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MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary 1 Slovenia The "Multifunctional Integrated Study Danube, Corridor and Catchment" (MIDCC) Partner Report Macrophytes of the Rivers Stržen, Obrh, Rak and Ljubljanica by Alenka Gaberščik Mateja Germ Nina Kržič Olga Urbanc-Berčič National Institute of Biology & Department of Biology, Biotechnical faculty, University of Ljubljana Večna pot 111, 1000 Ljubljana, Slovenia Ljubljana, 15th March 2005 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary 1.1 Introduction 1.1.1 Short general description In our study we surveyed four branches of the same river called the River Ljubljanica. It is characterized as a unique river of karstic character and no more than seven names. Special environmental circumstances are basic for the phenomenon of multiple appearing and disappearing of the river and to gain the designation, a river of seven names. The origin of the river defines two branches, each collecting waters from different mountainous areas. The reason for such variety is geological background. The geology of wider area indicates a stirred up history that is still recognized in recent earthquake activity. Trbuhovica is the name of the very source. It is a short stream, quickly disappearing underground among and through the limestone rocks. Waters come up again in the Loška dolina valley under the name Obrh. The river flows underground and after 1 km it appears again. Shortly it enters the Cerkniško polje under the third name Stržen. There the water leaked out through sink holes and the rest of it leaves the surface in two caves. It came out for only two kilometers as the Rak stream, disappearing again in a cave. From the west there comes the second branch of the Ljubljanica River, the Pivka stream. Underground in a cave Planinska jama two rivers from both branches come together and appear as the Unica stream. After some kilometers it leaves the surface. The scattered waters gather for the last time at the town Vrhnika coming on a surface in two sources. Finally the river gets the name Ljubljanica and becomes the main stream of the bogs of Ljubljansko barje. After flowing through the city of Ljubljana it joins the River Sava and the River Kamniška Bistrica at the confluence of the three rivers (ENCIKLOPEDIJA SLOVENIJE 1992). 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary Photo 1.1.1 A densely overgrown dry stream of Mali Obrh. Photo 1.1.2 The Veliki Obrh stream in the top of the season. The upper parts of the River Ljubljanica are formed by three streams, the Obrh, Stržen, and Rak stream. They flow subsequently through the karst poljes in SW Slovenia. Karst depression is defined as karst polje (karst field) if the bottom is at least 500 m wide. The bottom of the karst polje consists mostly of Triassic dolomite and limestone covered by Tertiary sediments (loam and sand). The typical form of karst polje is a vanishing stream and continuous steep periphery. The karst stream appears on one side of the polje, flows on the surface and vanishes in the sink holes on the other side. Karst polje is characterized by huge inter-annual water level fluctuation (Gospodarič & Habič 1979; Gams 1998). Loško polje 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary with the Obrh stream is classified as overflow poljes as described above (Gams 1994). The Obrh stream assembles Mali Obrh and Veliki Obrh. Mali Obrh dries out every year. Veliki Obrh has a permanent water supply as well as Obrh in the part after the confluence. When the Obrh stream enters Cerkniško polje it is given a name Stržen. The Stržen stream is characterized by a great water level fluctuation. The lake is formed at Cerkniško polje due to immense floods in spring and autumn. Usually in summers the lake becomes dry. The Lake Cerknica is locus typicus for intermittent lakes and poljes (Gaberščik & Urbanc-Berčič 2002; Gaberščik et al. 2004). The valley of Rak stream still has an uncertain geomorphologic origin. It can be described as an early stage of karst polje. The Rak stream has more or less permanent water supply, but the water regime is highly variable. Photo 1.1.3 The wetland areas surround the Stržen stream. The karstic character of the river is also recognized through its geomorphologic features. The underground length of the River Ljubljanica is 38 km. Its whole catchment is 1779 km2 large and almost 1100 km2 of it is karstic. Many springs of Ljubljanica are used as a reserve source of drinking water due to its permanent and substantial amount of water. The River Ljubljanica is exposed to the dispersed pollution from karstic watershed as well as to the point pollution from the settlements and industry. The main source of pollution is the Ljubljana city and its insufficient wastewater treatment plant. This is a huge impact for slow low-land river with low ventilation. In the dry seasons the conditions may become even anoxic (ENCIKLOPEDIJA SLOVENIJE 1992). The drainage canals and some small tributaries from farmland worsen the situation in a main channel. 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary Photo 1.1.4 Solid rocks are covered by mosses. Photo 1.1.5 A still water of the River Ljubljanica reflects a blue sky and a green canopy. 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary 1.1.2 Physical habitat settings Obrh: The most frequent bank structure type was fine inorganic material with vertical slope (42) sediment type was mainly fine inorganic material with solid rocks. The stream flow was mainly stagnant. There was no water present in one river stretch. Five different land use types were recognized, agricultural areas being the most frequent ones. Total length of the surveyed stream was 12.300 km. Stržen: Fine inorganic material with gentle slope (41) and vertical slope (42) were prevailing bank structures. Ten different sediment types were determined; with the fine inorganic material as the most frequent one. The flow was mostly stagnant. The majority of land use type was determined as wetlands (4). The stream length was 13.570 km. Rak: Fine inorganic material with gentle (41) and steep slope (42) was found. Solid rocks prevailed as a sediment type. A flow was mostly stagnant or with low velocity (1,2). The land use type was forest (31) and semi-natural areas (32). The stream was very short, 1.860 km only. Ljubljanica: Connectivity type was classified as 7. The most frequent types of bank structure were fine inorganic material with flat slope, marked as 41, and six variations of sediment type in the river were recognized. The prevailing sediment consisted of gravel and sand (2\3), and fine inorganic material with solid rocks (4\1). Mostly there was no visible flow (1). The most frequent land use type was marked as heterogeneous agricultural areas (24), with town (11) and villages – 11908. Riparian zone was mostly wide. Disturbances on many sites occurred due to reduced vegetation and some clear cuts in urban areas and also in a country - side. Concrete banks were present in the city of Ljubljana. Overview of surveyed rivers: The most frequent type of bank structure in all rivers was fine inorganic material with gentle slope (41), followed by fine inorganic material with steep slope (42). The prevailing sediment type was fine inorganic material combined with solid rocks on many stretches. Land use type was variable: Obrh and Ljubljanica flow mostly through agricultural landscape. The River Ljubljanica crosses settlements too. The Stržen stream is mainly surrounded by wetland and the Rak stream by the forest. 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary Previaling sediment type B ank structure Fine inorganic Solid rock Large blocks, Fine inorganic gravel, sand Large blocks Gravel Solid rock Large blocks, fine Sand inorganic Fine inorganic, Organic artificial Artificial Land use type Flow class No flow Artificial Dry Agricultural Low flow Forest Medium flow Wetland Figure 1.1.1 Share of different habitat settings, bank structure, flow class, prevailing sediment type, and land use type are presented for the four streams together. 1.2 Species composition In the Obrh stream 44 macrophyte species were observed, 18 hydrophytes and 26 helophytes. No natant species were found, probably because of shallow water. The genus Potamogeton was presented by 4 different species. 3 taxa of Characeae were found in the Mali Obrh stream, Chara sp., Nitella sp. and Tolypella sp. In the Stržen stream 40 species were observed, 11 hydrophytes and 29 helophytes. The water level of Stržen fluctuated a lot therefore a low number of hydrophytes were found. In the middle and the lower part of the stream Nuphar lutea was found because the water became deep and stagnant. In the Rak stream we found 35 macrophyte species, 13 hydrophytes and 22 helophytes. The dominant genus colonizing the stream was Potamogeton with six species. 2004, Gaberščik, Germ, Kržič, Urbanc-Berčič MIDCC 1st Year ReportChapter Fehler! Verweisquelle konnte nicht gefunden werden.- Fehler! Verweisquelle konnte nicht gefunden werden. Version: Preliminary In the River Ljubljanica 39 macrophyte species were determined from its source to the Ljubljana city.