The development of forest communities, as well as plant and animal communities evaluated in Part 7 – Biological Monitoring, was on both sides of the Danube, Slovak and Hungarian, influenced by abiotic conditions, which can be summarized as follows:

• The course of meteorological and hydrological conditions was relatively favourable. In the winter period low flow rates occurred, which were followed by higher flow rates after strong warming in the spring. Heavy rains during the third decade of June evoked a big flood wave at the end of the month. Two other significant discharge waves occurred in the middle of July and at the beginning of August, which were caused by precipitations above average. Significant part of the inundation area was flooded once or even more times under these flow rates, which is considered as a positive factor from the alluvial forest development point of view.

• Precipitations significantly below the average or even periods without precipitation were registered from the beginning of April till the middle of June and in the second half of September 2009.

• The average daily temperatures from the beginning of May till the end of August 2009 fluctuated around the long-term average values; no extreme summer heat was registered.

6.1. Evaluation of 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. The Slovak Party on monitoring areas in the actual year evaluated the development of basic growth parameters, weekly girth growth and the health state of trees by terrestrial survey. In the Slovak inundation area the development of the most productive cultivated poplars is observed. The poplar clone Pannonia gradually replaces stands of cultivated poplars I-214 and Robusta. The areal spreading of willow stands in the whole inundation area decreases as well.

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

* - on sub-areas marked by letters “a” or “b” temporary measurement of weekly girth growth is carried out only

The development of forest stands in the evaluated year mostly did not left the existing tendencies, and it was rather favourable.

The growth characteristics in the evaluated year were already observed at every monitoring area in young or middle-aged forest stands; forest stands exceeding the rotation age were already cleared on the respective areas. The quality classification according to the height increase remained unchanged in the middle-aged stands and reaches very good level (areas No. 3802, 3803). Gradually it becomes truth also for the stabilised young stands with the “Pannonia” poplar clones at areas No. 2685 and 2689. The growth increment of young poplars on areas No. 2684, 2687 and 2681 has stabilised as well, however on lower level. The growth increment of poplar seedling on areas No. 2683 and 2686 is observed for two years only, they growth is settled. Certain attention has to be paid to spreading of invasive plant species (Solidago gigantea, Impatiens glandulifera) on unforested area No. 2690 and in the young forest stands on areas No. 2684 and 2687 as well. Although a large part of the inundation area was flooded in the evaluated year, the retreat of invasive plant species was registered in certain areas only.

Based on weekly girth growth increments (according to data from substitutive areas No. 4219, 4447, 4349, 5504, 5573 and 4436) significant improving of width increments of poplar and white willow stands was registered in the whole area in previous two years. In the evaluated year the tendency of improving did not continued, but increments remained at this improved level. Zero weekly girth growth values were significantly reduced already in 2007, and in 2008 and 2009 they occurred very sporadically. The unambiguous reason of these positive changes was not identified. The growing period of the evaluated year was long; growing was registered already in the first week of April and lasted till the end of September (exceptionally longer). For most observed areas the growth of trees has been intensified at the turn of June and July, after improvement of hydro-meteorological conditions.

The monitored cultivated poplar stands are healthy, resistant to pests and immune to illnesses. The occurrence of illnesses and pests in most of stands was sporadic during the whole growing period. In comparison to the previous year there were minimal differences only in the spread of illnesses or pests. In general the spreading of illnesses in August was higher than in June.

Despite of the above-mentioned positive results it to be repeatedly emphasized the need of more efficient utilisation of existing weirs in the river branch system for elimination of groundwater level decrease and for application of artificial floods. Forestry observations also prove that the increase of discharge in the spring have to be commenced before the beginning of growing season. In the lower part, in the Istragov region, the water supply has to be solved for recharging of the river branch system. Also the impact of erosion of the Danube riverbed, below the confluence of the Danube old riverbed and the tailrace canal, has to be monitored.

6.2.  Evaluation of the Hungarian territory

The forest monitoring on the Hungarian side in year 2009 was carried out on 15 monitoring areas presented in Table 6-2, which are situated in the inundation area (Fig. 6-1). On these areas the dendrometric characteristics were measured and the health state of stands was observed. Furthermore on selected sites the weekly girth growths were registered as well (Lipót 4A/4, Dunasziget 22C, Dunasziget 16A).

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

Based on the detailed analysis of actual growth characteristics of forest stands it can be stated that in the existing growth tendency no change have been registered. The growth of trees is mostly in harmony with expected increments.

On the monitored areas poplar stands dominate, what correspond to the actual tree composition in the Szigetköz area. Cultivated poplar “Pannonia” forms the largest portion of forest stands. Their growth is basically satisfactory at current flow rate as well. No decline from the growth point of view occurred in case of slow-growing indigenous species as well.

From the weekly girth growth increment point of view in case of poplar stand on the area Lipót 4A it can be stated, that the increment gradually decreases in last years, while the increment intensity is basically in harmony with expected values regarding the age of stand. Trees reached the rotation age and further significant width growth cannot be expected. From May till September normal increment was registered with two peaks of growing. The most intensive growing was recorded in June thanks to optimal hydrological and meteorological conditions.

In terms of growing of oak and ash trees on the area Dunasziget 22C no significant change was registered in comparison to the previous years. The increment of ash trees slightly lags behind the expectable increment corresponding to their age. Relatively weak increments are registered in case of several oak trees, however they do not have enough growth space.

Following the recent thinning of the stand intensification of growth was registered on the area Dunasziget 16A. The favourable hydrological conditions contributed to this as well. The growth increment was exceptionally intensive, especially when taking into account the relatively high age of trees