Nitrogen is the major nutrient limiting plant growth in terrestrial ecosystems, and the transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil micro‐organisms. The last decade has witnessed many significant advances in our understanding of plant–microbe interactions with evidence that plants have evolved multiple strategies to cope with nitrogen limitation by shaping and recruiting nitrogen‐cycling microbial communities. However, most studies have typically focused on the impact of plants on only one, or relatively few, processes within the nitrogen cycle. This review synthesizes recent advances in our understanding of the various routes by which plants influence the availability of nitrogen via an array of interactions with different guilds of nitrogen‐cycling micro‐organisms. We also propose a plant trait‐based framework for linking plant nitrogen acquisition strategies to the activities of nitrogen‐cycling microbial guilds. In doing so, we provide a more comprehensive picture of the ecological relationships between plants and nitrogen‐cycling micro‐organisms in terrestrial ecosystems. Finally, we identify previously overlooked processes within the nitrogen cycle that could be targeted in future research and be of interest for plant health or for improving plant nitrogen acquisition, while minimizing nitrogen inputs and losses in sustainable agricultural systems. A plain language summary is available for this article.
Sclerococcum sphaerale, a lichenicolous fungus growing on Pertusaria corallina, has been obtained in culture for the first time. The behaviour of the species is described and compared to that on the host. Material in culture and on the host was also studied by SEM. The ability to grow lichenicolous fungi in culture should render physiological studies on them feasible.
Shrublands cover a large proportion of the world’s land surface, yet they remain poorly studied in comparison to other ecosystems. Within shrublands, soil organic matter (SOM) is replenished from inputs of both above- and below-ground plant litter, however, their relative importance depends on their respective turnover rates. To critically address this, we measured the biodegradation rates of the soluble and insoluble components of 14C-labelled above- and below-ground plant litter in soil. During the 150day incubation, the amount of plant-derived soluble-C lost as 14CO2 was similar for the different plant parts being 64.7±2.3% for roots, 72.1±7.4% for stems, and 72.4±1.8% for leaves. In comparison, the turnover of the insoluble fraction was much slower. However, again little difference in mineralisation was seen for the different plant parts with the total losses being 21.1±0.9% for roots, 19.5±1.6% for stems, and 19.6±1% for leaves. A double exponential first order kinetic model fitted well to the experimental data. It also allowed the partitioning of C between microbial anabolic and catabolic processes for the soluble C component. Using this model, we deduced that the soluble fraction turns over ca. 40 times annually, whereas it takes ca. 2.5 years to turnover the insoluble fraction. For the soluble plant component, the overall microbial carbon use efficiency (CUE) was estimated to be greater for root-derived C in comparison to that derived from aboveground (no difference was observed for the insoluble component). From this, we tentatively suggest that C sourced from belowground plant components may persist longer in soil than C derived from aboveground plant components.
Air travel mediates transboundary movement of SARS-CoV-2. To prepare for future pandemics, we sought to understand air passenger behaviour and perceived risk during the COVID-19 pandemic. This study of UK adults ( n = 2103) quantified knowledge of COVID-19 symptoms, perceived health risk of contracting COVID-19, likelihood of returning to the UK with COVID-19 symptoms, likelihood to obey self-quarantining guidelines, how safe air travellers felt when flying during the pandemic ( n = 305), and perceptions towards face covering effectiveness.Overall knowledge of COVID-19 symptoms was poor. Men and younger age groups (18–44) were less informed than women and older age groups (44 +). A significant proportion (21%) of the population would likely travel back to the UK whilst displaying COVID-19 symptoms with many expressing that they would not fully comply with self-isolation guidelines. Overall, males and younger age groups had a reduced perceived personal risk from contracting COVID-19, posing a higher risk of transporting SARS-CoV-2 back to the UK. Poor passenger knowledge and behaviour undermines government guidelines and policies aimed at preventing SARS-CoV-2 entry into the UK. This supports the need for stricter, clearer and more targeted guidelines with point-of-departure viral testing and stricter quarantining upon arrival.
International air travel is now widely recognised as one of the primary mechanisms responsible for the transnational movement and global spread of SARS-CoV-2. Monitoring the viral load and novel lineages within human-derived wastewater collected from aircraft and at air transport hubs has been proposed as an effective way to monitor the importation frequency of viral pathogens. The success of this approach, however, is highly dependent on the bathroom and defecation habits of air passengers during their journey. In this study of UK adults (n = 2103), we quantified the likelihood of defecation prior to departure, on the aircraft and upon arrival on both short- and long-haul flights. The results were then used to assess the likelihood of capturing the signal from infected individuals at UK travel hubs. To obtain a representative cross-section of the population, the survey was stratified by geographical region, gender, age, parenting status, and social class. We found that an individual's likelihood to defecate on short-haul flights (< 6 h in duration) was low (< 13 % of the total), but was higher on long-haul flights (< 36 %; > 6 h in duration). This behaviour pattern was higher among males and younger age groups. The maximum likelihood of defecation was prior to departure (< 39 %). Based on known SARS-CoV-2 faecal shedding rates (30–60 %) and an equal probability of infected individuals being on short- (71 % of inbound flights) and long-haul flights (29 %), we estimate that aircraft wastewater is likely to capture ca. 8–14 % of SARS-CoV-2 cases entering the UK. Monte Carlo simulations predicted that SARS-CoV-2 would be present in wastewater on 14 % of short-haul flights and 62 % of long-haul flights under current pandemic conditions. We conclude that aircraft wastewater alone is insufficient to effectively monitor all the transboundary entries of faecal-borne pathogens but can form part of a wider strategy for public heath surveillance at national borders.
