Beziehung Zwischen Struktur und Dynamik von Blattpopulationen und Sprosswachstum

Abstract

Structure and dynamics of leaf populations and shoot growth. — Shoot dry mass allocation patterns as well as morphological and physiological characteristics of leaf cohorts were studied over one growing season in an invading population of the perennial composite Solidago altissima near Basle (Switzerland) to determine whether individuals or stands would show predicted optimal designs and if these designs could be maintained throughout development. Results showed that carbon gain of shoots was optimized by decreasing nitrogen contents from the apex downwards and continous physiological transformation of sun into shade leaves as they were overtopped during height growth. However, leaf specific weight did not decrease during this process and most assimilates were probably exported to the stem and not re-invested in new leaves. Variation in shoot height produced a sub-optimal stand architecture for carbon gain. This demonstrates that the individual-based approach of population biology may better predict plant yield and fitness than do stand models based on area. A conceptual model linking the physiology and life history of leaves to shoot growth is introduced to show how population biology of plant parts could be used as a mechanistic approach in plant ecology. Thus, it should eventually become possible to scale up from leaves to entire ecosystems.