total N in the moss, inorganic and dissolved organic N (DON) in the moss water and extractable inorganic, organic and microbial N in the underlying peat. The proportion of added 15N taken up by the mosses two weeks after each addition averaged 72% and ranged between 11 and 100%, tending to be least during October when the rising water table reached the surface, particularly for S. recurvum. A small proportion of the 15N was detected in the moss water as NH4+ (0.01%) and as DON (0.03%) and on occasions a large proportion remained unaccounted for. In waters from S. capillifolium, DON was proportional to the amount of inorganic N added, but this was not the case for S. recurvum. Little or no 15N was detected in the underlying peat partly because of the large size and variability of the NH4+, DON and microbial N pools.     

Bio catalytic oxidation of sulphide laden wastewater from leather industry using sulfide: Quinone oxidoreductase immobilized bio reactor

Abstract

Anaerobic treatment of sulphate rich wastewater results in high amount of sulphide in liquid phase and gaseous phase. Sulphide is malodorous in gaseous phase and toxic even at very low concentrations in liquid phase and causes objectionable environmental issues. In the present investigation the sulphide present in the UASB treated post tanning wastewater was oxidised into elemental sulphur using Sulfide: Quinone oxidoreductase (SQR) immobilized Functionalized Carbon-silica matrix (FCSM) packed bed reactor. The variables employed for the production of Bacillus clausii biomass for the extraction of SQR were optimized using RSM. The purified SQR showed the maximum activity and stability at pH 6.0 to 8.0 and the percentage oxidation of sulphide at HRT of 24?h were 99.2%?±?0.2 at pH 6.0; 99.6%?±?0.2 at pH 7.0 and 99.6%?±?2.12 at pH 8.0. The effect of temperature on SQR activity was optimized and it established the maximum activity and stability at 40?°C with sulphide oxidation of 99.6%?±?0.8%. The optimum conditions for immobilization of SQR onto FCSM were time, 240?min; pH, 7.0; temperature, 40?°C and SQR concentration, 10?mg/g. The immobilization of SQR onto FCSM obeyed the Langmuir isotherm model. The immobilization of SQR onto FCSM was confirmed by SEM, FT-IR, XRD, TGA and DSC analyses. The SQR-FCSM packed bed reactor was operated separately for the oxidation of sulfide in UASB treated post-tanning wastewater under continuous mode at different HRTs and it recorded the maximum sulphide oxidation by 99?±?0.1% at HRT of 15?h with residual sulphide of 2.4?±?1.1?mg/L. The formation of elemental Sulphur was confirmed by XRD studies. The present investigation provides the scope for the removal of sulphide and thereby substantial reduction in Total Dissolved Solids from post tanning wastewater without addition of chemicals.     

Reconstructing terrestrial nutrient cycling using stable nitrogen isotopes in wood

Although recent anthropogenic effects on the global nitrogen (N) cycle have been significant, the consequences of increased anthropogenic N on terrestrial ecosystems are unclear. Studies of the impact of increased reactive N on forest ecosystems—impacts on hydrologic and gaseous loss pathways, retention capacity, and even net primary productivity—have been particularly limited by a lack of long-term baseline biogeochemical data. Stable nitrogen isotope analysis (ratio of ¹⁵N to ¹⁴N, termed δ¹⁵N) of wood chronologies offers the potential to address changes in ecosystem N cycling on millennial timescales and across broad geographic regions. Currently, nearly 50 studies have been published utilizing wood δ¹⁵N records; however, there are significant differences in study design and data interpretation. Here, we identify four categories of wood δ¹⁵N studies, summarize the common themes and primary findings of each category, identify gaps in the spatial and temporal scope of current wood δ¹⁵N chronologies, and synthesize methodological frameworks for future research by presenting eight suggestions for common methodological approaches and enhanced integration across studies. Wood δ¹⁵N records have the potential to provide valuable information for interpreting modern biogeochemical cycling. This review serves to advance the utility of this technique for long-term biogeochemical reconstructions.     

Nitrogen transformations in limed and nitrogen fertilized soil in Norway spruce stands

Nitrogen transformations in the soil, and the resulting changes in carbon and nitrogen compounds in soil percolate water, were studied in two stands of Norway spruce (Picea abies L.). Over the last 30 years the stands were repeatedly limed (total 6000 kg ha^–1), fertilized with nitrogen (total about 900 kg ha^–1), or both treatments together. Both aerobic incubations of soil samples in the laboratory, and intact soil core incubations in the field showed that in control plots ammonification widely predominated over nitrification. In both experiments nitrogen addition increased the formation of mineral-N. In one experiment separate lime and nitrogen treatments increased nitrification, in the other, only lime and nitrogen addition together had this effect. In one experiment immobilization of nitrogen to soil microbial biomass was lower in soil only treated with nitrogen. Soil percolate water was collected by means of lysimeters placed under the humus layer and 10 cm below in the mineral soil. Total N, NH₄-N and NO₃-N were measured, and dissolved organic nitrogen was fractioned according to molecular weight. NO₃-N concentrations in percolate water, collected under the humus layer, were higher in plots treated with N-fertilizer, especially when lime was also added. The treatments had no effect on the N concentrations in mineral soil. A considerable proportion of nitrogen was leached in organic form.