Effects of forest invasion and retreat on tundra biodiversity inferred from sedimentary ancient DNA of lake Levinson Lessing, Taymyr Peninsula, Russia

<p>One of the consequences of the amplified warming of the arctic ecosystems is tundra “greening” and northward expansion of Siberian boreal forests. However, it is still challenging to predict how northern tundra biodiversity will change with the ongoing climate warming as models usually overestimate forest invasion. The investigation of Quaternary records spanning different Pleistocene glacial and interglacial cycles can provide unique insights on past diversity dynamics following forest invasion and retreat events. Therefore, by “looking backward to look forward“, reconstruction of past vegetation can help to forecast the effects of global warming on northern biodiversity.</p><p>In 2017, a 46 m core was recovered from the Lake Levinson Lessing located in the tundra of the far north Taymyr Peninsula (northern Central Siberia), the upper 38 m of which span the last 62ka continuously and with a rather constant sedimentation rate. A high resolution of 84 subsamples were collected from the lake sediment core with the aim to characterise biodiversity changes between glacials and interglacials in Russian Arctic during Late Quaternary. We studied pollen and non-pollen-palynomorphs and extracted the ancient DNA (sedaDNA), from the same sediment core samples. We also investigated past vegetation composition changes by a plant metabarcoding approach (chloroplast trnL P6 loop). We compared both pollen and sedaDNA signals to reconstruct changes in biodiversity in the Taymyr Peninsula emphasizing changes in diversity during forest invasion and retreat events.</p>

Study on Response of Alpine Timberline in Taibai Mountain to Climate Changes

This article based on RS/GIS technology analyzed the spatio-temporal changes of mountain timberline in Taibai Mountain Nature Reserve from 1988 to 2009 which is aimed at reveal the response to climate changes. The study results shown:As the temperatures rise, timberline the overall position was on the move in recent 22 years; in the aspect of vegetation ,the rising line for the top of Larix chinensis forest invasion in shrub meadow vegetation areas proved the rising of timberline in Taibai Mountain Nature Reserve.

A proposed history of permafrost development in Labrador-Ungava

The recent history of mapping permafrost distribution in Labrador-Ungava is reviewed and an attempt is made to assess the accuracy of the most recent maps. Relationships between ground temperature and other environmental conditions are then discussed. These two introductory sections provide the basis for the main objective of the paper. A hypothesis of permafrost development is elaborated and rests upon two considerations: (1) that much of Labrador-Ungava is underlain by permafrost which is in approximate equilibrium with present-day conditions and that its distribution is largely controlled by vegetation cover rather than regional variations in climate, and (2) that patches of relic permafrost have been found widely throughout the southern section of the peninsula. It is proposed that, following disintegration and melt of the last ice sheet, permafrost developed over wide areas before tree species were able to migrate northwards. As the forest cover-types began to occupy areas comparable to those so occupied today ground thermal characteristics changed. This was caused not only by the direct effects of forest invasion but by the impact of the forest on the winter snow cover. As conditions more nearly approached those prevailing today, degradation of permafrost set in and the present relic patches are air that remains of this process. The hypothesis is supported by recent progress in palynological and vegetational history studies. These demonstrate that a tundra phase existed for 1000 to 2000 or more years between the time of ice sheet disappearance and establishment of the forest cover.