Exploring Holocene Changes in Palynological Richness in Northern Europe – Did Postglacial Immigration Matter?

Thomas Giesecke,Steffen Wolters,Susanne Jahns,Arthur Brande,John P Hart

doi:10.1371/journal.pone.0051624

Abstract

In mid to high latitudes glacial and interglacial cycles have repeatedly changed the area available for plant growth. The speed at which plants are able to colonize areas at the onset of an interglacial is hypothesized to limit their distribution ranges even today (migrational lag). If the spread of plants would have been generally slow then plant diversity in previously glaciated areas would be expected to increase over time. We explore this hypothesis using results from six palynological investigations from two previously glaciated regions: central Sweden and north-eastern Germany. Rarefaction, slope of rank order abundance, and taxa accumulation plots were used to evaluate richness and evenness in pollen data in an attempt to separate richness from evenness. These analyses show little change in palynological richness for the northern sites throughout the Holocene. In contrast, the southern sites show an increase in richness and evenness during the early Holocene; this may be explained by the different initial conditions at the onset of the Holocene. A strong rise in palynological richness around 6000 and 1000 years ago at the southern sites can be attributed to the regional initiation of agriculture and major opening of the forest, respectively. For the northern sites there is no evidence for increased taxonomic diversity through time that could be due to delayed immigration of species.

Highlights

To forecast the impact of climate change on biological diversity it is crucial to have knowledge on the ability of plants to shift their distribution in response to climate change [1]
All southern sites start with a low number of pollen types per samples, which is in some cases even lower than the values obtained for the northern sites
The southern sites increase in palynological richness in tree steps: during the early Holocene, after 6000 cal

Summary

Introduction

To forecast the impact of climate change on biological diversity it is crucial to have knowledge on the ability of plants to shift their distribution in response to climate change [1]. Many studies suggested that plants will not be able to track climate change [2]. New research indicates that plants are moving fast in response to a warmer climate [3]. The biodiversity of the temperate forests are shaped by glacial-interglacial cycles that repeatedly changed the habitat available to plants [9]. Studying the patterns and processes of changing plant distributions at the end of glacial periods will help to understand the spatial differences in biodiversity [10,11]

Objectives

Methods

Results

Discussion

Conclusion