Response of Soil Microbial Community to Vegetation Reconstruction Modes in Mining Areas of the Loess Plateau, China

Vegetation reconstruction and restoration is vital to the health of the mine land ecosystem. Different vegetations might change microbial community structure and function of soil, mediating the biogeochemical cycle and nutrition supply to the soil. To clarify the response of soil microbes to different vegetation reconstruction modes in the mining areas of the Loess Plateau, China, soil microbial community structures and functions were determined by the MiSeq high-throughput sequencing along with PICRUSt2 and FUNGuild tools. The fungal community richness was observed to be the highest in grassland soil and positively correlated with soil organic matter, total nitrogen, and nitrate-nitrogen. The bacterial and fungal community structures were similar in grassland and brushland areas, but were significantly differentiated in the coniferous and broadleaf forest, and the leading factors were soil pH and nitrate-nitrogen. Actinobacteriota, Proteobacteria, and Acidobacteriota were the dominant bacterial phyla under different vegetation reconstruction modes. The dominant phyla of fungi were Ascomycota, Basidiomycota, and Mortierellomycota. Different vegetation reconstruction modes did not affect the bacterial functional communities but shaped different functional groups of fungi. The grassland soil was dominated by saprotrophic fungi, while symbiotrophic fungi dominated the coniferous and broadleaf forests. The results suggested that shifts in vegetation reconstruction modes may alter the mining soil bacterial and fungal community structures and function. These findings improve the understanding of microbial ecology in the reclaimed mine soil and provide a reference for the ecological restoration of fragile mining ecosystems.

Vegetation Reconstruction From Siberia and the Tibetan Plateau Using Modern Analogue Technique–Comparing Sedimentary (Ancient) DNA and Pollen Data

To reconstruct past vegetation from pollen or, more recently, lake sedimentary DNA (sedDNA) data is a common goal in palaeoecology. To overcome the bias of a researcher’s subjective assessment and to assign past assemblages to modern vegetation types quantitatively, the modern analogue technique (MAT) is often used for vegetation reconstruction. However, a rigorous comparison of MAT-derived pollen-based and sedDNA-based vegetation reconstruction is lacking. Here, we assess the dissimilarity between modern taxa assemblages from lake surface-sediments and fossil taxa assemblages from four lake sediment cores from the south-eastern Tibetan Plateau and northern Siberia using receiver operating characteristic (ROC) curves, ordination methods, and Procrustes analyses. Modern sedDNA samples from 190 lakes and pollen samples from 136 lakes were collected from a variety of vegetation types. Our results show that more modern analogues are found with sedDNA than pollen when applying similarly derived thresholds. In particular, there are few modern pollen analogues for open vegetation such as alpine or arctic tundra, limiting the ability of treeline shifts to be clearly reconstructed. In contrast, the shifts in the main vegetation communities are well captured by sedimentary ancient DNA (sedaDNA). For example, pronounced shifts from late-glacial alpine meadow/steppe to early–mid-Holocene coniferous forests to late Holocene Tibetan shrubland vegetation types are reconstructed for Lake Naleng on the south-eastern Tibetan Plateau. Procrustes and PROTEST analyses reveal that intertaxa relationships inferred from modern sedaDNA datasets align with past relationships generally, while intertaxa relationships derived from modern pollen spectra are mostly significantly different from fossil pollen relationships. Overall, we conclude that a quantitative sedaDNA-based vegetation reconstruction using MAT is more reliable than a pollen-based reconstruction, probably because of the more straightforward taphonomy that can relate sedDNA assemblages to the vegetation surrounding the lake.

Paleoclimate and vegetation reconstruction of Abric Romani (Capellades, Spain) during MIS-3, 4, and MIS-5 (a-d)

<p><strong>Paleoclimate and vegetation reconstruction of Abric Romani (Capellades, Spain) during MIS-3, 4, and MIS-5 (a-d)</strong></p><p>Demet Biltekin<sup>1,2</sup>, Francesc Burjachs<sup>1,3,4</sup>, Josep Vallverdú<sup>1,4</sup>, Warren D. Sharp<sup>5</sup>, Regina Mertz-Kraus<sup>6</sup>, M. Gema Chacón<sup>1,4</sup>,  Palmira Saladié<sup>1,4</sup>, James L. Bischoff<sup>5</sup>, Eudald Carbonell<sup>1,4</sup></p><p> </p><p><sup>1</sup>Institut Català de Paleoecologia Humana i Evolucio Social (IPHES), Zona Educacional 4, Campus Sescelades URV, edifici W3, 43007 Tarragona, Spain.</p><p><sup>2</sup>Istanbul Technical University, Eurasia Institute of Earth Sciences, Ayazağa Campus, Maslak, Sarıyer, 34469, Istanbul/Turkey</p><p><sup>3</sup>ICREA, Barcelona, Catalonia, Spain.</p><p><sup>4</sup>URV, Universitat Rovira i Virgili, Facultat de Lletres, Avinguda Catalunya, 35, 43002 Tarragona, Catalonia, Spain.</p><p><sup>5</sup>Berkeley Geochronology Center, Berkeley, CA 94709, United States.</p><p><sup>6</sup>Institute for Geosciences, Johannes Gutenberg University, Mainz, Germany.</p><p> </p><p>This new pollen data provides the vegetation and climate history during ca. 110 ka-55 ka BP from Abric Romaní archaeological site using pollen analysis of a 30 m-long sedimentary sequence. The beginning of the MIS 3 starts an abundance in steppes and herbs, indicating cold and dry climate in the region. However, this was replaced by a slight increase in deciduous Quercus and Mediterranean trees. During the MIS 4, the pollen records reflect a predominance of Artemisia steppes and herbaceous communities (Poaceae and Asteraceae families), indicating dry and cold conditions in Abric Romaní. The MIS 5 was well recorded with its substages, including 5a, 5b, 5c and 5d. The MIS 5d is characterized by Pinus and Artemisia steppes with herbaceous assemblages. The higher abundance of Artemisia during the second part of the MIS 5b, reflecting cold and dry climate, while temperate forest and Mediterranean trees decline. Mélisey II stadial was marked by an increase in Artemisia and herbs. This suggests that cold climatic conditions existed during this time period. The abundance of oaks during the MIS 5c indicate warmer and humid climate in the region. Other deciduous and broadleaved forest developed as well, including Ulmus, Viburnum, Juglans and Castanea. A short cooling Montaigu event was also recorded within this interstadial, which is dominated by a high percentage of Ericaceae with Artemisia. The first part of the MIS 5a is characterized by Corylus, Carpinus, Hedera, Ulmus, Betula, pointing to warmer climatic conditions. In contrast, the high amount of Artemisia steppes may indicate an enhanced degree of continentality during the second half of the MIS 5a in the north-eastern Iberian Peninsula.</p><p><strong>Keywords:</strong> paleovegetation, climate, pollen analysis, Late Pleistocene, Spain</p>