Measuring forest damage of ungulates: what should be considered

Abstract Principles and criteria for the objective assessment of `damage' are presented as a basis for objective discussion and to promote targeted research. The topic will be considered from three different viewpoints – theoretical background, silviculture, and nature conservation. Examples of methods to assess `damage' are given, as are the criteria and indicators for target values for growing stock. The objective existence of damage must be established by comparing the current status against a target. Only if the present status no longer permits achievement of the desired target can damage be claimed. The same is true for verification of `benefit' resulting from an impact leading to a favorable status. Establishing the degree of browsing damage on forest regeneration allows forecasts of damage to be made, but the actual damage can only be determined at a future time, for example when the timber is harvested or when the function of the forest is seen to have been compromised. The earlier the forecast is made the more uncertain it is, because the compensatory responses of the forest can only be forecast to a limited extent. Silvicultural targets depend on the requirements of both, the forest owner and the public. Main indicators for assessing ungulate damage on forest regeneration are total tree density, species composition, and height structure. From the viewpoint of nature conservation the determination of target values is particularly difficult. The measurement of damage involves choosing the most relevant indicators of favorable condition of woodland habitats and assessing these in the field. With adequate resources this can be done quantitatively using a wide range of standard field measurement techniques. Alternatively, where resources are limited, it can be done qualitatively by scoring different areas for a range of indicators. As yet, such qualitative methods are in their infancy. Specific research is now being undertaken in some European countries.