High‐frequency fire alters C : N : P stoichiometry in forest litter

Fire is a major driver of ecosystem change and can disproportionately affect the cycling of different nutrients. Thus, a stoichiometric approach to investigate the relationships between nutrient availability and microbial resource use during decomposition is likely to provide insight into the effects of fire on ecosystem functioning. We conducted a field litter bag experiment to investigate the long‐term impact of repeated fire on the stoichiometry of leaf litter C, N and P pools, and nutrient‐acquiring enzyme activities during decomposition in a wet sclerophyll eucalypt forest in Queensland, Australia. Fire frequency treatments have been maintained since 1972, including burning every 2 years (2yrB), burning every 4 years (4yrB) and no burning (NB). C : N ratios in freshly fallen litter were 29–42% higher and C : P ratios were 6–25% lower for 2yrB than NB during decomposition, with correspondingly lower 2yrB N : P ratios (27–32) than for NB (34–49). Trends in litter soluble and microbial N : P ratios were similar to the overall litter N : P ratios across fire treatments. Consistent with these, the ratio of activities for N‐acquiring to P‐acquiring enzymes in litter was higher for 2yrB than NB, whereas 4yrB was generally intermediate between 2yrB and NB. Decomposition rates of freshly fallen litter were significantly lower for 2yrB (72 ± 2% mass remaining at the end of experiment) than for 4yrB (59 ± 3%) and NB (62 ± 3%), a difference that may be related to effects of N limitation, lower moisture content, and/or litter C quality. Results for older mixed‐age litter were similar to those for freshly fallen litter although treatment differences were less pronounced. Overall, these findings show that frequent fire (2yrB) decoupled N and P cycling, as manifested in litter C : N : P stoichiometry and in microbial biomass N : P ratio and enzymatic activities. Furthermore, these data indicate that fire induced a transient shift to N‐limited ecosystem conditions during the postfire recovery phase.     

Everything in moderation: Archaea as ‘non-extremophiles’

Well characterized and cultivated archaea are prokaryotic specialists that thrive in habitats of elevated temperature, low pH, high salinity, or strict anoxia. Recently, however, new groups of abundant, uncultivated archaea have been found to be widespread in more pedestrian biotopes, including marine plankton, terrestrial soils, lakes, marine and freshwater sediments, and in association with metazoa. Research efforts are presently focused on characterizing the physiology, biochemistry and genetics of these abundant and cosmopolitan but poorly understood archaea.     

Biogeographic bases for a shift in crop C : N : P stoichiometries during domestication

We lack both a theoretical framework and solid empirical data to understand domestication impacts on plant chemistry. We hypothesised that domestication increased leaf N and P to support high plant production rates, but biogeographic and climate patterns further influenced the magnitude and direction of changes in specific aspects of chemistry and stoichiometry. To test these hypotheses, we used a data set of leaf C, N and P from 21 herbaceous crops and their wild progenitors. Domestication increased leaf N and/or P for 57% of the crops. Moreover, the latitude of the domestication sites (negatively related to temperature) modulated the domestication effects on P (+), C (?), N : P (?) and C : P (?) ratios. Further results from a litter decomposition assay showed that domestication effects on litter chemistry affected the availability of soil N and P. Our findings draw attention to evolutionary effects of domestication legacies on plant and soil stoichiometry and related ecosystem services (e.g. plant yield and soil fertility).     

N : P stoichiometry and protein : RNA ratios in vascular plants: an evaluation of the growth-rate hypothesis

The growth-rate hypothesis states that fast-growing organisms need relatively more phosphorus-rich RNA to support rapid rates of protein synthesis, and therefore predicts, within and among taxa, increases in RNA and phosphorus content (relative to protein and nitrogen content) with increased growth rate. Here, we present a test of this hypothesis in vascular plants. We determined nitrogen : phosphorus ratios and protein : RNA ratios in pines growing at different rates due to nutrient conditions. In general, when comparing leaves of the same species at low and high growth rates, the faster-growing plants had higher RNA content, higher %N and %P, and lower protein : RNA ratios, but not consistently lower N : P ratios. We found no link between growth rate and foliar N : P or protein : RNA when comparing multiple species of different inherent growth rates. We conclude that plants adjust the balance of protein and RNA to favour either speed or efficiency of protein synthesis, but this balance does not alone dictate leaf stoichiometry.     

Determinants of seston C : P-ratio in lakes

1. The ratio of carbon to phosphorus (C : P) in seston is a major determinant of energy transfer in aquatic food webs and may vary more than an order of magnitude owing to various extrinsic and intrinsic factors. In this study, the determinants of C : P‐ratios in lake particulate matter (seston) was assessed in 112 Norwegian lakes, covering a C : P (atomic ratio) from 24 to 1842 (mean 250). 2. No overall effects of lake area, season or latitude on C : P was detected. Particulate P, but not particulate C, correlated with C : P. Multivariate analysis including a range of lake properties revealed total dissolved P, as the major determinant of sestonic C : P, with the fraction of detritus in total seston, chlorophyll or Secchi depth and lake colour as significant contributors. Together these parameters explained 30% of observed variance if using dissolved P and 81% if using total P as input variable to the multivariate model. 3. Chlorophyll and Secchi depth were highly correlated and substitutable in the analysis. Phytoplankton community composition did not affect seston C : P, probably reflecting the fact that live phytoplankton generally contributed <25% of the seston pool. 4. Total P correlated positively with C : P and is the key determinant of phytoplankton biomass and thus Secchi depth; the latter parameters contributed negatively to seston C : P, probably owing to increased light attenuation. These lake data thus support the light : nutrient ratio hypothesis, i.e. that high light and low P cause skewed uptake ratios of C to P. 5. Zooplankton biomass in general and Daphnia biomass in particular, was negatively correlated with C : P, probably reflecting a negative impact of poor seston quality at high C : P. Zooplankton grazing and nutrient recycling may also have contributed to a negative correlation between zooplankton biomass and sestonic C : P.     

Focus: Bioethics: Holy Simplicity: The Physician’s Role in End-of-Life Conversations

Early initiation of end-of-life (EOL) conversations has been shown to improve patient agency in dying, increase early access to hospice care, and facilitate a dignified death. Despite the benefits of early initiation, EOL conversations do not occur as readily as physicians or patients wish. While medicine is commonly considered both a science and an art, increasing medicalization may narrow a clinician’s focus towards procedures or specialized clinical frameworks rather than a patient’s end-of-life wishes. Since physicians are ambassadors of clinical knowledge and are trusted patient advocates, it is important they facilitate EOL conversations early in the dying process. Patients desire their physicians to convene these conversations. However, physicians are often hesitant to do so. Notable theologians, philosophers, and physicians offer a broad framework outlining the importance of physician-led EOL conversations.     

The C : N : P stoichiometry of autotrophs – theory and observations

Evolution has set biochemical constraints on the chemical composition of living organisms. These constraints seem to lead to increases in N : C and P : C ratios with increasing relative growth rate for all types of organisms. The N : P ratio also seems to decrease with relative growth rate for heterotrophs whereas autotrophs may show a more complex behaviour. Here I will show that, from biochemical considerations, N : C should increase linearly and P : C quadratically with relative growth rate in autotrophs with the consequence that N : P increases at low relative growth rates, passes a maximum and then decreases at high relative growth rates. These predictions are verified against observations for a freshwater alga (Selenastrum minutum) and a tree seedling (Betula pendula). Changes in temperature, light or other factors that affect the growth rate of autotrophs interact with nutrient supply in such a way that there are no simple rules for as to how N : P will change.     

Equivocal locations: being ‘red’ in ‘Red Bologna’

This article addresses a classic ethnographic problem in the study of Italy: how is it that people can subscribe simultaneously to seemingly contradictory ideologies, such as Catholicism and Communism? It does so by describing examples from Italy's ‘showcase city’ of the left, ‘Red Bologna’, in which to be ‘red’ is ubiquitous but each person's ‘red’ is a different thing: being ‘red’ (differently) is the idiom in which real political distinctions are expressed over issues like religion or immigration. In parallel, I discuss the relationship between the ‘field’ as a location and the ‘field’ as a conceptual topic. My account replicates internal ethnographic differences at the analytical level by highlighting the differences between being left‐wing in Bologna and its meaning as a concept in anthropology. Hence the ‘equivocal location’: a field‐site that is productively different, from what an inexperienced ethnographer expected from it, from conceptual discussions in anthropology, and from itself.