Dual community assembly processes in dryland biocrust communities

1. Biocrusts are critical components of drylands where they regulate a wide range of ecosystem functions, however, their response to the world‐wide phenomenon of shrub encroachment and to livestock grazing, the most extensive land use in drylands, is not well studied. Grazing by livestock and increases in shrub cover could influence biocrust communities directly via trampling or shading, or indirectly, by altering biotic interactions amongst biocrust taxa. The extent of these changes in biocrust cover, diversity and composition are poorly known. 2. We used linear models and structural equation modelling to examine the direct effects of grazing and shrubs on biocrust community composition and the indirect effects mediated by changes in species interactions. 3. Biocrust richness and cover increased with increasing shrub cover at the site level. This pattern occurred despite the negative response we found (lower cover and richness) under shrub patches versus open areas, which was consistent irrespective of the grazing level. Functional diversity and evenness were similar between shrubs and open at low grazing intensity, but at high grazing functional diversity was greater in the open. Competition between biocrust species was an important driver of their community assembly irrespective of shrub cover, grazing intensity or patch type. Structural equation models showed that the effects of grazing and shrub cover on functional evenness, functional diversity and richness were controlled by biotic interactions within the shrub microsites. In the open, however, these effects were either direct or mediated by changes in cover. 4. Biocrust cover, species richness and functional diversity increase with shrub cover at the site scale, despite the negative effects at the microsite level. We demonstrate here that drivers of community assembly differ markedly at small spatial scales. Though biocrust communities were directly driven by environmental filtering in the open, biotic interactions played a fundamental role in their assembly when growing beneath shrubs.Both authors acknowledge support from the Hermon Slade Foundation Grant no. HSF13/1. S.S. was supported by the Spanish Government under the Ramón y Cajal contract (RYC-2016-20604)

Subjective hunger, gastric upset, and sleepiness in response to altered meal timing during simulated shiftwork

Shiftworkers report eating during the night when the body is primed to sleep. This study investigated the impact of altering food timing on subjective responses. Healthy participants (n = 44, 26 male, age Mean ± SD = 25.0 ± 2.9 years, BMI = 23.82 ± 2.59kg/m2) participated in a 7-day simulated shiftwork protocol. Participants were randomly allocated to one of three eating conditions. At 00:30, participants consumed a meal comprising 30% of 24 h energy intake (Meal condition; n = 14, 8 males), a snack comprising 10% of 24 h energy intake (Snack condition; n = 14; 8 males) or did not eat during the night (No Eating condition; n = 16, 10 males). Total 24 h individual energy intake and macronutrient content was constant across conditions. During the night, participants reported hunger, gut reaction, and sleepiness levels at 21:00, 23:30, 2:30, and 5:00. Mixed model analyses revealed that the snack condition reported significantly more hunger than the meal group (p < 0.001) with the no eating at night group reporting the greatest hunger (p < 0.001). There was no difference in desire to eat between meal and snack groups. Participants reported less sleepiness after the snack compared to after the meal (p < 0.001) or when not eating during the night (p < 0.001). Gastric upset did not differ between conditions. A snack during the nightshift could alleviate hunger during the nightshift without causing fullness or increased sleepiness.Charlotte C Gupta, Stephanie Centofanti, Jillian Dorrian , Alison M Coates, Jacqueline M Stepien, David Kennaway, Gary Wittert, Leonie Heilbronn, Peter Catcheside, Manny Noakes, Daniel Coro, Dilushi Chandrakumar and Siobhan Bank

Establishing the acute physiological and sleep disruption characteristics of wind farm versus road traffic noise disturbances in sleep: a randomized controlled trial protocol

Advance access publication 6 September 2023Study Objectives: Despite the global expansion of wind farms, effects of wind farm noise (WFN) on sleep remain poorly understood. This protocol details a randomized controlled trial designed to compare the sleep disruption characteristics of WFN versus road traffic noise (RTN). Methods: This study was a prospective, seven night within-subjects randomized controlled in-laboratory polysomnography-based trial. Four groups of adults were recruited from; 15 s events) from sleep by each noise type with acute (20-s) and more sustained (3-min) noise exposures. Secondary analyses will compare dose–response effects of sound pressure level and noise type on EEG K-complex probabilities and quantitative EEG measures, and cardiovascular activation responses. Group effects, self-reported noise sensitivity, and wake versus sleep noise exposure effects will also be examined. Conclusions: This study will help to clarify if wind farm noise has different sleep disruption characteristics compared to road traffic noise.Gorica Micic, Branko Zajamsek, Bastien Lechat, Kristy Hansen, Hannah Scott, Barbara Toson, Tessa Liebich, Claire Dunbar, Duc Phuc Nguyen, Felix Decup, Andrew Vakulin, Nicole Lovato, Leon Lack, Colin Hansen, Dorothy Bruck, Ching Li Chai-Coetzer, Jeremy Mercer, Con Doolan and Peter Catchesid

No difference in net uptake or disposal of lactate by trained and untrained forearms during incremental sodium lactate infusion

A number of training adaptations in skeletal muscle might be expected to enhance lactate extraction during hyperlactataemia. The aim of the present study was to determine whether resting endurance-trained forearms exhibit an increased net lactate removal during hyperlactataemia. Six racquet-sport players attended the laboratory for two experiments, separated by 2 weeks. In the first experiment incremental handgrip exercise to fatigue was performed to identify trained (TRFA, n = 6) and untrained (UTFA, n = 5) forearms. In the second experiment net forearm lactate exchange was compared between TRFA and UTFA during an incremental infusion of sodium lactate. TRFA performed more work than UTFA during handgrip exercise [mean (SE) TRFA, 66.1 (9.5) J.100 ml(-1); UTFA, 35.1 (2.3) J.100 ml(-1); P = 0.02] and UTFA exhibited a greater increase in net lactate output relative to work load (P = 0.003). During lactate infusion net lactate uptake across the resting forearms increased linearly with the arterial lactate concentration in both groups (TRFA, r = -0.95 (0.03); UTFA, r= -0.92 (0.04); P < 0.02], with no difference in the regression slopes [TRFA, -1.06 (0.13); UTFA, -1.07 (0.27); P = 0.97] or y-intercepts [TRFA, 0.67 (0.20); UTFA, 1.36 (0.67); P = 0.37] between groups. Almost all of the lactate taken up was disposed of by both groups of forearms [TRFA, 99.6 (0.2)%; UTFA, 98.5 (1.0)%; P = 0.37]. It was concluded that the net uptake and removal of lactate by resting skeletal muscle is a function of the concentration of lactate in the blood perfusing the muscle rather than the muscle training status

Association of the arousal threshold with inflammation and sleepiness in men with obstructive sleep apnea

S L Appleton, D Eckert, A Vakulin, P Catcheside, D McEvoy, S Martin, G Wittert, R Adam

Erectile dysfunction is independently associated with apnea hypopnea index & oxygen desaturation index in elderly, but not younger, community-dwelling men

Abstract #MP81-03Sean Martin, , Sarah Appleton, , Robert Adams, , Anne Taylor, , Nicholas Brook, , Peter Catcheside, , Douglas McEvoy and Gary Witter

Different mechanisms of cardiovascular risk in men with OSA: the role of the arousal threshold

S L Appleton, D Eckert, A Vakulin, P Catcheside, D McEvoy, S Martin, G Wittert, R Adam