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| 13. |
- Petersson, L. K., et al.
(författare)
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Changing land use and increasing abundance of deer cause natural regeneration failure of oaks: Six decades of landscape-scale evidence
- 2019
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 444, s. 299-307
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Tidskriftsartikel (refereegranskat)abstract
- Many tree species worldwide are suffering from slow or failed natural regeneration with dramatic consequences for biodiversity and ecosystem services. However, it is difficult to disentangle the complex effects of factors influencing regeneration processes on long-lived tree species at large scales. In this study, we use long-term data from the Swedish National Forest Inventory (1953-2015) combined with deer hunting data (1960-2015) to reveal experimentally-intractable processes impeding oak (Quercus spp.) regeneration in southern Sweden. Oak-dominated ecosystems are widespread in northern temperate regions, where oaks are foundation species with disproportionate importance for biodiversity and ecosystem functions. Our study reveals that during the last six decades, oak tree numbers and standing volume have continuously increased, while natural regeneration of oak declined steeply after the early 1980s. We connect this decline to denser and darker forests, combined with increased abundance of deer. Land use changes during the six decades, such as abandonment of traditional practices and large-scale introduction of forest management oriented towards high volume production, led to continuously denser forests and thereby reduced the oak regeneration niche. In addition, the impact of changed game management was evident. This was particularly clear from a natural experiment on Gotland, a large island free of deer until roe deer were introduced in the late 20th century, at which point oak regeneration began a steep decline. At the stand level, natural oak regeneration could be expected to mainly occur in pulses after disturbance events, followed by a period of low regeneration success as the cohort ages. However, at a landscape scale one would expect a mix of successional stages that would even out such demographic patterns. A prolonged period of low regeneration at a landscape scale will eventually lead to a large gap in the oak size distribution as was observed in this study. This could eventually hurt the many species dependent on old and large oak trees. Active management to restore the oak regeneration niche, i.e. forest habitats with more light and less browsing pressure, therefore seems essential. The latter includes developing strategies that manage both deer populations and their available food across landscapes. Our study is the first to link oak regeneration failure to long-term changes in land use and increased deer populations at a landscape scale in this region. Furthermore, our study show how historical data can clarify confounded processes impacting long-lived forest species.
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| 15. |
- Villarroel, Beatriz, et al.
(författare)
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Launching the VASCO Citizen Science Project
- 2022
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Ingår i: Universe. - : MDPI AG. - 2218-1997. ; 8:11, s. 561-
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Tidskriftsartikel (refereegranskat)abstract
- The Vanishing & Appearing Sources during a Century of Observations (VASCO) project investigates astronomical surveys spanning a time interval of 70 years, searching for unusual and exotic transients. We present herein the VASCO Citizen Science Project, which can identify unusual candidates driven by three different approaches: hypothesis, exploratory, and machine learning, which is particularly useful for SETI searches. To address the big data challenge, VASCO combines three methods: the Virtual Observatory, user-aided machine learning, and visual inspection through citizen science. Here we demonstrate the citizen science project and its improved candidate selection process, and we give a progress report. We also present the VASCO citizen science network led by amateur astronomy associations mainly located in Algeria, Cameroon, and Nigeria. At the moment of writing, the citizen science project has carefully examined 15,593 candidate image pairs in the data (ca. 10% of the candidates), and has so far identified 798 objects classified as "vanished". The most interesting candidates will be followed up with optical and infrared imaging, together with the observations by the most potent radio telescopes.
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| 16. |
- Wieloch, Tadeusz, et al.
(författare)
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Protein phosphorylation and the regulation of mRNA translation following cerebral ischemia
- 1993. - C
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Ingår i: Neurobiology of Ischemic Brain Damage. - 0079-6123. - 9780444896032 ; 96, s. 179-191
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Bokkapitel (refereegranskat)abstract
- This chapter discusses the changes in protein phosphorylation following ischemia, with particular reference to the regulation of the initiation of protein synthesis. Transient cerebral ischemia seems to induce a post-ischemic imbalance between protein kinase and protein phosphatase activities, leading to a net dephosphorylation of proteins in the vulnerable neurons. This imbalance may lead to the persistent changes in processes crucial for neuronal survival such as post-ischemic protein synthesis. The depression of protein synthesis after an ischemic insult most probably is because of a decreased guanine nucleotide exchange factor (GEF) activity, leading to a limited availability of eukaryotic initiation factors (eIF-2) for initiation complex formation. The inhibition of GEF activity in the vulnerable regions could in turn be because of dephosphorylation of GEF, possibly because of tyrosine phosphatase activation and a decreased casein kinase II activity. Post-ischemic inhibition of protein kinase C and calcium calmodulin kinase II may in addition depress eIF-4 activity leading to a selective translation of mRNA such as heat shock mRNA.
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