The Impact of Changes in Species Richness and Species Replacement on Patterns of Taxonomic Homogenization in the Carpathian Forest Ecosystems

Tomasz Durak,Ewa Węgrzyn,Roma Durak,Konrad Leniowski

doi:10.3390/f6124376

Abstract

The Carpathians are Eastern Europe’s largest contiguous forest ecosystem and a hotspot of biodiversity. However, not much is known about changes in species diversity in these forests. Here we investigate the long-time changes in the diversity of plant communities in the Eastern Carpathian beech forests. We also inquire about the similarity of plant communities between managed and protected forests. We conduct our analyses using not only the broad-sense measure of changes in β diversity (βsor) but also the measures that reveal whether the changes result from spatial turnover (βsim) or nestedness (βnes). Our study demonstrated that the mean species richness did not significantly change over time in both forest types. However, we found a significant decrease of species diversity in protected forests and the same trend, but on a smaller scale, in managed forests. In both forest types the decrease of species diversity was mainly caused by spatial turnover, while nestedness-related changes were relatively small. However, the direction of changes in βnes differed in managed and unmanaged forests in such a way that it reduced the decrease of species diversity in managed forests and amplified the decrease of species diversity in unmanaged forests. We discuss our findings in terms of biotic homogenization.

Highlights

The changes in species composition and diversity are widespread in nature [1]
We addressed the above issues by testing the following hypotheses: (i) diversity of plant communities decreased over a long time-period in the Eastern Carpathian beech forests and (ii) patterns of changes in diversity of plant communities were different in managed and unmanaged forests
The results of our study revealed that the mean species richness of the herb layer did not significantly change over time both in managed and unmanaged Eastern Carpathian beech forests

Summary

Introduction

The changes in species composition and diversity are widespread in nature [1]. In most ecosystems, depending on population dynamics and the current set of multiple disturbances, species diversity increases or decreases. The average species composition rarely reaches a steady-state equilibrium [2]. Changes in species diversity and the direction of such changes (increase/decrease) are natural processes, and as such cannot be treated as positive or negative ones. Natural succession in forest plant communities often involves a decrease in species diversity during the establishment phase of colonization and an increase in species diversity during steady-state phases [3]. Beside natural disturbances, which are important forces in maintaining species diversity, forest ecosystems are subjected to human impacts, often resulting in biotic homogenization [4]. As the stability of ecosystems in the face of disturbances may be positively related to the diversity in these ecosystems [8], biotic homogenization is perceived as a global problem

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