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 2006. Evaluation of the health state of forest stands was not realized on Hungarian side in the previous year.

A review of abiotic conditions in 2006, 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 2006 was a typical year from the meteorological point of view. Atypical, however, was later beginning of the vegetation period (lower temperatures in March and April) and the extremely high temperatures in June and July accompanied with lack of precipitation, especially in July. These conditions strongly influenced the development of plant and animal communities, which started well thanks to the favourable hydrological and climatic conditions in April and May (rich precipitations). The situation got better in August, when the inundation area was flooded and the precipitation amount was higher as well. The autumn was dry again, atypically warm and long lasting.

• Hydrological conditions in the evaluated year were favourable, except the extremely low discharges in July. A big flood occurred at the end of March and at the beginning of April, and discharges over 4000 m³s^-1 remained till the beginning of May. Discharges in May and June fluctuated around 3000 m³s^-1 and at the beginning of June one lower flood occurred again. Unfavourable discharge conditions were characteristic for July. Flow rates reached values near minimums ever observed. The unfavourable situation was mitigated by another flood in August. Thanks to natural floods, no needs arisen to flood the inundation artificially 

6.1. The Slovak territory 

The forest monitoring on the Slovak side is carried out on monitoring areas in the inundation. The list of monitored sites is presented in table 6-1 and the situation is shown on Fig. 6-1. At these stands the development of the most productive cultivated poplars are observed, which are spread on the substantial part of the inundation area. In last years the cleared stands of cultivated poplars I-214 and Robusta are gradually replaced by a new resistible poplar clone Pannonia. The monitoring of willows was reduced to observation of weekly girth growth on an substitutional monitoring area. The areal spreading of willow stands in the whole inundation area decreases.

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

Based on the monitoring results it can be concluded that in general the growth of poplar clones in the different part of inundation is similar. The increment of the older stands after the growth culmination decreases slowly, their growth, especial in height is henceforth good (monitoring areas No. 2682, 2686, 2688). From the point of view of the young trees, it can be stated that at the monitoring restoration (at stands aged 3-5 years) slow growth was observed (except monitoring areas No. 3802 and 3803), which gradually got better in the following years (monitoring areas No. 2681, 2685, 2687.) In case of monitoring areas No. 2684 and 2689 there were problems with reforestation of cleared areas, dried young trees had to be replaced with new seedlings, so stands with age differences were created. However, the growth of these stands has already stabilised in the evaluated year.

The weekly and cumulative girth growth results on poplar and one willow stands show extraordinarily low increments. During the whole vegetation period the weekly girth growth on almost every observed stands reached values up to 0.1 cm only. These values are very low in comparison with the previous years. Slightly higher increments were recorded only at monitoring area No. 4349. Even after floods in the spring no higher increase of weekly girth growth increments were observed. No growth culmination could be detected during the rest of the vegetation period as well. Zero weekly girth growth values were often recorded. Start of growing in many stands was registered not until May, however the growing did not stop before end of October.

The health state of forest in the inundation area in 2006, evaluated on the basis of terrestrial survey, was good, similarly to previous year. From the point of view of poplar clones, it can be stated that the health state in June was better then that in August. Spreading of fungicidal or bacteriological illnesses, or insect pests was similar as in previous year, slight worsening or improving was registered alternately. Significant worsening of the health state was not registered, although the meteorological conditions were again favourable for their spreading. 

6.2. The Hungarian side 

The forest monitoring on the Hungarian side in year 2006 was carried out on monitoring areas presented in Table 6-2. All areas, except monitoring sites at Hédervár 11B and Ásványráró 45A, are situated in the inundation area (Fig. 6-1). 

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

According to dendrometric measurements in 2006 and in previous years as well it can be stated that the changed moisture conditions after diversion of the Danube affected the forest stands in the Szigetköz region, however the impact is strongly dependent on the forest type and its location. 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 was 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.

The rate of girth growth of the observed poplar stands was similar to that in previous years. The positive impact of floods and higher amount of precipitation was not reflected in higher increments. The impact of lower temperatures at the beginning of vegetation period was reflected by later initiation of growing. Increments in poplar stands were registered during the whole vegetation period. Analysing the results obtained in last several years it can be stated, that the growing potential of the quickly growing clones is slightly decreased.

The health state of forest stands was favourable. Locally damaged stands were registered, which were affected by a storm in August. However, the extent of damages was not considerable.

Concerning the species composition changes were detected through the past decades. There are more tree species in the Szigetköz today than they were 20 years ago. In the 1980s almost only poplars, willows and other water demanding species gave the main stock of forests (alder, pedunculate oak, ash). The proportion of cultivated poplars decreased significantly whilst other cultivated, improved domestic species were being involved. The proportion of native hardwood species did not alter however, the indigenous poplars dispersed. The American ash appeared in the area and the proportion of black locust is increasing