Patterns of modern pollen and plant richness across northern Europe

Abstract

Sedimentary pollen offers excellent opportunities to reconstruct vegetation changes over past millennia. Number of different pollen taxa or pollen richness is used to characterise past plant richness. To improve the interpretation of sedimentary pollen richness, it is essential to understand the relationship between pollen and plant richness in contemporary landscapes. This study presents a regional‐scale comparison of pollen and plant richness from northern Europe and evaluates the importance of environmental variables on pollen and plant richness. We use a pollen dataset of 511 lake‐surface pollen samples ranging through temperate, boreal and tundra biomes. To characterise plant diversity, we use a dataset formulated from the two largest plant atlases available in Europe. We compare pollen and plant richness estimates in different groups of taxa (wind‐pollinated vs. non‐wind‐pollinated, trees and shrubs vs. herbs and grasses) and test their relationships with climate and landscape variables. Pollen richness is significantly positively correlated with plant richness (r = 0.53). The pollen plant richness correlation improves (r = 0.63) when high pollen producers are downweighted prior to estimating richness minimising the influence of pollen production on the pollen richness estimate. This suggests that methods accommodating pollen‐production differences in richness estimates deserve further attention and should become more widely used in Quaternary pollen diversity studies. The highest correlations are found between pollen and plant richness of trees and shrubs (r = 0.83) and of wind‐pollinated taxa (r = 0.75) suggesting that these are the best measures of broad‐scale plant richness over several thousands of square kilometres. Mean annual temperature is the strongest predictor of both pollen and plant richness. Landscape openness is positively associated with pollen richness but not with plant richness. Pollen richness values from extremely open and/or cold areas where pollen production is low should be interpreted with caution because low local pollen production increases the proportion of extra‐regional pollen. Synthesis. Our results confirm that pollen data can provide insights into past plant richness changes in northern Europe, and with careful consideration of pollen‐production differences and spatial scale represented, pollen data make it possible to investigate vegetation diversity trends over long time‐scales and under changing climatic and habitat conditions.

Modern pollen rain predicts shifts in plant trait composition but not plant diversity along the Andes–Amazon elevational gradient

“…Second, the over-or underrepresentation of taxa may strongly influence diversity estimates. For example, many species many be underrepresented by pollen at low elevation, causing an underestimation of diversity (Reitalu et al, 2019). This suggestion is supported by our diversity estimates based on the original pollen count data (Appendix S4, which show increases instead of decreases with elevation.…”

“…Our results are in agreement with some studies (Gosling et al, 2018) but in disagreement with a review that compares diversity from pollen and vegetation (Birks et al, 2016). Studies that find an agreement between both measures of diversity are often measured in flat (Jantz et al, 2014) or temperate ecosystems (Felde et al, 2016), at coarser scales (Matthias et al, 2015;Reitalu et al, 2019), do not use actual diversity measured from the vegetation (Weng et al, 2007), or are based on very large pollen sums (Meltsov et al, 2011).…”

Postglacial change of the floristic diversity gradient in Europe

“…Pollen identification yields different taxonomic levels: rarely species, but often genera and sometimes only family level. The relationship between pollen and plant taxonomy is a form of higher-taxon surrogacy 20 and comparative studies have shown that spatial patterns in plant diversity are captured by pollen 21–24 . To evaluate the effect of higher-taxon surrogacy in this study we explore these patterns at two hierarchical levels based on pollen morphology following harmonisation of the full dataset.…”

Drivers of change and ecosystem status in a temperate lake over the last Post-Glacial period from 14.5 kyr

“…3b). There has been a similar increase in the number of species and diversity due to modest human activity, which we call generic human impact, in large scale areas of vegetation [63][64][65] and overall richness in the Eukaryote domain [29] in lakes of northeastern Europe. Although the modest human activity increased the patchiness of the boreal and semi-boreal forest, offering more niches for various terrestrial species, the similar increase in the lake's ecosystem is intriguing.…”