Future tree species portfolio in a dry environment – a comparison of endemic and non-endemic species

Introduction

Project site in Gampe Photo: A. Rigling (WSL)

The Swiss Rhone valley (canton Valais) is one of the driest regions of the inner-Alps. Recently, species composition changed: Scots pine, dominating the forest at low elevation, is threatened by drought-induced mortality. At the same time, pubescent oak showed increasing dissemination. However, previous studies on the two species indicated that not only pine but also oak might soon reach the limits of physiological capacity under severe drought. To warrant that these dry forests in Valais can provide the ecosystem goods and services even in an expected hotter and drier future climate, substitute species should be found. Also non-endemic species should be considered, as protective function regarding rock fall or avalanches cannot be fulfilled by other endemic species in Valais (e.g. whitebeam or juniper) due to their shrublike habitus.

Objectives

In this study we want to analyse how endemic and non-endemic species respond to periods of drought in Valais. Therefore we compare the growth response of Scots pine to drought with the one of black pine and Douglas fir. Aim of the study is to detect if non-endemic species might be an alternative under a drier climate.

Method

We analyse growth response of the species to recent drought years on a 50 years old afforestation site in the central dry part of Valais. Therefore, we combine dendrochronological and wood anatomical methods for ecological interpretation. For the species’ ability to establish and survive on xeric sites, the maintenance of an effective and safe water-transport system is of great importance. Thus the growth response of conducting cells, like vessels and tracheids, is of particular interest.

Contact

• Andreas Rigling