Plant diversity changes at the southeastern Tibetan Plateau during the last 21 ka and its drivers

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The preservation of the unique Tibetan plant diversity requires an understanding of its drivers. Cli-mate, natural disturbances and land use, the potential diversity drivers are spatially highly correlated. Thus, their specific effects on plant alpha diversity and their interactions can hardly be separated ap-plying a modern ecological approach that targets spatial gradients. Accordingly, we propose to perform a palaeoecological study focusing on the Late Glacial and Holocene plant alpha diversity change.We hypothesize that (H1) plant alpha diversity measures (richness, dominant taxa num-ber) on the eastern Tibetan Plateau shows complex spatio-temporal trends during the Late Glacial and Holocene. We expect that (H2) richness is related to landscape structure, which itself is a function of natural disturbances (wildfire, erosion) and human impact. Furthermore, we hypothesize that (H3) the dominant taxa number is mainly related to vegetation type driven by climate change and human im-pact.Our study will make use of proxy information gained from the analyses of lake sediments. It will combine the collection of new palaeoenvironmental data at three key sites (located along altitudi-nal transect at the southeastern Tibetan Plateau margin) and palaeoenvironmental data synthesis from the eastern Tibetan Plateau and surrounding area (25-40°N, 90-105°E). Interpretation of palaeo-environmental data will be based on relationships between modern environmental information and proxy information as derived from a lake sediment training set comprising 234 sites. At key sites, pol-len and sedimentary ancient DNA (plant metabarcoding) will be investigated as proxies for past pat-tern in plant alpha diversity and vegetation type. Independent information on past climate change will be inferred from stable oxygen isotopes measurements of sedimentary diatom silica and proxy-climate data synthesis. Natural disturbances and land use will be inferred from a multi-proxy approach including the analyses of proxies for fire, soil erosion, and land use. With respect to the synthesis study, an already available pollen data set will be used and complemented with further proxy data. Finally, by developing a novel modelling approach we aim to disentangle the relationship between alpha diversity measures, vegetation type and landscape structure, climate, natural disturbances and land use.Our research has the potential to identify critical thresholds in drivers of plant diver-sity that when crossed cause a tremendous and/or even irreversible diversity loss.