Post-fire Recruitment Failure as a Driver of Forest to Non-forest Ecosystem Shifts in Boreal Regions

Climate change and land-use are driving large changes in forest ecosystems around the globe. In the boreal biome it is likely that increases in temperature and the associated lengthening of the growing season will cause the forest to expand into the northern tundra and upwards in elevation, whilst potentially contracting at its southern limits. This increase in temperature is also driving an increase in the frequency and severity of boreal forest fires. A growing number of studies have observed the failure of forest species to re-establish after a standreplacing fire event, which results in the shift to a non-forested ecosystem. In this chapter, this process is referred to as post-fire recruitment failure. We provide multiple lines of evidence for boreal forests, and more specifically for southern Siberia forests, that a possible regional tipping point is unfolding, which could lead to the rapid replacement of large areas of forest ecosystems with low-stature non-forest ecosystems. This change would come with significant consequences for the carbon balance, surface albedo and the resulting altered energy balanc

Climate variability may delay post-fire recovery of boreal forest in southern Siberia, Russia

Prolonged dry periods and increased temperatures that result from anthropogenic cli-22 mate change have been shown to increase the frequency and severity of wildfires in the boreal 23 region. There is growing evidence that such changes in fire regime can reduce forest resilience 24 and drive shifts in post-fire plant successional trajectories. The response of post-fire vegetation 25 communities to climate variability is under-studied, despite being a critical phase determining 26 the ultimate successional conclusion. This study investigated the responses of post-fire recruited 27 species to climate change and inter-annual variability at 16 study sites that experienced high se-28 verity fire events, mostly in early 2000, within the Scots pine forest – steppe zone of south-eastern 29 Siberia, Russia. These sites were originally dominated by Scots pine; by 2018 they were recruited 30 by different successional species. Additionally, three mature Scots pine stands were included for 31 comparison. A Bayesian Additive Regression Trees (BART) approach was used to model the re-32 lationship between Landsat-derived Normalized Difference Vegetation Index (NDVI) time se-33 ries, temperature and precipitation in the 15 years after a stand replacing fire. Using the resulting 34 BART models, together with six projected climate scenarios with increased temperature and en-35 hanced inner-annual precipitation variability, we simulated NDVI at five-year intervals for 15 36 years post-fire. Our results show that the BART models performed well, with in-sample Pseudo-37 R2 varying from 0.49 to 0.95 for fire-disturbed sites. Increased temperature enhanced greenness 38 across all sites and across all three time periods since fire, exhibiting a positive feedback in a 39 warming environment. Repeatedly dry spring periods reduced NDVI at all the sites and wetter 40 summer periods following such dry springs could not compensate for this, indicating that a pro-41 longed dry spring has a strong impact consistently over the entire early developmental stages 42 from the initial five years to 15 years post-fire. Further, young forests showed higher climate 43 sensitivity compared to the mature forest, irrespective of species and projected climatic condi-44 tions. Our findings suggest that a dry spring not only increases fire risk, but also delays recovery 45 of boreal forests in southern Siberia. It also highlights the importance of changing rainfall sea-46 sonality as well as total rainfall in a changing climate for post-fire recovery of forest

“Breaking up is hard to do”: the formation and resolution of sister chromatid intertwines

The absolute necessity to resolve every intertwine between the two strands of the DNA double helix provides a massive challenge to the cellular processes that duplicate and segregate chromosomes. Although the overwhelming majority of intertwines between the parental DNA strands are resolved during DNA replication, there are numerous chromosomal contexts where some intertwining is maintained into mitosis. These mitotic sister chromatid intertwines (SCIs) can be found as; short regions of unreplicated DNA, fully replicated and intertwined sister chromatids—commonly referred to as DNA catenation—and as sister chromatid linkages generated by homologous recombination-associated processes. Several overlapping mechanisms, including intra-chromosomal compaction, topoisomerase action and Holliday junction resolvases, ensure that all SCIs are removed before they can prevent normal chromosome segregation. Here, I discuss why some DNA intertwines persist into mitosis and review our current knowledge of the SCI resolution mechanisms that are employed in both prokaryotes and eukaryotes, including how deregulating SCI formation during DNA replication or disrupting the resolution processes may contribute to aneuploidy in cancer

Identification and differential expression dynamics of peach small GTPases encoding genes during fruit development and ripening

The function of monomeric GTPases of the RAS superfamily in fruit development and ripening has been partially characterized. Here the identification of peach (Prunus persica) small GTPases of the RAS superfamily expressed in fruit and the characterization of their expression profiles during fruit development are described. Extensive searches on expressed sequence tag (EST) databases led to the selection of a total of 24 genes from peach encoding proteins with significant similarity to Arabidopsis small GTPases. Sequence similarity analyses and identification of conserved motifs, diagnostic of specific RAS families and subfamilies, enabled bona fide assignment of fourteen PpRAB, seven PpARF/ARL/SAR, two PpROP and one PpRAN GTPases. Transcriptional expression profiles of peach monomeric GTPases, analysed by real-time quantitative reverse transcription-PCR, were obtained for mesocarp samples, collected in two consecutive years. Reproducible patterns of expression could be identified for five peach RAB-encoding genes (PpRABA1-1, PpRABA2, PpRABD2-1, PpRABD2-2, and PpRABC2), two ARFs (PpARFA1-1 and PpARLB1), and two ROPs (PpROP3 and PpROP4). Interestingly, the transient transcriptional up-regulation of PpARF genes and of PpRAB genes of the A and D clades, putatively controlling the exocytic delivery of cell wall components and modifying enzymes, appeared to coincide with peaks of growth speed and sugar accumulation and with the final phases of ripening. To our knowledge, this is the first description of the co-ordinated differential expression of a set of genes encoding small GTPases of the ARF and RAB families which takes place during key moments of fruit development and maturation

Alcohol dehydrogenase 1 of barley modulates susceptibility to the parasitic fungus Blumeria graminis f.sp. hordei

Plant primary energy metabolism is profoundly reorganized under biotic stress conditions and there is increasing evidence for a role for the fermentative pathway in biotic interactions. However, the mechanisms regulating metabolic reprogramming are not well understood despite its critical function in the biotic stress response. Here the function of alcohol dehydrogenase (ADH) in the interaction of barley with the parasitic fungus Blumeria graminis f.sp. hordei (Bgh) is addressed. Challenge of susceptible barley leaves with Bgh resulted in transcriptional activation of HvADH1 and an induction of ADH enzyme activity starting 24 h after infection and reaching a clear-cut effect 4 d after infection. This increase in ADH enzyme activity was not observed in the resistant near-isogenic mlo5 line. Moreover, an induction of ADH enzyme activity by Bgh was enhanced in the presence of sucrose in hydroponically grown seedlings. Transient knock-down or overexpression of HvADH1 in barley epidermal cells mediated a decrease or increase in the penetration success of Bgh, respectively. Inhibition of ADH activity by pyrazole resulted in a delay in symptoms. The pyrazole effect could be overcome by adding glucose to the incubation medium, pinpointing a nutritional effect of ADH in the barley–Bgh interaction. Taken together, misexpression of pathogen-inducible HvADH1 or variation of ADH activity modulates the pathogen response of barley to the biotrophic fungal parasite Bgh. In this way, ADH knock-down/inhibition results in reduced fungal success. The possibility is discussed that ADH activity supports biotrophy by maintaining glycolytic metabolism in pathogen-stressed barley

The future of interpretive accounting research:A Polyphonic Debate

In 1997-99 the three of us organised a series of European Commission funded conferences aimed at building a network of young researchers in the area of accounting. At the time “young” was defined by the Commission as researchers under 35 years of age (allowing for maternity leave or national service). Over the intervening years our network had grown and we wanted to try and take stock of the field in which we had now been working for a surprising number of years. To that Page 1 of 29 Accepted Manuscript 2 end we put together the above email and a broad invitation list of people who had been at those first meetings, and others of the same generation (or even younger) whom we had met since. About half of those originally contacted managed to make the meeting where we spent a stimulating couple of hours of debate on the topics raised below—so stimulating that we developed a collective desire to leave a trace of the discussion. Writing a traditional paper with so many, so widely dispersed authors was not going to work. Instead we came up with a different form of collective writing that mirrored the original debate, and that might contribute to ongoing debates in this journal concerning the nature and status of our research (e.g. Arrington, 2004; Inanga & Schneider, 2005; Macintosh, 2004). We agreed a process in which each of us in turn would have one week to add a target of 300 words to a rolling document, going through the contributors alphabetically. After two rounds we would see what we had got

Distinct mechanisms for aerenchyma formation in leaf sheaths of rice genotypes displaying a quiescence or escape strategy for flooding tolerance

Background and Aims Rice is one of the few crops able to withstand periods of partial or even complete submergence. One of the adaptive traits of rice is the constitutive presence and further development of aerenchyma which enables oxygen to be transported to submerged organs. The development of lysigenous aerenchyma is promoted by ethylene accumulating within the submerged plant tissues, although other signalling mechanisms may also co-exist. In this study, aerenchyma development was analysed in two rice (Oryza sativa) varieties, ‘FR13A’ and ‘Arborio Precoce’, which show opposite traits in flooding response in terms of internode elongation and survival. Methods The growth and survival of rice varieties under submergence was investigated in the leaf sheath of ‘FR13A’ and ‘Arborio Precoce’. The possible involvement of ethylene and reactive oxygen species (ROS) was evaluated in relation to aerenchyma formation. Cell viability and DNA fragmentation were determined by FDA/FM4-64 staining and TUNEL assay, respectively. Ethylene production was monitored by gas chromatography and by analysing ACO gene expression. ROS production was measured by using Amplex Red assay kit and the fluorescent dye DCFH2-DA. The expression of APX1 was also evaluated. AVG and DPI solutions were used to test the effect of inhibiting ethylene biosynthesis and ROS production, respectively. Key Results Both the varieties displayed constitutive lysigenous aerenchyma formation, which was further enhanced when submerged. ‘Arborio Precoce’, which is characterized by fast elongation when submerged, showed active ethylene biosynthetic machinery associated with increased aerenchymatous areas. ‘FR13A’, which harbours the Sub1A gene that limits growth during oxygen deprivation, did not show any increase in ethylene production after submersion but still displayed increased aerenchyma. Hydrogen peroxide levels increased in ‘FR13A’ but not in ‘Arborio Precoce’. Conclusions While ethylene controls aerenchyma formation in the fast-elongating ‘Arborio Precoce’ variety, in ‘FR13A’ ROS accumulation plays an important role

Rethinking Visiting Friends and Relatives Mobilities

The increasing number of people leading more mobile lives, with spatially dispersed families, raises questions over how they maintain their family life and friendships, and how this is shaped and shapes different forms of migration, and different patterns of Visiting Friends and Relatives (VFR). This paper develops an explanatory framework for conceptualizing and analyzing VFR mobilities, seeking to draw together threads from migration, mobilities and tourism studies. In unpacking the notion of VFR, this paper understands VFR mobilities as being constituted of diverse practices, and discusses five of the most important of these: social relationships, the provision of care, affirmations of identities and roots, maintenance of territorial rights, and leisure tourism. While these five types of practices are considered sequentially in this paper, they are in practice often blurred and overlapping. The interweaving of these practices changes over time, as does the meaning and content of individual practices, reflecting changes in the duration of migration, life cycle stage, individual goals and values, and the broader sets of relationships with and social obligations to different kin and friends