Both countries examine the growth and the health state of forest stands in a similar way. Both the Slovak and Hungarian Parties in the present report evaluate the development of the basic growth parameters and the weekly girth growth of trees in forest stands for the year 2005. Evaluation of the health state of trees in forest stands in 2005 was realized only on Slovak side. The health state observation on the Hungarian side was not performed in 2005. However, it should continue in next years. There were new experimental plots established on the Hungarian side. The natural reforestation processes and possibilities of reforestation in silviculture will be studied on these plots.

A review of abiotic conditions in 2005, which essentially influencing the development of the forest communities (including fauna and flora evaluated in the Part 7 – Biological Monitoring), can be summarized as follows:

• The year 2005 was favourable for flood-plain forest development from the higher precipitation amount point of view. Moreover, the distribution of precipitation in the vegetation period was favourable as well. Significant amount of rainfall in the summer period postponed the signs of moisture deficiency in the tree and the plant layer as well. Comparing to the long-term average the yearly sum of precipitation was higher by 15%. Extremely high air temperatures were not recorded during the evaluated year.

• Apart from the favourable meteorological conditions, the lower part of the Slovak and Hungarian inundation area were favourable influenced by multiple flooding during higher discharges in the Danube. The distribution of floods during the year was convenient as well.

• In May 2005 an artificial flooding of the right side inundation area was realised.

6.1. The Slovak territory 

The forest monitoring on the Slovak side is carried out on monitoring areas presented in table 6-1. All of them are situated in the inundation area (Fig. 6-1), where the most productive, rapidly growing wetland forest communities occur. These communities have high demand on water and have relatively high resistance to pests and pathogens.

The monitored forest communities mostly represent the development of the stand conditions in different parts of the inundation area after putting the Gabčíkovo hydropower structure into operation. The main aspects of the moisture development in these regions were characterized in previous Joint Annual Reports on environment monitoring (e.g. in years 2003 or 2004).

Table 6-1: List of the forest monitoring areas on the Slovak side

The forest monitoring on the Slovak side is focused onto various cultivated poplar clones (Tab. 6-1). Monitoring of willows is restricted to weekly girth grow observation on one plot. The monitoring results show that the growth of poplar clones in different parts of the inundation area is similar. The height increase of the aged plots is good (plots No. 2682, 2686, 2688), even though it has a decreasing tendency. No significant decrease of growth was observed on plots where the ground water level dropped below the boundary between the soils and gravel layer. This can be explained by penetrating of roots downwards to deeper lying layers. On the other side the growth of newly planted forest seems to be problematic (plots No. 2684, 2689). The root system of planted trees is not developed, so the access to the water is difficult. Problems with reforestation of cleared area warn and emphasize the necessity of hydro-technical measures. The water regime in inundation area can be improved by ground water level increase, by artificial flooding of the area and with setting up the water supply into the river branches in lower part of the inundation area.

Girth growth decreased in last few years, but the high age of the observed trees can play an important role. Maximal weekly girth growth increases were usually recorded just after the flood in July. Zero girth growth increases become more frequent on several monitoring areas. However, this phenomenon was not observed on the willow plot, in spite of that willows have high demand on water.

In 2005 the health state of forest in the inundation area was evaluated according to aerial survey. The evaluation was based on defoliation of trees and terrestrial survey. Results in 2005 did not show any unfavourable effect of the hydropower plant on the forest health state. The health state of the forest is very good, the average defoliation reaches approximately 15 % (the Slovak average is about 19.2 % in greenwoods). Slightly and medially damaged stands are straggle in the area. Higher degree of defoliation is related to elder stands. Seriously harmed stands were not registered. In comparison to the results of previous survey in 2002 significant changes occurred sporadically only and were present equally at all classes of defoliation.

Significant worsening of the health state as a consequence of fungicidal or bacteriological illnesses, or insect pests was not registered by the terrestrial survey, although the meteorological conditions were again favourable for their spreading. Slightly increased occurrence was registered at the end of vegetation period only, which could not influence the production characteristics. The occurrence of pests and illnesses was in general lower in comparison to the previous year.

6.2. The Hungarian side 

The forest monitoring on the Hungarian side in year 2005 was carried out on monitoring areas presented in Table 6-2. All of them, except monitoring areas Hédervár 11B and Ásványráró 45A, are situated in the inundation area (Fig. 6-1). The forestry observations in 2005 included measuring of the wood yield (assessment of wood stock, increase of height and thickness) and the increase in girth growth of selected individuals. The tree health state observations have not been carried out in 2005. Newly introduced was an observation of mortality of trees and field investigation focused on natural regeneration processes. 

Table 6-2: List of the forest monitoring areas on the Hungarian side

* - no dendrometric data provided yet

According to dendrometric measurements in 2005, the changed moisture conditions in the Szigetköz region after diversion of the Danube affected the forest stands, however the impact is strongly dependent on the forest type and locations. The older and middle-aged poplar stands “I-214” and “Pannonia” with outstanding growing capabilities, which are situated in a good habitat, were not affected or the impact is very slight. However, there are seriously affected stands, which consist of willows or young poplars, which are situated on locations unsuitable for these kinds of trees.

In case of willows, the growth rate on suitable monitoring areas with younger stands can be still considered as favourable. However, their growth rate slow down before the expected growth culmination. In general, conditions for willow cultivation became noticeably worse at their original planting places. The girth growth of willow trees was similar to that in previous year, so in 2005 lagged behind the expected values. The girth increment rate of the observed poplar clones stagnate, the increments are constant in last years. The growing period of trees in 2005 covered the vegetation period.

Significant number of dried trees in planted stands is warning. Only a negligible number of naturally dried trees is expected in these stands, because of intensive forest management. In spite of this, increasing number of dried trees was registered in last few years. Based on these facts new investigation, focused on the natural regeneration processes and management procedures should be introduced. Several new experimental plots were established for this study on the Hungarian side