Effects of Drought and Rewetting on Growth and Gas Exchange of Minor European Broadleaved Tree Species

Jörg Kunz,Annemarie Räder,Jürgen Bauhus

doi:10.3390/f7100239

Abstract

Widespread and economically important European tree species such as Norway spruce, Scots pine, and European beech are projected to be negatively affected by the increasing intensity and frequency of dry and hot conditions in a future climate. Hence, there is an increasing need to investigate the suitability of presumably more drought tolerant species to ensure future ecological stability, biodiversity, and productivity of forests. Based on their distribution patterns and climatic envelopes, the rare, minor broadleaved tree species Sorbus torminalis ((L.) CRANTZ), S. domestica (L.), Acer campestre (L.), and A. platanoides (L.) are assumed to be drought tolerant, however, there is only limited experimental basis to support that notion. This study aimed at quantifying growth and gas exchange of seedlings of these species during drought conditions, and their capacity to recover following drought. For that purpose, they were compared to the common companion species Quercus petraea ((MATTUSCHKA) LIEBL.) and Fagus sylvatica (L.). Here, potted seedlings of these species were exposed to water limitation followed by rewetting cycles in a greenhouse experiment. Photosynthesis and transpiration rates, stomatal conductance as well as root and shoot growth rates indicated a high drought resistance of A. campestre and A. platanoides. Sorbus domestica showed a marked ability to recover after drought stress. Therefore, we conclude that these minor tree species have the potential to enrich forests on drought-prone sites. Results from this pot experiment need to be complemented by field studies, in which the drought response of the species is not influenced by restrictions to root development.

Highlights

Climate change poses one of the major challenges of our time to forestry
The high variability after 12 days within the dry group was caused by lower volumetric water content (VWC) values of Sorbus torminalis compared to the other seedlings, owing to the high transpiration of the species of Sorbus torminalis compared to the other seedlings, owing to the high transpiration of the species (Table 2)
The high water consumption in S. torminalis was only partially driven by high leaf area as the comparison with Acer platanoides, which had a similar leaf area, indicates (Table 2)

Summary

Introduction

Climate change poses one of the major challenges of our time to forestry. For CentralEurope, increasing temperatures accompanied by less precipitation during summer are expected [1].The exceptionally warm and dry summer of 2003 with its wide-spread negative effects on growth and vitality of lowland forest ecosystems [2,3] may be considered a warning of changes to come [4,5,6].Some of the most important timber species in Europe such as Norway spruce H. KARST .), Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) are already affected by climate change. A distinct sensitivity to drought is well known for Picea abies [7,8] and is currently being intensively discussed for Pinus sylvestris [9,10] and Fagus sylvatica [11,12,13]. Owing to the likely decline in the distribution areas of the currently dominant tree species [14], forestry is looking for alternative tree species to maintain forest ecosystems and their many functions in areas that may be affected by increasing drought severity and frequency [15,16]

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Conclusion