Estimation of absolute pollen productivity based on the flower counting approach: A review

Pollen productivity estimate (PPE) is one of the parameters necessary for pollen-based quantitative reconstruction of vegetation in the past. This paper summarizes and reviews the absolute PPEs (aPPEs) that were obtained with the area-based flower counting approach since the 1970s. The data for 23 species of trees are available from Japan and for 22 species of Poaceae from Japan, Spain, and Morocco. The aPPE values vary from 1 to 60 [1012 grains·ha−1·year−1], and are comparable to those previously reported in Europe and using different methods and approaches. The mean aPPEs of temperate conifers, such as Sciadopitys verticillata, Cryptomeria japonica, and Chamaecyparis obtusa, are as high as those of some of the common broadleaved trees, Castanea mollissima, Castanopsis cuspidata, and Alnus spp. The mean aPPEs of Abies firma, Fagus crenata, and Betula platyphylla are low, and those of Pinus densiflora, Quercus spp., Juglans ailanthifolia, Carpinus tchonoskii, Aesculus turbinata, and Poaceae spp. are intermediate. The relative PPE (rPPE) values of the arboreal taxa (relative to Poaceae), calculated using the aPPEs presented here, are smaller than those obtained in Western Europe and China based on the Extended R-value model approach. Differences in the sampling and analytical methods, as well as the interregional differences in Poaceae pollen productivity, might have contributed to the discrepancies observed. Although further studies are necessary, the flower counting approach is practical and informative for species-specific estimates of absolute pollen productivity and provides critical parameters for quantitatively reconstructing past vegetation in absolute units using the rates of pollen accumulation in sediments.