Characteristics of the crown as the basis of the method for assessing damage to black alder stands [Alnus glutinosa (L.) Gaertn.] – Elżbieta Dmyterko

Elżbieta Dmyterko. Forest Research Institute, Warsaw 2006, ISBN 83-87647-48-9, 104 pp., 16 EUR. In Polish with abstract, summary, tables and figures in English.

Detailed measurements of 2,275 trees were carried out in 235 tree stands. Defoliation of the sun crown (Def) and tree vitality (Wit) were assumed as the main criteria of damage to trees and stands and crown length as an auxiliary criterion. The tree vitality criterion was applied in accordance with Roloff’s classification modified to include shape of the top part of the crown. Those criteria were used to formulate the synthetic index of tree damage Syn= (0,03·Def+Wit)/2.

An alder crown development model was built in order to evaluate the criteria of tree damage, particularly of tree vitality. The model includes the length of shoots, the branch system, the number of internodes, the share of syleptic shoots, the absolute and relative length of the crown, its shape and leaf coverage, as well as the relationships between crown characteristics. The number of lateral shoots – both typical and syleptic – is positively correlated with the length of the main shoot and the number of internodes. Juvenile alders develop syleptic shoots of the 2nd order. A significant number of mature alders form syleptic shoots in their old age. Some trees establish a secondary crown on the trunk and boughs that previously had been cleared of branches. Such a crown lengthens in line with the shortening of the primary crown.

The increment reaction of trees to the environmental impact (determined on the basis of an analysis of alder dbh increment over the past 15 years in comparison with the previous periods) is related to the level of damage to tree stands. The more a stand is damaged, the greater is the share of trees that show negative reaction and the fewer is the number of trees showing neutral reaction. No relationship between the level of damage to tree stands and the share of trees with positive increment reaction is the result of the development of a secondary crown that causes quicker diameter increment in the lower part of a trunk.

The relationship found between the alder diameter increment and the damage assessment criteria (Def, Wit and Syn) confirms the legitimacy of incorporating these features into the method for assessing damage to tree stands.

A forest model object was created on the basis of empirical material, in which tree mortality is a natural process, unmodified by environmental factors causing damage. In this forest object/site, 70% of stands were undamaged, 27% – weakened, and 3% – both damaged and dying. Trees with positive or negative increment reaction accounted for 10% of the stand (respectively), while those with neutral reaction – 80%. The structure of damage to stands and the share of trees with a different type of increment reaction in other forest objects differed from the model.

3 variants of the method for assessing damage to alder stands were determined. The one based on the synthetic index of tree damage Syn turned out to be the most accurate, requiring the lowest number of sample trees.

Key words: crown development model, defoliation, vitality, synthetic index of tree damage, methods of assessing damage to trees and stands, increment reaction of trees, black alder

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