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eGUNliR¥ REeGRliS 23
The causes of pedunculate oak decline are partly similar and partly different from those
of sessile oak. They are as follows:
III outbreaks of defoliating insects
III too much gley and slack water, as well as chalk formation in compacted soils
III mildew
III disequilibrium in the water balance within the tree
III appearance of parasites (Armillaria spp.)
III outbreaks of scale insects and xylophagous insects.
Pedunculate oak decline is a periodical phenomenon. Intensive drying of trees occurred
when the outbreaks of Lymantria dispar followed periods with a rainfall higher than average.
This happened in 1907-08, 1914-17, 1924, 1962-65 and 1972-74.
Beech
The health state of beech stands has declined in recent years, but problems are less serious
than for oaks (Table 4). The most common cause associated with damaged beech trees is
drought. Air pollution or acid rains are not considered an important damaging agent in the
Carpathian basin.
liable 4. Percentage of health~ stems in beech
Difference
Difference
Region 1992 1993 {1993 - 1992} 1994 (1994 -1993)
Northern Central Mtns. 1 67.9 59.6 -8.3 55.7 -3.9
Northern Central Mtns. 2 45.4 32.0 -13.4 35.5 +1.5
Transdanubian Central 73.2 69.1 -1.4 71.4 +2.3
Mtns.
Transdanubian Hills 1 74.4 67.1 -7.3 63.1 -4.0
Transdanubian Hills 2 73.3 69.1 -4.2 71.6 +2.5
West-Transdanubia 87.7 82.7 -5.1 86 +3.3
Source: T6th et al. 1995.
Research activities related to genetic resources/diversity
We have hardly any information about the genetic variation of the Hungarian oak and beech
populations. In collaboration with other countries, we could only conduct a few
investigations including:
III Genetic differentiation by RAPD markers of oak species in Hungary (see Bordacs and
Burg 1997).
The genetic differentiation of four oak taxa in Hungary was investigated by RAPD
analysis. In total, 99 trees were sampled to compare levels of genetic diversity and to
identify the taxa. Among 26 single decamer primers screened, the four resulting profiles
showed significant differences among the four taxa.
III Genetic variation in beech populations along the Alpine chain and the Hungarian Basin
(Comps et al. 1998):
Seventy-eight European beech population from the Alp Chain and the Hungarian Basin
were analyzed using eleven alloenzymatic loci. Four pools of populations could be
discriminated.
Experiments are under way in the following fields:
III inter- and intraspecific variation of Q. robur and Q. petraea, and within the Q. petraea
aggregate for morphological traits
III controlled crossing among native oak species
III provenance tests.