Relative pollen productivity estimates for the dominant plant taxa in the Hoh Xil region of the Qinghai-Tibet Plateau

The use of relative pollen productivity (RPP) values is an effective approach for calibrating the relationships between pollen and vegetation, and they are key parameters for quantitative vegetation reconstruction based on the REVEALS method (regional estimates of vegetation abundance from large sites). In this study we used vegetation surveys and surface soil pollen data from 22 sampling points in the Hoh Xil region on the Qinghai-Tibet Plateau to estimate the RPP values of six pollen types, Cyperaceae, Aster-type, Saussurea-type, Potentilla, Artemisia and Caryophyllaceae, using different sub-models (SM) of the extended R-value (ERV) model. The results indicated that SM 2 is more suitable for the estimation of pollen production in this area compared to SMs 1 and 3. Using two weighting methods, Prentice and 1/d (inverse distance), the RPP results with Potentilla as the reference taxon show minimal differences between the methods. In descending order of RPP values, the pollen productivity compared with Potentilla using the Prentice weighting method are: Cyperaceae (12.31 ± 2.15), Artemisia (11.16 ± 1.75), Aster-type (1.78 ± 0.32), Caryophyllaceae (1.43 ± 0.06) and Saussurea-type (0.31 ± 0.06); while for the inverse distance weighting method they are Cyperaceae (13.91 ± 1.91), Artemisia (8.26 ± 1.92), Aster-type (1.56 ± 0.27), Caryophyllaceae (1.39 ± 0.08) and Saussurea-type (0.26 ± 0.07). Furthermore, modern vegetation reconstructions based on recent pollen from lake surfaces using the REVEALS model demonstrated that both sets of RPP reconstructions more closely approximate to the actual vegetation cover than the lake pollen percentages. Our findings provide insights for reconstructing past changes in vegetation cover and for predicting future vegetation changes in the Hoh Xil region.