Defoliation reduces soil biota - and modifies stimulating effects of elevated CO₂

To understand the responses to external disturbance such as defoliation and possible feedback mechanisms at global change in terrestrial ecosystems, it is necessary to examine the extent and nature of effects on aboveground–belowground interactions. We studied a temperate heathland system subjected to experimental climate and atmospheric factors based on prognoses for year 2075 and further exposed to defoliation. By defoliating plants, we were able to study how global change modifies the interactions of the plant–soil system. Shoot production, root biomass, microbial biomass, and nematode abundance were assessed in the rhizosphere of manually defoliated patches of Deschampsia flexuosa in June in a full‐factorial FACE experiment with the treatments: increased atmospheric CO (2), increased nighttime temperatures, summer droughts, and all of their combinations. We found a negative effect of defoliation on microbial biomass that was not apparently affected by global change. The negative effect of defoliation cascades through to soil nematodes as dependent on CO (2) and drought. At ambient CO (2), drought and defoliation each reduced nematodes. In contrast, at elevated CO (2), a combination of drought and defoliation was needed to reduce nematodes. We found positive effects of CO (2) on root density and microbial biomass. Defoliation affected soil biota negatively, whereas elevated CO (2) stimulated the plant–soil system. This effect seen in June is contrasted by the effects seen in September at the same site. Late season defoliation increased activity and biomass of soil biota and more so at elevated CO (2). Based on soil biota responses, plants defoliated in active growth therefore conserve resources, whereas defoliation after termination of growth results in release of resources. This result challenges the idea that plants via exudation of organic carbon stimulate their rhizosphere biota when in apparent need of nutrients for growth

Book review of Danish Humour – SINK OR SWIM

Book review of Danish Humour – SINK OR SWIM by Lita Lundquist and Helen Dyrbye, Samfundslitteratur, 2022

Facilitating Peer-feedback as Competence in Project-Oriented Online Teaching

Peer-feedback is a popular activity in the competence-oriented university education, which has been significant in Denmark since around 2000 (Christiansen et al., 2015). Learning not only how to receive, but also how to provide peer-feedback facilitates so-called “deep learning”, in which the students reflect on their own learning process and develop their own selfevaluation competences (Nicol et al., 2014). As such, peer feedback feeds into concepts of student centered and dialogue based leaning, which prescribe that students’ leaning outcome increase, when they act as active participants and co-producers of the teaching and learning situation (CookSather et al., 2014). Furthermore, in imitating the academic peer review process, peer-feedback has been highlighted as a way to construct research based learning that helps the students to develop a critical approach to academic knowledge production (Horst, 2018)

MOOC design – Dissemination to the masses or facilitation of social learning and a deep approach to learning?

This article accounts for the design of the massive open online course (MOOC) Hans Christian Andersen’s Fairy tales on FutureLearn and reports on the effectiveness of this design in terms of engaging learners in social learning and encouraging a deep approach to learning. A learning pathway was designed that provided learners with relevant knowledge, allowed them to practice their analysis skills and provided model responses. In the first run of the MOOC, a light facilitation approach was used to motivate and engage learners. In the second run, this was supplemented with live Q & A sessions and increased educator feedback. Course data show that that some learners use the space provided for social interaction and mutual support. A learning pathway that engages learners in discussion and progression from week to week facilitates a deep approach to learning. However, this requires more support from the educators and the course host

Microglial Priming and Alzheimer’s Disease: A Possible Role for (Early) Immune Challenges and Epigenetics?

Neuroinflammation is thought to contribute to Alzheimer’s disease (AD) pathogenesis that is, to a large extent, mediated by microglia. Given the tight interaction between the immune system and the brain, peripheral immune challenges can profoundly affect brain function. Indeed, both preclinical and clinical studies have indicated that an aberrant inflammatory response can elicit behavioral impairments and cognitive deficits, especially when the brain is in a vulnerable state, e.g. during early development, as a result of aging, or under disease conditions like AD. However, how exactly peripheral immune challenges affect brain function and whether this is mediated by aberrant microglial functioning remains largely elusive. In this review, we hypothesize that; 1) systemic immune challenges occurring during vulnerable periods of life can increase the propensity to induce later cognitive dysfunction and accelerate AD pathology, and 2) that 'priming' of microglial cells is instrumental in mediating this vulnerability. We highlight how microglia can be primed by both neonatal infections as well as by aging, two periods of life during which microglial activity is known to be specifically upregulated. Lasting changes in (the ratios of) specific microglial phenotypes can result in an exaggerated pro-inflammatory cytokine response to subsequent inflammatory challenges. While the resulting changes in brain function are initially transient, a continued and/or excess release of such pro-inflammatory cytokines can activate various downstream cellular cascades known to be relevant for AD. Finally, we discuss microglial priming and the aberrant microglial response as potential target for treatment strategies for AD