Pollen-based quantitative land-cover reconstruction for northern Asia during the last 40 ka

Abstract

Abstract. We collected the available relative pollen productivity (RPP) estimates for 27 major pollen taxa from Eurasia and applied them to estimate plant abundances during the last 40 cal. ka BP (calibrated thousand-year before the present) using pollen counts from 203 fossil pollen records in northern Asia (north of 40° N). These pollen records were organised into 42 site groups; and regional mean plant abundances were calculated using the REVEALS (Regional Estimates of Vegetation Abundance from Large Sites) model. Time-series clustering, constrained hierarchical clustering, and detrended canonical correspondence analysis were performed to investigate the regional pattern, time, and strength of vegetation changes, respectively. Reconstructed regional land cover for each site group is generally consistent with in situ modern vegetation in that vegetation changes within the regions are characterized by minor changes in the abundance of major taxa rather than by invasions of new taxa, particularly during the Holocene. We argue that pollen-based REVEALS estimates of plant abundances should be a more reliable reflection of the vegetation as pollen may overestimate the turnover, particularly when a high pollen producer invades areas dominated by low pollen producers. Comparisons with vegetation-independent climate records show that climate change is the primary factor driving land-cover changes at broad spatial and temporal scales. Vegetation changes in certain regions or periods, however, could not be explained by direct climate change, for example inland Siberia, where a sharp increase in evergreen conifer tree abundance occurred at ca. 7~8 cal. ka BP despite an unchanging climate, potentially reflecting their response to complex climate-permafrost-fire-vegetation interactions and thus a possible lagged climate response.

Did long‐term fire control the coniferous boreal forest composition of the northern Ural region (Komi Republic, Russia)?

“…The REVEALS model tends to correct the regional signal of large‐area sites (Sugita, 2007a) and therefore, following Cao et al. (2018), the Yaksha vegetation signal was compared with other signals within a 500 km diameter around the site. Five previously analysed pollen sequences were used from south to north, for which construction of a new age‐depth model was necessary (Appendix S6): Baika (Borisova, 2002), Sedkyrkesch (Golubeva, 2008), Kalya (Karmanov, Zaretskaya, Panin, & Chernov, 2011), Cherny Yar (Marchenko‐Vagapova & Marieva, 2001) and Syndorsky (Golubeva, 2008) (Figure 1b, Table 1).…”