Abstract:

Modern climate change poses a huge threat to plants in the arid Central Asia. Due to the short instrumental interval, we are unable to better understand the long time-scale relationship between plant diversities and climate change in this region. However, pollen records in the geological archives provide us an opportunity to understand the existence, distribution and diversity of plants in the past. In this study, we selected three pollen sequences from different elevations (Halasazi Peat, Narenxia Peat and Kanas Lake) in the Altai Mountains to investigate the characteristics of plant diversities and their response patterns to Holocene climate change. The results revealed that the changes of pollen taxa diversity in the Altai Mountains showed a unique pattern. As the climate was warming in the early Holocene, the upper forest limits began to migrate upward, leading to an increase in pollen taxa diversity at high elevations. In the middle Holocene, the climate was warm and wet, and the upward and downward migration of the upper and lower forest limits resulted in higher diversities at high and low elevations, but the lower diversities in the taiga-dominated forest belt mainly resulted from a decreasing species evenness. In the late Holocene, the climate became cooler and wetter, and the upper forest limits moved downward, leading to a significant increase in diversities at middle elevations. The largest changes of plant diversities were observed in the forest belt during the Holocene, which means this belt is the most sensitive and vulnerable area for climate response. This study not only helps us understand the response model of mountain vegetation belt to Holocene climate change, and also provides key evidence for exploring the history of mountain vegetation migration in the arid Central Asia.

Key words: Holocene climate, pollen taxa diversity, Altai Mountains, arid zone, Central Asia