Zs. K. Komáromy szerk.: Studia Botanica Hungarica 17. 1984 (Budapest, 1984)
Siklósi, Engelbert: The flora of the pits in the Nature Preservation Area of Ócsa
Lakes 1 and 2. These are the oldest lakes, in some places they include the original lakes and bogs. Both are of large size. Usually they have shallow water although the depth may reach 1-1.5 m. The average water depth is 40-50 cm. The mud cover is rather thick on the bottom of the lake. Organic matter has accumulated in large quantity, the eutrophication process is at an advanced stage. The pH of water is alkaline, 7.6-8. There are few open water surfaces. The reed ( Phragmites communis ) and bulrush species ( Typha latifolia , Typha angustifolia ) form the coastal vegetation. First of all Typha latifolia is the species in the largest abundance and we could find many Typha angustifolia , too. In some places Typha laxmanni occurs. Large specimens of Rumex palustris are characteristic among the reeds. Carex elata forms closed stand on higher parts of the beach. It associates with Typha latifolia from the water and Glyceria maxima from the meadow. Polygonum lapathifolium occurs in great number and Alisma plantago-aquatica in the coastal region, too. The following cenological arrangement seems to be acceptable: Reeds: -Phragmition communis -typhetosum and Sedge: -Magnocaricion elatae-Caricetum elatae. Here we could find the transition between Caricetosum acutiformis-ripariae and Cypero-Juncetum on high ground. In some parts of the high turfy places appear the characteristic species of Schoenetum nigricantis: Schoenus nigricans , Cladium mariscus . The vegetation of the lakes surpasses that of the canal in abundance and species richness. Widespread bulrush fields and clumps alternate with open water surfaces. Utricularia vulgaris is characteristic for the floating reed-grass that in some places forms mixed stand with Hydrocharis morsus-ranae and Utricularia minor . Here and there Utricularia minor form isolated spots. Lemna minor is a characteristic species of this floating reed-grass, too. The association is placed into the following category: a) Hydrocharietalia-Hydrocharition and b) Lemno-Utricularietum. Myriophyllum verticillatum and Ceratophyllum demersum constitute the rooted reed-grass. Usually they appear together, but Ceratophyllum dominates. It could be placed into the following category: a) Lemno-Utricularietum and b) Ceratophylletosum demersi. Lakes 3. 4 and 5 These are the youngest lakes. They are poor in species. Their water surfaces are small, especially those of lakes 3 and 4. The water depth is shallow, it varies between 30 and 50 cm. Their organic matter and mud layers are thinner than in the case of lakes 1 and 2. Their chemical composition corresponds to those of the previous lakes. The vegetation is poor in biomass, too. Here we do not find the transitional reed zone between the beach and the water surface. The reason for it is that the beach drops too steeply because of its artificial origin. An exception is lake 4 which is really a shallow pit with reeds and some square metres of open water surface. The vegetation of the littoral zone can be placed into the Caricetum elatae category in the case of lakes 3 and 5 Phragmition communis-Phragmitetosum in the case of lake 4. The transition towards Schoenetum nigricantis could be found in the case of lake 5, too. The vegetation of the water surface is poor in species as well. Typha latifolia occurs only in few numbers. The few floating reed-grass consist of Lemna minor alone, Ceratophyl lum demersum and Potamogeton pectinatum dominate in the rooted reed-grass. Stands of large mass of these species form the bottom vegetation of the lake. Their groups are separated from one another. COMPARISON OF THE STUDIED AREAS It is clear from the detailed descriptions of the areas and the segment of the canal and the lakes that in the appearance of the vegetation there are not great differences. We observed the following characteristic succession in the sample plots: Schoenetum nigricantis, Cypero-Juncetum, Caricetum elatae, Phragmition communis, Lemno - Utricularietum, Ceratophylletosum demersi. The differences between the lakes appear in the numerical aspects of the species and in the succession of the associations. In lakes 1 and 2 everywhere a wide belt of reeds follow the shoreline. Typha latifolia and Typha angustifolia are more frequent species along the lakes than in the canal. This latter species and Typha laxmannii do not occur in the vegetation of the canal.
