Effect of the root temperature on growth parameters of various European tree species

Abstract

European forest tree species have been investigated regarding the reaction of growth of shoots, roots and leaves during an incubation of the root system at various temperatures ranging from 5 to 35 degrees C for 4 months. Species-specific differences in the reaction to root temperatures could be demonstrated. Growth optima (total dry mass increment) ranged from about 15 degrees C (Picea abies, Larix decidua, Pseudotsuga menziesii, Betula verrucosa) to 25 degrees C (Quercus robur, Carpinus betulus) and up to 30 degrees C (Pinus nigra). Chilling of the root system of Juglans regia down to 2 degrees C resulted in a rapid and long-lasting decrease of net photosynthetis, but only in a moderate decrease of stomatal conductance and transpiration. Respiration was stimulated after some days. The ecological consequences of different optima for root temperatures among various species are discussed regarding their natural distribution and their reactions to increasing temperatures caused by the greenhouse effect.