P and K additions enhance canopy N retention and accelerate the associated leaching

This study evaluated the interactive effects of combined phosphorus (P) and potassium (K) additions on canopy nitrogen (N) retention (CNR) and subsequent canopy leaching at a long-term N manipulation site on Whim bog in south Scotland. Ambient deposition is 8 kg N ha-1 year-1 and an additional 8, 24, and 56 kg N ha-1 year-1 of either ammonium (NH4+) or nitrate (NO3-) with or without P and K has been applied over 11 years. Throughfall N deposition below Calluna vulgaris and foliar N and P concentrations were assessed. Results showed that 60% for low dose and 53% for high dose of NO3- contrasting with 80% for low dose and 38% for high dose of NH4+ onto Calluna was retained by Calluna canopy. The CNR was enhanced by P and K addition in which 84% of NO3 - and 83% of NH4+ for high dose were retained. CNR for NO3- increased the canopy leaching of dissolved organic N (DON) and associated organic anions. NH4+ retention increased canopy leaching of magnesium and calcium through ion exchange. Even over 11-years N exposure without P and K, foliage 29 N:P ratio of Calluna did not increase, suggesting that N exposure did not lead to N saturation of Calluna at Whim bog. Our study concluded that increases in P and K availability enhance CNR of Calluna, but accelerate the associated canopy leaching of DON and base cations, depending on foliar N status

Comparison of Different Strategies for Providing Fecal Microbiota Transplantation to Treat Patients with Recurrent Clostridium difficile Infection in Two English Hospitals: A Review

Fecal microbiota transplant (FMT) has emerged as a highly efficacious treatment for difficult cases of refractory and/or recurrent Clostridium difficile infection (CDI). There have been many well-conducted randomized controlled trials and thousands of patients reported in case series that describe success rates of approximately 90% following one or more FMT. Although the exact mechanisms of FMT have yet to be fully elucidated, replacement or restoration of a ‘normal’ microbiota (or at least a microbiota resembling those who have never had CDI) appears to have a positive effect on the gut dysbiosis that is thought to exist in these patients. Furthermore, despite being aesthetically unappealing, this ‘ultimate probiotic’ is a particularly attractive solution to a difficult problem that avoids repeated courses of antibiotics. The lack of clarity about the exact mechanism of action and the ‘active ingredient’ of FMT (e.g., individual or communities of bacteria, bacteriophage, or bioactive molecules such as bile acids) has hindered the ability to produce a standardized and well-characterized FMT product. There is no standard method to produce material for FMT, and there are a multitude of factors that can vary between institutions that offer this therapy. Only a few studies have directly compared clinical efficacy in groups of patients who have been treated with FMT prepared differently (e.g., fresh vs. frozen) or administered by different route (e.g., by nasojejunal tube, colonoscopy or by oral administration of encapsulated product). More of these studies should be undertaken to clarify the superiority or otherwise of these variables. This review describes the methods and protocols that two English NHS hospitals independently adopted over the same time period to provide FMT for patients with recurrent CDI. There are several fundamental differences in the methods used, including selection and testing of donors, procedures for preparation and storage of material, and route of administration. These methods are described in detail in this review highlighting differing practice. Despite these significant methodological variations, clinical outcomes in terms of cure rate appear to be remarkably similar for both FMT providers. Although both hospitals have treated only modest numbers of patients, these findings suggest that many of the described differences may not be critical factors in influencing the success of the procedure. As FMT is increasingly being proposed for a number of conditions other than CDI, harmonization of methods and techniques may be more critical to the success of FMT, and thus it will be important to standardize these as far as practically possible

Ammonia exposure promotes algal biomass in an ombrotrophic peatland

Nitrogen pollution affects many peatlands with consequences for their biodiversity and ecosystem function. Microorganisms control nutrient cycling and constitute most of the biodiversity of peatlands but their response to nitrogen is poorly characterised and likely to depend on the form of deposition. Using a unique field experiment we show that ammonia exposure at realistic point source levels is associated with a general shift from heterotrophic (bacteria and fungi) to autotrophic (algal) dominance and an increase in total biomass. The biomass of larger testate amoebae increased, suggesting increased food supply for microbial predators. Results show the widespread impacts of N pollution and suggest the potential for microbial community-based bioindicators in these ecosystems

Long-term interactive effects of N addition with P and K availability on N status of Sphagnum

Little information exists concerning the long-term interactive effect of nitrogen (N) addition with phosphorus (P) and potassium (K) on Sphagnum N status. This study was conducted as part of a long-term N manipulation on Whim bog in south Scotland to evaluate the long-term alleviation effects of phosphorus (P) and potassium (K) on N saturation of Sphagnum (S. capillifolium). On this ombrotrophic peatland, where ambient deposition was 8 kg N ha−1 yr−1, 56 kg N ha−1 yr−1 of either ammonium (NH4+, Nred) or nitrate (NO3−, Nox) with and without P and K, were added over 11 years. Nutrient concentrations of Sphagnum stem and capitulum, and pore water quality of the Sphagnum layer were assessed. The N-saturated Sphagnum caused by long-term (11 years) and high doses (56 kg N ha−1 yr−1) of reduced N was not completely ameliorated by P and K addition; N concentrations in Sphagnum capitula for Nred 56 PK were comparable with those for Nred 56, although N concentrations in Sphagnum stems for Nred 56 PK were lower than those for Nred 56. While dissolved inorganic nitrogen (DIN) concentrations in pore water for Nred 56 PK were not different from Nred 56, they were lower for Nox 56 PK than for Nox 56 whose stage of N saturation had not advanced compared to Nred 56. These results indicate that increasing P and K availability has only a limited amelioration effect on the N assimilation of Sphagnum at an advanced stage of N saturation. This study concluded that over the long-term P and K additions will not offset the N saturation of Sphagnum

Sphagnum can ‘filter’ N deposition, but effects on the plant and pore water depend on the N form

The ability of Sphagnum moss to efficiently intercept atmospheric nitrogen (N) has been assumed to be vulnerable to increased N deposition. However, the proposed critical load (20 kg N ha− 1 yr− 1) to exceed the capacity of the Sphagnum N filter has not been confirmed. A long-term (11 years) and realistic N manipulation on Whim bog was used to study the N filter function of Sphagnum (Sphagnum capillifolium) in response to increased wet N deposition. On this ombrotrophic peatland where ambient deposition was 8 kg N ha− 1 yr− 1, an additional 8, 24, and 56 kg N ha− 1 yr− 1 of either ammonium (NH4+) or nitrate (NO3−) has been applied for 11 years. Nutrient status of Sphagnum and pore water quality from the Sphagnum layer were assessed. The N filter function of Sphagnum was still active up to 32 kg N ha− 1 yr− 1 even after 11 years. N saturation of Sphagnum and subsequent increases in dissolved inorganic N (DIN) concentration in pore water occurred only for 56 kg N ha− 1 yr− 1 of NH4+ addition. These results indicate that the Sphagnum N filter is more resilient to wet N deposition than previously inferred. However, functionality will be more compromised when NH4+ dominates wet deposition for high inputs (56 kg N ha− 1 yr− 1). The N filter function in response to NO3− uptake increased the concentration of dissolved organic N (DON) and associated organic anions in pore water. NH4+ uptake increased the concentration of base cations and hydrogen ions in pore water though ion exchange. The resilience of the Sphagnum N filter can explain the reported small magnitude of species change in the Whim bog ecosystem exposed to wet N deposition. However, changes in the leaching substances, arising from the assimilation of NO3− and NH4+, may lead to species change

Meteorological measurements at Auchencorth Moss from 1995 to 2016

The Auchencorth Moss atmospheric observatory has being measuring meteorological parameters since 1995. The site was originally set‐up to measure the deposition of sulphur dioxide at a site that represented the vegetation and climate typical of NW Europe, in relatively clean background air. It is one of the longest running flux monitoring sites in the region, over semi‐natural vegetation, providing infrastructure and support for many measurement campaigns and continuous monitoring of air pollutants and greenhouse gases. The meteorological sensors that are used, data processing and quality reviewing procedures are described for a set of core measurements up to 2016. These core measurements are essential for the interpretation of the other atmospheric variables

Satellite-based terrestrial production efficiency modeling

Production efficiency models (PEMs) are based on the theory of light use efficiency (LUE) which states that a relatively constant relationship exists between photosynthetic carbon uptake and radiation receipt at the canopy level. Challenges remain however in the application of the PEM methodology to global net primary productivity (NPP) monitoring. The objectives of this review are as follows: 1) to describe the general functioning of six PEMs (CASA; GLO-PEM; TURC; C-Fix; MOD17; and BEAMS) identified in the literature; 2) to review each model to determine potential improvements to the general PEM methodology; 3) to review the related literature on satellite-based gross primary productivity (GPP) and NPP modeling for additional possibilities for improvement; and 4) based on this review, propose items for coordinated research

Concentration-dependent deposition velocities for ammonia: moving from lab to field

Estimates of the dry deposition of ammonia (NH3) gas in a field fumigation experiment on an ombrotrophic bog have been made by the inferential technique, using measured wind speed at 2 m, and air concentrations at two heights above the vegetation. The parameters for a concentration-dependent surface resistance term were derived from flux measurements over the same vegetation in a chamber study, separating stomatal from non-stomatal resistances (Jones et al., Atmos Environ, 41, 2049-1061, 2007). Application of these values to the field experiment led to estimates of NH3-N deposition from 3 kg N ha−1y−1 in ambient air, with an NH3 concentration at 0.5 m above the canopy of 0.7 μg m−3, to 70 kg N ha−1y−1 where annual average air concentrations were 100 μg m−3 and concentrations during fumigation were up to 1600 μg m−3. The equivalent deposition velocities (at z=0.5 m) were 0.016 m s−1 in ambient air and 0.003 m s−1 at100 μg m−3. The differences between annual deposition estimates made from independent air concentration data at 0.1 m and 0.5 m above the canopy were small for distances more than 10 m from the source, after vertical mixing was complete. Over 4 years (2003 to 2006) and at 8 sampling points more than 10 m from the NH3 source, the mean difference between the dry deposition estimates, using NH3 concentrations measured at 0.1 m and 0.5 m above the canopy, was 2%. Use of a constant surface resistance, with no concentration dependence, as commonly used in inferential models of dry deposition, would have predicted deposition up to 8 times too large for this experimental examination of the direct effects of NH3 on bog vegetation

Effects of dry and wet N deposition on vegetation and biogeochemistry of an ombrotrophic bog

It has repeatedly been shown that increased nitrogen (N) deposition results in dramatic shifts in vegetation composition. The sources of N-deposition vary from agriculture (mainly NH3 and NH4) to industry and traffic (mainly NOx). Effects of these different N forms on the vegetation and biogeochemistry of an ombrotrophic peat bog, Whim Moss (~15km southwest of Edinburgh), have been investigated since April 2002, by employing an automate N manipulation system. This field experiment, uniquely, offers the possibility to investigate the effects of the different N forms at the same site and at application rates and deposition scenarios simulating natural variation in rainfall. Within the manipulation system there are two N manipulations: Dry, where gaseous NH3 is released over a 60 m transect at concentrations that simulate a 100,000 bird poultry unit (0.4-200 μg m-3), and Wet, as soluble nitrate or ammonium, covering the full range of UK wet N-deposition (8 – 64 kg N ha-1yr-1). The effects of dry N deposition on the vegetation and biogeochemistry at different distances from the NH3 source have been analysed. In the wet N deposition experiment, 5 treatments were followed, ranging from 8-64 kg N ha-1yr-1 and differing in N form as either oxidised or reduced N. Samples of soil water were obtained using mini-rhizon samplers and were tested for pH, NH4, NO3, P and base cations. Young (1 year old) shoots of Calluna vulgaris L. (Hull), Erica tetralix L. and Sphagnum capillifolium Ehrh. (Hedw.) were harvested and tested for chlorophyll concentrations, aminoacids and P and base cation concentrations in acid digests. The preliminary results show differences between treatment N forms and N doses and along the NH3 gradient. In this presentation we will focus on the plant responses to the changes in the biochemistry. CAPER Conferenc