Microscopical aspects of foliar alterations in declining trees : Waldschadensforschung - Wissensstand und Perspektiven. Internationaler Kongress

1990

S. 431-443

1 Abb., zahlr. Lit. Ang.

Unselbständiges Werk

200068715

Through the present review is mainly concerned with microscopical aspects of damaged foliage from trees in the context of "New-type Forest Decline", more "classical" damages through pollutants close to known point sources or in areas with high concentrations caising acute damages are included for comparison and as a help for interpretation. The man problem in actual "Forest Decline" is that it cannot yet be related to the well established direct influences of, e.g., So2, and thus should be regarded separately from these. It is intended in the following to review publications which (a) aid in understanding fundamental damaging processes from controlled experiments and in areas of established high impact of certain pollutants, (b) describe approaches to use microscopical aspects as diagnostic tools in clarifying pathological processes related to "Forest Decline", and (c) develop hypotheses relying mainly upon structural changes as the base explaining causes of the damage. The article is structured according to the main tissue zones (cuticle/epidermis, mesophyll, vascular bundle) affected. In each case, first a description is given of what is known and has been established as cause-effect relations. Then the related observations in the field of "Forest Decline" are described and their possible interpretation in the light of the first mentioned results is evaluated. It must be taken into account, however, that all microscopical research in the field of "Forest Decaline" has concenrated on conifer needles exhibiting symptoms of "montane yellowing", whereas nearly no information is available on the widespred premature needle fall not associated with yellowing. Furthermore, very little research has been conducted on trees.