Development and refinement of proxy-climate indicators from peats

Peat, especially from acidic mires (bogs), is a natural archive of past environmental change. Reconstructions of past climate from bogs commenced in the 19th Century through examination of visible peat stratigraphy, and later formed the basis for a postglacial climatic scheme widely used in Northwest Europe. Nevertheless, misconceptions as to how bogs grow led to a 50-year lacuna in peat-climate study, before the concept of "cyclic regeneration" in bogs was refuted. In recent decades, research using proxyclimate indicators from bogs has burgeoned. A range of proxies for past hydrological change has been developed, as well as use of pollen, bog oaks and pines and other data to reconstruct past temperatures. Most of this proxy-climate research has been carried out in Northern Europe, but peat-based research in parts of Asia and North America has increased, particularly during the last decade, while research has also been conducted in Australia, New Zealand and South America. This paper reviews developments in proxy-climate reconstructions from peatlands; chronicles use of a range of palaeo-proxies such as visible peat stratigraphy, plant macrofossils, peat humification, testate amoebae and non-pollen palynomorphs; and explains the use of wiggle-match radiocarbon dating and relationship to climate shifts. It details other techniques being used increasingly, such as biomarkers, stable-isotopes, inorganic geochemistry and estimation of dust flux; and points to new proxies under development. Although explicit protocols have been developed recently for research on ombrotrophic mires, it must be recognised that not all proxies and techniques have universal applicability, owing to differences in species assemblages, mire formation, topographic controls, and geochemical characteristics

Snapshots in time: precise correlations of peat-based proxy climate records in Scotland using mid-Holocene tephras

Mid-Holocene tephra layers have been located and geochemically analysed from seven ombrotrophic bogs in Scotland. The tephras found in these Scottish peats occur as stratigraphically discrete horizons, not visible to the naked eye, and originate from volcanic activity in Iceland. Identifying and geochemically typing the tephra layers can enable precise correlations between sites on regional scales, depending on the spatial extent of the airfall events. Dispersal of both the Glen Garry and Hekla-4 tephras is excellent over Scotland, enabling snapshot views of the past at the time of these tephra depositions. Palaeoecological analyses have also been undertaken on these bogs, providing detailed reconstructions of past changes in bog vegetation and surface wetness, a proxy for past climates. Correlations between the ombrotrophic bogs at the time of the Glen Garry tephra revealed significant differences between the proxy climate records in the north and the south of Scotland, suggesting asynchronous changes between northern Scotland and the rest of Great Britain

Introduction history and population genetics of intracontinental scotch broom ( Cytisus scoparius

Abstract Aim: Biological invasions at the intracontinental scale are poorly studied, and intracontinental invasions often remain cryptic. Here, we investigate the recent range expansion of scotch broom (Cytisus scoparius) into Norway and clarify whether the genetic patterns indicate natural spread or human introduction. Furthermore, we investigate whether plants were moved within the native range and how this influences invasion success. We also infer the level and structuring of genetic diversity within and between the putative native and introduced range. Location: Europe. Methods: We analysed the chloroplast sequence variation in 267 scotch broom samples from its northern expansion front and from its native range across Europe, including herbarium samples dating back to 1835. For 37 populations, we analysed variation in nuclear single‐nucleotide polymorphic markers to study gene flow and genetic diversity. Results: We identified 20 different haplotypes, which lacked spatial and temporal distribution patterns in the recent expansion range in Norway. They also mostly lacked patterns across the native European range of scotch broom. The genetic diversity of nuclear genomic SNP markers across populations in the introduced range was similar to that of populations in the native range, with limited differentiation among populations. Main conclusions: Scotch broom is alien to Norway and was introduced by humans on multiple occasions from diverse origins over a long period of time. High propagule pressure has probably maintained the high genetic diversity in the novel range through a combination of genetically diverse source populations and high gene flow among them. Within the native European range, our results suggest the presence of cryptic intraspecific admixture, most likely mediated by humans moving genotypes among the regions occupied by distinct native genotypes. Intracontinental invasions may easily go unnoticed and revealing these invasions and the factors driving them may be of great importance for the management of alien species.publishedVersio