Franz Gruber

UNTENABLE FAILURE CRITERIA FOR TREES: I. THE RESIDUAL WALL THICKNESS RULE

Summary The Visual Tree Assessment (VTA) rule t/R = 0.32, which has been described as a universal rule of tree safety for hollow trees with full crowns is scientifically insupportable and must be rejected. Many full crown trees with t/R ratios of more than 0.32 can be broken by loading from external sources, and trees with such ratios are not necessarily safe. It can be stated that the risk of stem failure will diminish with increasing thickness of sound wood, but stem failure is significantly dependent on the loading applied to the tree, and the 0.32 rule does not take this into account. Tree safety needs to be assessed individually rather than using general “mono-parametric” safety rules. There is little scientifically tested knowledge about the complex matter of tree safety, and it seems absolutely essential to carry out research, both fundamental and applied, into this subject.

Kombinierte Altersbestimmung und Altersentwicklung von Jungbuchen - Fagus sylvatica L. -nach morphologischen und anatomischen Merkmalen

Summary Tree ring analyses from cuttings through the middle of the hypocotyle and the following length increments were done on young beeches of known age with and without “lammas shoots”. It could be pointed out that the accurate age can be certainly determined by analyses of ring formation. Endogenous-proleptic shoots do not cause a false wood ring. During these investigations there could be found false wood rings only in few cases. These false rings (additional rings) are distinguished from true rings by the blurred boundary between the first increment area and the following additional increment. It is also possible to determine morphologically the acurate age of young beech plants by counting the length increments produced regularly along the axis of the primary leaf axil shoots including the hypocotyle. Thus, the number of the length increments is identical with the number of the true rings in the hypocotyle. The different branching patterns of one year old beech seedlings are morphologically described. A field method for testing the accurate age of young beech seedlings is presented.

Aufbau und Anpassungsfähigkeit der Krone von Picea abies (L.) Karst

Summary The present paper deals with the different shoot forms of Norway Spruce Picea abies (L.) K arst , resulting from a bud. These are the regular, the proleptic and the proventitious shoots. They are seen here as the result of shoot elongation from buds with growth induction at different phases of development. Thereby Norway Spruce acts and reacts variously depending on tree ages and stand conditions. The ecologic importance of shoot formation is the optimal exploitation of growth on the one hand, and a means for regeneration on the other hand. Besides the architectural model the “opportunistic” architecture of Norway Spruce is described and figured in detail. The structure of the crown of Spruce is illustrated as an ideal normal-model. The variability of branching forms is also shown. With regard to the state of healthy of trees, different degrees of crown states are defined, which were derived from typical branching forms. Besides the needle state of the crown and the branching types also the activity of proventitious shoots is considered.

Morphologie der Weisstanne (Abies alba Mill.): II. Wurzelverzweigung, Architekturmodell und Kronenanalysen

Summary The work presented describes the branching pattern of both the crown and the roots of fir. To describe the branching pattern (crown and root system) a terminalogy is suggested, using which, the type, order, time of development (ontogenesis) and localisation of structural elements can be assessed. A simple whole tree model for fir is used as a basis to assess changes. A detailed crown analysis was carried out on old crowns. the yeady height growth increment traced back morphologically and the branching of the S1-axes were investigated. Further, the age of the needles on various branches of crowns differing in the degree of damage were determined. Using longitudinal sections of the crown, information could be gained about the distribution and contribution of regular and proventitious branches and needles within the crown. Firs are able to develop secondary crowns, which must be divided into those with light-adapted or shade-adapted crowns. The character and the size of these crowns has important influence on the length growth of the branches and thickening of the lower trunk. The high regeneration capacity of firs using proventitious shoots is especially considered. Possible causes for crown thinning are discussed.

Diskussion und Folgerungen

Uber den Zeitpunkt des naturlichen Ablebens der Fichtennadel gibt es keine speziellen Untersuchungen. Allgemein wird der Monat des Nadelfalls auch als die Zeit des Absterbens betrachtet (May, 1894). Die Mechanik des Nadelfalls der Fichte zeigt, das Absterben und Abfallen der Nadel zeitlich weit divergieren konnen. Deshalb kann auch nur vorausgesetzt werden, das eine apparativ abgefallene Nadel immer schon abgestorben oder zumindest geschadigt war. Aus diesem Grund ist von der Rhythmik des Streufalls nur unter Einbeziehung der standortlichen Dynamik auf den Ablebezeitpunkt der Nadeln zu schliesen. In der Rhythmik des Streufalls spiegeln sich jedoch vor allem die klimatischen Schwankungen wider.