Projecting Tree Species Composition Changes of European Forests for 2061-2090 Under RCP 4.5 and RCP 8.5 Scenarios.

Allan Buras,Annette Menzel

doi:10.3389/fpls.2018.01986

Abstract

Climate change poses certain threats to the World’s forests. That is, tree performance declines if species-specific, climatic thresholds are surpassed. Prominent climatic changes negatively affecting tree performance are mainly associated with so-called hotter droughts. In combination with biotic pathogens, hotter droughts cause a higher tree vulnerability and thus mortality. As a consequence, global forests are expected to undergo vast changes in the course of climate change. Changed climatic conditions may on the one hand locally result in more frequent dieback of a particular tree species but on the other hand allow other—locally yet absent species—to establish themselves, thereby potentially changing local tree-species diversity. Although several studies provide valuable insights into potential risks of prominent European tree species, we yet lack a comprehensive assessment on how and to which extent the composition of European forests may change. To overcome this research gap, we here project future tree-species compositions of European forests. We combine the concept of climate analogs with national forest inventory data to project the tree-species composition for the 26 most important European tree species at any given location in Europe for the period 2061–2090 and the two most relevant CMIP5 scenarios RCP 4.5 and RCP 8.5. Our results indicate significant changes in European forests species compositions. Species richness generally declined in the Mediterranean and Central European lowlands, while Scandinavian and Central European high-elevation forests were projected an increasing diversity. Moreover, 76% (RCP 4.5) and 80% (RCP 8.5) of the investigated locations indicated a decreasing abundance of the locally yet most abundant tree species while 74 and 68% were projected an increasing tree-species diversity. Altogether, our study confirms the expectation of European forests undergoing remarkable changes until the end of the 21st century (i.e., 2061–2090) and provides a scientific basement for climate change adaptation with important implications for forestry and nature conservation.

Highlights

In the course of climate change, the World’s forests will likely undergo significant changes
Most prominent changes are related to the northward migration of the four most abundant species, i.e., Scots pine, Norway spruce, European beech, and English oak and at the same a remarkable decrease in abundance in Central Europe, regarding Norway spruce and Scots pine (Figure 2)
For large parts of Central and Northern Europe, the currently dominant tree species experienced remarkable reductions in abundance, for relative concentration pathway (RCP) 8.5 while for most Mediterranean areas an increase in abundance of the currently dominant species was projected (Figure 4)

Summary

Introduction

In the course of climate change, the World’s forests will likely undergo significant changes. Because of changing distributional tree species ranges and typically long rotation periods (often more than 100 years), forests have to be adapted to anticipated climate conditions by altering management strategies and selecting better adapted and more resilient tree species (Halofsky et al, 2018; Sousa-Silva et al, 2018). In this context, foresters, stakeholders, and policy makers are targeting at so-called climatesmart forests (Halofsky et al, 2018; Nabuurs et al, 2018). The widespread European beech (Fagus sylvatica, L.) is likely to suffer (Scharnweber et al, 2011, 2013; Dulamsuren et al, 2017; Huang et al, 2017; Walentowski et al, 2017) while other abundant species such as oak [Quercus robur, L. and Quercus petraea, (Matt.) Liebl.] may benefit from climate change (Scharnweber et al, 2011, 2013; Perkins et al, 2018)

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