Öko-Physiologische und phylogenetische Grundlagen der Verbreitung der Coniferen auf der Erde.

Dargestellt am Beispiel der Alerce (Fitzroya cupressoides) in den südlichen Anden

Abstract

Working from an analysis of the locational demands of the south Andean relict conifer Fitzroya cupressoides and a comparison with its north American counterpart Sequoia sempervirens, it is shown that the recent expansion of coniferous forest over the earth's surface has taken place in line with laws which can be derived from the organisational stage reached in phylogenetic development. This is significantly demonstrated by the fact that, in contrast to the angiosperms, they only have a vascular conducting system (Tracheids) of low efficiency. If one takes account, with H. Walter, of the fact that the living substance protoplasm can only be physiologically active in a strongly hydratised situation, and that transpiration is an indispensable partner to gas exchange, we can deduce from the low efficiency of their vascular conducting system that conifers will find their optimal site conditions in places where, on the one hand, they have during the growing season easily absorbable soil moisture and, on the other hand, transpiration-reducing atmospheric conditions occur with sufficient frequency. In addition, their assimilation optimum occurs at relatively low temperatures. In consequence of these characteristics, conifers show a decided affinity to interference in thermal and hygrial seasons typical of warm to moderately cold climates and of particular parts of the tropics. It is maintained that these regularities can serve as the key to understanding the fossil distribution of conifers. Conifers differ ecologically from their phylogenetic predecessors, the Pteridophytes, in their adaptation to a seasonal worsening of environmental conditions and a periodicity in growth.