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

保护西藏独特的植物多样性需要了解其驱动因素。气候、自然干扰和土地利用等潜在多样性驱动因素在空间上高度相关。因此，它们对植物α多样性的特定影响及其相互作用很难通过以空间梯度为目标的现代生态学方法分离出来。因此，我们建议开展以晚冰期和全新世植物α多样性变化为重点的古生态学研究。我们假设青藏高原东部地区（H1）植物α多样性指标（丰富度、优势类群数量）在晚冰期和全新世表现出复杂的时空变化趋势。我们认为（H2）丰富度与景观结构有关，而景观结构本身是自然干扰（野火、侵蚀）和人类影响的函数。此外，我们假设（H3）优势类群数量主要与气候变化和人类活动驱动的植被类型有关。我们的研究将利用从湖泊沉积物分析中获得的代理信息。它将结合青藏高原东南部边缘沿海拔样带的三个重点站点的新古环境数据收集和青藏高原东部及周边地区（25-40°N, 90-105°E）的古环境数据综合。古环境数据的解释将基于现代环境信息与由234个站点组成的湖泊沉积物训练集派生的代理信息之间的关系。在重点站点，将研究花粉蛋白和沉积古DNA（植物元条形码）作为植物α多样性和植被类型的过去模式的代表。关于过去气候变化的独立信息将从沉积硅藻的稳定氧同位素测量和代用气候数据合成中推断出来。自然干扰和土地利用将从多代理方法推断，包括对火灾、土壤侵蚀和土地利用代理的分析。在合成研究方面，将使用现有的花粉数据集，并补充进一步的代理数据。最后，通过开发一种新的建模方法，我们旨在理清α多样性测量、植被类型和景观结构、气候、自然干扰和土地利用之间的关系。我们的研究有可能确定植物多样性驱动因素的关键阈值，当跨越这些阈值时，会导致巨大的和/或甚至不可逆转的多样性损失。

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.