RESUME
Damage of forest stands in the Orlické hory Mountains
František Šach, Daniela Fottová, Vratislav Balcar, Vladimír Černohous, Dušan Kacálek, Václav Nárovec (pp. 452-455)A severe damage of young Norway spruce forest stands of a great extent, mainly higher than 800 m a.s.l., appeared in the SE part of the Orlické hory Mountains in spring 1999. The Norway spruce needles are reddish (rusty) and fall off from the last-year or older twigs at the main ridge of the Orlické hory Mountains. Deficiency disease has been observed on needles of blue spruce at summit localities (brownish to reddish coloration of needles with transition zones into violet coloration) and a mass dying of European birch. The damage and dying of last-year twigs of Norway spruce is the most severe thing. Dying is in progress not only at summit localities, but at lower altitudes as well (at about 800 m a.s.l.). It gives serious concern about the future development of forest in the Orlické hory Mountains. Damage of forest stands has been probably caused by complex circumstances, in which air pollution obviously plays an important role. The authors, after extensive analysis, arrived at the following conclusions:
- In spite of decrease of SO2 emission (and thus also its concentration in the air), deposition of sulfur is still at a high level and it can participate in damaging the health conditions of forest ecosystems (mainly Norway spruce) of the Orlické hory Mountains. Content of SO2 was accused of damages on forest stands in the Orlické hory Mountains in the eighties.
- Nitrogen depositions (ammonium and nitrate ions) exceed the critical limits many times and by cooperation of frequent and long dry periods in the vegetative season they can create serious threat to the spruce ecosystems.
- High levels of air pollution caused by fluorine, chlorine and ozone are also the threat.
- The year 1998 is a warning season in which air pollution caused by NO3 (depositions on a free area and below the forest stand) has been considerably increased in the Orlické hory Mountains. A considerable increase has also been recorded in air pollution caused by sulfur, fluorine and chlorine caught by the tree crowns, and also the concentration of ozone in the air.
ICP FORESTS - results of monitoring in the Czech Republic in 1998
Petr Fabiánek, Jitka Hejdová (pp. 462)The authors state that defoliation rating in the Czech Republic was practiced till now in compliance with a long-term tradition in the older forest stands only. To compare the course of defoliation it is necessary to divide the results of assessment in 1998 into two groups according the age of a forest stand: trees younger than 60 years and trees old 60 years or more. It is possible to compare the course of defoliation only in forest stands older than 59 years. It is possible to evaluate the defoliation of younger forest stands only, as a comparison of state of the older forest stands evaluated in the same year. In conifers (forest stands 60 years old or more) the state became considerably better in comparison with 1997. Level 2 (defoliation 26-60 %) decreased from 71,2 % in 1997 to 57,4 % in 1998 and level 1 (11-25 %) increased in the same time from 25,7 % in 1997 to 37,9 % in 1998. This change was the most remarkable in Scots pine (Pinus sylvestris). In the monitored season 1986-1998 the average level of defoliation was ranked the same as presence of levels 2-4 (26-100 %) and they both culminated in 1996.
In the same age category of broad-leaved tree species the comparison of defoliation with the year 1997 is similar. The percentual proportion of trees rated by level 2 decreased from 25,5 % in 1997 to 15,4 % in 1998 and also level 1 increased from 45,2 % in 1997 to 54,0 % in 1998. This favourable change was mainly recorded in oak (Quercus petraea, Q. robur), in case of beech (Fagus sylvatica) its state remained almost without any change. In the monitored season 1991-1998 the development of broad-leaved tree species is not so considerable as in conifers until now. The highest average defoliation and the highest number of levels 2-4 as well were recorded in 1993. In the following years the successive decreasing of monitored parameters took place. Younger forest stands of both groups of woody plants have generally lower defoliation. This difference in comparison with the older forest stands is the most considerable in conifers. Damages by wind (windbreaks, windfalls), damages by insect and the occurrence of epiphytes were recorded on the same average level as in the last year. General improvement of health conditions of the forest stands is a reaction mainly to more favourable climatic conditions and partly also to continuing improvement of situation in air pollution. This reaction takes place naturally with some time delay. It is the reaction of forest stands to the changes of environment.