Ecology of elms in Romania

G. F. Borlea

Abstract


The resistance of indigenous elm species to Dutch Elm Disease (DED) has been studied since 1991 with emphasis on natural forests. The situation varies with altitude, local conditions, species and with stand origin. The variability in morphological characteristics is important and some varieties are described. The taxonomy of elms in Romania, as in the whole of Europe, seems to be confusing (Ulmus ambigua was described in 1952 by Beldie in Flora of Romania). Natural hybrids between field elm and mountain elm were observed both in natural and artificial stands, especially in border zones for the altitudinal distribution of the species. Seedlings from the natural provenances and open pollinated seedlings from hybrids produced in the Dutch breeding programme were artificially inoculated with Ophiostoma ulmi- Buism.. Most of the seedlings died, but results show an important number of surviving individuals from natural provenances. In some natural and artificial stands, it was observed that beside transmission of the disease by insects (Scolytus spp.), it was spread through root sprouts especially in field elms, from the dead «mother tree» within a few years, as well as by root grafts to proximal healthy trees («biogroups»). Because of the genetic incompatibility of individuals in some cases, the grafting cannot succeed and neither can infection. In the natural forest where the ecosystem is in equilibrium and functions normally, DED is present but its damages are not so important. The study of elms in natural forests provides valuable information for the problems caused by DED.

Keywords


glacier refuge; taxonomy; provenance; population; ecotypes; natural forest ecosystem

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