The vertical distribution of modern pollen in the southeastern edge of Tibetan Plateau, China

AbstractThe tropical mountainous area of the southeastern Tibetan Plateau (TP) is a hotspot of ecological environment research because of its rich biodiversity. However, limited knowledge regarding modern pollen rain within this area has impeded further investigation research on eco-environmental evolution by using pollen record. Here, we collected 62 modern pollen samples from lowland tropics to the subalpine (740-3550 m a.s.l.) in Medog County, located in the southeastern TP, and performed pollen analysis. Cluster analysis, redundancy analysis, variance partitioning analysis, boosted regression trees were employed to investigate the relationship between pollen and vegetation-climate. Additionally, Hill numbers (N0, N1, N2) and specificity-occupancy plots were utilized to explore plant diversity. The results indicate that modern pollen rain in Medog can reflect well the current characteristics of vegetation, encompassing both primary and secondary features. Pollen of Cyclobalanopsis, Tsuga and Abies, which are dominant components of the primary vegetation above 2100 m a.s.l., can serve as indicator species for palaeovegetation reconstruction. Mean annual precipitation is the most important climatic determinant affecting pollen distribution. Pollen diversity indices reveal that the plant diversity in this study area has a bimodal pattern of “relatively high-low-highest-low” with altitude. The plant diversity above 2100 m a.s.l. is mainly decided by primary vegetation, whereas below 2100 m a.s.l. can be explained by the intermediate disturbance hypothesis. Furthermore, it is advisable to exercise caution when dealing with arboreal pollen evenness in open mountainous environments due to the increased potential pollen source area caused by valley wind.Keywords: Modern pollen rainvegetation-pollen relationshippollen-climate relationshippollen diversityaltitudinal gradientsoutheastern Tibetan PlateauDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. Declaration of InterestsThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.AcknowledgementsThe authors are grateful to Zhao Wenqian and Li Mingjia for help with fieldwork. We also thank two anonymous reviewers who gave us important advice that let us improve the manuscript’s quality. This work was supported by National Key Research and Development Program of China (2022YFF0801101) and National Natural Science Foundation of China (Grant No. 42077424, 42277446).