History of Picea abies in west central Sweden

Early Holocene Picea megafossils found in west central Sweden have challenged the prevailing theory based on pollen analysis that Picea migrated to Scandinavia during the second half of the Holocene. Pollen analyses is the most used method for the study of past vegetation dynamics; however, in the study of the postglacial immigration of Picea or for studies at the forest-tundra ecotone where the local pollen production is low, it is crucial to be able to separate locally produced tree pollen from pollen coming from distant forests. This thesis aims to explore methods to facilitate the separation of local pollen from background pollen and thereby enable the inference of the local establishment of Picea abies at a site, to evaluate whether the Picea megafossils can be confirmed by pollen analysis, and to investigate the pollen-vegetation relationship at the forest-tundra ecotone. Pollen analysis was carried out from mires situated near early to mid Holocene Picea megafossil sites in west central Sweden. The relationship between pollen from moss polsters and the surrounding vegetation was analysed with models for pollen dispersal and deposition. In a simulation study a landscape model for Holocene tree-line fluctuations based on palaeoecological data representing different time slices was evaluated by the comparison of numerous simulated pollen counts from different elevations with actual pollen diagrams. The results show that it is possible to confirm the megafossils with pollen analyses, provided that the pollen sampling site is within tens of meters from the megafossil site. The timing of local Picea establishment and expansion differed between nearby sites. Parameters to facilitate the understanding of pollen-vegetation relationships at the forest-tundra ecotone were established: pollen productivity estimates (PPE), relevant source area of pollen (RSAP), and background and local pollen. The PPE at the forest-tundra ecotone differed from estimates in southern Sweden, showing varied responses to climate on pollen production for assorted taxa. It was concluded that the use of multiple adjacent sites for pollen analyses, calibration of modern pollen and current vegetation, and the simulation approach are applications that facilitate the interpretation of pollen analysis in terms of local presence of trees

Vegetationsutveckling och brandhistorik i Tyresta under 9000 år : en pollenanalytisk studie av en skvattramtallmyr i Tyresta nationalpark, Södermanland

Analyses of pollen and charcoal in peat cores, together with age-structure data of Pinus sylvestris from a Ledum-Pinus-mire in the Tyresta National Park (south-east Sweden) show the regional vegetation succession and fire history over the last 9000 years. Five major stages of mire development are identified: 1. Lake (c 7000-6400 cal BC); 2. Wet fen (c 6400-6000 cal BC); 3. Deciduous fen (c 6000 cal BC to c cal AD 700); 4. Open Sphagnum-mire (c cal AD 700-1100); 5. Pine bog (c cal AD 1100-present). The relationship between the occurrence of Ledum-Pinus-mires (a swampforest-type frequent in the area) and fire is discussed. Climate, fire and human activity are the three most important factors that have influenced the vegetation succession in the Tyresta area. Changes in climate have affected the species composition of the forest. Fires have been common from c 5600 cal BC to c cal AD 1650 in both the forest and the fen. They have strongly influenced the mire development and fen vegetation. A positive correlation may exist between fire and the occurrence of Ledum palustre. The reduction of forest fires in the 17th century was due to a change in the utilisa-tion of the forest by man. The commercial use of the forests for fuel and timber, as well as the forest law of 1647, which prohibited deliberate burning of the forests, led to a partial cessation of deliberate burning and an initiation of fire control. The past 350 years during which there has been a low fire influence, might be atypical for the 7000 years of fire history. It might therefore be appropriate to reintroduce forest fire as an ecological disturbance factor in order to preserve the natural properties of the National Park

LC–MS/MS Screening Strategy for Unknown Adducts to N‑Terminal Valine in Hemoglobin Applied to Smokers and Nonsmokers

Electrophilically reactive compounds have the ability to form adducts with nucleophilic sites in DNA and proteins, constituting a risk for toxic effects. Mass spectrometric detection of adducts to N-terminal valine in hemoglobin (Hb) after detachment by modified Edman degradation procedures is one approach for <i>in vivo</i> monitoring of exposure to electrophilic compounds/metabolites. So far, applications have been limited to one or a few selected reactive species, such as acrylamide and its metabolite glycidamide. This article presents a novel screening strategy for unknown Hb adducts to be used as a basis for an adductomic approach. The method is based on a modified Edman procedure, FI<i>R</i>E, specifically developed for LC–MS/MS analysis of N-terminal valine adducts in Hb detached as fluorescein thiohydantoin (FTH) derivatives. The aim is to detect and identify <i>a priori</i> unknown Hb adducts in human blood samples. Screening of valine adducts was performed by stepwise scanning of precursor ions in small mass increments, monitoring four fragments common for the FTH derivative of valine with different N-substitutions in the multiple-reaction mode, covering a mass range of 135 Da (<i>m</i>/<i>z</i> 503–638). Samples from six smokers and six nonsmokers were analyzed. Control experiments were performed to compare these results with known adducts and to check for artifactual formation of adducts. In all samples of smokers and nonsmokers, seven adducts were identified, of which six have previously been studied. Nineteen unknown adducts were observed, and 14 of those exhibited fragmentation patterns similar to earlier studied FTH derivatives of adducts to valine. Identification of the unknown adducts will be the focus of future work. The presented methodology is a promising screening tool using Hb adducts to indicate exposure to potentially toxic electrophilic compounds and metabolites

fig_S2b_rev &ndash; Supplemental material for Metabarcoding of modern soil DNA gives a highly local vegetation signal in Svalbard tundra

Supplemental material, fig_S2b_rev for Metabarcoding of modern soil DNA gives a highly local vegetation signal in Svalbard tundra by Mary E Edwards, Inger Greve Alsos, Nigel Yoccoz, Eric Coissac, Tomasz Goslar, Ludovic Gielly, James Haile, Catherine T Langdon, Andreas Tribsch, Heather A Binney, Henrik von Stedingk and Pierre Taberlet in The Holocene</span

Metabarcoding of modern soil DNA gives a highly local vegetation signal in Svalbard tundra

Environmental DNA retrieved from modern soils (eDNA) and late-Quaternary palaeosols and sediments (aDNA and sedaDNA) promises insight into the composition of present and past terrestrial biotic communities, but few studies address the spatial relationship between recovered eDNA and contributing organisms. Svalbard’s vascular plant flora is well known, and a cold climate enhances preservation of eDNA in soils. Thus, Svalbard plant communities are excellent systems for addressing the representation of plant eDNA in soil samples. In two valleys in the inner fjord region of Spitsbergen, we carried out detailed vegetation surveys of circular plots up to a 4-m radius. One or three near-surface soil samples from each plot were used for extraction and metabarcoding of soil-derived eDNA. Use of PCR replicates and appropriate filtering, plus a relevant reference metabarcode catalogue, provided taxon lists that reflected the local flora. There was high concordance between taxa recorded in plot vegetation and those in the eDNA, but floristic diversity was under-sampled, even at the scale of a 1-m radius plot. Most detected taxa grew within &lt; 0.5–1.0 m of the sampling point. Taxa present in vegetation but not in eDNA tended to occur further from the sampling point, and most had above-ground cover of &lt; 5%. Soil-derived eDNA provides a highly local floristic signal, and this spatial constraint should be considered in sampling designs. For palaeoecological or archaeological studies, multiple samples from a given soil horizon that are spatially distributed across the area of interest are likely to provide the most complete picture of species presence